602 GM Crate vs. Built Engine

[Brian W]

Raceman14, there is about 4 or so different classes of IMCA racing being discussed here...and then I brought up the other outlaw hobby class.. kinda confusing, I know. But all relative, sorta!

So I got this 632 BBC with split dominators on it... they are 2bbls!! LOL

[Brian W]

I am working to get some 487x heads to get to the flow bench. The work there is not that complicated as you can usually get 15-20 cfm on the valve job and selecting the right valves for the port, and then if you are allowed to de-shroud the intake valve 1/8" to 1/4" past the seat you can pick up another 5-10 cfm.

Here is the results of the testing I have did. All heads flowed on a superflow 600 @ 28" on a 4.155 bore.

487X 2.02 X 1.600
Chamber unshrouded and bowl hogg'd. Valve job complete with custom cutters on a VGS-20, port untouched.
Lift IN EX
.100 62.3 52.8
.200 136.9 100
.300 144.9 129.2
.400 209.8 143.8
.500 221.9 145.1

IMCA spec CH350I 1.94 X 1.500
stock head out of the box, no work done.

Lift IN EX
.100 63.8 56
.200 122 96.3
.300 185.7 129.6
.400 218.6 144.6
.500 229.5 150

[IMCADW]

You got a set of 487's that's not been bowl hogged? Not exactly legal either.

[Brian W]

I think I have a virgin 487x head out in the shop, pretty sure its a 1.94 valve head though. I will throw it on the bench tomorrow if I have time. However you have got to bowl hogg it a little bit when you cut the head out to a bigger valve unless you want a big ass step...and bowl hogg'n is perfectly legal to do as it was done by GM on the factory 2.02 heads.

[IMCADW]

You must have different rules, I've seen multiple heads tossed for bowl hogging.

[Brian W]

IMCA hobby rules. Kirk Niehouse at 515-231-9757

You just have to do it as the factory did it... and nothing more.

[Brian W]

Would not be legal on the EQ CH350I head though.

[IMCADW]

I know Kirk personally, sorry.

And no, not legal on the EQ because you cannot enlarge the valves.

[IMCADW]

I believe the OEM heads with the right valve job would flow better than the EQ... What angles and such are on your OEM right now?

[Brian W]

Me too, he's a nice guy.
I'd have to look at the cutter specs to be sure, all I can tell you for sure is that the seat angle is 45, but that is not what your wanting to know. The cutters were designed by Mike Chapman of Chapman racing heads for use on the Brodix ASCS head. And they just happen to work really well for heads like the 487x too.

[IMCADW]

I'm thinking that is where you are going to gain the most. My 882's I had done years ago had something like a 7 angle valve job.

Yeah, he is. They all are, and they do well teching what they can.

[Brian W]

Well the cutter I have for the intake seat is three angles, I follow that up with a light top cut and a bottom cut to blend everything in. So a total of 5 angles. The EX cutter is basically a radius on the throat side, that has a 45 cut for the seat and a 30 top. Both cutters are the best I have found for this type of head.

[IMCADW]

I'll have to find out what my head guy did last time. He's not doing work anymore so I'm sure he'd share.

[Brian W]

I have a few secrets, but I am pretty much open to telling anybody what I know on cyl head development, I'm not racing anymore myself so someone might as well use it if they can. I worked for a high end race shop for many years as the cyl head specialist. The only work that was done in that shop on this type of head was my own stuff. We specialized in 360 and 410 sprint car engines and never did any of the lower end stuff for customers.

[jed]

Raceman can you explain your statement about the engine being rich, so you went and leaned it out and the power droped of.
I have read where others have posted the same thing. That confuses me.