Quote:
Originally Posted by Joe K
Back in the 70's and 80s, valve seat replacement was RECOMMENDED during an engine rebuild. Many put it to "necessary for using modern gasolines" but in reality I suspect that reason was generated simply to sell valve seats. Modern gasoline is MORE resistant to knocking than even the fuels of the 30s was.
However, the real reason for valve seats may have been finding and a repair for nascent valve seat cracks - and re-establishing valve height in a seat which may have been ground "deep." A new seat finds and cures all of that - automatically.
If I were having an engine rebuilt - I would trust to whomever was doing it. If you're doing it yourself (and it sounds like you are) then its your choice and you deal with the result whatever.
Seating DOES get you an opportunity to "get familiar" with your block - and you go away without any questions with the possible exception of the seats staying in place.
One of the reasons I keep now (ahem) three "spare" engine blocks is you never know going into a rebuild whether the block of choice is uncracked. Cracks can be fatal but if you have a choice to rebuild an uncracked block or trying to "mend" a block - which do you choose?
Joe K
|
Joe,
I was looking for machinist's recommendations of current production seats they are using. Like you mention the evolution of technologies is considerable, I am relatively sure that better alloys have been developed since I have done this last and I was hoping to get a jump on what is currently best. Yes, I do all or very near to all of my on machine work. Crank grinding, some cylinder boring, (jugs, singles, or twins I do my self) I have to farm out.
In 1971 the compression ratios of the big three's production offerings was cut drastically and the phase out of anti-knock compounds began. Namely Tetraethyllead (Pb4) abbreviated TEL. Along with its ability (TEL) to support normal combustion in high compression engines by preventing detonation, allowing them to produce more power, it was also acted as a upper cylinder and valve train lubricant.Modern engines designed to run on "Unleaded" fuels had much harder valve seats and valves.
Modern gasoline
is not more resistant to development of detonation. The research derived octane number (R+M)/2, indicates a fuels suitability to prevent detonation. Higher numbers indicate greater ability to sustain greater combustion chamber pressures and in so doing normal combustion. The highest octane ratings found on pump gasoline in my area is 93 on the premium fuels. I can recall a day where Ethyl pump gas was 98 octane on average, and Sunoco had their "Blend-O-Matic" or as others called it "Dial-An-Octane" 200-260 registers. As I recall (don't quote me, this was a long time ago) 200 was regular and 260 was the super premium. What one of us Eisenhower babies does not remember "Sunoco 260"? Or how about Purple Martin's 110 octane Ethyl, I remember how it looked like grape juice in the fuel pump sediment bowl. Sinclair's "Sky Chief" Ethyl was also purple (Fire Chief was red) as was aviation fuel of the day. Those were the days, but sorry for the digression, please excuse this old man for ranting.
I like you would be collecting old blocks and other related parts, not for fear of destroying them in the machining process, but rather because they are old and are only going to become harder to find. Yes, if I had my choice of the cracked block/head or one the did not have this malady, of course I would be using the latter...
So help me out here fellas, who is making the best valve seat inserts these days?