harden valve seats

[tony'n wea]

ok, got the '71 500 with less than 12,000 miles on it and i'm taking it apart to see what the 25+years of sleep has done to it. pulling the heads and going to put 'em in the shop. does this engine already have harden valve seats in installed? if not, should they be installed? looking at the book it says 8 to 1 comp. any chance of it being higher? how can i tell?

thanks, tony'n wea

[DOC]

Yeah, your motor is 8 to 1, and, you don't have hardened valve seats. Not to worry though. Gasoline manufacturers have added stuff to keep the seats from being pounded out for a long time. In fact, on the east coast, Amoco had lead free premium fuel in 1968.

DOC

[Nashalac]

Stainless valves are a good Idea and the seats should be just fine

[SMITH29]

The question is how hard is the engine going to have to work.
If it will have to pull heavy loads the intakes should have
real seats installed instead of just using the head material for the seat.
Stainless valves would be a good idea too.

[Nashalac]

The cylinder head material in these Cads is a higher nickel content than other GM engines. Most engine builds do not require installing hardened seats and is not recommended. I suppose if the engine is going into a 2 ton truck it might be required but then there are plenty of these in over 2 ton cars that are ok.

[Modly]

I guess for me, because I work at a machine shop, I'll have a slightly different answer, because I can do a set of heads for under $20. While the Cadillac engines don't require it as badly as others do, if I were to take it to a machine shop, and have them go through the effort of doing a valve job, I'd have new seats installed on almost any pre-'75 block.

I guess see how much it will run you. Some shops have a fairly good price on their work.

Stainless valves are very nice, especially in a race engine. When things go horribly wrong, they are more likely to just bend, compared to breaking into dozens of pieces. They are less likely to burn out, and while not a scientifically proven fact, I think they stay cleaner compared to normal valves.

[SMITH29]

To contain valve and seat damage be sure to install a " air fuel ratio "
guage.
Having to pull heads because of valve recession isn't my idea of fun.
Do you have Doc Frohmader's book " BIG INCH CADILLAC" ?
page 81 shows a severely sunken valve seat caused by a lean mixture.
You can run lean of stoich with good manifold vacuum but if you are working the engine lean of stoich with low or no vacuum for any length of time you WILL experience valve recession.

[dave_brode]

Tony,

No offense meant to anyone here, but unless the engine will go into a tow rig that'll see long term, steady wot under heavy load, I would not do the seats, even if they did them for free.
Dave

[Nashalac]

What Dave said

[SMITH29]

http://news.thomasnet.com/fullstory/25223/1620

People who don't install valve seats simply love to work on engines.
I have no problem with that at all. It gives a guy an excuse to get out of the house :-)

My FE390 in my F-250 was overhauled by a speed shop and I accidently ran it lean with a fuel pump that didn't quite do the job. I had no indication it was lean but within 4000 miles at 10,000 lbs gvw I had to pull the heads for hardened intake seats. The stainless valves were fine but the head cast iron simply couldn't take the gaff. I bought a air fuel ratio set up after that and trouble shot the system.

[Nashalac]

Let's see --- I run a 520 Cad with 10 lbs of boost from a 10-71 BDS blower on pump gas with no hasrdened seats. 800+++ hp im a 4000lb car. Guess I like pulling cly heads, but have'nt had to for quite some time.
Just lucky, I guess.

[SMITH29]

Hook a 15,000 lb. trailer to the car and tour the United States.
Climb the Rockies with your foot to the floor.
Have tow insurance :-)

[Nashalac]

I didn't intend to get into a pissin' contest - BUT ask MTS, POTTER, or CAD CO what their recommendations are about valve seats and they will all say you are be tter off without them. Nuf said

[Terrible One]

Hey Nashalac any pics of your engine? I would love to see that setup, sounds awesome

[SMITH29]

I didn't intend to get into a *' contest - BUT ask MTS, POTTER, or CAD CO what their recommendations are about valve seats and they will all say you are be tter off without them. Nuf said
xxxx
I will follow the big engine manufacturers and run intake seats for pump gas.
You do as you like. :-)

[SMITH29]

I guess for me, because I work at a machine shop, I'll have a slightly different answer, because I can do a set of heads for under $20. While the Cadillac engines don't require it as badly as others do, if I were to take it to a machine shop, and have them go through the effort of doing a valve job, I'd have new seats installed on almost any pre-'75 block.

xxxx
That's the best bet.

I guess see how much it will run you. Some shops have a fairly good price on their work.

Stainless valves are very nice, especially in a race engine. When things go horribly wrong, they are more likely to just bend, compared to breaking into dozens of pieces. They are less likely to burn out, and while not a scientifically proven fact, I think they stay cleaner compared to normal valves.