Changing heads and carb, what do you think?

[pauld]

I am thinking of changing the intake manifold, carb, distributor and heads to achieve more power.

I am thinking of Edelbrock performer aluminium heads with 64cc combustion chamber, Edelbrock performer 600cfm carb, Mallory HEI dist and Edelbrock performer intake manifold. I will be doing away with the computer.

I don't want to change the cam just now, but do you think this will make a noticable difference without the cam change.

I have already have the true dual exhaust setup.

What horsepower do you think I will achieve with these mods?

Thanks guys in advance.

Paul.

 

[Hib Halverson]

First, make sure when you go to those heads, you're not going to end up with a compression ratio, too high. I believe 81 L48s had heads with 72cc (or even larger) chambers. Going to a 64 cc chamber might push your CR pretty high.

The Edelbrock Performer carb is a poor choice for Corvettes because it has lousy fuel handling in turns and under brakingj. I'd go with the Edelbrock Quadra jet clone. Much better fuel handling and can be tuned more accurately to your engine.

For ign, the Mallory is probably ok although I'm partial to MSD.

I do not think you're going to see a significant power increase without changing the cam. In fact, if this is a budget issue, I'd trade the aluminum heads for a Crane roller hydraulic cam and valve train to match then have your stock heads ported and polished. Do that, get the carb dialed in properly and the increase could be 50-70hp

 

[dfw81shark]

I just upgraded my car. I'll give you my 2 cents about edelbrock...

I took out the stock motor and am storing it.

I bought a built 89 camaro to part out (and keep the roller cam motor and tranny for myself).

I used the 89 camaro lower end and serpentine belt drive, which required some slight modification to fit, fyi.

I put in Edelbrock Etec 200 heads, Edelbrock Performer RPM Roller Cam, Performer RPM Vortec intake manifold, and 750cfm Performer Carb, among other smaller things. I wanted to use Edelbrock because I figured they had their act together in putting parts together and them working great out of the box together. I have been pretty disappointed and may not buy anything from them again. Their documentation is horrible and their tech support and website are bad. There is pertinent information missing from the instructions of everything I received.
For instance, when we put the cam in, the stock timing chain didn't fit. So digging through the directions I found that it says to use "a 7800 series timing chain." I looked up edl-7800 in summit's catalog and it says "Chevy, 262-400, 1955-94, 90deg v-6 200-262, 1978-86, execpt factory roller cam." I figure, "except factory roller cam" explains why my factory chain wouldn't fit and now I have an edelbrock roller cam so it should fit. Does it fit? No. After sitting for an hour or so on Edelbrock's tech line, I get the answer that I need a 7801, which in Summit's catalog is for "Chevy, 90deg v-6 4.3L, 1987-95." I don't see any V8 in that description, so I think Edelbrock should have noted that in their instructions. The 7801 did fit though, which set me back a week and some shipping cost.

Little things like that irritated me, and they like you to use .100 longer than stock pushrods, with no real explanation why, and which aren't cheap from Compcams ($129). Had to buy new rockers because the head instructions say to torque rocker stud bolts to 45ft-lbs. I know how to adjust valves, so this was kinda weird to me, but I figure it had something to do with the vortec heads. After busting 2 rockers, I had to get a new $215 set and that set me back again. All I have to say on that is that the new ones are REALLY nice. I misread which one to torque, but the instructions just were not clear imo. You do adjust the valves old-school style with these too. Needless to say I blew my budget in this mess. You have to guess which holes are which on the intake manifold, I got confused on the NOS ports - having never worked with something like that before, I thought they may be extra heater ports for vortec. I had to ask their tech support about that. I didn't think I was a moron, but after putting their "performance matched" parts together I feel like an idiot. YMMV, but I'll think twice before I build my next motor with them...

 

[dfw81shark]

First, make sure when you go to those heads, you're not going to end up with a compression ratio, too high. I believe 81 L48s had heads with 72cc (or even larger) chambers. Going to a 64 cc chamber might push your CR pretty high.

The heads on my 81 are GM 462624, which are 76cc. They are also very prone to cracking, so whatever you do, you probably don't want to reuse them..

 

[Sensei]

If your carb, distributor and computer are still working well, you can get better performance for less money with the following mods. A set of dart iron eagle 165 cc intake runner street / strip heads (great heads, about $550 new on ebay) and a decent camshaft (you'll spend about $250 with lifters, timing chain, springs etc). There are some easy mods for your stock carb that will make it work better than an edelbrock (my opinion for what it's worth). I'm getting respectable performance as well as good fuel economy with the stock computer. Add an MSD 6a box ($150) and an Edelbrock intake ($120) if you want (I did), but you probably won't feel the difference in the seat of your pants. God bless, Cris