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Bought a '60 235 engine for my '55 1st series. Heard engine run and checked the compression before removing the engine from the '60. Compression on all cylinders read 85 lbs to 90 lbs. Pulled engine, cleaned engine and painted engine. Engine was out of truck and in my garage for a couple months. Installed engine in my '55 1st series. The compression now reads 55 lbs to 60 lbs and will not run. Any ideas concerning the reduced compression?

I would think the rings are sticking a bit. I don't think that should stop it from running.

Two different compression gauges, two different electrical systems i.e., batteries and cables. Was engine hot the first time and cold the second. Running engine wet rings, non running engine dry rings. Was the carburetor on or off the engine the first/second times. Try blocking open the throttle plate when you do the compression check.

Denny Graham
Sandwich, IL

Just try to be consistent when ever you do a compression check. I always do it with all the spark plugs in place (accept the one), choke full open, and push the throttle down and hold open. Then I watch and record the first 3 compressions.

What difference is it going to make either way? Are you going to rebuild it just because of one check? Get some miles on it before deciding. Drive it some to loosen it up and get heat into it, then check the compression, but in the long run, as long as they are even across all six, it will run just fine. Its going to be a rare find that all six are low and still be even with each other. One or two low is a problem, all six is a gauge or test problem.

The correct way to test is have the engine warm but not hot, all six plugs out, carb wired open, fresh battery with strong cables, and four to six rotations per cylinder test. This should be a running engine with oiled cylinders, if its not, oil all six cylinders and crank the engine to coat each one top to bottom. You want each cylinder test to be identical in time and conditions.

Joe

I did the first compression check myself when the engine was in the '60 truck. I let the engine get warm and removed the plugs one at a time. Engine seemed to be good. When I tried to start the engine in the '55, it turned over but did not want to start. After many tries, I finally took the truck to a local shop. They are familar with these old trucks. They tried to start it and finally pushed the truck to get it started. I paid for a couple hours labor. It ran but coughed and spurted. Did not want to run. I am now faced with a dilemma.

1. Open up the engine, find the problem and replace the bad parts.
2. Rebuild the engine.
or
3. Buy another used engine.

Before you start taking it apart, do a cylinder leakdown test and find out where the compression is going. Engines don't just suddenly develop major compression problems from sitting idle for a few weeks. I'm guessing you've got valve adjustment problems.
Jerry

The hard starting will not be the fault of something inside the engine. Buying another used engine would be a waste of money. I am shocked that a professional shop would resort to that. I wouldn't go back there ever!

I just want a running engine. What would you suggest? I am out of answers.

recheck compression,first dry with all plugs out.write down compression 1 thur 6 cyc.then repeat wet.put a few squarts of oil on each cyclinder.if pressure increases after oil (WET).rings are the problem.stay the same valves.Ive always was taught at least 100 lb compression.it may run with low compression but it will be a DOG,no power.how many mi on the engine????.Yes if you have two cyclinders side by side with low comp it;s more than likely a head gasket.Don't press the throttle down.Never heard this done.but I guess i;ll hear a few remarks on that.good luck on your engine.they are a simple engine to work on;not like todays engines,pick up the hood and what the hel# is it

Recheck the compression, but- - - - -

ADJUST
THE
VALVES
FIRST!

If some valves are too tight, the compression will be erratic, and the engine will run lousy. Sound familiar?
Jerry

If you say that engine ran ok in the '60 then my suggestion would be to find a mechanic that has a basic understaning of automobile engine mechanics and have him time, adjust and just over all tune the engine. I'd bet the farm that there isn't a thing wrong with the basic engine and the its' just in the way that it is set up.
As far as checking compression with the plugs in EN O to that. You want the engine to crank over with as little resistance as possible so as mentioned, pull all the plugs.
DG

You should go through all the checks.

Timing: the points should be just starting to open when the triangle marked UDC is at the pointer. Some say use the steel ball but I would use the triangle.

Spark: Put a plug on top of the valve cover and hook #1 plug wire to it. Turn it over to see if you have a good spark.

Plugs: They should be clean and gapped.

Carburetor: If gas is running out while you are trying to start it, it is flooding.

Choke: You need to have full choke to start it.

Hint: Power the coil from a battery charger to get the best possible spark.

There are a lot of suggestions and I appreciate all the input. I took the truck to a local automotive repair shop known for quality work. They were not able to get the engine to run. I took it to the shop as I wanted to get the truck on the road and just drive it. Minor setback. I'm going to convert the truck to 12 volt and try starting it again. The engine was originally 12 volt. Maybe that will make a difference.

I just bought a '62 261 engine. Hard to find and now I own it. Its a complete engine removed from a dump truck. Been sitting in a garage for about a year. I plan to do a complete rebuild, maybe add dual carbs and dual exhaust. I also have a T5 transmission removed from a '85 S10. The truck will run.

Just because a shop is known for quality work doesn't mean that they know how to trouble shoot a 50 year old engine. Find you some guy in his 60's who worked on them 50 years ago. I would suggest quit worrying about the compression numbers and figure out what is wrong. What all did you have apart? Have you checked the simple things like is it popping a fat spark and are you getting gas to the carburetor and is it going through the carburetor?

Are you using a 12-volt coil or a 6-volt coil? If the 12-volt coil is on there it's going to run lousy or not at all on a 6-volt system.

The engine is setup for a six volt system. I bought a new 6 volt coil and battery, new points, new rotor, new distributor cap, new plugs and plug wires. I even replaced the new coil with coil from a friends 6 volt truck. I rebuilt the carb and then borrowed a carb from a friends truck. The fuel tank anf fuel lines have been cleaned. The fuel pump is new. The timing and the points setting is correct. I'm getting gas and spark. I am going to change the truck to 12 volt and then try it again.

should start on 6 or 12v. are you absolutely sure the distributor isn't 180 degrees out. does it even pop and sputter?

Unless you are willing to diagnose it step by step by elimination, you may be a long time in getting it started. And just because something is now, that doesn't assure you that you did not buy a new defective part. These old machines are from simpler times when people took time to systematically diagnose problems.

The engine ran good while in the '60 truck. The distributor was never removed. The main difference it is now a 6 volt system with a 6 volt starter.

Usually when the problem persists, we tend to "over think" the problem. Stop everything....and start over simple.
Check your battery and grounds. Is your engine grounded to the body and/or chassis? Check the wiring and verify voltage to coil/distributor. Plug gaps, valve adj.etc.

Stop looking at everything you did and just start over and rethink it like it is a different vehicle. When things get difficult, many times it turns out to be something simple.

Are you sure you have power to the coil when the engine is cranking?