C2 - Hardened valve seats in a SB engine

[Garry E.]

I am thinking about pulling my SB 327/300hp engine and going through it to ensure all the tolerances are okay. In the process, I was wondering about taking the heads and having hardened valve seats installed along with new valves, etc.

Question: In a car that is driven only about 2-3,000 miles per year, does putting in the hardened valve seats make any sense? Are there any real advantages? I have also heard that some of these old heads have been damaged when trying to machine the casting to accept the new seat. Apparently, the thickness of the casting can vary in some of these old heads. Has anyone else heard of this?

Garry #38705

[John H.]

Re: C2 - Hardened valve seats in a SB engine

Garry -

No need for hardened seats - don't bother.

[Jack H.]

Re: C2 - Hardened valve seats in a SB engine

I'd say let your machinest guide you. Hardened seats can solve problems on heads that've been 'hammered' resulting in valve recission OR for engines you expect to push to their limits (e.g. race use). Basically the advice John gives on it not being necessary for a typical street machine is on-base conditioned by what the machinest sees regarding the condition of the head's current valve seats.

[Harry Sadlock]

Re: C2 - Hardened valve seats in a SB engine

Gary, just had an estimate today to redo my 63 base engine heads, 250hp. It was $125.00 more for hardened seats. I only drive about 500 to 1000 miles a year. I'm still trying to figure out what to do. But I'm leading towards original.

Harry

[Clem Z.]

Re: C2 - Hardened valve seats in a SB engine

i think a better idea than installing valve seat inserts if the original head valve seats are in bad shape is to go to a larger size valve head and move the seat outward. less danger of something going wrong.

[Duke W.]

Re: C2 - Hardened valve seats in a SB engine

"I am thinking about pulling my SB 327/300hp engine and going through it to ensure all the tolerances are okay."

Unless you are sure that the engine has an internal problem from diagnostics such as a compression or leak down test, I recommend you leave it alone.

Duke

[Randy R.]

Re: C2 - Hardened valve seats in a SB engine

The machinist that refurbished my engine told me that the installation of hardened valve seats increases the posibility of cracking the heads.

[Mike McKown]

Re: C2 - Hardened valve seats in a SB engine

This is the best advice here. If you proceed with "checking your tolerances" you could spend a lot of money for nothing.

[Dave Suesz]

I did, but

the heads were off anyway for an unrelated problem, and I had the heads looked over. 5 of the seats were recessed enough to require seats (there was at least one recut of the seats in the past) so I went for 16. However, if there is no existing problem, the kind of mileage you plan would mean your children might have a valve problem, after you are long gone. This has proved to be much less of a problem than was first believed when the lead was removed.

[Garry E.]

Re: I did, but

To everyone who responded to my question...... thanks for the advice! My '64 has ~55K miles on the original 327/300 engine and was always "lady-driven" - no racing or abuse. The engine smokes like crazy when started so this got me thinking about new piston rings, valves, hardened valve seats, etc.

I think I'll stay away from the hardened seats...... thanks again

Garry #38705

[Timothy B.]

Re: I did, but

Garry,

If your engine only has 55000 miles I would do a good tune up including carburetor and go from there. No way I would take apart a 55000 mile engine before doing as Duke suggested. "Smokes like crazy when started" could be a stuck choke or valve stem seals.

[Duke W.]

Re: I did, but

Oil smoke on startup or on engine overrun usually means the valve seals are hardened/cracked. At only 55K miles I doubt if the rings/cylinders/bearings/valves/etc. have excess wear. Run compression and leak down tests. If the numbers are okay, replace the valve stem seals, which is a fairly easy job - probably no more than three to four hours flat rate labor, which is about 300 bucks versus at least $2000 for a proper engine overhaul assuming you do most of the labor. The parts cost of valve seals and a couple of new valve cover gaskets is maybe 30-40 dollars.

Remember the old adage: If it works don't fix it! And they are only original once.

I'd also recommend overhauling/blueprinting the distributor (The upper bushing grease well dried out 30 years ago.), and rebuilding the AFB. The biggest problem with the AFB is the choke mechanisms gets dirty and the choke doesn't function properly.

Duke

[Garry E.]

Re: I did, but

Duke:

Thanks for the comments.... much appreciated..... Now, for a really dumb question - Do you have to remove the heads to replace the valve stem seals? I would think you would have to but I'm not sure.....

Also, I had the AFB rebuilt. However, when depressing the accelerator when starting, the accelerator will "stick" open and the engine will rev like crazy. Could this be the choke sticking?

Also, I have the original PowerGlide trans in this car and it is leaking. I was hoping to pull the engine and the transmission and have new seals put in it to stop the leaks. The car spent all of its life in Maryland (cool/damp) and is now residing in Arizona (hot/dry). I think it is still trying to adjust to its new home.....

Thanks.....

Garry #38705

[Duke W.]

Re: I did, but

No, the heads do not have to be removed to replace the valve seals. The procedure is in the 1963 Corvette shop manual.

Without looking at the carb. it's impossible to say what is sticking. You can always send the carb to one of the vintage carb experts if you feel don't don't have the skills to troubleshoot and repair the problem. AFBs are very simple, and are fully detailed in the Shop Manual.

Minor to moderate leaks are primarily a nuissance. Clean off all the accumulated oil and dirt and then look for the leaks. Most engine and transmission leaks can be corrected without removing them from the car.

Duke

[Patrick H.]

Re: I did, but

Same thought I had.
Valve stem seals are your likely culprit.

Save yourself time and aggravation, and replace these first.

Patrick