Hyd Roller SBC bracket drag car

[Walter R. Malik]

The car is clearly not optimized. Of course, bracket racing is more about consistency, but everyone likes to go quicker. He is worried about killing the FT cam with today’s oil since he only races 8-10 times/year. Very much on a low budget. 1.7 60 ft times and 115 mph in 1/4. Seems like a lower gear set, maybe 4.88 would help, but he has no interest in running through the lights beyond 7000 rpm. Maybe he’s better off staying where he’s at until he can build more cubes and go solid roller. Dollars add up quickly for a regular guy when you start changing a bunch of stuff. Always appreciate learning from St folks with real world experience. Thanks!

What is the suspension set up like ? You can buy oil that is right for a FT cams . The 1.7 60' is the killer here . It should be low 1.60's for the et and mph . What s his finish line rpm? What 's the rear tire diameter . Dan

In your opinion, what would be a good 60 for a well sorted out 3150 pound foot brake car?

Foot brake, NHRA Super Stock cars around that caliber power are easily around the 1.45 to 1.50 mark.
I would say they are well "sorted out".

[CamKing]

The biggest reason I see, for not running hydraulic lifters, in a bracket car, is performance repeatability.
Bracket racing, is about consistency.
Hydraulic lifters are not very consistent.
There are many variables, that will make a hydraulic lifter change the actual valve lift curve.
Heat, Oil Pressure, Oil Volume, Oil Viscosity, Oil Contamination, Change in spring pressures, and Aeration can all change the effective duration, lift and area.

[Orr89rocz]

The biggest reason I see, for not running hydraulic lifters, in a bracket car, is performance repeatability.
Bracket racing, is about consistency.
Hydraulic lifters are not very consistent.
There are many variables, that will make a hydraulic lifter change the actual valve lift curve.
Heat, Oil Pressure, Oil Volume, Oil Viscosity, Oil Contamination, Change in spring pressures, and Aeration can all change the effective duration, lift and area.

Wouldnt lash on a solid change enough with heat and oil temps? Or is it insignificant? If you monitor your oil temp and water temp to be consistent on the run, wouldnt a hyd roller be the same?

[CamKing]

Wouldnt lash on a solid change enough with heat and oil temps? Or is it insignificant? If you monitor your oil temp and water temp to be consistent on the run, wouldnt a hyd roller be the same?

With a mechanical type lifter, you set the lash for running temp, and it'll stay within .001" of that. Even if it moves .001", you've changed the seat duration by less then 4 degrees, and it won't get worse, as the RPM increases.

A hydraulic lifter is a dynamic device, where many factors effect the rate of compression, and expansion. A change in bleed rate will effect the duration, differently as the RPM changes. Maybe it only loses 4 degrees at 3,000rpm, but by 6,000rpm it's down 12 degrees.
If you get any aeration in the oil, you can lose 20+ degrees of duration in an instant.

[paulzig]

Ok so lets say you go 142 MPH @ 3600 how much HP @ the wheel is this? Do you dyno test? Heres a better example: I have a truck which runs 101 MPH in 1320, it weighs 4200 pounds, as you probably know I dyno test @ 6400 feet elevation, my truck engine made 329 observed in the room uncorrected HP dyno HP, SF 901. To run 101 MPH @ 4200 pounds in a truck-how much RWHP is this?

For the 101MPH at 4200 the Moroso would show that 329 uncorrected... RWHP would be different depending on which chassis dyno was used, if I threw out a number for RWHP it would be a wild ass guess at best.

[F-BIRD'88]

Something aBout the stated sFT camshaft 255°@.050 and .570" lift (1.5 rr)
A high lift sbc ft cam 255° cam will usually be around .555" lift.

A.570" lift sbc ft cam will usually be more like 265°@.050
(1.5rr)

hummm
Is the cam LSA and intake C/L known?

[F-BIRD'88]

Don't need a chassis dyno to measure net true RWHP when you got a car (known weight w/driver and s 1/4 mi drag strip.

. If you know the weather conditions of the drag test session you can correct to standard air and sea level from the actual test data .. The actual test data is the true car power that day. It is VERY ACCURATE. (When you drive the car half decently)
The time slip tells the tale. That day at that track that car
made 370 net rwhp at the wheels. 115mph #3150

A lot of things can effect NET rear wheel power.
Find the things Most all of the hop up, tune up, dial it in solutions to better car performance and improved net real rwHP are low cost and not that hard. Much of it is "Low Hanging Fruit."

If the true car weight with driver is not known, then you work with Power to Weight Ratio
.1175 or 8.510 LBS,/Horsepower
I believe this car/engine should be in the 7.70 P/W ratio range. 40 to 50 HP is missing (engine power down) or is being absorbed-wasted (as heat) excessivily in the car. The track air and elevation could be very bad too.

[vortecpro]

Ok so lets say you go 142 MPH @ 3600 how much HP @ the wheel is this? Do you dyno test? Heres a better example: I have a truck which runs 101 MPH in 1320, it weighs 4200 pounds, as you probably know I dyno test @ 6400 feet elevation, my truck engine made 329 observed in the room uncorrected HP dyno HP, SF 901. To run 101 MPH @ 4200 pounds in a truck-how much RWHP is this?

For the 101MPH at 4200 the Moroso would show that 329 uncorrected... RWHP would be different depending on which chassis dyno was used, if I threw out a number for RWHP it would be a wild ass guess at best.

And I completely agree, I had 329-331 measured or observed uncorrected HP on the dyno.

[vortecpro]

Don't need a chassis dyno to measure net true RWHP when you got a car (known weight w/driver and s 1/4 mi drag strip.

. If you know the weather conditions of the drag test session you can correct to standard air and sea level from the actual test data .. The actual test data is the true car power that day. It is VERY ACCURATE. (When you drive the car half decently)
The time slip tells the tale. That day at that track that car
made 370 net rwhp at the wheels. 115mph #3150

A lot of things can effect NET rear wheel power.
Find the things Most all of the hop up, tune up, dial it in solutions to better car performance and improved net real rwHP are low cost and not that hard. Much of it is "Low Hanging Fruit."

If the true car weight with driver is not known, then you work with Power to Weight Ratio
.1175 or 8.510 LBS,/Horsepower
I believe this car/engine should be in the 7.70 P/W ratio range. 40 to 50 HP is missing (engine power down) or is being absorbed-wasted (as heat) excessivily in the car. The track air and elevation could be very bad too.

If the car ran 115 mph @ 3150 it made 370 crankshaft HP that day. I understand your saying the HP is higher than 370 on the dyno, yes, but when that engine is put into a power robbing car the result is 370 crankshaft HP. Conditions have nothing to do with this. Heres the problem with your math, you take my 774 corrected dyno HP production oval port 10.8 comp 496, put it in a 3600 pound car and run 142.2 mph, its not making 800 RWHP, its making roughly 800 crankshaft HP that day. It would be nice to say I have a 781 headed 10.8 comp 496 that makes 900 HP, but its bullshi.

[F-BIRD'88]

You cannot measure "crankshaft horsepower" when there is a converter, transmission, driveshaft, rear axle and wheels and tires attached and transmitting the power through.

Thats net rwhp. not crankshaft hp. Crankshaft hp is measured when the dyno absorber is attached to the engiine crankshaft without a car's drivetrain ... attached
Do you have any help for this poster?

[Orr89rocz]

You cannot measure "crankshaft horsepower" when there is a converter, transmission, driveshaft, rear axle and wheels and tires attached and transmitting the power through.

Thats net rwhp. not crankshaft hp. Crankshaft hp is measured when the dyno absorber is attached to the engiine crankshaft without a car's drivetrain ... attached
Do you have any help for this poster?

I dont believe thats how those calcs work. Trap speed and weight always seem to work out to flywheel hp. Same motor say 350 hp factory ls1. One car 6 spd one car auto. 6 spd will dyno 20-30 more on average. Mph may be 1-2 higher for the higher dyno number.

My 383 dyno 372 whp thru an auto and ran 115 mph at 3450 lbs at 2500 ft da. Dyno tuned to 400 whp ran 119

[F-BIRD'88]

Which do you not believe? The chassis dyno numbers
(highly variable ) or the track mph result? Can be variable, you do not state the track weather on the 2nd test day
Nore what else you changed.

Chassis dyno results vary z lot even same car same dyno different day ... The contact interface between the car tire and the dyno roller wheel is a big issue.. Change tires ,change air pressure ,change car strap down pressure on the roller and dyno test power Changes ..
This tire/roller interface is not the same as the interface between car tire and road.. It is so bad in fact most racing tire companies will not warranty a tire thats been run on a chassis dyno . Cause the interface contact friction And Tire Distortion fubars the tire This effects the dyno result big time. Did I mention it FUBARS the tire, especially slicks.

Chassis dyno numbers are only revelant to same car same dyno same day numbers to compare to find gains in perf.
The track does not lie ..

You found gains by tuning on the dyno.. Thats great. Thats what its for ..

The point is you got your car running 119 from 114
AT THE TRACK.. That is , as they say "Where the rubber meets the road" Do you have any help fir the OP?

[Orr89rocz]

Im saying the mph weight calc says i used 404 hp when i dyno’d 372 whp. Car is not optimized for drag so that makes sense. More tuning it made 400 whp and ran 119. The calcs say thats 450 flywheel hp. 11:1 383 with afr 195’s and a .600” 230 deg cam is 450-500 hp flywheel all day long

My turbo car 1200 whp ran 170 at 3750 lbs. calcs put it at 1400-1440 flywheel which seems right to me

Im saying the calcs show flywheel hps not rwhp

[F-BIRD'88]

Note I do not try to make any suggestion ss to how this guys engine will do on a engine dyno test or on a chassis dyno test .. Why? Because I don't know (for sure) And IT DOES NOT MATTER What matters is making the car quicker and faster...I think this combo should go 119 mph if when sorted out.. (or close to it) It will as a result run at least a bit quicker ET.. Even if the OP only gets to 117 mph thru tuneing.. It will still run at least a bit quicker too.
Thats the point.. You can dyno it or not dyno it..
(You can dyno it at 6400 ft on a mountain top and yhem drag test it at a different much lower elevation and make up a story all about that or not... bla bla bla...
The dyno numbers don't matter.. The result matters.
There is a big diffrrence between quoting dyno numbers
and mAking a car RUN BETTER AT THE TRACK..
Got any help for this guy? or........

If I was going to change the cam it would not be to a hyd roller.. It would be to a different better SFT cam or a SOlid Street Roller setup (custom grind version of..)
I don't see it in the cam for the $$$.
I think the performance can be gained thru other tunes and tweeks for a fraction of the $$$ of a HR cam swap.
More info helps... Your dyno numbers about your car does not help...

The car may (or may not) run a bit better down the track if you play with the valve lash and or the installed position of the current cam .. Something to look at. if you dare...

Lits of things you can look at

[Orr89rocz]

Well you claiming 372 whp for 115 mph at 3150 lbs is not helping either lmao


I wouldnt fear a hyd roller. But do it right it will cost decent money he may not wanna spend.

To me that combo seems off by alot. 115 mph 1.70 60 foot times with 5000 stall and 5.13 gears? Work on the combo the tune and then go from there