Thanks Mouse, Exactly the info I was looking for I looked all over the net for this, where did you find it? What I am going to do, is blueprint my engine as part of a restoration an thought while I was in there I crank it up a little without changing the outside appearance. So I guess my final question is if I change the crank, pistons to bring up the CR's and the cam but not the heads, just the springs, will this give me some more HP and keep it looking like the L48 block.

Danny

 

I'm old enough to have lived it don't have to look it up, my first
vette was a 72 L/48, turbo 400 auto, 3.08 rear, I bought used in late 1972 with 6,500 miles. in 78 I ordered a new 78 L/82, 4 speed, 3.73 rear. The truth of the matter is for
a low rpm hydraulic street engine that your not adding any of
the modern nitrous to, the 4 bolt mains, forged crank, forged pistons
are nice to have if you just already have them they are really
not needed. Cast iron crank, a set of new hyper pistons, two bolt
block will handle quite a bit of power as long as revs are held to
hydraulic cam rpm levels 6500 rpm, really I have seen them turned
more rpms but if that were your plan to go high in revs you would be
better off building with forged stuff.
The 76cc heads make it hard to end up with any compression, even with the flat top pistons of the L/82 it had a 9.00 comp, factory rating
if you get into checking things its not really even a true 9.00.

If your not wanting a completely original engine but want to just keep it
looking original, you could buy a new set of the summit heads they
would give you 165 runners, 64cc chambers, 202/160 valves, screw in studs, the new valve springs will handle your upgrade in flat tappit cam.
SUM-152123= $649.00.
www.summitracing.com

There may be a small dome piston you could use with your 76cc heads
that would give you good comp, but not to much that you run in to detonation
problems.

 

You could build a 434 ci SB with a set of firebreathing iron heads and still have it look like an L48. The intake and manifolds would kill performance but all SB blocks look pretty similar. The heads to all but a few die hards will look the same. I have even seen some aluminum heads painted that look pretty much like stock. It all depends on how much HP you want and how big your wallet is.

 

Once again, Thanks for all the info.. This is a great forum to be at.

Danny

 

Well if you're up for a rebuild take a look at these.

http://www.jegs.com/webapp/wcs/store...10002_57954_-1

I believe these were made just for this purpose. That is, a cheap way to raise the compression of the '70's motors to allow using the stock heads and keeping the motor looking stock. Only it has a surprise inside. These along with your 76cc heads and you'll be able to use a better camshaft. Say something with about 230 degrees duration at .050".

BigBlockk

Later.....

 

Getting out my check book!

 

I think that's the GM 962 Cam. Talk to a good Chevy Parts guy...I built the engine in my Nova when I was working for a Chev dealer as a tech...and when I asked him for cam advice back then, he suggested that. And I'm sure that he said it was the L82 cam.

Even if that part isn't right, the 962 worked in my Nova 350 greatly ... it would EASILY spin up to 6,000 between shifts and I was using an Edlebrock 650 carb. Never had that one dyno'd but I do know this: Those 6,000 + shifts over the first two years after I built that car, took out two Turbo 350's and two 10-bolt axles. I eventually put a Turbo-400 in place and a Camaro 12-bolt 4:11 Posi. That thing was a rocket ship!

Wish my '76 was that quick ...

By the way the '962' designation came from the 9-digit (I think?) GM part number; on OEM cams the first six all had the same part # and they were defined by the last three. It's been a bunch of years since I worked at the dealer so for all I know that may not be true anymore; but if you get hold of a good Parts Guy that should be no issue.

 

hicswa you have a PM

 

Thanks Mouse, I sent you a reply PM