Lack of power from low compression?

[tomcattoy]

My jeep has pretty good power in 1st and 2nd gears on the flatland, but any type of incline and in 3rd causes it to bog down.  I got a little more pep by tweaking the timing, but not enough.

I had checked the compression some time ago with an old gauge I've had for about 30 years.  Decided to get a new gauge and found the following compressions:  #1=110 psi; #2=110 psi; #3 = 90 psi; #4 = 105 psi.

So, is the low compression in #3 enough to cause a marked decline in power?  I also put some oil in #3 and retested, which came up to 105 psi.  This would indicate the rings are bad.

Thoughts?

[athawk11]

110lbs is pretty good compression in these engines.  That #3 is a few pounds under the rest would indicate a possible ring or valve issue, but it's not severe.  It's hard to gauge a drop off in power while on the internet, so opinions may vary.  Do you have someone close by that also has a Willys?  ...and would let you drive it?

I've got a tired engine showing compression in the high 70s on all four cylinders.  It is able to keep up with most fresh rebuilds on the trails of Colorado.  I will say, long steady inclines were a killer with mine until the timing was adjusted correctly.  Are you pretty sure your timing is dialed in and points adjusted? 

Another thought...one other killer was a faulty condenser in the distributor, but for me, this caused a soft back fire under load, along with a lack of power, so it may not be your issue.

Tim

[tomcattoy]

No other Willys near by....

The points and condenser are new, but I will recheck the gap.  I believe the timing is right, and I have moved it and driven it a couple of times to get the most out of it without backfiring. 

Thought it might be the distributor, but then I would think it would be missing and running rough.  It has a miss periodically at idle or higher rpm, but very sporadic.

Just not much power on the high end...can barely hold 45 mph at best.

[Ryan_M]

Do yourself a favor and buy a dwell meter, a vacuum gauge, and a timing light if you don't already own them. Without these tools it is unlikely you will be able to maximize the running output of the little motor these 3A's are equipped with. I went through the same problem you are describing and although there may be other culprits, tuning your engine with these tools certainly can't hurt.

It's a pretty delicate balance of getting everything adjusted properly but once it is it'll feel like a completely different vehicle. We can help walk you through the process.

[garage gnome]

My freshly rebuilt L head in my '53 does just fine on the roads. However, the tired one in my '49 just barley does 45 mph. Its fine for putting around on the trails. The '49 has 85psi across all 4 cylinders.

Check to see if your throttle linkage is opening up all the way. Had that issue when I first finished my '53. Make sure the timing and mechanical advance are correct too. Do what what others have said and go right through everything to make sure it is running at peak performance.

[garage gnome]

BTW, I moved this to the tech section since it isn't FAQ related.

[tomcattoy]

Thanks for advice...I will go back thru the tune-up process.  Sounds like the compression difference isn't necessarily the problem.

[oldtime]

Adjust the carburetor last.
Adjust the valve before you mess with distributor.
Do a precision valve adjust.
Click on the 3B page and search "Precision Valve Adjustment".
The F head is different than the L head yet the basic procedure is identical.

[tomcattoy]

I adjusted the valves some time ago, and really didn't want to go through that again.  But, I might as well start from the beginning to make sure everything is right.


One last question...is it worth replacing the distributor to eliminate that as a problem?  If so, can anyone recommend a good source for one?

[athawk11]

Just a note...I had an old condenser installed.  The Willys was running fine, but I hadn't ever replaced it, so I figured I'd freshen it up.  I installed a brand new condenser, and that's when my trouble started.  I switched back to the old one and all was right with the world again.  Moral...just because it's new doesn't mean it's good.

The distributor may be fine, but the bushing it rides in may be worn.  Pull the cap and rotor.  Try to wiggle the shaft.  If you have a fair amount of movement, you might want to replace the bushing.  The distributor might have springs that have worn out or the spring mechanism may need some cleaning and oiling.  There are a couple guys here that have freshened up their distributors.  I haven't had to do this.  Maybe someone will chime in.

I agree with the others.  Start with the easy stuff.  Make sure you have the timing and valves adjusted to their peak.  This may be all you need.

God luck.


Tim

[tomcattoy]

Thanks for all the info and suggestions. 

[oldtime]

It is imperative that you first address the valve timing by correctly adjusting the valve backlash.
Make sure to adjust valve lash when the cam lobe is at it's lowest point of contact with the tappet.
Let us know if you have changed the adjustment of the tappets.

After performing a "precision valve adjustment" you should retest the compression reading to see if that has changed.
Please post the new compression readings for comparison to the previous set of readings.
It is important that the compression readings be uniformly taken and ideally should be within 10% of one another.

The distributor generally does not effect the engine power output very much unless the ignition timing is way off.

A worn distributor shaft bushing eventually becomes notable as shaft side play.
A good dwell meter can be used to determine if the shaft has a small amount of excess play.
See if your dwell meter provides those specific instructions.

Distributor components such as the condenser ideally should be tested for microfarads of capacitance.
Is this a 6 volt or a 12 volt system ?
And can you further identify the specific coil ?

Remember the carburetor will be the final adjustment in the tune-up sequence.

[tomcattoy]

Here is an update:  I went back through the valve adjustment and carefully adjusted to .016.  I bought a dwell meter and set the points to 42*.  I got a little better power and less tappet noise, so I gained something.  But, when I was setting the timing, I revved the engine and found that there was no advance at high RPM....the centrifugal advance was not working.  So, I bought a replacement distributor from KaiserWillys and installed it last Saturday.  What a difference!  I was able to accelerate through third gear up to an easy 50mph and then dropped into overdrive for almost 60 mph.  It was the distributor all along....

Thanks everyone for the input.

[macrisel]

Good to hear you got it figured out!  These little motors are pretty amazing in their simplicity and durablilty.  There can be several things (timing, fuel, valves) off spec and they will still run, just not that well.  With the L-134 everything must be working exactly right to squeeze every single horse out of them!  A 6 HP loss doesn't sound like much, but on these motors that is a decrease of 10%.

Enjoy your new found horsepower!

[athawk11]

Congratulations! 

Tim