Valve seals on 1966 Mustang

[GregH]

I'm putting in valve stem seals on a 1966 Mustang with a 289 and the kit came with two sized of seals. Do the large seals go on the exhaust or intake? Thanks!

[Jim Warman]

From memory - I've seen 289s with either/or the small stem seals on all the valves or both large and small stem seals crumbled and laying in the valve area and at the bottom of the pan.

 

While some may chastise me for saying, you will find that placement of large and small isn't super-critical as long as they fit snug on the stems. Whenever I assembled heads, I would bear in mind that the intake valve guides are subject to high amounts of vacuum and I would select the seal that gave the most "protection" to the intake valves (some of the large OD umbrella seals offered in some gasket kits would not be as deep as the smaller OD seals).

 

I don't recall if the engines using same size seals were 5 bolt, 6 bolt or didn't matter though your engine will be a 6 bolt....

[GregH]

Thanks, Jim.

[lmorris]

While some may chastise me for saying, you will find that placement of large and small isn't super-critical as long as they fit snug on the stems. Whenever I assembled heads, I would bear in mind that the intake valve guides are subject to high amounts of vacuum and I would select the seal that gave the most "protection" to the intake valves (some of the large OD umbrella seals offered in some gasket kits would not be as deep as the smaller OD seals).

Using that theory worked well for those of us that used these Ford positive seals on many Chevy small block heads in place of the umbrella seals. Especially when they started burning oil past the valves.