Compression question

[chard]

With a compression fig of 58 and all that crankcase compression I would whip the head off, and take a look, not difficult or expensive. Then you'll know and be able to plan/budget.

 

[Robbo]

Thanks. I think it's time to do a top down look at the springs, valves and head to the cylinder itself. What has me a little is that I get that the cylinder and/or valve might go (rings, piston, etc.) but the oil leak, not sure where that came from. Even after topping it back up, can't seem to figure out where that significant a leak came from. For example, if I indeed found a valve issue, I'll probably still have that leak issue. Strange. One thing at a time though. Thanks all for your generous time to help me figure this one out. I'll keep you posted.

 

[RootesRich]

This is why I suspect a broken ring over valve issues. You've lost compression in one cylinder and have oil forcing its way out of every orifice.

If the compression was equal across the board and you had blow-by, I would lean towards a stuck PCV, etc. However, the lost compression, blow-by and ticking at high rpms is not a good combination.

As stated before, I hope I'm wrong, but I doubt it.

 

[todd reid]

Guys, I don't disagree with any of your diagnosis, but I think we might be getting ahead of ourselves. You should always check the easy stuff first! Let's pull the valve cover off and reset the valve clearances on cylinder#1. Then redo the compression test with the valve cover off, keeping an eye and ear out for anything unusual. If no change, then we can continue on with the head removal.

 

[Stephen]

Robert I agree start at the begining Do you have a good service manual on the Ser V if not you can download one from a site
if you send me a email Sjjsmith@aol.com I can send the site to you
Stephen

 

[Robbo]

I have a good one and will be at it again this weekend. Like I mentioned, the leak has me baffled. I will diagnose top down, at the beginning, but I'm not blowing smoke and can't find a significant leak that would have dropped that oil so fast. Good thing is I was close to home to get her right back in the garage. Am going to start with the valve cover removal and compression check with oil in the bad cylinder before I go any further to the head. Thanks for the help and encouragement. Finding this site and donation has been worth every penny!

 

[RootesRooter]

I'd double-check the bad cylinder compression 'dry' a second time before adding oil.

With only 58 lbs on one cylinder, I'm surprised you're not blowing at least a little oil smoke out the tailpipe. Maybe it'll be just a bad valve after all.

 

[sunbby]

Robert I agree start at the begining Do you have a good service manual on the Ser V if not you can download one from a site
Stephen

The Series V shop manual WSM145 is now available on this site! (as is the earlier Series manual)

Select the "Technical Data->Original Tech Manuals" pull down menu at the top of the forum.

( or follow this link: http://www.sunbeamalpine.org/index.php?categoryid=89 )

 

[Robbo]

I haven't started on the valves yet but will this weekend. Intersting observation while I was poking around tonight. Engine started right up, normal tapping, no smoke out the back, but some type of blow smoke coming from under the fuel pump. I plan to crawl under tomorrow to inspect closer, but curious. Will post an update as I get into the valves.

 

[Robbo]

UPDATE: Compression Question

OK, well, I checked the compression again before I started anything. Got the same readings 130, 130, 130, 60 on dry test. I did a wet compression test and got the same readings. So, as I check through I'm keeping hope its the valves. No massive leaks at low RPM, but good drip out the front on high RPM. Let you know more as I progress through the diagnosis.

 

[puff4]

Well, as #4 is usually the hottest of the lot, I'm betting on burned valve and /or seat in #4, with leakage being caused by same, as denoted by your wet/dry test. Or a holded piston, though that's far less likely and your compression pressure would likely be even lower.

 

[Robbo]

Well, quite an evening. I've adjusted the valves and the timing was off. Just to be sure on the leads, I hooked my timing gun up to each lead to see if there was constant spark - just to be sure. Oddly, intermittent spark on cylinder 4 - the low compression cylinder. Now, could be coincidence, but I've got figure it out. By the time I was done, there was no spark on that lead. I switched leads too just to eliminate that possibility. Still nothing. Oh, the mysteries that unfold! Will keep you updates as we go, but these little steps seem to be helping...but I remain cautiously optimistic. Will post updates after more work this week.

 

[RootesRooter]

What condition where the plugs in, particularly #4? With Strombergs, a light coating of soot is normal.

 

[Robbo]

All of them are sooty. It is firing, but just seemed like it was missing every 4th or so. Question so I am sure. For #1, how many degrees BTC is recommended for the 1725 engine? I really want to cross the fundamentals of the list. I'm getting new leads tomorrow too.

 

[RootesRooter]

Just wondering: What's the distributor cap condition? Worn terminals perhaps?

 

[Robbo]

At this point - ANYTHING is possible

Checking and replacing the simple things first. Terminals included.

 

[todd reid]

At the risk of stating the obvious, #1 is the cylinder closest to the radiator and #4 is closest to the windshield. Just so we are all on the same page. Your problem cylinder is #1 or #4?

 

[Robbo]

Fair question. It's #4. No question off limits here. I've over though on many occasions.