Rich's'78

I just got a working L-82 long block really cheap. I know the differences between the engines and that L-48 heads are crap but aren't L-82 heads at least somewhat better (larger valves and ports plus smaller chambers)? The L-48 was completely rebuilt, including flat top pistons, KB hypers, but I don't know what their effect on the current CR is. The cam is a CC 268H and she has full length headers and full dual exhaust.
I am out of work so new heads are out of the question, but assuming the heads are in good condition, is the swap worth doing for only the cost of the gaskets? And what is the best head gasket to use?
I am hoping for more compression and flow for some cheap HP gains.
Thanks.

jackson

No significant diff between L48 & L82 heads.
Same size ports, same size chambers.
L82 may have 202/160 v. L48 194/150 ... Not sig.
L82 may have screw in studs v. L48 pressed ... only sig if one pulls out.

has motor been decked? If so, how much?
How far does piston set below deck when at TDC?
exactly which part number are the KB hypers?
felpro 1094 is a thin shim gasket 0.015" with small volume 3.2cc.

If no dough?? Suggest install whichever heads are in best shape.

Rich's'78

Thanks.

Info I have is: L-82 has 9.0:1 compression ratio, 2.02-inch intake/1.60-inch exhaust valves vs. L-48 had an 8.0:1 compression ratio, 1.94-inch intake/1.50-inch exhaust valves -> I thought the higher comp came from smaller chambers, not taller pistons.

Don't have the heads off yet to check. Builder didn't provide me with details on L-48, even though he said he would.

Aflac

i wouldn't be shocked if the heads were the same 882 castings.

TheSkunkWorks

Should you find yourself in need of an L82 head, I've got one good bare casting #462624, date code E318 (May 31, 1978) which needs to find a home. 2.02", 1.60", 76cc's, and not the same head as the L48's, BTW...

http://forums.corvetteforum.com/c3-p...post1573800286

Little Mouse

L/48 uses a dished piston, L/82 uses a flat top, this is the reason for the comp. diff.

Rich's'78

Thanks.
I have ben reading up on the different aftermarket head's CC volumes and I got confused about the L-82s.
Can't afford new heads so I thought these would be an improvement.
There is nothing wrong with my current L-48. I just thought I might make a cheap improvement..........

jackson

Those w/ spring 1978, 624 castings & who care about number-match... all 1978s are all lite weight thin castings ... & prone to cracks ... y'all oughta get that spare head from TSW.

I did Not say they are same head ... I Did say there's No significant diff ... particularly street performance.

TheSkunkWorks

They didn't earn the nickname "crack-o-matics" for nothing. (It's still available, BTW, as the OP has passed on it.)

...and I knew that you knew they weren't the same ones. Just clarifying for other viewers.

prostreet c3

I wouldn't waste your time swapping out the heads, no noticeable gain.
Did the same swap few years back, with 76cc head went from 1.94 int.
to 2.02/1.60, also went with flat tops & small cam. It actually ran
better when it was a stock L-48! Those are not good heads period.
I finally installed Alum.Trick Flow 64cc 195's ($850) unbelieveable
performance difference! I gained compression & flow.

Rich's'78

Thanks guys!
BTW, where are they prone to cracking and why?

TheSkunkWorks

IME they tend to crack between the valve seats in one or both of the two inner chambers. Having always been pretty hard on my equipment, I've cracked a few myself before BB'ing my SA, and figure this lone survivor I've got must be one of the better ones. Seems in the late '70's the General wasn't paying much attention to performance or quality.

However, I've also got to say that with a mild solid tappet cam, valve springs, roller rocker arms, carb and headers that L82 responded very well, tho it would have never held its own against any of the BB's I've had since.

Rich's'78

BTW, is there any way to check for a crack between the valve seats in one of the two inner chambers w/o pulling the head? The reason I ask is I now thinking to resell the long block and am a bit concerned a new buyer may think I 'pulled a fast one' if he finds a head is cracked. The only experience I have with a head crack was in the rocker boss, which is easy to tell just by pulling the valve covers (which I have done on the L-82 - looks good to me).
The L-82 is sitting on a shipping skid that he got when he bought a crate engine and it's missing a few external pieces so I can't fire it up w/o a re & re.
The heads are marked B 1 9 and L 2 9 so it appears one is early and one is end of the year. Do you think that production date difference is kinda odd?
If I pull the heads and pan to check for no destruction, and just sell the short block, do you want the heads for free (you pay shipping )?
Thanks again.
Rich.

TheSkunkWorks

As many of them as have cracked (I'd guess most often under severe duty), I'm sure there are plenty of them out there which are still OK, but I don't know of any way to check between the seats other than to pull them.

I've gotten heads over the GM counter on the same purchase before that were a year or so apart, so it wouldn't surprise me to see something similar come off the the line.

Thanks for the offer, but currently I have no use for any additional SB bits.

prostreet c3

Somebody out there is looking for L82 engine, they are somewhat rare, sell it as is. You could do yourself a favor and check all numbers, block, heads, intake etc. Probably should be 010 block, Alum. intake (later years L82) also had finned valve covers.

Rich's'78

Thanks.

I checked the head numbers and block numbers are correct for a '79 L-82 and the heads do have the valve guides. I am surprised the head numbers are the same for the larger valves as the smaller ones. Whatever.