396 valve question

[Daniel W.]

I am following Clem's advice to replace the valves in our 40K mile 396 engine. Purchased the spring set 12371061 from GM (it did come with the retainers and the plastic umbrella seals), the rubber valve stem seals 460527, the keepers 3947880 (they are not purple, the parts manager called and was told they have been trying to get that statement regarding purple out of the PP parts books for years but have been unsuccessful), the .015" thick hardened shims 3875916, and new rocker nuts 3896648.

Here is what I have completed so far:
marked the balancer in 90 degree increments,
have the engine located on #1 TDC preparing to replace the parts on #1 and #6,
then rotate the engine clockwise 90 degrees and complete #8 and #5,
then rotate the engine clockwise 90 degrees and complete #4 and #7,
then rotate the engine clockwise 90 degrees and complete #3 and #2.

Have the car in first gear with the parking brake on with the wheels chocked.

Have air supplied to the #1 cylinder through the spark plug hole (about 65 psig).

Removed #1 exhaust keepers (copper colored), the retainer and springs. I was expecting to find a .015" thick shim below the spring but found a .050". Put it back together and removed #1 intake parts, same .050" shim. Can someone tell me what is the correct thickness? Thank you

[Clem Z.]

Re: 396 valve question

the correct installed height of the springs you bought is 1.880 or 1 7/8". what are the part # 460527 as i do not remember any other seal other than the nylon one installed in the retainer? the orignal keepers were purple as i still have some in stock but like i have said i have not bought any parts for 10 years. just hit the edge of one of the keepers with a file to make sure that they are hardened

[Daniel W.]

Re: 396 valve question

Clem,
The 460527 part is a orange rubber cupped seal; it was listed in the PP book for big blocks. I went ahead and ordered a set but was not sure if they were going to be needed. It is intended to be placed over the top end of the valve guide. I don't think there is going to be room for both the plastic umbrella and this rubber seal.

What I found on #1 exhaust were the original copper colored keepers, a replaced retainer (with the plastic umbrella seal), a replaced set of valve springs, and NO rubber seal on guide. I have a receipt from a previous owner of the car that #1 exhaust springs were replaced after the original was found broken.

What I found on #1 intake was the original copper colored keepers, the original retainer (labeled "O"), NO plastic umbrella seal, the original spring/damper (not a double spring setup) and a black rubber seal on guide. I expect to find this setup on the remainder of the valves as they are original.

Can you tell me how to determine what the correct thickness of shim should be below the springs? Thank you

[Clem Z.]

Re: 396 valve question

install the new retainer with the new keys without the spring. pull up on the retainer to seat it on the keys and them measure from the under side of the retainer to the spring seat on the head and using the shims set this distance 1-7/8" make sure the shims you use are hardened,file to check. if you have any other questions call me at 724-468-5692 after 9 PM ET as i talk better than i can type.

[Mark #28455]

Re: 396 valve question

When I was assembling motors, I would carefully cut and file a piece of metal rod (coat hanger is ok) to the same length as the correct spring installed height. As previously noted, install the new retainer and keepers on the valve and use feeler gauges to check the clearance between the rod you made and the retainer - that's how thick the shim should be. It takes only a minute to set the length of the rod.

Good luck,
Mark

[Clem Z.]

Re: 396 valve question

the easist way is to use a machinist internal "snap gauge" and take the reading with a vernier caliphers