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L98 TPI 350 endurance race combination

General engine tech -- Drag Racing to Circle Track

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CastIron
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Re: L98 TPI 350 endurance race combination

Post by CastIron »

n2omike wrote: Tue May 04, 2021 10:49 am It's going to be HARD to run with modern Japanese sedans... especially with their all aluminum DOHC engines, advanced suspensions and light weight... and that's without even considering fuel mileage and 'family car' fuel tanks. I would think a Honda Accord, Acura equivalent or similar offerings from Nissan/Infinity would be the hot ticket. I had a Nissan Maxima at one time, and that thing was nice... I can imagine it with the stick shift!
Nissan Maxima's and the already mentioned Altima SER do very well. As do Ecotech swapped Miata's and a 1988 CRX with some high winding Honda motor swapped in. There is one '94 Mustang Cobra that does well. The rest of the field is mostly BMW's, a number of which (e30's and e36's) also do very well. For most light weight is the most important thing with Miata's being under 2000lbs and the e30's being 21-2200. Porsche Boxsters are coming and running fast as well.

I have zero interest in any of those cars however, so it comes down to sciencing out a G body. AL heads, extreme weight loss, and engine set back will help as will almost 22 gallons of gas. The chassis can be made pretty good without much trouble, so it's balancing power and fuel. The great torque and lower rpm from the TPI should help with the mileage I'd think.

A second gen Camaro might be as good or slightly better as it has a little more gas, 1974-81 cars, and wouldn't require spending points to swap the engine. The engine would require a lot however starting with one of those smoggers and finding one that doesn't have the rear rails rusted out of it isn't the easiest in my area.

The late C3 Vette has shown to be very good with 24 gallons stock and not terribly heavy once stripped. Riley Motorsports built one that dominated which led to a points increase to slow it down. It's still very good but I don't fit in them well with a cage and really don't want to do the typical "convertible" as seen in vintage racing. Currently it is the best choice but the crack prone 882 heads are a concern. Last year the Riley car had fast burns on it. This year without them it had overheating issues at Daytona. Don't know for sure that is the cause but assuming they are related.
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Re: L98 TPI 350 endurance race combination

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How many points to run after market runners? I assume you can port anything that you want?

You can find a great thread on here on what a max effort TPI porting looks like and it's a horiffic amount of labor; I'm guessing it's why so many max effort tests focused on TPI intakes instead just send them to get extrude honed. (Which will also cost about $1000 if you want the lower intake, runners, AND plenum extrude honed...)

If you're only looking for around 370 hp and 450 ft lbs of torque, there's an old Lingenfelter 383 L98 build that used a ported plenum and base and a set of the large aftermarket runners (I am assuming Accel because Lingenfelter was using tons of Accel stuff), I'm not sure if hte L98 heads were ported or stock, but a 210/210 .525/.525 112 LSA lingenfelter cam that he used in a bunch of his longer runner builds, stock corvette cast mainfolds and he ended up with 368HP and 451 ft lbs of torque. Better heads and a solid roller could help out a 355 if that's what you're stuck with.

Most of the really good power TPI builds I see seem to be running larger intake port volumes that you'd expect for the cubic inches and RPM that they run.


Stock TPI intake flow #'s:
203 runners only
199 stock base
181 stock base/runners.

Not the best starting place.

Adam
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Re: L98 TPI 350 endurance race combination

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CastIron wrote: Tue May 04, 2021 11:46 am The late C3 Vette has shown to be very good with 24 gallons stock and not terribly heavy once stripped. Riley Motorsports built one that dominated which led to a points increase to slow it down. It's still very good but I don't fit in them well with a cage and really don't want to do the typical "convertible" as seen in vintage racing. Currently it is the best choice but the crack prone 882 heads are a concern. Last year the Riley car had fast burns on it. This year without them it had overheating issues at Daytona. Don't know for sure that is the cause but assuming they are related.
An 82 Vette had the best Cd, lightest weight, and definitely the best fuel economy of any C3 with it's baby rear gears, 700r4, 3349 lbs, and basic electronically controlled "fuel injection" system. Power was horribly limited by the intake ports but they can be easily opened up and then flow a LOT more. "Performance Plus Systems" released an aftermarket cross-fire intake called the "XRam" that from the exterior, looked exactly like the stock intake but flowed almost 3x as much."...

Seems useful for what it seems like you're trying to do, but those 624 smogger version of the 882 heads ARE bad news. (Mine had 14.4k miles on them and were cracked...)

Not sure what you can and can't do to the suspension but one with the FE41 Gymkhana suspension (550 lb front springs, 1 1/8" sway bar, stiffer rear composite monospring, and a BABY 7/16" rear sway bar (you could swap for an earlier BigBlock 9/16" rear sway bar and it goes from significant understeer to about properly balanced and it would LOOK super stock. No way anyone would notice it because 9/16" sway bar still looks tiny today.) isn't terrible; although the 84 C4 is a huge leap better for a single model year...

Sorry... Back to the L98 TPI F-body... (I've got a later C3 with a long-runner TPI-style intake and a Gymkhana suspension that I've made some improvements to, so you're talking about somethings that interest me in this thread...)


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Re: L98 TPI 350 endurance race combination

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Here are some pics of the C3 to give an idea where it was and just how gutted some of these cars are. The Fast Burns are now gone as mentioned above due to a points increase.
Image
Image

335 width Rival S tires on all four corners with a "Turbo" body or whatever they were called back in the day. It had the field covered by 5 seconds or more, and carries more gas than anyone, so obviously it caused quite an uproar which led to a points adjustment.

I'm pretty sure it was running a 604 crate motor, but like I mentioned hardly anyone in this series would recognize it as such. They just saw the AL heads which were claimed on their points. (100pts) Note it had rams horns on it. Headers are 25 points so apparently they didn't have room. It didn't need them...

This just gives an idea of one of the competitors and what a Champcar C3 is like. Next post I'll hit where I am with the TPI idea.

eta-A modded but stock looking Cross Fire would likely melt some brains if it was actually fast. hah
Last edited by CastIron on Thu May 06, 2021 11:00 pm, edited 1 time in total.
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Re: L98 TPI 350 endurance race combination

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NewbVetteGuy wrote: Thu May 06, 2021 7:27 pm How many points to run after market runners? I assume you can port anything that you want?

You can find a great thread on here on what a max effort TPI porting looks like and it's a horiffic amount of labor; I'm guessing it's why so many max effort tests focused on TPI intakes instead just send them to get extrude honed. (Which will also cost about $1000 if you want the lower intake, runners, AND plenum extrude honed...)

If you're only looking for around 370 hp and 450 ft lbs of torque, there's an old Lingenfelter 383 L98 build that used a ported plenum and base and a set of the large aftermarket runners (I am assuming Accel because Lingenfelter was using tons of Accel stuff), I'm not sure if hte L98 heads were ported or stock, but a 210/210 .525/.525 112 LSA lingenfelter cam that he used in a bunch of his longer runner builds, stock corvette cast mainfolds and he ended up with 368HP and 451 ft lbs of torque. Better heads and a solid roller could help out a 355 if that's what you're stuck with.

Most of the really good power TPI builds I see seem to be running larger intake port volumes that you'd expect for the cubic inches and RPM that they run.


Stock TPI intake flow #'s:
203 runners only
199 stock base
181 stock base/runners.

Not the best starting place.

Adam
Finding articles with TPI builds from back in the day hasn't been easy as they were 30 years ago for most, like the Lingenfelter stuff. I did find the build for the 383 in the vid I posted a link to in the first post. The 383 was;
The 383 featured a 2-bolt block equipped with a forged stoker crank and 6.0-inch rods from Speedmaster. These components were teamed with a set of forged (dished) JE pistons and Total Seal Rings. The short block was further augmented with a COMP XR288HR cam and a set of AFR 195 Street heads. The AFR heads offered intake flow that exceeded 280 cfm (enough to support 550+ hp) and when combined with the healthy cam specs (.520/.540 lift split, a 236/242 duration split and 110-degree lsa), made for a stout little small block.
https://www.streetmusclemag.com/tech-st ... -upgrades/

Made 410HP at 5100rpm and 501 torque at 3900 with a stock untouched TPI. HP was flat as a table out to 6000rpm.

Same 383 engine with extrude honed base, big tubes, 58mm tb and ported plenum made 453hp and 533torque.

My thinking is that lower rpm is good as this is an endurance racing engine and the power numbers shown above with the stock TPI intake are more than enough. Now I'm not sure how important head flow is on something like this due to the inherent restriction of the TPI. If I could just pocket port some iron heads and get somewhat close to the same power I save 100 points. Which is very good as that is a huge points hit for AL heads.

To add, after a bit more thinking the past couple of days, my thought has gone to a 400sbc with TPI. Max rpm of 5500 is fine with 2.73's and the torque will get it off the corners well. My thought is really strong torque coupled with the highway gears will help the mileage so it doesn't have to stop every hour. Immense low end will also allow short shifting without much impact on lap times, further helping mileage. The slightly larger engine might make a slightly milder cam work as well? Since it has headers perhaps a custom cam giving more help to the intake than a shelf cam?

As this isn't a drag or sprint engine, getting the last bit of power isn't all that important. Reliable and decent mileage while making decent power is important.

edit to add-Different runners are a grey area as the points call for 25 for an intake. Well, the TPI is kinda unique that way, but they would not allow them for free. As mentioned above, I don't know that they are needed. I know I am leaving loads of power on the table. That is fine.
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Re: L98 TPI 350 endurance race combination

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CastIron wrote: Thu May 06, 2021 10:27 pm Finding articles with TPI builds from back in the day hasn't been easy as they were 30 years ago for most, like the Lingenfelter stuff. I did find the build for the 383 in the vid I posted a link to in the first post. The 383 was;
I've got a large digital notebook full of them...

TPI Magazine Builds with Dyno Sheets
http://www.hotrod.com/articles/hppp-091 ... ck-engine/

355 (4.030") 6" rod, Vortec heads (278/210 CFM), 24" total intake tract with TPI intake; 10.95:1 CR
Stock TPI cam PN 08-304-8 Comp- 210/220@ 0.050", 0.332", 0.342" cam lift; 114 LSA, ICL 110.5, 1.6RR, 0.531/0.513 actual lift, FAST EFI; 35 lb/hr injectors -45 PSI;
Accel Large-tube runners and Edelbrock High-flow TPI-style manifold

487ft lbs@ 4,000 rpm (400+ from 2,300-4,000)
416.3 hp @ 5,000 RPM


http://www.powerperformancenews.com/tec ... -upgrades/ Inductive Reasoning TPI Upgrades: Sept 21, 2015
383 (60 over), Comp XR288HR 236/242 .520/.540, 110 LSA, AFR 195 street; FAST EFI
501 ft lbs @ 3,900; 410 HP @ 5,100 (1.31 ft lbs/ in3)

Added TPIS runners and extrude honed the base; dual 58mm throttle body
533 ft lbs @ 4,000; 451 HP @ 5,900 (1.392 ft lbs / in3)

Dual plane speedmaster eliminator: 498 ft lbs @ 4,300; 502hp @ 6,000 RPM

Lingenfelter SBC 420: AFR 190 heads, 11:1 CR, SuperRam, 58mm throttle body, 36 lb/hr injectors;
Comp Cams 236/244 @ 0.050" .549/.549 110 LSA 1.5 RRs
543 ft lbs @ 4,500; 525 HP @ 5,500

Lingenfelter SBC 420: 11:1 CR, Lingenfelter 219/219@0.050" .525/.525, 112 LSA; 1.6 RR; CNC ported Brodix TrackI, 67cc; Super ram, 58mm throttle body 30lb injectors; 1 3/4" headers
561 ft lbs @ 4400; 509 HP (1.34 ft lbs / in3)

Lingenfelter 383; L98: TPI modified plenum & base; large tube runners 210/210 .525/.525 112 LSA; stock corvette mainfolds
451 ft lbs; 368 HP

TPI Stealth Induction
http://www.superchevy.com/how-to/engine ... induction/
Extrude hone; XR264 HR cam 212/218, 110 LSA, 0.487/0.495"; ported L98 heads (260 cfm); tpis big tube; 383; FAST XFI; 1.5 RR;
534 ft lbs @ 4,200; 458 hp?? (dyno shows 398hp…) (1.394 ft lbs / in3)

Something Old, Something New TPI 355 from Super Chevy (5 Part Article Series): 420 HP, 490 ft lbs (1.38 ft lbs / in3)
SBC 355, Vortec Heads, Scroggin-Dickie TPI Vortec base, Accel Runners, stock plenum 6" rod, Accel DFI Gen 7 ECM, Accel Dual Sync Distributor with Sequential injection, Comp custom roller cam, probe pistons -metric ring grooves; Comp Roller 210/220 deg @ 0.050", 114 LSA, 110 installed; 1 3/4" headers, 2.5" flowmaster dual exhaust
Part 1: https://thirdgenfbody.wordpress.com/201 ... ober-2005/
Part Stall Tactic: Worthless: http://www.superchevy.com/how-to/0601gm ... thing-new/
Part 2: Advertising trash: http://www.superchevy.com/how-to/engine ... hine-work/
Part 4: Finally on the Dyno 416HP, 486 Ft LBS http://www.superchevy.com/how-to/0611gm ... all-block/

TPI Turbo:
http://www.superchevy.com/how-to/vemp-0 ... o-install/ bolt on 8.5psi kit for L98 C4 corvettes; 60mm turbo

http://www.superchevy.com/how-to/0907gm ... dyno-test/
383 10:1 CR; 248/254 hydraulic 0.545/0.565; holley stealth ram; Cnc 210cc heads (491 hp; 457 ft lbs-no turbo) = 6.9 PSI of boost = 712 hp; 673 ft lbs

There was an older 1991 Popular Hot Roddign article with a 9:1 355 388 HP @ 5,000; 460 ft lbs @ 4,000 but I didn't save many details on that one...

Richard Holdener YouTube Videos March 2020
• TPI tech Plus Boost-Faster than Ford?
○ 5.0L 305 SBC LB9;
○ Stock: 267 HP @ 4,700; 333 ft lbs @ 3,700 RPM; long-tube headers
○ Upgraded Heads, cam, & intake upgrade: 372hp; 353 ft lbs (TFS Super 23 175cc heads 56cc chamber, Stealth Ram Intake; XR276HR Comp 570"/575" 218/224 113LSA)
○ Boost: TorqueStorm @ 10PSI w A2W intercooler: 612hp; 546 ft lbs
○ 5.0L Ford
• "Turbo TPI-Boosted Tune Port" youtube video
○ Stock 394 ft lbs; 330 HP @ 4,700hp
○ Single turbo stock cam; 602 ft lbs @ 3,800 rpm; 470hp @ 4,600 rpm @ 8.8 lbs intercooled
○ Change to a Nitrous Cam NX256H .434/.464 212/222 duration 113 LSA -> improved HP past 4,200 RPM made 500 hp @ 4,750 RPM
• Tune Port Tech-L98 vs Carb
○ TPI XE250
○ StealthRam
○ -Add Cam XE 268
○ Carburetor

TPI Crate Engines (both use FIRST intakes):

RCS Racing Engines (a past Engine Master's Participant) currently sells a 383 crate motor that makes 460hp @ 5,200 rpm and 520 ft lbs @ 4,000 rpm.
http://www.rcsracingengines.com/Perf%20 ... 20EFI.html

Precision Race Engines used to sell a crate motor with a FIRST intake. 383, Brodix 200cc heads 425hp, 500 ft lbs. Comp XFI with 224 @ 0.050". No longer available.

Precision also used to sell a 434 cubic inch FIRST crate engine that made 575 ft lbs of torque @ 4,000 RPM and 450 HP @ 5,000 RPMs with a 224 @ 0.050" cam. (I think it was the same Comp XFI cam used on their 383, but I forgot to write it down before they pulled it from their site.) Now dead link: https://precisionraceengines.com/crate- ... ine-450-hp

ThirdGen.org Builds:
There's also some guys on ThirdGen.org who have posted some very detailed TPI builds and a few of them have posted dyno results.
• 1989GTATransAm 368 SBC 420 RWHP @ 6,350 , 417 RWTQ (initially 370 RWHP @ 6,200, 361 ft lbs) -freak-of-nature completely modified
○ 228/228 cam Mike Jones- Dart 200 heads 280 CFM 0.600"
○ 11.57 @ 115.7mph; AFR Comp 195; 11.1:1; insane amount of modification including SLP runners, Mike Jones Cam, 4000 RPM stall -Yank
30 # Ford Racing injectors 50psi fuel, 75% duty cycle

• 1rolmos ThirdGen 380 HP @ 5,000; 430 ft lbs @ 4,300 -Engine dyno?
○ 1st Gen Twisted Wedge Heads, 355 SBC, 212/224 .487/.552 9:1 comp
Very small cam-

BaddSS on ThirdGen has built a couple including a FIRST intake-based engine and he's gotten really good at doing EA Pro Engine Sims of TPI combos, too.



-The "easy" power combos seem to either use good modern aluminum heads, a FIRST intake, and an aggressive cam that can still provide plenty of lift in a hurry with the smallish seat-to-seat durations required to keep the wave tuning in the runners' tuned lengths range or vortec heads and one of the aftermarket vortec bases and aftermarket large runners, and a ported TPI plenum.

No idea what rules or limitations you have to deal with but at least more data points and examples.



Adam
Last edited by NewbVetteGuy on Fri May 07, 2021 4:36 pm, edited 1 time in total.
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Re: L98 TPI 350 endurance race combination

Post by CastIron »

That's a lot of info. Thanks! Will be a big help.

I've looked through thirdgen a bit but finding actual builds has been difficult as most of the TPI section is troubleshooting and such.

The rules are difficult to explain so I'll post the pertinent parts here. The full rules are here; https://champcar.org/web/pdf/2021bccr/B ... dlines.pdf

Page 12 for the points list for various mods.

4.3.1. Non-stock Component Values: ChampCar has
assigned a FIXED POINT VALUE that will be
applied to MOST non-stock and/or performance
components.
4.3.2. Fixed Point Value List:
• ABS, Non-OE, from a vehicle on VPI list: 25 pts
• Aerodynamic Devices (See 9.22 for more info)
o Spoiler / Wing / Splitter / Diffuser / Aero
Pan / Air Dam / Side Skirts: 10 pts/ea
o Any added aero component outside of the
defined components will be charged points
based on square feet of material.
• Automatic Transmission - Subtract 75 pts
To qualify for this deduction, the transmission
must be equipped with a fluid-coupling device
(torque converter). Dual clutch gearboxes are not
considered automatic and do not qualify for the
deduction.
• Brake Caliper - 5-piston or more: 5 pts each
• Camber / caster adjustable plates / apparatus:
o Aftermarket (pair): 20 pts front, 20 pts rear
o Homemade (pair) 5 pts front, 5 pts rear
o Stock components (strut towers, suspension
arms, sub-frames) re-drilled/slotted for
adjustment: 0 pts
• Camshaft - Aftermarket, reground or reprofiled
OE camshaft: 50 pts per engine

• Carburetor: 25 points
• CV’s / axles, non-OE (pair): 25 pts
• Cylinder head(s), non-OE and/or non-matching
to your specific engine claimed. 100 pts per
engine.

• Differential cover, non-OE: 5 pts
• Differential swap: 25pts for any diff not originally
available for your year, make, and model or
chassis generation (excluding specialty highperformance models not listed on the VPI table).
Includes axles and CV’s.
• Distributor, non-OE, or aftermarket ignition
system: 20 pts

• Driveshaft, non-OE: 10 pts per single driveshaft
• Dry-sump assembly: 100 pts
• Exhaust header: 25 pts per engine
• Fiberglass/Composite Hood-Bonnet: 25 pts per
engine
• Flywheel / Clutch - Aluminum / performance
“light-weight” SFI recommended rated flywheels
with stock type clutch: 10 pts
• Flywheel / Clutch - Multi-disc and / or smaller
diameter clutch/flywheel systems: 50 pts
• Heim joints: 5 pts each
• Hood Vents - Aftermarket: 2.5 pts each
• Hub, non-OE: 2.5 pts each
• Ignition coil(s), aftermarket: 10 pts
• Intake Manifold: 25 points
• Mounts, non-OE, engine/transmission:
10 pts per engine / 10 pts per transmission
• Offset bushings: 5 pts/corner
• Oil accumulator (e.g. – Accusump): 10 pts
• Oil cooler, non-OE (engine, transmission and/or
differential): 20 pts each
• Oil pan, non-OE: 25 pts
• Power Steering - Electro-Hydraulic Power
Steering conversion - 10 pts
• Pulleys, engine accessory, non-OE: 5 pts for one
pulley, 10 pts for multiple pulleys
• Radiator:
o Non-aluminum, non-OE: 5 pts
o Aluminum non-OE, less than $300: 10pts
o Non-OE, greater than $300: 30 pts
• Shock absorbers / struts with damping/rebound
adjustment, includes remote reservoir, 25 pts per
corner
• Shock / strut-tower reinforcement bar
(commercial or homemade): 10 pts each
• Suspension Springs, non-OE coil springs are
5-points per corner.
Exemption: Vehicles may replace OE coil springs
for 0-points provided that the replacement
spring:
a) Is the same shape as the OE spring
(straight, frustum, beehive/keg, etc.).
b) Maintains the exact same ID/OD
measurements as the OE spring (+/- 0.25”)
when measured at the midpoint and at
each end of the spring.
o Springs may be cut and/or used with
spacers (spring rubbers) for no additional
points
o Shape and measurements must match
when the springs are in their original
unaltered condition.
o Torsion bars may be replaced with non OE
torsion bars for 0-points if they are used
in conjunction with OE mounting points
and hardware.
o Additional leafs may be added to leaf
spring packs for 0-points.
• Adjustable spring perches, or any non-OE part
or modification giving ride height adjustability
10-points per corner. Any metallic spring may be
used in conjunction the adjustable corner for no
additional points.
• Suspension component (not otherwise listed
in this table), non-OE: 10 pts per corner per
component.
• Sway-bar, non-OE, including end-links: 20 pts
each axle
• Throttle Body: 25 points
• Transmission / Transaxle swap:
25pts for any transmission / transaxle from a
vehicle on the VPI list, includes adapters
• Tubular front sub-frame/K-member (bolt on
only): 10 pts
• Turbochargers and superchargers, non-OE: 100
pts
o Parts included with non-OE turbocharger/
supercharger installations are: exhaust/
intake manifold, pressure tubing, cooling
lines, oil lines, and boost control systems.
• Turbocharger and supercharger intercoolers,
non-OE: 25 pts
• Valve train, non-OE: 50 pts per engine
• Wheel spacers/hub adapters: 0 pts set of 4, max.
30mm/1.25” wide, max. 1/wheel
• Materials will be charged at the following rate:
o Interior bulkheads: 0 pts
o Plywood: 1 point per sq.ft.
o Sheet aluminum/steel: 2 points per sq.ft.
o Sheet plastic/polycarbonate/fiberglass:
3 pts per sq.ft.
o CARBON FIBER: NOT ALLOWED


And they wonder why people bitch about the rules. hah

You have 500 points to play with. My car starts at 150. Engine swap, to one of 200hp or less, if 50 points so real starting point is 200 unless I was to start with a 305 4bbl as came with the car.

Like I said this doesn't need to be a max effort build like a drag car. It has to go 15 hours and get some semblance of mileage.

I have considered a 305 with the TFS heads but I'm thinking a TPI 400 will be fewer points, way better low end torque and possibly better mileage.

I'll go through all those articles as I can and see what ideas I get. Thanks again for those.

eta-A lot of the builds change parts of the TPI or change it out completely to something like a Stealthram. A Stealthram isn't a TPI as far as I'm concerned. Only the factory piece is a TPI.
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Re: L98 TPI 350 endurance race combination

Post by NewbVetteGuy »

CastIron wrote: Fri May 07, 2021 4:36 pm I have considered a 305 with the TFS heads but I'm thinking a TPI 400 will be fewer points, way better low end torque and possibly better mileage.
25 pts for an aftermarket TPI intake like the FIRST seems like a no-brainer vs. a true GM TPI intake...

Look at what RCS Racing says about their FIRST-based 383 crate engine: they're limiting it to a 10:1 static compression ratio because they're hitting 120% VE at their torque peak which is the limit for 93 octane.

Will a 400 vs a 396 make a difference in fuel economy?

-The 396's extra stroke gets the piston speed up a tiny bit for the RPM you're stuck at which might make the quench action better, but with a 400 you're going to run a D-Dish / Reverse Dome/ Inverted Dome piston so maybe that increases the quench more vs. the extra piston speed of the 396?

I feel like whatever you can do to maximize cylinder pressure and keep detonation away is important here... Piston Oil squirters to pull out heat for detonation resistance AND because you're in an endurance racing scenario seems great here, oil filter sandwich plate to an oil cooler.

DynoDon used to be a specialist at these motors, but he's shut up shop...


-Does the fact that you could purchase an L98 C4 directly from Lingenfelter make Lingenfelter an "OEM" and therefore his L98 cam an "OEM" cam that avoids the 50 point penalty? (Wishful thinking, huh?)

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Re: L98 TPI 350 endurance race combination

Post by CastIron »

On a 400 the TPI is going to be 25 points if it's factory or a FIRST as the Monte never came with it factory and it wasn't offered on the 400.

However, and I stress this again, I don't need, nor really want, 450+ hp so spending $1500 or whatever it is for the FIRST is just a waste of money. I figure just under 400hp should allow it to make close to 1 hour and 20 minutes on 22 gallons. More power means an additional pit stop for fuel. Fuel stops are regulated at 5 minutes minimum so it is important to pay attention to fuel. It will already be making one more stop than most anyone else so will have to lap a bit faster than the front runners to make that up.

And frankly, if it is insanely fast it will be banned for scaring the Miata drivers.

The stock TPI flatlines with a decent cam versus the falloff seen with the milder choices. Basically at this point my question is 350 vs 400, AL vs mildly ported stock heads (aftermarket heads are 100 points that could be spent elsewhere. Like suspension), and just how much cam it needs. And, as far as the cam, will a custom designed for the long runners be better for mileage and power than a shelf cam.

eta-It will have an oil cooler and road race oil pan. Probably a diff cooler as well.
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Re: L98 TPI 350 endurance race combination

Post by dannobee »

Bitch about the rules? I was a nascar crew chief long enough to look at those rules and salivate at the possibilities. But one thing is certain, and you touched on it; you can't go out there and kick everyone's ass from day one. You NEED to sandbag and just barely eek out the other cars if you're blisteringly fast. Putting everyone 20 laps down is a sure fire recipe to win only one race.

400's are prone to overheat. Stick with a 350. Use the 10 points for a good nascar late model radiator. Even the AFCO ones retail for 299.95.

By the looks of it, reliability and handling are key. HP, not so much so.

Just to clarify, will you be running a G body or an F body?
CastIron
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Re: L98 TPI 350 endurance race combination

Post by CastIron »

As far as bitching about the rules, I should note not all cars start at the same base points. Stuff that is naturally fairly quick stock start at higher points so they have fewer to play with. Older cars, especially domestics, are valued fairly low as they were not built for road course work. A few more get built though and I'm sure the base points will be raised as one can really build a monster if so inclined. Fuel is always the equalizer however as the 5 minute stops penalize gas guzzlers. Weight is also against most of the domestics when compared to sub 2000 pound Miatas and 2100 pound BMW's. Handling and braking will cut more laptime than horsepower will, so their low weight is a big advantage. There no tire size rules so you have 1900 pound Miatas running 245 and even 255's with splitters and wings. They corner very well to say the least.

I have a G body roller, but am considering a 2nd gen F body as it has a few advantages; 350 came factory so no swap, 4 speed stock so no points for swap, better front geometry, 21 gallons stock for 74-81 cars means 23 gallons with a cell. The stock heads are a concern, cracking and basically being crap, but with the points saved spending 100 for AL wouldn't be a killer and would bump compression up to a reasonable number. Not a fan of leafs but they are workable. Just not a lot of experience with them.

There is some stuff that is free of points. Here's the performance related stuff;
• Air intake components ahead of throttle body
(including air filter, air filter housing, air intake
tubing, AFM/MAF)
• All fuel-system components (Excludes the fuel
tank/fuel cell)
• Alternator or Generator
• All brake system components, excluding ABS
units and brake calipers over 4 piston per 4.3.2
• Clutch - Stock type single disc. Excludes smaller
diameter or multi-disc clutches, see 4.3.2.
• Cooling system hoses and vacuum lines
• Computers: ECU = Engine - TCU = Transmission
- ECU, non-OE or chip replacement or chip
re-programming
- TCU, non-OE or chip replacement or chip
re-programming
• Engine accessory brackets
• Exhaust systems downstream of the header/
exhaust manifold (from the collector back)
• Final drive ratio is open to all factory offered
ratios for that body style or chassis generation.
If that body style or chassis generation was
offered from the factory with an LSD, its use is
permitted. Specialty high-performance models
not listed on the VPI table are excluded.
• Flywheel - All flywheels must be OE, OE
equivalent, or SFI rated.
Unmodified, SFI rated steel flywheel with similar
dimensions and stock type / single disc clutch
are zero points.
Dual-mass flywheels may be converted to singlemass meeting above specifications for zero
points.
• Fuel Injectors / Carburetor Jets
• Non-adjustable Shock Absorbers
• Pedal Assembly Sets
• Power Steering Components
• Shifters, provided the original function is
maintained (Conversion to paddle shift or
sequential shift is not permitted)

The one that is important concerning the engine build is the free ECU. No need to be burning chips with the TPI as something like a Holley HP or even a factory LS ecu will run it.
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Re: L98 TPI 350 endurance race combination

Post by dannobee »

Do the rules state the engine must match the VIN of the car?

Regarding G-bodies, In 1984 Chevy had a Mexican made Monte Carlo SS with the LM1 350 4bbl rated at 175hp. If the rules merely state that if it's produced from the factory, but not in your particular car, then call it that.

Regarding 2nd gen F-bodies, there are plenty of options. Leaf springs can be made to work. At least the Trans Ams had huge sway bars that you can use without using any points. 1 1/4" and 3/4" rear, if needed.

OK, I just looked through the rules. Call it a Mexican Monte Carlo SS with the 175hp LM1 and run an aftermarket intake.

Are you planning on using the stock rear end? I'd strongly recommend running a nascar full floater 9" and take the 25 point hit. The axles on the 8.6" rear ends had a tendency to break off at the wheel flange when racing. With a floater that problem is gone.
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Re: L98 TPI 350 endurance race combination

Post by CastIron »

I'm familiar with the Mexican Monte SS but there is this;
2.1.1. Race entry is limited to mass-produced (over 1,000
units), four-wheeled vehicles certified for US Or
Canadian street and highway use at the time of the
vehicle’s manufacture.

I'm assuming you couldn't buy one new in the US, so it appears to not be legal. Came with a 4 speed as well, but just a Saginaw so would still cost 25 points to replace it.

VIN does not have to match on the engine. Without going all in depth, there is a "platform swap" rule. What that means is you can make a V6 Monte into an SS or a 6 cylinder 78 Camaro into a 78 Z28. All of the drivetrain, suspension and fuel capacity has to match however (Or you pay points for parts that do not match). You can't make a 87 Iroc with a 350 and 4 speed, combo not available from Chevy, without paying the trans points. (Even though someone did. They watch for that now.)

They don't really look at block numbers and such. Like an 010 vs 379 350 block isn't going to matter. Frankly, a Vortec block should be fine and would gain rollers but I'm sure some butthurt BMW owner would howl if they somehow recognized it. The heads, intake, carb etc can all be replaced for points.

It seems more complicated than it is. Basically you can make a Z28 from a 6 cylinder car. Or you could just swap a Vortec 350 in for points. Or you could put the Vortec heads on the 350 the Z28 would have came with. Simple, right? hah You are generally ahead on points by modifying versus swapping in a stock, already high powered, engine depending on the car. G bodies especially as they have the weights artificially low on those. (They use weight for swap calculations. Way to complicated to explain in this post)

I've talked with tech about a full floater rear. That would be 45 points as he wants to charge for the hubs. This is on 200tw tires so there isn't as much side loading as with slicks, but if the points are there in the end I do plan on a floater for reliability.

Something I have kicked around would be a 70 LT1 Z28 "clone". Has a smaller fuel capacity than the later cars however which is a downfall. Only 20 gal allowed with cell. (74 and later F bodies had 21 gal from the factory. 18 gal 70-73) That would be 150 points same as a late 2nd gen however. Power is already there for the most part, would probably add some cam/rollers, but like I say it's lacking fuel.

I am thinking the juiced up TPI is a good way to go due to the torque and hopefully better mileage versus a higher winding, higher horsepower engine. The late, big tank, F body may be the best choice for platform to put it in other than the C3 which I don't want due to my height.

Interestingly, a 1978 Z28 4 speed with a 240HP L98 with AL heads out of the Vette has a swapped value of 219 points. So that goes back to an earlier question; How much does head flow effect power on an intake restricted TPI engine? Will pocket porting get in the ballpark on power to some 245cfm aftermarket heads or are the stock heads a bigger restriction than the intake? Saving the 100 points by avoiding aftermarket heads would allow some pretty major mods in other places.

These posts get very wordy but I know you guys have not dealt with the rules of this series so I explain a bit more than would be normal. Thanks for taking the time to read and share ideas.
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Re: L98 TPI 350 endurance race combination

Post by dannobee »

Get a clarification from the tech guys on the Mexican SS. Don't assume anything. It IS a north american car, and plenty of chevy engines (and vehicles) are made in Mexico. Argue the point that their rules need to include Mexico. Throw NAFTA in there to confuse them further.

I've had good luck with the Saginaw boxes in lower hp race cars, btw. Just run synthetic oil in them. Not ideal, but still an option.

One way to approach the whole points thing is to add up what you'll need for handling and reliability (first priorities, IMHO) and see what's left over for engine swap/hp improvements. By the looks of it, you can do quite a bit with suspension without incurring any points. And since they break down points per corner, think a bit outside the box and have only one adjustable spring perch instead of 4 to set your cross weight.

I have quite a bit of experience racing both the F and G bodies. One thing that needs to be fixed on the G body is that wicked bump steer problem. The center link needs to be modified where the inner tie rods attach. The holes need to be dropped by an inch or so. The F bodies respond favorably by using the taller factory B car spindles and ball joints. This also gets you bigger wheel bearings and brake rotors (although the bolt pattern is 5x5, same as a nascar floater) and never get noticed by tech officials. Both chassis could be had with 1 1/4" front sway bars, you just need to look in the parts catalog to find them.
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Re: L98 TPI 350 endurance race combination

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5x5 won't work due to wheel availability. No one makes 18x10.5's in that pattern while I can get Vette repros in that size fairly inexpensively. Tires do more for handling than about anything else, so combining 315 up to 335 tires with an intelligently modified suspension will provide what it needs in that area. While coil overs and such are nice, they aren't really needed and won't be used unless I have spare points. Springs, as long as they are essentially stock appearing are free.

There are aftermarket spindles for the F body that allow the use of Vette C7 hubs solving the bearing issue while making C6 Vette style brakes a simple bolt on. Wilwood Superlites, or Aero's, made for Vette's on 14" rotors are free points. On the G I've already designed a spindle using Coleman parts with a custom plate to do the same.

Tall Howe ball joints are available in different lengths so one can tune the camber curve with those and the upper control arm mount can be cut off and moved back to gain caster.

In the F body, the Vette L98 with factory AL heads with a cam (50 points) and valvetrain (50 pts) is 319 points. Any porting on the heads is free. With my figuring 181 points is more than enough for all the other mods needed on the car.

The G body would need to use the 210HP iron head version of the L98 due to how they calculate swap values.

With the low RPM, one could likely avoid the valvetrain expense and use stamped rockers if decent ones are still available. The made them live on the Penske/Donohue TA Camaro's 50+ years ago at much higher rpm. Traco said something about microsealing which I have not been able to find any info on.
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