how can i tell if my heads are open of closed chambered? and which are better for performance..and please feel free to explain why one is better than the other and other info. Also, i was wondering if anyone has any good combos for a 468 bb, i want to put out around 550hp and keep it streetable but i don't mind some lope to it...thanks guys..



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71 velle black with silver, 350 sb soon to be 355, aiming to put around 450rwhp to the ground through a soon to be installed 200-4r with 3.73 posi
just scored a new .040 over 350 with a scat crank..and might have pretty new pistons to sell very shortly

Futwa, do a search either on my user name or this topic. Plenty of info available.

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racer's '68 (http://www.homestead.com/headsupchevelles/page13.html)

10.73@123MPH n/a
1.43 60 foot
3900 lbs.

Easier yet,
look here>>>>http://www.chevelles.com/forum/Forum9/HTML/004096.html

Jim R

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My 70 Chevelle (http://www.angelfire.com/pa4/jim/)

At the 550 HP level, I think either will do you just fine. Once you start looking for maximum power (in excess of 600HP), I might tend to lean toward the closed chambered head and spend some time & money with a head porter who knows how to unshroud the valves, yet maintain a shape to promote swirl. Also, milling to retain the small chamber (close to factory spec) cc's.

The modern idea in combustion chambers is to stay small so a smaller dome piston can be used for the same given static compression ratio. The smaller dome makes for better flame travel & more even combustion.

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Malibu Muscle Racing (http://www.MalibuMuscle.cjb.net)
79 Malibu
Naive...I was.
Skeptical...I am becoming.
Determined...I have always been.
"The only way to fail is to stop trying."

To my eye, open chambers have a triangular look, while closed chambers have a "kidney-shaped pool" look, and are decidedly smaller. Either will work, open chambered is a more modern design ( nobody casts them anymore - all aftermarket are open), but closed will work and their smaller chambers will allow you to run lesss dome to hit your compression goal of btween 10-11:1. This is what you'll need, IMHO to get to 550 HP. 11:1 with aluminum heads and 10-10.25:1 with irons. Assuming you want to run it on 93/94 octane.

The only thing to keep in mind that piston configurations are different for open and closed chambers.

Its really hard to build a sad rat, but a simple 10.5:1 oval port motor with a solid or solid roller camshaft of approx 235-245 duration @0.050 and .550-.600 lift should get you there.

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Gene Chaas
Gold Member 62/ACES 3112
67 SS 427 (http://www.chevelles.com/feature/october2000.html)
"Be big. Be a builder."

[This message has been edited by 427L88 (edited 04-18-2001).]

how about this camshaft...
comp cams xe274h
1800-6000
274 280 duration
230 236 @.05 lift
.552 .555 lift
us this too small?? i'm planning on a 2800-3200 stall..and i wanted to try and keep the comp ratio down around 9.5:1 so i can put 89 octane if i needed to...is that too low of a compression to get 500+ realistically? my weakest part of my motor will be the heads but i plan i buying the cam in the next day or two and i know the cam is one of the most important choices to build your motor around..thanks all who replied

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71 velle black with silver, 350 sb soon to be 355, aiming to put around 450rwhp to the ground through a soon to be installed 200-4r with 3.73 posi
just scored a new .040 over 350 with a scat crank..and might have pretty new pistons to sell very shortly

You can run on 89 octane gas on a 10,25 comp machine. just retard the timing. easiest is a retard box for this. then switch back for full power when premium gas is in the tank...

Dont go the Hydralic way, if you know how to adjust valves go for a solid one or even better a roller. I use cranes smallest roller and it works great have strong powerband and the Hp that you want. 11.2 in a 4000lbs chevelle.
238/244 595/615 specs.

that sounds like a pretty big cam...but my father and i both agree that this wouldn't bee a good time to run a solid cam...beleave me...i would LOVE to run a solid...but i don't want to adjust valves all the time and this is a mild street car...when i build up a 540 for my car in about 10 years when i'm out of college and i have another car...i'm definantly going solid roller..but for now..i think i'm going to stick with hydra roller, even if i don't get the horse power i'm aiming for...and thanks for the info on the compression ratio....now i know which comp ratio i want...but i still need to get the combustion chamber size of my heads...

thanks again

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71 velle black with silver, 350 sb soon to be 355, aiming to put around 450rwhp to the ground through a soon to be installed 200-4r with 3.73 posi
just scored a new .040 over 350 with a scat crank..and might have pretty new pistons to sell very shortly

Before you spend money on a hydraulic roller, do a search on solids. The idea that you have to set them all the time is not true. A friend of mine has one in his 350 and we have set it twice in 2 and a half years. You can get pretty much the same ramp speed with a regular solid as you can a hydraulic roller for a lot less money. But don't forget to research the topic, there is a lot of information out there and will help you make the best decision.

thanks, I'll read up on that tonight...and thanks to everyone else who replied..i appriciate it..



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71 velle black with silver, 350 sb soon to be 355, aiming to put around 450rwhp to the ground through a soon to be installed 200-4r with 3.73 posi
just scored a new .040 over 350 with a scat crank..and might have pretty new pistons to sell very shortly