True or false

An L-head engine will not run with cylinder compression readings of 50 psi avg.

 

:iagree:

 

It'll run, just not real well. Prolly smoke a bit too.........................

 

It won't even start. We adjusted the valves, set the timming, rebuilt the carb and all new tune up parts..........nothing but a few pops through the exhaust. Blake and I have been straining over the location of the number one cylinder on the dist. cap. If we use the thumb over the plug hole trick, I get number on at the 12 o clock position looking from the pass fender. Blake says he thinks it's at the 3 o clock position. With 30-50 psi comp. readings, it's prolly not an issue anyway. Rip it out and drop a 4.3 in it's place. We just wanted to hear it run once before starting the flatty build.

 

If you're getting pops from the exhaust, how loud are they? Just low rumbly-type pops, or loud POPS? Double and triple check your initial timing. If it's out 180 degrees, it'll never run, but will POP out of the exhaust like a .22 caliber pistol. Low runmbly pops usually mean that you're close. If that's the case, have your friend turn the engine over while you move the distributer back and forth to see if it will catch and start.

Also, just for giggles, have you checked to make sure you're getting fuel? Are you getting fire, and is it a good strong spark? A plugged fuel filter, no gas, weak coil, bad plugs, or bad plug wires could also be the culprit. Sometimes we can look right over the simplest of things. I know I have in the past R)

Wish I could help you more.....

One more thing, location of #1 on the distributer cap is a moot point since a distributer can be removed and its shaft can be moved all around. Run the #1 piston to TDC on the compression stroke, and where ever the distributer's rotor is pointing is where you should rotate the distibuter & cap to the nearest contact for #1 firing. It's nothing set in stone as to it's location.

 

I'm not sure about this timming thing. Blake installed all new parts for the fuel and ignition systems so I am confident that it's all in working order. We have spark at the plugs, fuel in the carb and a fully charged 6 volt battery. The issue that is tripping me up is that the piston is not directly under the spark plug. Im used to finding TDC by the #1 piston topping out from the plug hole. We had to find it a different way by turning the crank until we felt pressure at the #1 plug hole, then continue to turn until we got to the timming mark on the flywheel. Does this sound reasonable or are we out in space somewhere??? I won't even fire on a little starting fluid.

 

Make sure you're on the compression stroke, not the exhaust. Pull the side cover and watch the valve action if you're not sure. The dist only goes in one way with the offset tang on the bottom so I'm sure thats OK. Find #1 TDC, rotate dist if you have to to get the rotor pointed at one of the contacts on the cap. Note dist rotation and put the rest of your wires on (1342).If all else is good it should start. Here's a link , towards the bottom of the page shows timing.http://www.thecj2apage.com/specs.html

 

Did you remove the distributer,if it's worn it will go in 180 out.

 

Have you poured some Marvel Mystery oil in the cylinders? Sometimes that will allow the rings to seal enough, and raise the compression a bit to get it going. Obviously not going to work if the rings are completely toast though.

 

We did'nt take it out.

 

If you take the plugs out and jack the drivers side of the jeep up, will the oil run over and into the cylinders????

 

I wouldn't worry too much with putting oil into the cylinders. You may foul the plugs, then it will never start. Squirting a little oil in there when you're doing a compression check is the way to tell if your rings are worn, or if you've got other problems (compression goes up with oil in cylinder=worn rings, compression doesn't go up with oil in cylinder=blown head gasket or leaking valve seat).

Heck, I know a guy that runs a 4.0 in his XJ that has 25psi on one cylinder (wet), and the rest aren't that great, either

Just do your best to find TDC on the compression stroke, and let the distributor's rotor fall wherever it does. Orient your plug wires from that point. Easy!

As long as you have the 4 main ingredients (air, fuel, spark, timing), it should run no matter how bad the compression is. However, when compression is really low, don't expect too much out of the little bugger....