350 small block valve stem diameter
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,995
Likes: 61
From: Fort Wayne IN
350 small block valve stem diameter
Hi all - Newbie to SBC engine work: I've got to replace the valve seals on my 350 CI engine. It's not totally stock but I don't know exactly what's been done to it. I don't think I can measure the stems without removing a spring and I'm not yet ready to do that. Can anyone hazard a guess what the diameter of the valve stems are on a typical Chevy SBC? 11/32 or 5/16. The size determines which Viton seals I order. If worse comes to worst, I'll order both sizes and return the one I don't need.
Thanks in advance
Greg
Thanks in advance
Greg
Last edited by Tigershark3; Nov 21, 2024 at 10:08 PM.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
So your choices are: 11/32 or 10/32.
I always figured SBC were the 11/32. And that's what Google said also.
However, glancing over stem seals on Summit Racing list both diameters. Even when I entered GEN 1 engine.
So, I am not 100% sure either.
You can measure YOUR (non-stock) stem without removing the valve-spring.
Pick any rocker arm with a closed valve. Loosen the rocker just enough to swing it to the side.
There is enough of the stem protruding to get a measurement.
I always figured SBC were the 11/32. And that's what Google said also.
However, glancing over stem seals on Summit Racing list both diameters. Even when I entered GEN 1 engine.
So, I am not 100% sure either.
You can measure YOUR (non-stock) stem without removing the valve-spring.
Pick any rocker arm with a closed valve. Loosen the rocker just enough to swing it to the side.
There is enough of the stem protruding to get a measurement.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Tigershark,
Your stem seal choice of Viton is a wise decision.
Steer clear of those cheap black rubber umbrella junk that are over $2 for 16.
And worse yet is the little rubber "O" ring at $1 for a thousand pcs.
However, double check on the Vitons specs. It should say, "No Machining Required".
Some of the Viton seals require pulling the heads to have the valve guides milled down.
You don't want or need to go down that road.
The Vitons will come with two clear plactic sleeve protectors. Once the stem is exposed (no spring) you slip the sleeve over the end of the valve.
That protects the brand new seal from nicking or damage during installation. I guess one sleeve will do 8 valves over & over.
Highly recommended placing rags in each and every drain hole in the cylinder head. You don't want tiny parts going down into the lifter valley.
Your stem seal choice of Viton is a wise decision.
Steer clear of those cheap black rubber umbrella junk that are over $2 for 16.
And worse yet is the little rubber "O" ring at $1 for a thousand pcs.
However, double check on the Vitons specs. It should say, "No Machining Required".
Some of the Viton seals require pulling the heads to have the valve guides milled down.
You don't want or need to go down that road.
The Vitons will come with two clear plactic sleeve protectors. Once the stem is exposed (no spring) you slip the sleeve over the end of the valve.
That protects the brand new seal from nicking or damage during installation. I guess one sleeve will do 8 valves over & over.
Highly recommended placing rags in each and every drain hole in the cylinder head. You don't want tiny parts going down into the lifter valley.
Last edited by HeadsU.P.; Nov 22, 2024 at 06:17 PM.
