Compression questions
 

I am trying to find what is causing overheating problems on my 36 pickup with the original stock engine. I thought I had it solved last fall but it is acting up again. I bought a new compression gauge and checked the compression trying to determine if I had a blown head gasket. This is my readings from 1-8, 70-65-65-80-70-60-70-70. The truck runs fine except for the over heating, I have read on some previous sites here that this not the best but if it isn't broke don't fix it. I am going to get one of those combustion leak detectors that you put a chemical in it and if it changes color when exposed to combustion gases you could have blown head gasket cracked block etc. as a double check. What do you think of the compression readings? Thanks

Re: Compression questions
 

Remove the upper hoses then remove the belt so the pumps can’t turn. Then fill the engine with water via the water necks until you can see a level. Then start the engine and look for bubbles in the water necks. That will tell you if it’s leaking and which side.

Re: Compression questions
 

And if you give it a rev and see bubles,you can short out each plug and find the cylinder that has the leak
Lawrie

Re: Compression questions
 

My water pumps are on the top front of the heads I don't think that will work.

Re: Compression questions
 

Watch the water levels in the water outlets of the water pumps on your heads. You need to have the block and radiator as full as the pump outlets so you can watch the water for bubbles in the pump outlets. You can add additional length of hose to the pump outlets and watch the water that way as well.
Ronnieroadster

Re: Compression questions
 

Learn sumpin every day. great forum here!!

Re: Compression questions
 

Or clamp a balloon or rubber glove on the water necks and see if they start blowing up.

Re: Compression questions
 

Ken
Saw this the other day on a Facebook page, was gonna say, why go through all the trouble of taking the hoses loose, just put a nitrile glove/surgical type glove on the neck of the radiator and crank it up and run it, if it inflates? You got problems !!

Re: Compression questions
 

Any pressure build up from a compression leak will simply vent outta the overflow tube if you put the balloon on neck of radiator!

Re: Compression questions
 

Must put it on the water necks on the engine

Re: Compression questions
 

I know, my answer was to rock

Re: Compression questions
 

Hell, might look like the "hand of the proctologist" sticking above your radiator . . . a new type of "ornament" for age old hot rodders. LOL

Re: Compression questions
 

EASY, just plug the drain tube off!!!

Re: Compression questions
 

The compression readings are a little low. Tell us more about your engine. Did it sit for a long period of time (years) before you started to run it? What is the condition of your radiator? How are the fins, are they smashed flat? Did your radiator sit without coolant for a long period of time? Is the inside of your engine block rusty? What about your distributor, is it properly timed?

There are a lot of questions, along with the possiblility of a bad head gasket.

Re: Compression questions
 

Seth
I had ALL those questions AND "ARE there any thermostats in the system?" from the very start of the post

Re: Compression questions
 

Some of the cars I have I bought after they had sat for decades. The engine blocks and radiators were long dried out and full of crusty, rusty, scale and dirt. A good cleaning was in order. Also, on one occasion I had to have the radiator rodded out. On another, I bought a NOS service replacement radiator.

On all of them I had the distributors rebuilt and timed.

I have found that a flathead will cool and work fine when all of these systems are working at 100%.

As for the low compression, I put over 1200 miles on a 21 stud with similar compression readings last summer before I pulled the engine and installed a rebuilt engine. It used a lot of oil but I was having fun.

Re: Compression questions
 

Seth in answer to your question yes this truck has been sitting idle for most of it's life. The guy I bought it from owned it about 5 years. The first year he owned it he had the gas tank cleaned and sealed and the mechanical brakes completely gone thru and rebuilt. He went to some early ford V8 meetings decided that was not his thing and I think just left the truck set in his garage for the next 4 years. I spoke to the owner prior to him and he owned the truck for about 30 years and he said he only drove it around his neighborhood occasionally. That owner bought it from a guy in Georgia who was old and selling his car collection. So setting idle most of the time has taken a toll.
Today I backed it out in the driveway opened the petcocks on the block and put a hose in the radiator and flushed the block for about 30 minutes. It flushed brown water for a little bit and then cleared up. I flushed it last year and put prestone antifreeze in it with some cleaner but that's not what it looked like today. I don't want to pull the engine and rebuild it if I don't have to, it probably has babbit bearings and that could get exspensive.

Re: Compression questions
 

I forgot to mention the radiator looks pretty good there are no damaged fins they look even and straight, I did see two small places that were repaired but look fine and are not leaking. I put distilled water in it today. I could only put in 14 quarts and it would heat up spit out a little in the overflow tube. Its supposed o take 18 quarts. Will the block fill up with water from the upper and lower hoses on the radiator?

Re: Compression questions
 

Or some XX Large Trojans !!

Re: Compression questions
 

Jers36,

You might want to remove the top and bottom radiator hoses. Use a garden hose and flush the engine block as well as you can. Try to remove as much loose crud as possible. It might also be worth your time to do a flow check on the radiator. With the hoses removed you can fill the the radiator and observe the rate of flow coming out the bottom. This is kind of subjective but you should be able to tell if the flow is slow or fast. Shine a light inside of the radiator tank and see if any of the tubes are blocked. I'm willing to bet many of them are.

I have this problem with every engine I start after they have sat for a long time.

I'm not discounting the possibility of the bad head gasket. That is worth a check also. I have never had that problem....yet. Or perhaps you have a crack in the block near a valve?

Also, you'll eventually need to put some miles on the engine to try and get the rings to seal better. You might use a liberal about of MMO in the gas for a while.

Don't give up. When you solve your overheat issue, you will want to drive that old truck everyday.