454 Mag/502 valve seals
 

Hi, just had a valve job done on my 088 heads and now i realized that the machine shop threw away the old umbrella seals. I can't seem to find any that will work with the dual springs other than from mercruiser. Should I have the guides machined and go for positive seals? My concern is that the positive seals will allow less lubrication to the exhaust valve stems and they will gall up. After all, I boat in salt water. yes or no to positive seals on the exhaust?

Some builders don't even do any seals at all on the exhaust valves, to enhance lubrication there. Seals are more important on the intake side.

Take spring off the seal on exhaust

Are you running 3/8" or 11/32"valves?

What do you have setup for guides? Original iron, bronze, bronze liners?

What is the current valve guide clearance?

The SBC/BBC never used to have seals on the valves...they had these little o-rings on the stems to stop the oil flowing down from the rocker arm ball cup.

It's a PITA, but you can change the seals on the engine if you have too much oil getting in there.

On the other hand...if you're not getting enough...you'll be pulling the heads anyway... best case.

088 head exh umbrellas.

OD: 0.0777"
ID: 0.710"

Stock spring ID: 0.815"

Stock guide OD" 0.615"

Note: BBC iron heads, the guide bore is often not centred in the guide OD.

So you have some data to help find umbrellas that work.

https://cimg6.ibsrv.net/gimg/www.off...e574a16177.jpg

Did yours have the plastic umbrellas that fit into the retainer like the ones that Tartilla showed ? I have not been able to find them aftermarket. I usually machine the guides for positive seals on just about everything. I have taken the springs off the exhausts but not sure if it is really necessary.

I used to take a small triangular file and cut a groove in the Teflon positive seals.