Derrick

got a 268 high energy comp cam. what do you all think would be the best heads to go with this to create ....oh....let's say 350 horsies? It's an 81 vette.

Derrick

Kalway

Put a vortec style intake on and put aluminum vortec heads on.

MIKER

Lot's of good cylinder head choices out there. Let your budget be your guide.
Nice comparison of Vortech vs. Trickflow heads at this link: http://www.2quicknovas.com/vortecheads.html

Here's an interesting read if you haven't seen it before.
The Goodwrench Quest, Part 1 thru 8
http://www.chevyhiperformance.com/te...320/index.html

http://www.chevyhiperformance.com/te...20/index5.html

Derrick

Thanks for the input. The trickflow heads look appealing. I want 10.5:1 or 11:1 compression. Will 64cc heads get me where I want to go with my compression?

Derrick

stingr69

You need to step up the cam for that much compression. The 268H will not like the 10.5-11:1 C/R Probably the 270H or the next step up depending on the rest of the combo.

-Mark.

bobs77vet

i have that cam and i'm using "fuelie heads" double camel hump small valve with final CR of 9.25 :1 i must be close to that HP range

mandm1200

Vortec heads are great when rebuilding the top end. If you're planning on changing the intake, then one of the biggest complaints is null and void. The other downside is the limited lift the stock head is capable of. Crane sell new springs and retainers that will allow for approximately .550 lift; however, they cost $150. The Vortec heads have a different combustion chambers as well as raised intake ports. There are other heads that seem similiar but I have not seen any flow data. Unless there is some 'proof', aka test data, then I would not suggest using them.
So my bottom line is if you only want heads and or are planning on using a cam with a limited amount of lift, then choose something else.

page62

You're asking a lot from an L81 motor. Take a look at some other recent threads about head choices...

Derrick

Well then, let me hear some combos from you guys for cam/heads and setups. Let's say: $3,700 for complete engine build = 350 HP. Hydraulic flat tappet.

Derrick

Pauld

I don't think that there would be any trouble getting to 350hp with the right heads, intake and carb set up. Unless I am missing something.

mandm1200

To get to that level of horsepower with today's parts should not be impossible. The advantage they had 30+ years ago was the gas was available in higher octane. You'll need an engine that make peak power in the higher rpm's, maybe in the 5000-5500 area. As you go with a larger cam, longer duration/more lift, the compression of the engine will be lower. I'm not sure if your engine has dished or flat top pistons. Flat tops would be almost a requirement for a larger cam. You'll have to figure out your dynamic compression to get an idea if the combination will work.

page62

What's the redline on an L81? If, as stated, the car would need to reach 5500 to get peak HP, wouldn't that be asking a little much from the existing internals?

comp

good reading

mandm1200

5500 rpm on the stock bottom end should be OK. Perhaps I should try and explain what I meant by peak horsepower in the higher rpms. HP is a derivative of torque. Lets say the HP of an engine making X torque at 2500rpm wll yeild Y HP. The same torque and 5000 rpms will make 2Y or twice the horsepower. Essentailly what you need to do is move the torque up higher in rpms.

Glensgages

I wouldn't think-so:
I believe the '79 Z28, with it's LM-1, isn't much different than the L-81 (or even L-48 from earlier eras), and we turned my stock (as-delieverd from the Chevy dealer) bottom-end LM-1 to 5500 RPM for many seasons, with no problems.

My buddy built his '80 Z28 (we all bought them new) with the as-built bottom-end, with 'double-hump' heads, L-79 cam, L-82 (aluminum) intake, re-built Q-Jet, headers, etc., and ran 14-sixties with open-pipes, shifting at 5000 RPM (he was scared to wind-it to 5500, altho I had shown it could be safely-done), on 225/60R15 UNIROYALS, thru 3.42 gears.

I ran an almost identical set-up (cam had slightly-less duration @ .050"), but with a 327/365 HP intake and a 650 Holley dbl-pump carb, shifted at 5500 RPM, and ran easy 14.40s at 97+ MPH:
with 4.11s, it picked-up to 14-teens (best of 14.09) at 97+ MPH, on the OEM tires.

A 3rd local Z28 owner/buddy built HIS '78 LM-1 Z28 as above, but with the 268H camshaft, and he was consistently .15/.20 quicker than me with identical gearing, so even 25+ years ago, the GM cams weren't as effecient as the after-market pieces offered.

81corvettevortec

I have a 81 with a KB piston rotating assembly, vortec heads, performer vortec intake, comp cam 268 grind, headman headers, and am using a 80 carb. i like to think i am right around the 350 mark but not entirely sure. thought i would give you that as a reference. the combo seems to work very well.

AGVI

for $3700 I'd get a 383.
http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW

Derrick

Well, what's wrong with 74cc heads? 270 cam and74 cc heads seem to be the best combo for my wallet......am I missing something here? Flat top pistons. 625 Barry Grant Demon Jr., Hooker headers, Vortec intake.......combo sounds like it would run AT LEAST 300 HP. Anybody have suggestions for psi on a fuel pump....ideally?

Derrick

mandm1200

74cc heads are typically used in low compression engines with flat top or dished pistons. There is nothing 'wrong' with low compression; however, there are advantages and disadvantages. As you increase the duration of a camshaft there is less dynamic compression. The static compression remains the same no matter what cam is chosen. A cam manufacture will recommend a certain range of static compression pistons to go with a cam. Increasing the compression will give a little more power. More compression typically means using gas with higher octane. Of the two compression ratios, the dynamic is the one that is the more important and often overlooked.
If you are unsure what cc head you'll need, I would call the cam manufacture and talk to them. They should be able to recommend several cams and give you an idea as to what compression you'll need for it to work reasonably well. There are many web sites that have calculators to determine compression. You should then be able to see if 74cc or 64cc heads will be needed to get you in the range supplied by the cam manufacture.