Overhaulin'

The likelihood of engine work already done?

I have a 1966 Pontiac Bonneville that I recently picked up. Don't know anything about it's history. What work's been done, what hasn't, etc. Recently asked a question about octane, and it was pretty unanimously decided that the concern was the lack of lead in current fuels, and that I should get new valve seats, or use a lead additive. So, I went to a store, to buy lead additive, and had an interesting conversation with the sales rep (who owns two 1960's Vettes). His comment was whether anyone had done a rebuild prior to now, and if they had...wouldn't they have switched to hardened seals by now? Bottom line: The car was made in 1966. In 1973, unleaded fuel started phasing out leaded. Which means, in the 36 years since the intro of unleaded:, how likely is it that the engine has been rebuilt, and if so, does it seem reasonable to assume that the seals would have been changed at some point? I know the direct way to find out, is to rip the engine apart, and check them out. That's not an option right now. And I know that some cars have their original parts, never rebuilt, trailer queen kind of deals....this has definitely been a commuter car, so I doubt that's the case. So....thoughts on how safe an assumption this is....until I am able to have the engine worked on?

Public Comments

1. I would think it is safe to assume that the heads were done already, but the questions is, are you willing to take that chance? I also own a Classic Corvette and i removed the heads and had them done, but that was me. I had an oil burn and vacuum issue that i needed to deal with. Good luck with the car and your decision....
2. I don't have a direct answer to your question but some repair shops have borescopes that can easily examine the valves. That should tell you the answer without tearing down the engine.
3. How many miles on it? Do a compression test. A 1966 with an original engine should be pretty bad as far as compression is concerned. Change the oil, and with the plug out, stick something in the pan to scrap the inside bottom of the pan. is there a bunch of gunk? Oil wasn't very good back then, and sludge was a problem. Does it smoke at startup? Check the back two plugs for oil fouling. Both are indications of worn valve seals. Seals from an engine that old would probably be all cracked apart, if they are still in one piece. Look inside the oil fill cap. Does it look fairly clean? I've got a hunch that it was rebuilt.
4. heres another way to think...you just use high octane unleaded...it will either be ok and run fine because it has hardened seals or after a while will get valve leakage and you get a new 3 way valve job done.... my way is drive it and next summer or now buy a 40 dollr compression gage and check how the valves/rings are doing...easy no worry.. look at summit racing or jegs.com for aluminum heads they have them for 389/400/421 ci...for 1200 you lose 40 pounds of front end and gain 40/50 horsepower..
5. I agree with the logic you are using. A commuter car would have had the problem by now, and had it resolved, unless the past owner(s) faithfully used a lead additive. Do you know the mileage on this car and engine? If the car has had multiple owners, its hard to believe they all would have used additive consistently. One last thought, ask about the damage that could result other than valves and valve seats. If it would be contained to those, then do the math and decide if you want to take the risk. seems like a pretty safe bet though, that its already been resolved.
6. your going to have to find out if the last owner changed the heads so he could run unleaded gas or not.