1946 L Head

Hello all,

I'm wondering if I can get some assistance from the experts. I've got an L head motor that has been in storage for about 15 Years. Same old story, ran fine when put away, put away with MM in cylders etc.

Pulled it out of the barn a few weeks ago, rebuilt the Carter, new fuel pump, cap, rotter, wires and plugs, new battery but no go. Turns over nicely, fuel to the carb, great spark.

It will burb once or twice then just turn over. Compression seems a bit week.

Any Ideas?

 

The compression should be around 90 psi. If there was oil in the cylinders, it will might have to burn off before it starts.

 

Thanks everyone, I'll give that a try. Could the valves be stuck? If so how would you free them up?

 

If the cylinders dried out over the 15 years you may not have compession. I have solved that problem by adding a couple of squirts of motor oil down each spark plug hole. Then presto, she fires right up.

 

Let's assume the carburetor is good, the fuel is fresh and you have proper ignition dwell and timing.

When you say "compression seems a bit weak", do you mean the engine cranks over faster than normal? Have you actually taken a compression test with a gauge? If you don't have your own gauge, auto parts stores in your area (like Murray's Auto - now O'Reilly's Auto) will "loan" you a compression tester for a small refundable deposit.

If / when you find a low cylinder - and you're sure there were no compression problems 15 years ago - it would be very reasonable to suspect a stuck valve (most likely an exhaust valve). Those 15 years of humidity and condensation can act on any residual carbon in the valve guide and bind up the valve in the open position where it was positioned by the cam lobe - resulting in no (or very low) compression in the involved cylinder. It's possible you could encounter this situation in a couple of cylinders. I've experienced this scenario in several old "L" head engines I've torn down prior to rebuild.

You can further confirm a stuck valve problem by removing the "valve cover" (actually the lifter galley access cover provided to adjust tappets) and examine the clearance between the base of the valve / valve spring area and the top of the lifter tappet. That clearance is specified as .014 inch. If you see one that is open more than that - like an 1/8 of an inch or so, you definitely have a valve stuck in the valve guide. Unless you're an Olympic gymnast, you may have to use a small mirror to properly examine this area (assuming the engine is still in the Jeep).

If you suspect a stuck valve, try to wiggle the stuck valve's spring at the base of the spring (nearest to the tappet). You might even try to tap the base of the spring LIGHTLY with a small wood mallet. With some luck and perseverance, the combination of your wiggling / tapping the spring and the force of the compressed spring trying to close the valve - may loosen up the valve and cure your problem. Penetrating solvents are often helpful, but don't usually travel uphill into the valve guide (against gravity). Once the valve works itself free from the guide, the problem is typically (permanently) resolved.

(Always remember: diagnosis from afar is like calling your family Doctor and informing him you have a pain in your chest. Is it a heart attack - or too many beans for lunch? Without some "hands on" evaluation, all you can hope for is some sincere effort to help a fellow Jeeper, but not necessarily the correct diagnosis). Good luck!

 

Thanks again for all the tips. The jeep is a few hours north of me and i'm heading up there this weekend.

I'll check all these items out and get this thing started.

 

Thanks everyone for the suggestions. I'm up north this weekend visiting my sick Jeep.

Here's what I've tried/confirmed:

1. Took tank out, cleaned and replaced with fresh fuel.
2. New fuel pump and filter.
3. Lots of fuel at the carb.
4. Rebuilt Carb. Good spray of fuel when pushing throttle.
5. Removed Intake Manifold and fuel seems to be puddling inside it.
cleaned it out, fresh gasket, reinstalled.
6. Removed valve cover and turned over engine. All valves move easily.
7. Confirmed and adjusted each valve to .014" when at TDC.
8. Checked timing as best I could with TDC mark on flyweel and #1 on comp.
9. Rotor is not on plug as outlined in the book. But I set #1 wire on rotor and
used the firing order 1-3-4-2 from there.
10. New points, condenser, rotor, cap, wires, plugs. Gap to .20
11. Excellent spark.

Questions/other observations:

1. Spark plugs seem dry as if not getting fuel.
2. Haven't removed head.
3. Is it possible flywheel is not indexed/on correctly? #1 seems to be on
compression stroke when firing.
4. Didn't get a chance to pick up a compression gauge.