Advice: Heavy VAN TPI -torque and MPG build: Knock Risk

[NewbVetteGuy]

All,

I'm posting this for a fellow TPI enthusiast (Richard) who's pretty far along in his build. I'm hoping he'll chime in and take over answering any follow-on questions.

Vehicle: 1993 G20 van -heavy box that will do plenty of towing.
Goals: Loads of low-end towing torque and the best possible MPG. There's a LOT of focus on fuel economy, as you'll see. Keep it budget-friendly and reuse as much of the old parts he's got laying around.

Engine:
1990 or 1993 SBC OE Roller Block -> 30 over bore
Not decked but supposed to be .010" piston-to-deck clearance
Machined 400 crank with 5.565" 400 rods
Older KB hyper D-dish pistons (M9890-30) -I couldn't find this piston but they look identical to the KB102-030, so I'm guessing -18cc dish.
Big thick truck ring packs, but some sort of Total Seal oil ring (napier second?) -Richard?

The piston top, combustion chamber, and intake and exhaust valve have all been thermal barrier coated.

64cc (I think actually 65.3cc) Swirl port heads #14102193 1.94" / 1.5" valves; with good valve guide seals to keep oil out of the chamber.
1.5 ratio roller-tipped rockers

Head Gasket: A felpro gasket that came in a rebuild kit with a 0.045" compressed thickness

Rhodes VMax lifters

Cam is from Oregon Camshaft:
Adv duration: 265 / 270, 0.050": 206/113, lift: 431"/428", LSA: 114, ICL: 110
9.25:1 static CR

Intake: He's got a bunch of old TPI intakes an 85 and a 90 and a few different TPI PCMs; the plan is to enable Lean Burn mode at highway cruise. (16.5 AF target at cruise)
-Cold Air Intake (which he'll need...)

I think he currently doesn't have EGR, but COULD add it back if he needed to.
He's running cast iron exhaust manifolds.


Rear Gears & Transmission:
.343 rear gears
Rebuilt 4L80e out of a motorhome and a US Gear Vendor additional overdrive -> I believe he's calculated a 1,600-1,700 RPM highway cruise @ 75 mph with the 4L80 in OD and the gear vendor in OD with his .343 rear gears and tire diameter.


Questions / Concerns:
What's the safe "guideline" for the DCR of this motor and things he should do to minimize detonation risk? (Yes DCR is only a super rough ball-park.)

The Rhodes lifters can be setup to reduce the advertised duration by as much as 20 degrees, so we did a DCR calculation for that cam with the ADV duration reduced from 265 down to 245 (to calculate the highest risk scenario) and ended up with a DCR of 8.07:1 Dynamic -on an iron-headed, thermal barrier coated 23 deg SBC with a quench of 0.055" in a heavy brick of a vehicle that has the ability to run with a lot of OD gear AND it's got KB hyper pistons..

-It sounds like a very high risk situation; and we haven't done a calculation using PipeMax that would look at the extra cylinder pressure from the TPI intake...

I've heard many times on here that improving the piston-to-head distance / squish generally provides a greater increase in knock resistance vs. the increase in CR; but if he moved to a 0.030" compressed gasket that gives him a squish of 0.040" but the DCR increases to 8.13:1.


He's got all sorts of options for how to reduce the dynamic compression or knock risk, but which are the right ones?
-Cold Air, Cool Coolant and Cool Oil seem no-brainers, but beyond that?

Retard the cam 4 degrees to reduce the DCR (just pull out those 4 degrees that were ground in)?
Setup the Rhodes lifters so they only reduce the adv duration 10 degrees instead of 20? -That puts him back at 8.08 DCR alone -with the 0.040" squish. -Heck he could adjust them so they don't bleed off any duration during hot summer months, and then readjust for cool weather months to get back that added cylinder pressure.

[Edit] Richard says the engine is installed pretty far back in the engine bay and it's hard to get the valve covers off in the van so adjusting the Rhodes lifters amount of bleed-down sounds like a painful solution he'd like to ideally avoid.

Just pull timing from the tune where it tends to knock?


Make major changes from a potential knock monster engine + vehicle combination?


P.S. The owner DOES have a couple of water / water-meth systems lying around and he's spent time chasing MPG on several previous engine builds, like a LOT...

Thanks,
Adam

[NewbVetteGuy]

@F-BIRD'88

You seem to be one of the more conservative posters on this subject, often taking the stance of (my paraphrase):"if you're going to push a street engine's DCR be prepared to feed it with good (high-octane gas) or just DON'T; cause you're gonna probably eventually detonate it to death."

-Thoughts on this one? -I'd love to have Richard hear your opinion on this.


Adam

[racprops]

So a couple of corrections.

1990 or 1993 SBC OE Roller Block -> 30 over bore
Not decked but supposed to be .010" piston-to-deck clearance (I think)
Machined 400 crank with 5.565" 400 rods
Older KB hyper D-dish pistons (M9890-30) -I couldn't find this piston but they look identical to the KB102-030, so I'm guessing -18cc dish. bought 2/12/2004



Big thick truck ring packs, but some sort of Total Seal oil ring (napier second?) -Richard?

As far as I know stock type rings…SEA 251K -.030 Ring Set (Premium) bought 2/12/2004

The piston top, combustion chamber, and intake and exhaust valve have all been thermal barrier coated. Ceramic

64cc (I think actually 65.3cc) Swirl port heads #14102193 1.94" / 1.5" valves; with good valve guide seals to keep oil out of the chamber.
1.5 ratio roller-tipped rockers

Head Gasket: A felpro gasket that came in a rebuild kit with a 0.045" compressed thickness

Rhodes VMax lifters Rollers

Cam is from Oregon Camshaft:
Adv duration: 265 / 270, 0.050": 206/113, lift: 431"/428", LSA: 114, ICL: 110
9.25:1 static CR

Intake: He's got a bunch of old TPI intakes an 85 and a 90 and a few different TPI PCMs; the plan is to enable Lean Burn mode at highway cruise. (16.5 AF target at cruise)
-Cold Air Intake (which he'll need...)

I think he currently doesn't have EGR, but COULD add it back if he needed to.
He's running cast iron exhaust manifolds.

I plan to run EGR and even more EGR lots of EGR and perhaps water injection...


Rear Gears & Transmission:

.343 rear gears
Rebuilt 4L80e out of a motorhome and a US Gear Vendor additional overdrive -> I believe he's calculated a 1,600-1,700 RPM highway cruise @ 75 mph with the 4L80 in OD and the gear vendor in OD with his .343 rear gears and tire diameter.

Correction: US Gears Dual Range Over Drive.I wanted a van that could tow but I am not planing on much...


Questions / Concerns:
What's the safe "guideline" for the DCR of this motor and things he should do to minimize detonation risk? (Yes DCR is only a super rough ball-park.)

The Rhodes lifters can be setup to reduce the advertised duration by as much as 20 degrees, so we did a DCR calculation for that cam with the ADV duration reduced from 265 down to 245 (to calculate the highest risk scenario) and ended up with a DCR of 8.07:1 Dynamic -on an iron-headed, thermal barrier coated 23 deg SBC with a quench of 0.055" in a heavy brick of a vehicle that has the ability to run with a lot of OD gear AND it's got KB hyper pistons..

-It sounds like a very high risk situation; and we haven't done a calculation using PipeMax that would look at the extra cylinder pressure from the TPI intake...

I've heard many times on here that improving the piston-to-head distance / squish generally provides a greater increase in knock resistance vs. the increase in CR; but if he moved to a 0.030" compressed gasket that gives him a squish of 0.040" but the DCR increases to 8.13:1.


He's got all sorts of options for how to reduce the dynamic compression or knock risk, but which are the right ones?

-Cold Air, Cool Coolant and Cool Oil seem no-brainers, but beyond that?

Well I already was running an oil cooler, in fact it was what took out the stock engine when a 12 year old line slipped off.

Retard the cam 4 degrees to reduce the DCR (just pull out those 4 degrees that were ground in)?
Setup the Rhodes lifters so they only reduce the adv duration 10 degrees instead of 20? -That puts him back at 8.08 DCR alone -with the 0.040" squish. -Heck he could adjust them so they don't bleed off any duration during hot summer months, and then readjust for cool weather months to get back that added cylinder pressure.

[Edit] Richard says the engine is installed pretty far back in the engine bay and it's hard to get the valve covers off in the van so adjusting the Rhodes lifters amount of bleed-down sounds like a painful solution he'd like to ideally avoid.

Vans are nightmares to do engine work…Stock PCMs with knock sensors…I plan on running stock PCMs

Just pull timing from the tune where it tends to knock?


Make major changes from a potential knock monster engine + vehicle combination?


P.S. The owner DOES have a couple of water / water-meth systems lying around and he's spent time chasing MPG on several previous engine builds, like a LOT...

Afraid so…did a few things like HHO, Gasoline vapor, lean burn.

Thanks,
Adam
Last edited by NewbVetteGuy on Mon Apr 25, 2022 1:51 pm, edited 1 time in total.
Top

[F-BIRD'88]

I'd skip the Rhoads lifters.
The TBI heads swirl port will need a lot less spark timing than a TPI head does with a TPI induction.
Its a bit of a mismatch.
Yes EGR tuning will be critical.
If you do want fuel mileage efficientcy take out the perf cam and Rhoads and use the 350 RamJet cam.
196-203? .450" 109 LSA. or a OEM cam from a L31 vortec engine.

[Tom68]

High torque cams don't give the best mpg, they waste fuel creating too much vavuum at cruise. Egr could fix that.

[RCJ]

I just finished a1998 k1500 (4x4) 350 vortec,flat top mahle .045 total deck,cam very close to yours, headers,3.73 gears. Gets 15Mpg in every day driving. Around 30 to 32 timing, I haven’t pulled anything with it and run 91 octane but it does not pull any timing with the knock sensor .Cam is ground on 112 c/l 4 degrees advance.

[dfarr67]

Get on Thirdgen and hunt down fast355, right up his alley.

[racprops]

"Tom68 » Mon Apr 25, 2022 4:38 pm
High torque cams don't give the best mpg, they waste fuel creating too much vacuum at cruise. Egr could fix that."

I take it you talking about pumping losses, feed in EGR forcing a more open throttle will help fix that. Yes I am aware of the problem.

One of the good things about diesels, no throttles and no vacuum, no pumping loses.

Rich

[racprops]

"Get on Thirdgen and hunt down fast355, right up his alley.
Top"


I will try.

We thought we might get deep help here.

Rich

[Tom68]

Didn't know Rhoads lifters were still around, put a set in a 327 with a TRW TP112 cam back in '83, 64cc fuellies, flat tops, 20 thou steel gaskets, worked pretty good not that I did a back to back, 3.08:1 diff, 2000 stall converter, manual powerglide, would take off from the lights in 2nd gear, 1st was just for playing. Had high speed detonation with 36 degrees timing, cold air feed fixed that.
Motors still going now in another car, different cam and Powerpack heads.

[Circlotron]

High torque cams don't give the best mpg, they waste fuel creating too much vavuum at cruise. Egr could fix that.

What about some kind of load actuated flap valve that allows hot air intake at part throttle but cold air above a certain throttle opening?

[bobmc]

headers will provide power and mpg you won't find with other tactics

[Tom68]

High torque cams don't give the best mpg, they waste fuel creating too much vacuum at cruise. Egr could fix that.

What about some kind of load actuated flap valve that allows hot air intake at part throttle but cold air above a certain throttle opening?

Hot air/manifold can be good for economy with a carb, doubt it helps with a good set of injectors.

[NewbVetteGuy]

Get on Thirdgen and hunt down fast355, right up his alley.

Dfarr,

If I remember correctly (and I might not be); don't you have / had a FIRST Fuel injection-based TPI engine yourself?

Adam

[dfarr67]

Fast355 has a 90s GM van that he has tricked out- various engines TPI, vortec. I would say very close application to yours. Sounds like he is an accomplished tuner as well.

I think there was one oem ecu that was a stand out for capabilities (95 TBI?)- or the EBL.

Yes I have the FIRST intake and have been struggling for some time- turns out it may be a cam problem and a pesky dynamic compression issue.