The Stovebolt Site Forums The Shop Area Engine Shop Valve seats and guides on 235?

While i have the head off of my 55.2 235 c.i. engine, I decided to check if the seats were in good shape as well as the guides. When I turn the head on edge and fill the intake and exhaust ports with fluid, the exhaust ports leak down pretty quick. Making me think they need seats? OR maybe just a good lappin' in? The truck has a little over 40,000 on it and it sat in a building for a LONG time without being run. When I got the truck, I did get it to run, but after a a couple hours of simple tinkern'... I wonder what can of worms I am going to open up by having the seats and guides replaced? Brian.

You can maybe get by with just having the seats ground?

I'd go with a good lapping before spending a lot of money.

It depends on how much money you have to work with, if your on a budget then you have to do what you can do with the money you have, but if your going to drive that truck and your going to keep it then spend the money and get the head done, like valve job and surface,you dont have to replace the guides, you can knurl them if you want to ,but if it was me i would replace them. and have the seats cut,or ground whatever your machine shop does. If fluid is leaking badly then do a valve job and call it good.

After pulling all of the valves out, the guides seem to be ok. But I ordered a new valve seal kit and all it contained was small round "O ring" like seals that fit into a groove near the top of the valve stem. THis is fine except I found there to be umbrella seals in addition to the small round seals on the intake valves only. Was this a factory thing? Why only on the intakes? Did someone put these on by their own accord? Should I just put the small round seals on and call it good? Thanks Fellas, Brian

Factory was just the small seal and that is good enough.

To answer your question about why on intakes only? Because the intake sucks and the exhaust blows meaning the intake can suck oil down the guides and the exhaust blows oil back up the exhaust guide. So, many people put a umbrella seal on the intakes only to help with oil seal. If your guides are nice and not too loose then the o-ring will work just fine like Dave said. And no they didnt put on umbrella seal from factory.

what ever you do, don't use the positive seal valve seals, In theory, it should work better than any of the others, as they presumably don't actually "SEAL" the valve rather controls the amount of oil that gets by for lubrication. However I tried it, and had to tear my engine all apart after about 300 miles, with 3 valves stuck in the open position. These engines don't run well on 3 cylinders

Brokenhead,
What are you calling the Positive valve seals? From the replies, it seems the small round oring style seals will do just fine? What are positive seal valve seals? Brian

"Positive" valve stem seals clamp onto the top of the valve guide, and the valve stem slides through them. Umbrella seals hold onto the valve stem, and ride up and down over the guide to deflect oil away from the top of the guide. Positive seals require a machined surface at the top of the guide for the seal to clamp onto that's concentric with the valve stem. The only time I use them is on a race engine with dual valve springs that has no room for an umbrella seal inside the spring. Positive seals also require extra clearance between the valve stem and the guide, or the valve stems will sieze up in the guide.
Jerry

thank you for your comprehensive explanation Jerry, thats what I was trying to say. It sure looks like they should have worked though.......