IMCA 500 cfm engine option, what heads?!

[roybeckett13j]

Gonna be running IMCA's 500 cfm engine this year, so unfortunately my double humps have to go, and with it my 10.75:1 compression...sad day.

Ive heard that 441 heads aren't bad, about the best option, but I'm open to any ideas!

How far down could one mill a 76cc combustion chamber head, to get compression back up?

any other thoughts?

thanks.

[dynoman14]

If you have to run 441's the 441X head is about 15-20hp better. With decent angle milling and the right valves with seats set up high in the combustion chamber you can get 50-55cc's. Overheating above 250 will kill the heads ( milling makes deck thin ) but they will run great if you keep them cool. I might have a couple sets sitting on the shelf if you can't find any they are pretty $$$ cause drag racers love them for NHRA Stockers.
Are stock gm vortecs legal ???

[stockcar5]

your going to want the eq head. since you can only flat mill i'd guess you'll be able to get down to the high 60cc range safely.

[stock car driver]

I used 487x. 66.7cc with small valves.

[turner]

Hello Jeff.Were your 487 x heads flat milled to the 66.5 cc,s?I have a pair milled down to 70, but not sure how much more i can go.Do you think its worth changing an engine with 487 heads to the 487 x heads?My new engine has the 487 and my old engine has 487 x.

[stock car driver]

I only went with x because they had them and they were only 50 bucks more. I would take 487 gladly next time.

I used 2.05/1.65 valves and cut them down to 194/15.

I was told x head vs 993,441,487 isnt enough difference to matter.

I think that its more like the 4 bolt blocks. guys want them but I use 2 bolt?

[roybeckett13j]

What IMCA 500 carb legal heads are the best(Better) heads to run? Like to keep compression up, but still want to be legal. I dont think vortecs are legal, there is a list of head numbers that can be ran. I can post them if someone wants me to.

[stock car driver]

Why are the Eq better?

[megadeath]

Why are the Eq better?

i know a guy that ran a set of darts 230 runner 64cc 2.08 1.60 with 4412 500cfm WILLYS 2 barrel! just fine at lincoln il oh with shaft rockers

[roybeckett13j]

...not legally he didnt.

Im not going to cheat on this, so if your (general statement, not pointing a finger at anyone) gonna say to use an illegal head, just keep it to yourself.

From what I've looked at, the EQ is the same head as what the Southern Sport Mods run.

In the long run, what would cost a few bucks less. Buying the EQ's, and milling them down. Or getting a set of not cracked stockers, adding screw in studs, guide plates, pushrod clearencing, adding some springs and milling them down?

And last, is there a stock head that uses a bigger valve spring? I like the dual 1.65's on my double humps...and I dont like 1.25's.

[stock car driver]

...not legally he didnt.

Im not going to cheat on this, so if your (general statement, not pointing a finger at anyone) gonna say to use an illegal head, just keep it to yourself.

From what I've looked at, the EQ is the same head as what the Southern Sport Mods run.

In the long run, what would cost a few bucks less. Buying the EQ's, and milling them down. Or getting a set of not cracked stockers, adding screw in studs, guide plates, pushrod clearencing, adding some springs and milling them down?

And last, is there a stock head that uses a bigger valve spring? I like the dual 1.65's on my double humps...and I dont like 1.25's.


oem and eq need the same machine work, the imca eq head is just a stock replacement.

The rules state oem diameter springs. So your stuck with the 1.25 for now.

[stockcar5]

i would say the eq is the best way to go. no wasting time searching for 30 year old castings and hoping they are usable. the eq's also dont need machining for screw in studs and guideplates. also they have thicker decks so you should be able to flat mill them further to get the compression up.

somebody on another message board posted they may be changing somes rules for the 360ci motor..maybe call imca before you buy anything.

[stock car driver]

i would say the eq is the best way to go. no wasting time searching for 30 year old castings and hoping they are usable. the eq's also dont need machining for screw in studs and guideplates. also they have thicker decks so you should be able to flat mill them further to get the compression up.

somebody on another message board posted they may be changing somes rules for the 360ci motor..maybe call imca before you buy anything.


Are they milled for guide plates now? Last I knew they were not.


Are you trying to sway people to run the eq because you know like I do that they flow less than the oem gm heads, because you know they have so much core shift if you try and use small valve relief pistons like the -1.8cc from JE theyll end up cutting the pistons for clearance and have to check each and every valve?

It really doesnt seem very nice to push people towards using inferior junk. Not to mention junk that costs 550 a pair bare.


There are many sources on ebay for oem gm 487/441/993 heads bare or built. I paid $801.00 for mine shipped and completely assembled from a reputable machine shop. I never searched more than the www..... Didnt touch them till they were on my porch in a box!

[stockcar5]

no swaying here..i would tell guys not to waste their money and build a nice 406 and use the 350 carb. i picked up power with the race version of eq heads and havent had any core shift problems. they all have nicely cast ports imo. the few guys i know of that run hobbys and switched to the eq's said they made more power.

and yes they are machined for screw in studs and guideplates

[stock car driver]

no swaying here..i would tell guys not to waste their money and build a nice 406 and use the 350 carb. i picked up power with the race version of eq heads and havent had any core shift problems. they all have nicely cast ports imo. the few guys i know of that run hobbys and switched to the eq's said they made more power.

and yes they are machined for screw in studs and guideplates

Yes Ive heard of a hobby guy switching at super nats and picking up more power. It was someone up your way that bobo talks to..

Simple truth is as I told bobo if the guy put on 194/15 eq and took of 202/16 487 that could explain the difference, though the guy is talking BUTT dyno so not sure its even worthy of discussing. Everyone knows sbc heads flow better with smaller valves as the valve isnt as shrouded.

As far as eq quality control, the IMCA stamped head is a stock replacement head, theres a reason it sells for less than the race heads. As for you not having core shift issues, have you checked piston to valve on EVERY valve? Have you tried to squeeze all the compression you can with any eq head?

I saw you selling dome mahles, those have HUGE valve reliefs so I think I can go out on a limb and say you havet ever actually tried to push the envelope with eq heads, much less this junk stock replacement head you are pushing on people.

[stockcar5]

all of my motor now are flat top mahle or srp 5cc reliefs. heads are angle milled to 48cc..as far as they will go until they get to the valve seat. always have had good piston to valve clearance on all valves with plenty of room on the sides of the valve. i dont run much over .600 lift so clerance isnt an issue. plus like i said they make more power on the dyno. i'd be interested in seeing a eq vs stock gm head dyno comparison. even if the power was the same the eq head is still much better quality and has the thick deck for milling. its a no brainer.

[hogracer3d]

Iron Eagle Platnium with Brzezinski 441 disguise package

[stock car driver]

i dont run much over .600 lift so clerance isnt an issue.


bahahaha now Ive heard it all...

Strange I stay under .550 lift and have had to fly cut mahle 5cc pistons.


Maybe all that lift explains why your dome motor was a slug compared to a flat top motor? Ive got a file folder full of dyno sheets from 4 different dome 406s that all are equal in hp and tq to my one flat top motor and the flat top had darts on it ALL the dome were humps.

[parrot69777]

Only thing I believe after listening to all this is: IMCA must be slacking on their tech.

[stock car driver]

Only thing I believe after listening to all this is: IMCA must be slacking on their tech.

Thats makes zero sense...

You clearly must not know IMCA stock car rules.

[hpontap]

Ive built several Southern Sportmod engines using the EQ stamped head/882's/993's and 487's.
The southern sportmod class has a cranking compression rule of 180lbs and 12" vacuum @1,200 rpm.So squeezing all the compression out of it is not an issue.
On these engines the 487 casting seems to have a little more down low and the EQ head picks it up on the top end a little. Not very much difference at all after they are both cleaned up a little because the EQ IMCA stamped head is a copy of the 487 casting. The EQ is more consistant in the casting.
If you have a good set of 487 heads then depending on their condition it might be cheaper to build them but if you have to buy a set then do all the machine work to them the EQ might be cheaper.
Hope this helps.

[parrot69777]

Really a moot point. To be legal.....the most compression you will ever get with this combo is 11:1 and that is a stretch. A good 406 with a 350 carb will destroy this spec engine. IMCA's only option will then be to outlaw the open engine. Once they outlaw the open engine....and find out how everyone has 11:1 compression. They will then change it to 9:1 or bring in a crate.

[parrot69777]

Thats makes zero sense...

You clearly must not know IMCA stock car rules.

Makes perfect sense. Since IMCA very seldom ever pulls a head off...can get by with quite alot.

[stock car driver]

Makes perfect sense. Since IMCA very seldom ever pulls a head off...can get by with quite alot.

What head would they have EVER needed to pull for IMCA stock cars?

Thats the topic of discussion here.



Now that youve read the rules you predict the 360 wont work, lol...

[parrot69777]

Not a prediction....it's a fact. No different than an IMCA late model going up against an open late model with a 390 carb. 14:1 compression against 10.5:1.

Going to be alot of arguing with this IMCA spec engine this year. Too many loop holes. Too many ways to read inbetween the lines. This stock car engine isn't cut and dried like the sport mod and hobby 9:1 engines are.

IMCA has quite a few other classes that use the EQ or GM heads and other than Boone....have never seen them pull one yet.

"Now that youve read the rules you predict the 360 wont work, lol..."

If you go back to a post I made on 11-30-2010.....I said the same thing about this spec engine not keeping up with the open engines. Stockcar5 had the next post right after it and agreed 100%.

[stock car driver]

Not a prediction....it's a fact. No different than an IMCA late model going up against an open late model with a 390 carb. 14:1 compression against 10.5:1.

Going to be alot of arguing with this IMCA spec engine this year. Too many loop holes. Too many ways to read inbetween the lines. This stock car engine isn't cut and dried like the sport mod and hobby 9:1 engines are.

IMCA has quite a few other classes that use the EQ or GM heads and other than Boone....have never seen them pull one yet.

"Now that youve read the rules you predict the 360 wont work, lol..."

If you go back to a post I made on 11-30-2010.....I said the same thing about this spec engine not keeping up with the open engines. Stockcar5 had the next post right after it and agreed 100%.

Yes, stockcar5 did and I been laughing about it since. He also put new eq 64cc heads on ebay for a loss of $$ when the 360 rule came out. I believe hes not as dumb as hes playing and knows a 360 at his home track will dominate.

Where do you race?

Have you raced IMCA legal against 360s with 4412's? I have for 4 years.


Oh yeah last I knew the IMCA late model package was the package of choice at our local Nascar track vs a 390 carb open motor, lol.... So not sure what your comparing there. A little more air thru the carb effects a motor all the way down the straight..

None of our big cube motors pull to the end of the straight, they all drop in hp from 5k on. A 500cfm carb motor will pull till near 7000 without any drop in hp.

Pretty simple to comprehend if you can keep gaining speed on the straight over a guy that cant you will win.... Unless you cant corner I suppose since there are 4 corners and two straights!

[parrot69777]

I don't race anymore....gave it up because I was tired of wasting money and just didn't have the time anymore. Most of the help I had decided education, families, etc. was more important than racing and I got tired of doing it all myself. So I just build engines now and it has been taking up all my spare time. I have been building since 1987 and yes all the 383-420's I build on a 350 cfm carb pull out of the corner, all the way down the straights, and never have to get over 6200. And I don't use dyno's or flow benches.

Never have had the chance to run against the 360's on the 500 carb because this is the first year IMCA is doing it in the stock cars. Never have claimed to know everything...maybe there is something better....but I don't believe in ghost and I don't believe anything on a race track until I have seen it personally.

Since the IMCA late model package is so great.....that is why the Corn Belt series has to give the IMCA guys something like 5 different rule changes to make them competitive.

[stockcar5]

no 360 motor for me. the 350 carb is low enough on power..i dont need any less. lol

[stock car driver]

no 360 motor for me. the 350 carb is low enough on power..i dont need any less. lol

Good luck with that at Jackson.

[roybeckett13j]

I don't think that the 500 engine would get smoked by the open motor, I ran a very mild 355 with the 350 carb this year, and ran with big 406 and 434 powered cars. It gets REALLY slick out here, and when those big motors even touch the gas, they just spin the tires off!

Putting a bigger carb on it is gonna change everything. Your getting not quite twice the airflow into the engine, take any engine and run half the air through it...be surprised!

[drivingexcitement]

So is stockcar5 still running a 350 Carb motor? And is parrots prediction of the spec motor still true?

[stock car driver]

Lol.. Stock car 5 went to a 360 in 12 and won around 20 races... Not sure about this year, never saw his name anyplace but did notice he won a championship at one track on a sheet I saw.

[llm4]

Good info! So if you had to run a 500 cfm and had no head or cubic inch rule, are 406 & 421s the best engine to use with the limited carburetor?

[stockcar5]

yea i switched in early 2012 after getting second all the time to a couple of 360's lol. on the 1/2 mile tracks it's amazing how much better they are. and jeff is right. 20 wins and 5 track championships in the last 2 years.

[Mopar40]

What kind of HP are the spec engines making?

[stockcar5]

380-390hp 400-420tq is a good one where i dyno.