602 GM Crate vs. Built Engine

[dirtracr5]

Looking at the rules I must be missing something.
Built engine gets :
As good or better head choice
Better intake manifold
Open flat tappet camshaft
No RPM limiter
Any race gas

you must be looking at the wrong rules. open engine gets worse heads (smog 76cc heads no work allowed) spec intake (edelbrock 2701 no work allowed) limited flat tappet (.842 roller tip rockers and 3/8 studs only) non oxygenated gas only no ethanol or methanol. compression rule is 9 to 1.

[CamKing]

limited flat tappet (.842 roller tip rockers and 3/8 studs only)

What limit? We're running 249@.050" with .575" net lift solid flat tappet. The crate is stuck with a 212/224 .435" hydraulic flat tappet.
Any engine builder that can't build an engine that'll put 40hp on those crate engines should find a new career.

PS, we're doing this with the edelbrock 2-plane. Wait until we get the single plane figured out.

[MidgetMotorsports07]

We can run the EQ head also but I don't think they flow as well as a Vortec either. I have seen one sport mod engine make 425+ but It was an EQ headed 355 with a lot of "work" done to it.

[MidgetMotorsports07]

limited flat tappet (.842 roller tip rockers and 3/8 studs only)

What limit? We're running 249@.050" with .575" net lift solid flat tappet. The crate is stuck with a 212/224 .435" hydraulic flat tappet.
Any engine builder that can't build an engine that'll put 40hp on those crate engines should find a new career.

PS, we're doing this with the edelbrock 2-plane. Wait until we get the single plane figured out.

I think the single plane would work ok Mike, but we are limited to a 1 inch carb spacer and the edelbrock is already taller than the Weiand.

[1997bird]

Looking at the rules I must be missing something.
Built engine gets :
As good or better head choice
Better intake manifold
Open flat tappet camshaft
No RPM limiter
Any race gas

you must be looking at the wrong rules. open engine gets worse heads (smog 76cc heads no work allowed) spec intake (edelbrock 2701 no work allowed) limited flat tappet (.842 roller tip rockers and 3/8 studs only) non oxygenated gas only no ethanol or methanol. compression rule is 9 to 1.

Which class are you looking at? I assume your looking at a hobby stock, but the rules tha were kind of outlined are for a Sport Mod. The Sport Mods are limited by 175 psi cranking compression after 5 revolutions of the engine. You can almost get 11.5:1 SCR if you know what your doing and still be IMCA legal. IIf you look at the rules there is an advantage to stay with a GM 487 or 487x head castings over the IMCA EQ head that can have nothing more than it being flat milled. If you can't crack more than 400 HP with a 0-4412 carb then you may want to start consulting another builder, with last years rules of having to have 12" of vaccum @ 1200 rpm & a hyd flat tappet cam we were seeing 410-425 HP. With being able to use a solid cam and no vaccum rule this year that opens up even more HP to be had over the crate engine.

[dirtracr5]

What limit?

limited to me is the stock dia lifter, roller tips only and 3.8 studs. also no girdles. if it were not limited we'd be talking about larger lifters, shaft rockers or at least a 7/16 stud and some much higher rocker ratios. i dont see anything more than a 1.6 surviving the current rules.

[CamKing]

I think the single plane would work ok Mike, but we are limited to a 1 inch carb spacer and the edelbrock is already taller than the Weiand.

It's only taller because it's a 2-pane. Look at the plenum size. Distribution is an issue with the Weiand, but I think I may have an answer for that. I think if we do it right, we can pick up 20hp at 6,800, over the Edelbrock.

[dirtracr5]

Which class are you looking at? I assume your looking at a hobby stock, but the rules tha were kind of outlined are for a Sport Mod. The Sport Mods are limited by 175 psi cranking compression after 5 revolutions of the engine. You can almost get 11.5:1 SCR if you know what your doing and still be IMCA legal. IIf you look at the rules there is an advantage to stay with a GM 487 or 487x head castings over the IMCA EQ head that can have nothing more than it being flat milled. If you can't crack more than 400 HP with a 0-4412 carb then you may want to start consulting another builder, with last years rules of having to have 12" of vaccum @ 1200 rpm & a hyd flat tappet cam we were seeing 410-425 HP. With being able to use a solid cam and no vaccum rule this year that opens up even more HP to be had over the crate engine.

im looking at imca northern sport mod rules which is what the OP is asking about.

https://imca.com/wp-content/uploads/201 ... rtmod3.pdf

rules clearly state 9 to 1 and solid cams have always been allowed. never had a vacuum rule either. not sure what rules you are reffering to?

[CamKing]

What limit?

limited to me is the stock dia lifter, roller tips only and 3.8 studs. also no girdles. if it were not limited we'd be talking about larger lifters, shaft rockers or at least a 7/16 stud and some much higher rocker ratios. i dont see anything more than a 1.6 surviving the current rules.

The 602 has the same .842" diameter lifters, but is also limited to Hydraulic flat tappet lifters, and limited to a 212/224, .334" GM spec cam.
That's what I call a limit.

[MidgetMotorsports07]

Looking at the rules I must be missing something.
Built engine gets :
As good or better head choice
Better intake manifold
Open flat tappet camshaft
No RPM limiter
Any race gas

you must be looking at the wrong rules. open engine gets worse heads (smog 76cc heads no work allowed) spec intake (edelbrock 2701 no work allowed) limited flat tappet (.842 roller tip rockers and 3/8 studs only) non oxygenated gas only no ethanol or methanol. compression rule is 9 to 1.

Which class are you looking at? I assume your looking at a hobby stock, but the rules tha were kind of outlined are for a Sport Mod. The Sport Mods are limited by 175 psi cranking compression after 5 revolutions of the engine. You can almost get 11.5:1 SCR if you know what your doing and still be IMCA legal. IIf you look at the rules there is an advantage to stay with a GM 487 or 487x head castings over the IMCA EQ head that can have nothing more than it being flat milled. If you can't crack more than 400 HP with a 0-4412 carb then you may want to start consulting another builder, with last years rules of having to have 12" of vaccum @ 1200 rpm & a hyd flat tappet cam we were seeing 410-425 HP. With being able to use a solid cam and no vaccum rule this year that opens up even more HP to be had over the crate engine.

Maximum compression ratio is 9.0 to 1, no tolerance. Compression ratio checked using Whistler and cubic inches checked using pump, OR by visual inspection of part and/or casting numbers, pistons.



That is directly from the website!!!!

[CamKing]

With Wistler, 9.2:1 checks as 9.0:1

Do they CC the heads?, or do you just have to check at 9:1

[1997bird]

Which class are you looking at? I assume your looking at a hobby stock, but the rules tha were kind of outlined are for a Sport Mod. The Sport Mods are limited by 175 psi cranking compression after 5 revolutions of the engine. You can almost get 11.5:1 SCR if you know what your doing and still be IMCA legal. IIf you look at the rules there is an advantage to stay with a GM 487 or 487x head castings over the IMCA EQ head that can have nothing more than it being flat milled. If you can't crack more than 400 HP with a 0-4412 carb then you may want to start consulting another builder, with last years rules of having to have 12" of vaccum @ 1200 rpm & a hyd flat tappet cam we were seeing 410-425 HP. With being able to use a solid cam and no vaccum rule this year that opens up even more HP to be had over the crate engine.

im looking at imca northern sport mod rules which is what the OP is asking about.

https://imca.com/wp-content/uploads/201 ... rtmod3.pdf

rules clearly state 9 to 1 and solid cams have always been allowed. never had a vacuum rule either. not sure what rules you are reffering to?

IMCA Southern Sport Mod

[dirtracr5]

[quote="CamKing]The 602 has the same .842" diameter lifters, but is also limited to Hydraulic flat tappet lifters, and limited to a 212/224, .334" GM spec cam.
That's what I call a limit.[/quote]

my comments were in referance to raceman14s posts about unlimited valvetrain. never was comparing anything to a crate valvetrain.

[dirtracr5]

Which class are you looking at? I assume your looking at a hobby stock, but the rules tha were kind of outlined are for a Sport Mod. The Sport Mods are limited by 175 psi cranking compression after 5 revolutions of the engine. You can almost get 11.5:1 SCR if you know what your doing and still be IMCA legal. IIf you look at the rules there is an advantage to stay with a GM 487 or 487x head castings over the IMCA EQ head that can have nothing more than it being flat milled. If you can't crack more than 400 HP with a 0-4412 carb then you may want to start consulting another builder, with last years rules of having to have 12" of vaccum @ 1200 rpm & a hyd flat tappet cam we were seeing 410-425 HP. With being able to use a solid cam and no vaccum rule this year that opens up even more HP to be had over the crate engine.

im looking at imca northern sport mod rules which is what the OP is asking about.

https://imca.com/wp-content/uploads/201 ... rtmod3.pdf

rules clearly state 9 to 1 and solid cams have always been allowed. never had a vacuum rule either. not sure what rules you are reffering to?

IMCA Southern Sport Mod

gotcha thats a totally different ballgame than what we are talking about. dont they allow quadrajets down south?

[CamKing]

BTW, I'd look at the GM heads, and go with bigger valves. The EQ is stuck with the 1.94"