Hi all. I soon want to build a new engine for my circle track car, and I will use my current engine as a backup. I have a .010 .020 block at the machinest now, waiting to be bored to .040 (it's a real loose .030 now).

Some rules of our class:

9.5:1 compression max
No lightweight pistons (pretty vague)
No vortec heads
No aftermarket heads

Here's my current setup:

KB flattop pistons, about 4.5 cc volume
Pistons .025 below deck
.015 gasket shim
.040 squish dimension (near perfect according to my Smokey Yunick book!)
76cc heads (regular old generic 2.02 smogger heads I think)
Calculator on Keith Black website tells me this setup gives me a bit under 9.4:1 compression

My question:

Would it be worth it to switch to KB dished pistons and 64cc Camel Hump heads?

According to the KB calculator, if I used their 18.6cc dished pistons, .015 shims, and 64cc heads, that will put me at 9.2:1 compression.

I need pistons before my machinest finishes my block, and I need to decide which pistons first. If I decide to put the 76cc heads back on, I'll get flat top. If you guys suggest it, I need to find some 64cc heads and I'll get the dished.

:bowtie: thanks in advance!!! :bowtie:

I would run the flat tops, and give those heads a roundy round port massage...:)

Not allowed to port and they do pull your intake and check! You really think flat tops and 76cc heads make more HP than dished with 64? I really wouldn't mind sticking with the 76ers. Thanks for your input!!

Not allowed to port and they do pull your intake and check! You really think flat tops and 76cc heads make more HP than dished with 64? I really wouldn't mind sticking with the 76ers. Thanks for your input!!

Since you've already got the 76cc heads use them , you get better flame travel with flat tops then with a dish , I'd forget about the steel shim gasket because to make sure that they seal properly you'll need to deck the block flat and if you're going to do that you'd be better off going zero deck and a composite gasket it works out to the same quench and seals better . Get the shop to bowl hog the area below the seats [allowed as long as it's done by a conture cutter because it looks factory ] grinding isn't but you usually can get away with knocking off some of the rough stuff as long as you keep discreet
Each area and track is a little different but most allow you to tack the heads down to 74 cc ment so that you can resurface the heads , so take advantage of what they allow , remember it's interpreting the rules until they tell you , you can't then it becomes cheating;) ;)

Since you've already got the 76cc heads use them , you get better flame travel with flat tops then with a dish , I'd forget about the steel shim gasket because to make sure that they seal properly you'll need to deck the block flat and if you're going to do that you'd be better off going zero deck and a composite gasket it works out to the same quench and seals better . Get the shop to bowl hog the area below the seats [allowed as long as it's done by a conture cutter because it looks factory ] grinding isn't but you usually can get away with knocking off some of the rough stuff as long as you keep discreet
Each area and track is a little different but most allow you to tack the heads down to 74 cc ment so that you can resurface the heads , so take advantage of what they allow , remember it's interpreting the rules until they tell you , you can't then it becomes cheating;) ;)

Good ideas here. .025 is the deck height in my current race motor...I don't know what the new height will be in my 2nd block. And yes, I have had problems with shims but at least they're cheap!

Can anyone throw out some nubmers for good 76cc heads? I'd like to set up another pair so I can quickly swap motors without taking heads off.

Good ideas here. .025 is the deck height in my current race motor...I don't know what the new height will be in my 2nd block. And yes, I have had problems with shims but at least they're cheap!

Can anyone throw out some nubmers for good 76cc heads? I'd like to set up another pair so I can quickly swap motors without taking heads off.

We build a lot of circle track engines and we have done a few for a class with similar rules lkie yours we are restricted to .030 over bore, We zero deck the block and use a 993 casting which seem to be the better of the 76CC castings.

We have always made more power with a dish piston think how the flame travel works when it hit the edge of the dish on the piston!! On an average on or 11:01 engines we would see about an 11 horse gain with dish pistons. But our rulle says no dome pistons flat tops but during teck they had a problem with our dish pistons and called the reverse domes LOL

If you can find a set of the 461X castings and use a dish and zero deck that migh be your best bet.

And a good cam that will build good dynamic pressure is a must.

Whats the cam and rocker rule???????

Any flat tappet cam you want, with stock rockers. I use solid lifters.

Lift is .510 and .519 duration at .050 is 240 and 246

I do have the opportunity to buy some fresh 487x heads for $475, but I think that's too much. They're also 1.94s

Phadreus?

Would this fall into a claimer class?

I have a couple sets of different factory heads but all would need to be rebuilt. Will have to check what castings I have and see if any of these would be to your liking. I'm pretty sure I have some 64-68cc's and know there should be some 74-76cc castings as well.

Luckily, this is not a claimer class. If it were, I'd be running my Hecho En Mexico Targetmaster motor with cast pistons I got at the flea market!

Once I decide what I want to do, I'd be interested to know what you have for sale. Thanks !

there are ways to port those stock smoggers and no one would ever know.. the guys that win i bet do this all day long... iits expensive tho......

there are ways to port those stock smoggers and no one would ever know.. the guys that win i bet do this all day long... iits expensive tho......
Yeah! Just look at Brezinski's Undercover stuff!

http://www.castheads.com/

Phaedrus, PM me when you find out what you need or I'll try to check and PM you when I find what I have...

It was asked all ready, but what cam can you run? Valve springs are important too as they must match the cam. DO NOT OVER CAM THE ENGINE. When Larry (youngest son's best friend) bought a dirt track car, he had NO idea what cam was in it nor would the owner tell him what it was. After a whole season of running that cam, the engine needed to be freshened up. I made them send the cam to Crower to find out what it was. Would you believe that it was for a 1 mile or bigger track (the track where we run is UNDER a 1/2 mile). New cam that fit the track and he started finishing in the top five week after week!

It probably goes without saying, but make sure that you degree the cam in. Try to get it to be advanced or nearly advance no more than 4 degrees. Reason: as the timing chain gear set wears, it will retard the cam so put a very little advance into it so it will "zero" as it wears.

A good valve job is THEE most important thing you can have done to those heads. What kind and size valves are you supposed to run (or not run)? Run the biggest, lightest valves you can. Make sure that you have screw in studs too. Can you run pushrod guide plates? If so, have them put on too.

I have NEVER understood why tracks make aftermarket heads illegal! They say that it's the expense. Most racers spend $1000 to $1500 on crap GM heads that crack as soon as you overheat the engine! Why not allow aftermarket heads like World Sportsman II heads that cost less than $1000 assembled a pair and will take a few times of overheating before they are junk!

I do have the opportunity to buy some fresh 487x heads for $475, but I think that's too much. They're also 1.94s

Thats not a bad head to use and what the intake and carb you have to use??

Most certainly you can use the 0.015" Felpro 1094 head gaskets with the 0.025" deck, Get a gasket that compliments your deck height so you stay in the 0.040" quench area.
The block and heads are more than smooth and flat enough if they are in GM's manfacturing tolerences. GM used steel shim gaskets when assembling milllions of SBC for over 50 years.

An angle mill of the 76cc heads would get you closer to the 9.5:1 compression.

441 and 487 castings are a good choice too. Stay away from the lightweight smog heads.

The "X" heads are replacement heads and aren't special in anyway shape or form EXCEPT the 461X which has better and larger ports.

Most certainly you can use the 0.015" Felpro 1094 head gaskets with the 0.025" deck, Get a gasket that compliments your deck height so you stay in the 0.040" quench area.
The block and heads are more than smooth and flat enough if they are in GM's manfacturing tolerences. GM used steel shim gaskets when assembling milllions of SBC for over 50 years.

An angle mill of the 76cc heads would get you closer to the 9.5:1 compression.

441 and 487 castings are a good choice too. Stay away from the lightweight smog heads.

The "X" heads are replacement heads and aren't special in anyway shape or form EXCEPT the 461X which has better and larger ports.

Most new engines came without exhaust manifold gaskets too but have you ever machined any of this stuff and saw how much it's moved around after several thousand miles

Thanks for all the advice...seems there are some diverse opinions here. Here are the specs for my cam since it was asked

Lift is .510 and .519 duration at .050 is 240 and 246

Comp says it has 4 degrees of advance already built into it, so I did degree it and set it straight up.

Seems that some folks think flat top pistons will make more power than dished, and some think vice versa.

Considering that the power the pistons makes is the same, would it be worth it to switch to camel hump heads for their better flow?

At least I know what I can't do...can't run dished with 76cc heads even with shims (too low compression), and can't run flat with 64cc heads, even with composite gasket (too high compression).

Thanks for all the advice...seems there are some diverse opinions here. Here are the specs for my cam since it was asked

Lift is .510 and .519 duration at .050 is 240 and 246

Comp says it has 4 degrees of advance already built into it, so I did degree it and set it straight up.

Seems that some folks think flat top pistons will make more power than dished, and some think vice versa.

Considering that the power the pistons makes is the same, would it be worth it to switch to camel hump heads for their better flow?

At least I know what I can't do...can't run dished with 76cc heads even with shims (too low compression), and can't run flat with 64cc heads, even with composite gasket (too high compression).


Curious,why can't you run 64cc heads and flat top pistons? I have this combo and my cam is 520/540 lift. 10.3 to 1 compression with a .041 gasket on 93 octane....ALL DAY LONG!

i think he said he had a 9.5 limit as per class rules.

i think he said he had a 9.5 limit as per class rules.

Yep. I'd love the setup that Tater mentioned, but the limit is 9.5:1. They tech the top 5 cars each night, and once in a while they do check your compression...

Must have missed the 9.5 limit, sorry.

But you know....It's all legal until you get caught! Just ask Chad Knaus! LOL

Must have missed the 9.5 limit, sorry.

But you know....It's all legal until you get caught! Just ask Chad Knaus! LOL
Good one! :bowtie:

haaaaaaaaaa brezinski !!!!!!!!!!!!!!

I got some more info on this from one of the faster (and constantly winning) drivers at the track. He said to absolutely go for the higher flowing 461x heads, but also get flat top pistons. He told me to sacrifice an ideal quench distance and use thick gaskets to get the compression down under 9.5:1. Any thoughts on this?

I have an opportunity to buy some 461x heads fresh off a donor car for $500. Is that a decent price?

Dished will make more power than flat tops. I've seen it happen on a dyno and at the track, as has Carl (CNC Blocks). It goes against logic, but more power is made with a smaller chamber and reverse dome piston.

I think you're right....

I called Keith Black and got some tech tips. The guy on the phone told me that you lose the effectiveness of quench when it reaches 50-55 thousandths

Here's what I think I might do:

-12cc dish pistons (these have a flat portion for quench and a ring all the way around the top)
-64cc 461x heads
-I don't know how far in the hole these pistons will be. I'll use the proper gasket to get a .050 quench

This will yield a 9.45:1 compression ratio.

Any thoughts?