head range for 77 L48s and L82's

[Mike Engler #37320]

I've been lurking/searching around the discussion board for awhile now... I have one burning question about 'numbers matching' cylinder heads.

Is there a casting# range? Or multiple casting #'s that would have been installed on 1977 L48 and L82 engines?

From the discussion board, and through searching in google for casting numbers, one casting number keeps coming up for 1977 350sb... 333883. Which, I've heard are 'prone to cracking' on the exhaust ports...

I have the task of restoring my 77 L48, and I'd like to know what my options are. In previous posts, we've discovered that the L82 tags on my hood don't match my VIN# 1Z37L7S431394(Thanks again for the help!) So I'm looking for options in purchasing a set of heads..

Thanks
Mike Engler #37320

[Joe Lucia (12484)]

Re: head range for 77 L48s and L82's

Mike-----

For 1977, both L-48s and L-82s used the GM CASTING #333882 cylinder heads. The L-48 versions were machined for 1.94/1.50" valves and the L-82 versions were machined for 2.02/1.60" valve size. Usually, if I recall correctly, the L-82 versions can be identified by having screw-in studs whereas the L-48 have pressed in studs.

These heads were not the most popular small block heads of all time, but many folks have used them successfully. They would likely not be used for racing purposes, though, except in stock classes. Just about any cylinder head with induction hardened exhaust valve seats, like these heads, is going to have a somewhat greater propensity for cracking than non-hardened versions. But, I wouldn't worry about it.

[Joe Lucia (12484)]

Re: head range for 77 L48s and L82's

Mike-----

For 1977, both L-48s and L-82s used the GM CASTING #333882 cylinder heads. The L-48 versions were machined for 1.94/1.50" valves and the L-82 versions were machined for 2.02/1.60" valve size. Usually, if I recall correctly, the L-82 versions can be identified by having screw-in studs whereas the L-48 have pressed in studs.

These heads were not the most popular small block heads of all time, but many folks have used them successfully. They would likely not be used for racing purposes, though, except in stock classes. Just about any cylinder head with induction hardened exhaust valve seats, like these heads, is going to have a somewhat greater propensity for cracking than non-hardened versions. But, I wouldn't worry about it.

[Mike Engler #37320]

Re: head range for 77 L48s and L82's

Thanks Joe!

I recall that -1- of the heads on my motor was a casting of 333882. Unfortunately I didn't get the date code from it. It was the one that was cracked on the exhaust valve seat. I don't recall the code on the other head, but I do know it was a different casting #, with a different exhaust bolt hanger pattern...

The shop I had the heads magnafluxed at, said they could find me another 333882 head. They would grind down the seats, and put nickel seats in. Is this what you mean by 'induction hardened'... The shop told me putting the nickel seats in would eliminate the weak exhaust seat problem ..

To bring the car back to as original as possible, should I start hunting down 333882 heads with 77 date codes on them? Does NCRS judging remove valve covers?

[Mike Engler #37320]

Re: head range for 77 L48s and L82's

Thanks Joe!

I recall that -1- of the heads on my motor was a casting of 333882. Unfortunately I didn't get the date code from it. It was the one that was cracked on the exhaust valve seat. I don't recall the code on the other head, but I do know it was a different casting #, with a different exhaust bolt hanger pattern...

The shop I had the heads magnafluxed at, said they could find me another 333882 head. They would grind down the seats, and put nickel seats in. Is this what you mean by 'induction hardened'... The shop told me putting the nickel seats in would eliminate the weak exhaust seat problem ..

To bring the car back to as original as possible, should I start hunting down 333882 heads with 77 date codes on them? Does NCRS judging remove valve covers?

[Joe Lucia (12484)]

Re: head range for 77 L48s and L82's

Mike-----

The original seats were induction hardened. In this process, the existing cylinder head material around the valve seats is hardened in place. This is what can create cracking problems. Your machinest advised you correctly---the installation of hardened valve seat inserts will virtually eliminate this problem. It's a lot of work to grind out existing induction hardened seats, though.

NCRS or NCCB ("Bloomington") judging does not involve removal of the valve covers. For 69+ small blocks, I think judges may peek in the oil fill hole to see what they can see.

[Joe Lucia (12484)]

Re: head range for 77 L48s and L82's

Mike-----

The original seats were induction hardened. In this process, the existing cylinder head material around the valve seats is hardened in place. This is what can create cracking problems. Your machinest advised you correctly---the installation of hardened valve seat inserts will virtually eliminate this problem. It's a lot of work to grind out existing induction hardened seats, though.

NCRS or NCCB ("Bloomington") judging does not involve removal of the valve covers. For 69+ small blocks, I think judges may peek in the oil fill hole to see what they can see.

[Mike Engler #37320]

Thanks Again Joe! *NM*

[Mike Engler #37320]

Thanks Again Joe! *NM*