602 GM Crate vs. Built Engine

[dan__olson]

Took me about 10 minutes of tracing the board layout and a single 10 cent resistor to hop up the rev box... just saying... no question that stuff is going on and the tech guys just don't know what to look for and not that I can blame the drivers... who wants a tech guy tearing apart his $100 rev box under the lights in the infield and poking around looking for modifications and accidently doing who knows what kind of damage to the box in the process? I guess if IMCA would just spend the money with MSD to come up with an untamperable, potted (and even that isn't foolproof if you want it bad enough) box it would be better for all the racers crate or open... it's obvious to at least me (and I'm sure many others) that the rev box is by far the easiest and cheapest place to cheat if a person wants to do so... I definitely don't condone it, but I'm an uninterested third party and for all I know the box I played with ended up on somebody's street car.

[Baprace]

Took me about 10 minutes of tracing the board layout and a single 10 cent resistor to hop up the rev box... just saying... no question that stuff is going on and the tech guys just don't know what to look for and not that I can blame the drivers... who wants a tech guy tearing apart his $100 rev box under the lights in the infield and poking around looking for modifications and accidently doing who knows what kind of damage to the box in the process? I guess if IMCA would just spend the money with MSD to come up with an untamperable, potted (and even that isn't foolproof if you want it bad enough) box it would be better for all the racers crate or open... it's obvious to at least me (and I'm sure many others) that the rev box is by far the easiest and cheapest place to cheat if a person wants to do so... I definitely don't condone it, but I'm an uninterested third party and for all I know the box I played with ended up on somebody's street car.

I want to know what resistor value and what location that resistor is located at ? I think I could catch you while having a beer after the races

[dan__olson]

Been a long time since I did it, and I didn't keep notes or anything of the like since it was just a one off deal, but basically you can look up the datasheet for the main controller chip and figure out which pins and circuitry components it uses for it's feedback loop... that's all I'm gonna say, but if you make it that far it's pretty easy to see what resistor needs changed and to figure out the value needed to do what you want.

[IMCADW]

They check the chip and box pretty regular. No real way of getting around it.

[Brian W]

Finally finished up my testing of a IMCA hobby stock engine. The engine is not very trick, just run of the mill parts. We did it that way so it would be like most of the engines the lower budget home engine builders would put together. We were not trying to build an engine to make the most HP, but merely trying to see what different combo's of bolt on parts do to the numbers. Short block was a 4.020 bore SRP flattop 2 relief piston. Scat 3.48 stroke crank. Eagle 6" SIR rod. Cam was the Jr Motorsports PRC105 cam ( IN 251 Ex 248 @ .050)with comp roller tip rockers 1.6 on intake and 1.52 on ex. Compression was 9.0 :1 and we ran a Edelbrock 2701 intake and a Rochester 2bbl carb and VP-110 for fuel. We calibrated the Superflow 901 right before we did the testing.
Test 1.
Stock IMCA spec heads. These heads flow 225 @ .500 on the intake side. We put a set of my modified log Ex manifolds on with 2.5" ex pipes.
Peak Tq was 355 @ 3500, Peak HP was 285 @ 4900. @ 6200 Hp was 260.
Test 2.
Stock spec heads, modified Ex manifolds and 2" pipes.
Peak Tq 337 @ 3500 and peak HP 271 @ 5200 HP@ 6200 was 247.
Test 3.
Stock spec heads, Stock EX manifolds with 2" pipes.
Peak Tq, 327 @ 3500 and peak HP, 260 @ 4900 HP@ 6200 was 235.
Test 4.
Stock spec heads, and just for kicks we threw a set of 1 3/4 tube 3" collector headers on.
Peak TQ was 366 @ 3500 and peak HP was 324 @ 4900. Hp@ 6200 was 298
Test 5.
We changed the cyl heads to a set of my "disguised" IMCA spec heads with the same headers bolted on. These heads flow 266cfm @ .500 lift.
Peak TQ was 375@ 4300 and peak HP was 349 @ 5500. Hp @ 6200 was 327. This set of heads really needs a bigger cam, the flow curve is way different then the stock spec heads...

That ended our testing as this took up the day. Would have really liked to get some EX manifold numbers with my "disguised" heads but we just flat ran out of time. Also had a set of my "stealth" ported IMCA spec heads to run and from the flow bench these would fall right in between the stock head and the "disguised" heads. I also wanted to try the LT1 ex manifolds but did not get around to it. I have another engine to test in a month or so. Maybe I can test some other stuff on that. Not really a apples to apples comparison but might give me some idea.....If only I had my own dyno!!

As compared to a New, Stock, straight from GM 602 crate dyno'd with the same carb and fuel. 300HP @ 5000 with stock ex man and 2" pipes... the crate is probably the way to go unless you want to build a good $$ engine.

[IMCADW]

You didn't have a Holley 4412 to test?

[IMCADW]

I've always wondered why guys run 110 race fuel when you've only got 9-1 compression...

[raceman14]

Brian,
You have a things going on I don't understand???

Why the rochester carb on the built engine and not the 4412??? Unless you have a Super Trick rochester they are usually down 25HP to an average 4412. If you drop a good 4412 on a 283" NHRA Stocker they are usually 30-40hp better than a decent Rochester.

Why test the 602 crate with the rochester carb when it can run any 4B Holley? It establishes a good baseline for your test...but a 602 with a 4412 is down 30HP against a 650HP on my chassis dyno and that is RWHP.

The second set of heads should have the potential of being 70-80hp better even with that camshaft.

That cam does not look like the shaft I would select for either set of heads. 251-248@ .050" is ton of camshaft to run peak tq#@3500 and power @4900. What was the lobe separation and where was the intake installed???

I am not so sure they are cheated up spec heads are that great if they are +40cfm's better and only 25hp better.

I do appreciate all the info you listed and I am not criticising your testing or methods, just curious about some of the info.

You have got some real credible numbers and one of the only folks on here to actually post what you tested, GREAT JOB !!!

Why do you say crate is the way to go when your stock legal engine made +25hp at 5000 roughly ???

I would be interested to see what your built engine would do with a good 4412 and then compared to a 602 with a 650HP, that would be real close to real world what folks would run at the track.

[JDR Performance]

IMCA Hobby Stock.

[CamKing]

Finally finished up my testing of a IMCA hobby stock engine. The engine is not very trick, just run of the mill parts. We did it that way so it would be like most of the engines the lower budget home engine builders would put together. We were not trying to build an engine to make the most HP, but merely trying to see what different combo's of bolt on parts do to the numbers. Short block was a 4.020 bore SRP flattop 2 relief piston. Scat 3.48 stroke crank. Eagle 6" SIR rod. Cam was the Jr Motorsports PRC105 cam ( IN 251 Ex 248 @ .050)with comp roller tip rockers 1.6 on intake and 1.52 on ex. Compression was 9.0 :1 and we ran a Edelbrock 2701 intake and a Rochester 2bbl carb and VP-110 for fuel. We calibrated the Superflow 901 right before we did the testing.
Test 1.
Stock IMCA spec heads. These heads flow 225 @ .500 on the intake side. We put a set of my modified log Ex manifolds on with 2.5" ex pipes.
Peak Tq was 355 @ 3500, Peak HP was 285 @ 4900. @ 6200 Hp was 260.
Test 2.
Stock spec heads, modified Ex manifolds and 2" pipes.
Peak Tq 337 @ 3500 and peak HP 271 @ 5200 HP@ 6200 was 247.
Test 3.
Stock spec heads, Stock EX manifolds with 2" pipes.
Peak Tq, 327 @ 3500 and peak HP, 260 @ 4900 HP@ 6200 was 235.
Test 4.
Stock spec heads, and just for kicks we threw a set of 1 3/4 tube 3" collector headers on.
Peak TQ was 366 @ 3500 and peak HP was 324 @ 4900. Hp@ 6200 was 298
Test 5.
We changed the cyl heads to a set of my "disguised" IMCA spec heads with the same headers bolted on. These heads flow 266cfm @ .500 lift.
Peak TQ was 375@ 4300 and peak HP was 349 @ 5500. Hp @ 6200 was 327. This set of heads really needs a bigger cam, the flow curve is way different then the stock spec heads...

So from this we learned, if you don't know how to build a race engine, buy a crate motor.
You're 100hp down from a well built legal engine.

[MidgetMotorsports07]

I don't know for sure if I am right or not, Mike would be the one to ask... I always figured you should run the reverse split cam if you had a good exhaust package (nice set of 1 3/4 headers w/a 3 or 3.5 inch collector) when you have an exhaust manifold i would probably run a 4 degree split with the exhuast duration being the larger of the 2. I still think the stock heads with a 2.02/1.60 setup would be the way to go. Sport Mod or Hobby.

[dirtracr5]

good info brian thanks.
looks like your dyno is pretty tight and you shelf cam is leaving alot of power on the table. on the dyno i use, a good hobby motor will do about 330hp and 360tq with legal spec heads and manifolds and the legal rochester 2bbl.

[Brian W]

[/quote]
So from this we learned, if you don't know how to build a race engine, buy a crate motor.
You're 100hp down from a well built legal engine.[/quote]

This is correct, and is what I was kinda trying to prove. I would be willing to bet that 85% of the engines around here at least are built very close to the engine I had on the dyno. Numbers are just that, numbers... to me it doesn't mean a damn thing comparing my numbers to somebody elses dyno numbers. My numbers are the only ones that matter to me, because they come off the same dyno that is operated by the same person. Like I said before, if I had more time I would have did alot more testing but, testing takes time!! The next engine I will have on the dyno will be a "good" engine, one that is put together right, with the correct parts. Should run way better, but also will have around $8,000 in it.

[Brian W]

Brian,
You have a things going on I don't understand???

Why the rochester carb on the built engine and not the 4412??? Unless you have a Super Trick rochester they are usually down 25HP to an average 4412. If you drop a good 4412 on a 283" NHRA Stocker they are usually 30-40hp better than a decent Rochester.

Why test the 602 crate with the rochester carb when it can run any 4B Holley? It establishes a good baseline for your test...but a 602 with a 4412 is down 30HP against a 650HP on my chassis dyno and that is RWHP.

The second set of heads should have the potential of being 70-80hp better even with that camshaft.

That cam does not look like the shaft I would select for either set of heads. 251-248@ .050" is ton of camshaft to run peak tq#@3500 and power @4900. What was the lobe separation and where was the intake installed???

I am not so sure they are cheated up spec heads are that great if they are +40cfm's better and only 25hp better.

I do appreciate all the info you listed and I am not criticising your testing or methods, just curious about some of the info.

You have got some real credible numbers and one of the only folks on here to actually post what you tested, GREAT JOB !!!

Why do you say crate is the way to go when your stock legal engine made +25hp at 5000 roughly ???

I would be interested to see what your built engine would do with a good 4412 and then compared to a 602 with a 650HP, that would be real close to real world what folks would run at the track.

This is a IMCA hobby stock engine, must run a Rochester carb on either the crate or built engine. The carb we used is probably one of the best legal Rochester you can buy...
In the testing we did, on this engine, the crate has the legal engine beat by 15 hp if you put the same EX system on it. It was pretty interesting what the difference was between the 2" (largest legal pipe on a crate) and 2.5" pipes (largest legal pipe on a built engine)

[jpankey]

Took me about 10 minutes of tracing the board layout and a single 10 cent resistor to hop up the rev box... just saying... no question that stuff is going on and the tech guys just don't know what to look for and not that I can blame the drivers... who wants a tech guy tearing apart his $100 rev box under the lights in the infield and poking around looking for modifications and accidently doing who knows what kind of damage to the box in the process? I guess if IMCA would just spend the money with MSD to come up with an untamperable, potted (and even that isn't foolproof if you want it bad enough) box it would be better for all the racers crate or open... it's obvious to at least me (and I'm sure many others) that the rev box is by far the easiest and cheapest place to cheat if a person wants to do so... I definitely don't condone it, but I'm an uninterested third party and for all I know the box I played with ended up on somebody's street car.

I want to know what resistor value and what location that resistor is located at ? I think I could catch you while having a beer after the races

techwestracing.com for your msd extras or a 7531 with tunable slew rates