The Stovebolt Site Forums The Shop Area Engine Shop Opinions please on 235 comp

I'm almost done the body work on my one ton. Ready to start stripping chassis and such.
This truck will not be a show queen; I intend to drive it often. I did not intend originally to begin a 1 ton but I couldn't see a good truck go to waste.
I will build up my 1/2 ton to be the looker.
This is my question: as I am doing all the work on this truck and it is on a strict budget is 100 lbs of compression on all 6 pistons adequate to justify not rebuilding the engine at this time? The 1/2 ton's 261 was a little pricey to buy all the parts. I don't know if 235 is in budget now.
It runs well enough and I think if I completely rebuilt the carb it would run even better. Thanks for your input.

100 lbs. is OK as long as they are within 10 lbs. of each other. Check for smoke coming from the crankcase vents. If it has very much it indicates worn compression rings. A good tune up & carb rebuilding will probably get it running like a top.

Uniformity of compression pressure between cylinders is far more important than the actual pressure reading. If you use three different gauges, you're likely to get different readings on all of them. I usually plug my compression gauge into the shop air line to get an idea of how accurate it is before starting a test.

A 7:1 compression ratio at atmospheric pressure of 14.7 PSI per atmosphere would be 103 PSI under ideal conditions (no leakage, and a very accurate gauge) That's not likely to happen, so a reading of 100 on the compression gauge is going to indicate somewhere around an 8:1 ratio with a little piston ring wear and/or an inaccurate gauge. Early stovebolts don't come anywhere close to an 8:1 compression ratio, so compression in the 80-90 PSI range should be close to normal for a 216, slightly higher for a late model 235 with an 848 head.
Jerry

What Hotrod said. Lots of smooth running and still working at 65 pounds cold cranking. If they are balanced, and don't smoke too much, run it. Rings are cheap. You can get by with worse if it has not been run in some time. I worry when they get blow by and smoke. But lots of those get better when run. If it won't clear up with some miles. Then the question, would be to tear down, replace, or some version of rebuild and repair. Money, skills, and time. These are not fussy motors. They last a long time. But the parts are more than a small block. The performance is what you would expect for a working truck. So you get to decide.

What are your opinions on those "super" oil additives that are supposed to help "tighten up" worn cylinders? Do they have a leg to stand on? I've never used or seen, heard an actual person's testimonial.
I don't believe anything I see on tv/internet but I trust this site!!
Thanks for the help.

In my decidedly biased opinion, oil additives are sucker bait, for the most part. The only times I've been successful with an additive is doing a heavy overdose of a lightweight solvent like kerosene or Diesel fuel to flush sludge out of a badly gunked-up engine. Run the mix for about 20 or 30 minutes at fast idle and don't put any driving load at all on the engine. Then drain and refill with fresh oil. The heavy additives like "Motor Honey" or STP just don't make much sense to me. A little Marvel Mystery Oil to free up a sticky hydraulic lifter might be OK, but I've never seen one of the "overhaul in a can" treatments do much good in the 50-something years I've been tinkering with engines.
Jerry

Fox, I used rislone ring seal on my wife's camry. Hasn't smoked in over a year.

Can't hurt to try it I guess. The engine wasn't smoking before I disassbled the body and interior. Thanks

Static compression ratio × atmospheric pressure = cranking pressure only by accident.