IMCA 500 cfm engine option, what heads?!

**roybeckett13j** · 02-01-2011, 10:56 AM

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** · 02-01-2011, 11:56 AM

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** · 02-01-2011, 12:41 PM

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** · 02-01-2011, 05:01 PM

I used 487x. 66.7cc with small valves.

**turner** · 02-01-2011, 05:12 PM

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** · 02-01-2011, 05:49 PM

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** · 02-01-2011, 07:46 PM

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** · 02-01-2011, 09:07 PM

Why are the Eq better?

**megadeath** · 02-01-2011, 10:15 PM

Originally Posted by stock car driver

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** · 02-01-2011, 10:59 PM

...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** · 02-02-2011, 10:16 AM

Originally Posted by 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.

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** · 02-02-2011, 12:54 PM

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** · 02-02-2011, 01:14 PM

Originally Posted by 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.

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** · 02-02-2011, 03:11 PM

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** · 02-02-2011, 04:22 PM

Originally Posted by 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

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** · 02-02-2011, 05:21 PM

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** · 02-02-2011, 05:25 PM

Iron Eagle Platnium with Brzezinski 441 disguise package

**stock car driver** · 02-02-2011, 05:37 PM

Originally Posted by stockcar5

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.