Time for new valve seals? New head gasket? ...or something worse (1 Viewer)

[BeerM3]

Backstory: I've had this '76 for a couple years now. While I'm no engine expert, I know my way around the basics from rebuilding a couple small block chevy's as a kid. That said, I figure it wouldn't hurt to reach out to the MUD community to see what the consensus is.

There's been a small puff of the telltale bluish-white smoke on startup for most of the times I can remember. By and large it runs and idles just fine. The plugs were replaced as part of the general "tune up" back in the fall of 2017. Knowing what I know now, they probably weren't gapped properly for the DUI distributor, but I don't think that's the issue. I finally got around to checking the compression and below are the results. 2 things: I did warm up the engine but it had to of cooled down some in my 15min run to the auto store when I realized my spark plug socket was MIA and 2) I didn't prop open the carb which apparently I should have. I hope to test it again this weekend with all the proper steps, but I suspect the results will mirror these, hopefully with a little higher numbers.

Not knowing any of the history of why or when someone put a '79 2f in my '76, my inclination is to just pull the head, have it machined if necessary, and see what lies underneath. I suspect the valve seals and possibly the guides are shot, but it might be something more substantial in #5?

 

[BeerM3]

The upside to having some weekend time to crawl under the truck...looks like i get to buy new exhaust too!

 

[Jdc1]

When was the last time you adjusted the valves?

 

[BeerM3]

When was the last time you adjusted the valves?

That would be....never. Also on the list of things to do. There's definitely an audible rattle coming from somewhere. I need to order new gaskets so I can pull the cover.

 

[rkymtnflyfisher]

You shouldn’t need a new gasket for the valve cover to adjust valves, it’s easily replaced later if it’s leaking. A good place to start would be a good valve adjustment, check timing, and check out the carb while you’re there.

 

[BeerM3]

Thanks @Jdc1 and @rkymtnflyfisher. That's the kind of "been there, do this first!" expertise I'm needing. I think about every gasket I have leaks to some degree so that's a good point about not getting overly concerned with a little more oozing.

 

[BeerM3]

Got the valves adjusted today. It seems to be running really smooth but I didn't get time to re-check the compression or timing. That'll have to wait another week.

Adjusted correctly, is it not unusual for these engines to have a slight audible tick when idling? It's consistent and varies with the speed. Is that status quo with solid lifters? Or just a 40 year old engine showing its age...

 

[vipergrhd]

When you get to do another compression test do it dead cold then warm it up to operating temp. and do another set and after that
do a wet compression test a few drops of clean oil in each cylinder should do it. This should give you an idea if your compression loss is from the head or your rings also if you can do a leak down test it would really pin point why you have a low compression on #5.

 

[4Cruisers]

Got the valves adjusted today. It seems to be running really smooth but I didn't get time to re-check the compression or timing. That'll have to wait another week.

Adjusted correctly, is it not unusual for these engines to have a slight audible tick when idling? It's consistent and varies with the speed. Is that status quo with solid lifters? Or just a 40 year old engine showing its age...

Should tick like a well-oiled sewing machine.

 

[4Cruisers]

It's cheap and easy to build a leak-down tester, I built one many years ago by following this article:

Building and Using a Cylinder Leakdown Tester www.motorcycleproject.com

 

[BeerM3]

Should tick like a well-oiled sewing machine.

That’s pretty much what she sounds like.

 

[SteveH]

Your plugs look like typical plugs on an older 2F with leaky valve stem seals - mine looked much like yours. I doubt your guides are shot and valve stem seals can be installed without pulling the head, if you don't need head work.

Every 2F I have ever owned has a random tick, like you didn't get one valve just right - even if you did. I sometimes drive it for a day or two, then recheck the valves, and run with it. As long as it's a tick, and not a 'pounding sound', you should be ok.

 

[BeerM3]

Your plugs look like typical plugs on an older 2F with leaky valve stem seals - mine looked much like yours. I doubt your guides are shot and valve stem seals can be installed without pulling the head, if you don't need head work.

Every 2F I have ever owned has a random tick, like you didn't get one valve just right - even if you did. I sometimes drive it for a day or two, then recheck the valves, and run with it. As long as it's a tick, and not a 'pounding sound', you should be ok.

Thanks! It's definitely quieter now. Some of the valves were tightened down to zero clearance before adjusting. It's a pretty light, consistent tick, the pushrods are all spinning, and it purrs about as good as I expect it to until I get the exhaust replaced. I'm gonna try to get more test results this weekend.