Re: Valve Guide Seals for Big Block
Larry------
I think what you have here are the GM #3989354 springs. You cannot use these with umbrella-type seals and that's probably why someone previously installed the PC-type seals. Personally, I would not use this for a street engine IF the cam is a stock L-72. If you want to keep using these springs you will have to stay with the PC seals, although I'd install new ones.
I think I'd just go back to stock----not all the way back to 1966 stock, but with the late 1969+ valve springs and retainers which are also SERVICE for 65-E69. You can buy a set of the 3970627 springs, retainers, and seals under GM #12371061 for about 250 bucks, GM list.
Will you need the shims? Well, the only way you'll know that if you change the springs is to measure the installed height as clem suggested. If you go back with the springs you have, I'd install the shims that were under each spring, just as you found them. Then, measure the installed height to confirm it's right.
Larry------
I think what you have here are the GM #3989354 springs. You cannot use these with umbrella-type seals and that's probably why someone previously installed the PC-type seals. Personally, I would not use this for a street engine IF the cam is a stock L-72. If you want to keep using these springs you will have to stay with the PC seals, although I'd install new ones.
I think I'd just go back to stock----not all the way back to 1966 stock, but with the late 1969+ valve springs and retainers which are also SERVICE for 65-E69. You can buy a set of the 3970627 springs, retainers, and seals under GM #12371061 for about 250 bucks, GM list.
Will you need the shims? Well, the only way you'll know that if you change the springs is to measure the installed height as clem suggested. If you go back with the springs you have, I'd install the shims that were under each spring, just as you found them. Then, measure the installed height to confirm it's right.
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