Probably the 270H or the next step up depending on the rest of the combo. 
1981 vette heads
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
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
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
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by 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
Derrick
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
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.
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.
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Melting Slicks
Joined: May 2003
Posts: 2,253
Likes: 1
From: Rochester Kent
Originally Posted by page62
You're asking a lot from an L81 motor. Take a look at some other recent threads about head choices...
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.
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
Originally Posted by 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.
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.
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Originally Posted by 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.
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Originally Posted by 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
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
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
Originally Posted by 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?
Race Director
Joined: Jan 2003
Posts: 15,172
Likes: 86
From: State of Confusion
Originally Posted by 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?
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.
Racer
Joined: Dec 2003
Posts: 384
Likes: 8
From: Alberta
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.
Race Director
Joined: May 2003
Posts: 11,814
Likes: 9
From: Science Bitch! Mississauga, Ontario
Canadian Events Coordinator
Originally Posted by 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
Derrick
http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW
Thread Starter
Intermediate
Joined: Jul 2004
Posts: 25
Likes: 0
1981 corvette heads
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
Derrick
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
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.
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.
