78 -- 120 -- 120 -- 120

JC Whitney used to sell a similar setup. It also reduces detonation (pre-ignition) in high compression engines. And the alcohol would cool the mix and make it denser, kind of a supplemental supercharging.

 

That's what I am thinking. Not sure why the oil would bring up the compression if this were the case, though. Maybe I have both issues. How about a broken ring piece stuck in a valve?

 

Unca, now I remember how to do that. The compression gauge kit I got actually has a fitting for that purpose, with a quick release connector on one side and the other side screws into the plug threads. Thanks for jogging my memory. I haven't had to do car work for so long, because I have been buying new cars since I could afford it, that I have forgotten a lot about what I used to do. Thanks!!

 

Good point, Petel, and that makes me feel better because there is a good chance that it could still be a top-end problem -- something in the valve train -- which is what I want it to be. So much easier than having to pull apart the bottom end. Thanks for sanity check...

 

Glenn,

Supposedly, there were less than 5K put on the engine since rebuild. The engine has been running fine. No smoke, no stutter, nothing. I have always been a firm believer in "if it ain't broke, don't fix it" so I have left it alone, until this backfire issue started. I thought it was a problem maybe with the new distributor I put in, but it didn't start right after I did that. As a double-check, I put the old distributor back in and the problem still exists.

 

That's exactly what I am hoping is the issue. I have a can of carb cleaner so I will try that first.

 

I remember reading somewhere about that now that you mention it...

 

Pretty cool!!!!

 

That's what I have been thinking, so I will tackle this first and then go from there.... Thanks...

 

90-60-90 is better IMO

 

Oil introduced into the cylinder would have zero effect on a valve issue.
Your results indicate ring/piston problem(s).

 

Yeah, neighbor kid borrowed mine, took about four months to get it back. It sounds like most of the people are voting for a carbon or valve issue but the leakdown test will tell you more. It isn't fun to pull a head off. Want to come and help pull a straight eight head off of my Buick?

 

Unca, my parents owned a 1955 Special with the straight eight it in. I loved that engine, and like the F-134, it had a sound that was distinctly its own. You could tell it a mile away. If you lived close to me -- I live in Central California -- I would more than be happy to help you rebuild that engine.

 

123 --124 --120--122

OK, I pulled the valve cover, which is a job, because in order to do it, I have to pull the carb, because the carb interferes with its removal. You have to do them both at the same time and the inboard hold-down nut on the carb is a bear to do. Remember I put that Weber 2-bbl on this thing and that was part of the price to pay for trying to stuff a 2-bbl in place of a 1-bbl. But I pulled all this stuff off and it was worth it. There was no valve to rocker arm clearance (lash) in cylinders 1 and 2. In fact in cylinder 1 the intake valve never closed all the way. The leak down test I did had more or less indicated that it was a valve issue. So I adjusted the lash to .016 as specified making sure each cylinder was at TDC as I did. I guess I am not used to mechanical lifters. They sound noisy as hell, but I know they are adjusted correctly now. Since these are so far off, I think I will have to pull the cam side cover and check the exhaust valve clearance. Question: Could this be caused by unleaded fuel? Valve recession? I know I had to use additives in the 280Z engine I built to keep it from happening. Please advise...

When I first started the Jeep, I re-adjusted the carb and everything was fine. It was accelerating as it should with no backfire, etc. Then it started doing it again. But this time, I noticed it seemed that the carb was leaning out. Will/can this cause it? Intermittent or bad fuel delivery? Just so you know, I put the compression gauge back on each cylinder and they were reading the same numbers above. So I don't think it is an intake valve problem causing my backfire issue. Let me know what you all know. Thanks for the help on the 78-120-120-120 thread. A lot of great knowledge in here...

 

Re: 123 --124 --120--122

"the inboard hold-down nut on the carb is a bear to do"

I just took an old box-end wrench, heated it, and bent it into a Z-shape (and extended the 'handle' end). Works great on the carb nut.

Personally I've never had a problem with an F-head maintaining valve clearances. Set and forget.


Can't explain your backfiring, unless the spark (timing) is possibly erratic for some reason. But you say you tried re-installing the old distributor. HT wires inductance cross-firing?

Could it be random dieseling/pre-ignition caused by a lean mixture and hot carbon deposits?

Maybe a sticky valve not closing properly at times?

 

Overhead valves with hydraulic lifters.

 

Thanks for the offer. I think all it needs is a new head gasket, and I need to fix that darn fuel pump.