Can someone tell me what the compression should be on this old 6 cyl. 215? I have a 1953 F100, and am trying to decide if it needs a total rebuild, or just the top end. Any advice would be appreciated. My first post, by the way.
Mike

 

Acc;ording to the 1952 Ford shop manual a 6-Cylinder 215 @ sealevel : cranking pressure at cranking speed 130 psi. The Ford Shop manual is an excellent resourse . Get two if you want to have a clean one.

I think this specification is really high for an engine with a 7.0:1 compression ratio. I would expect more like 100 psi for a good engine. 90 would be good for an engine with some miles on it. Kinda depends on how strong the starter is. Look for any clyinders that are lower than the others. When enough of them get below 60 the engine gets hard to start.

If your not sure of the history of the engine its not a bad idea to pull the head off and have a look at the valves and make sure there are no broken rings. If the engine was out of service and rusted up the top rings sometimes get broken when the engine gets freed up usually by someone lettin it role down a hill and popping the clutch. You can really screw up an engine running it on broken rings.
I know because thats what happenned to mine. If the cylinders aren't getting scratched up and the top rings are good you might have a good engine.

Not a bad idea either to drop the oil pan. There is probably some stuff in there you can clean out and you can see how your bearings are doing.

When you get it going make sure you have oil pressure right away.

Good luck and keep us posted.

 

Thanks Craig,
My shop manual has been ordered and on it's way. The cyclinder walls look good. This engine would start and run, when I bought it. One cyclinder has zero compression (probably a valve). After pulling the head it appears that two other cylinders were not firing (top of pistons wet). Compression on 5 cylinders range from low at 65 to high at 90. I am at about 4500 feet above sea level, so I guess the compression may read a little lower? I will check the valves and pull the oil pan. So do you think, maybe top end rebuild could get me down the road a ways?

 

You are way up there. According to some data I found in World Book your average barametric pressure would be around 12.4 psia vs 14.7 at sea level. So you would be getting about 15 percent less air in and I would expect you would read about 15 percent low. I'm quite sure thats how it works. Years ago I had some schoolin on these kinds of things. Nothin about engines though. Kinda been figurin it out as I go along.

I've always been a little reluctant to offer people much advise. Sometimes it turns out that I'm talking to someone no smarter than I am and they get themself in trouble. You sound like you know what you're doin.

You might have a pretty good engine there. While you have your head off measure your cylinders to see if it has ever been rebored. Just a good piece of information to have. You don't need a fancy inside micrometer. A good caliper should do for this purpose. Check the ridge at the top of the cylinder. If its less than a business card and the engine wasn't blowing smoke your rings are likely in servicable condition. Get your head fixed up and get it running.

Does the oil stay pretty clean? do the seals leak? If yes and no or sorta and not too bad you might not want to mess with the oil pan for a while. Usually but not always, if the engine developes a serious problem and something real bad is going to happen you will have some warning -- like strange tapping of grinding sounds or drop in oil pressure.

One last word of advise. If you're not already equiped get seat belts for the kids.

 

Thanks again Craig. I will measure these cyclinders, good idea.
The ridge at the top is not very thick. It was blowing some smoke, but had two cyclinders not firing. Oil was dirty when I got it, have not run it much. I think I will just go ahead with the valve job, change the oil, new top gaskets and see what happens. I also need to get the oil pressure, and temp gauges working.
Seat belts for sure, when I get it road ready. Thanks again.