I recently helped a friend acquire his deceased father‘s F1. He’s not super savvy on old cars and he’s also not very well off moneywise so the plan was to hopefully get it running with the stock flat head but when I got it to my house I could only turn it over maybe a 16th of an inch. So I soaked it in 530 weight oil.i pulled the heads to find a very low mile std bore 8ba/8rt engine. It has zero ridge and no sludge. I mean it’s spotless with the exception of 3 rusted cylinders. All the valves are operational and I got the engine freed up after a quick home of the rusted cylinders and some pb blaster. They move freely now but my worry is with the cylinders in question. Has anyone ran Flatty’s with questionable cylinders? I plan on tearing it down and honing the cylinders proper but if we can re ring the 3 and run it that would be awesome or worst case just boring the 3 cylinders. Any input would be great Sent from my iPhone using The H.A.M.B. mobile app
Well my assumption is due partially to lack of ridge yes but also because of no oversized markings on the pistons and the truck shows 20k miles and it’s been a family truck since the early 60s so I assume it’s a stocker. But your right I need to measure it but I can’t find my caliper Sent from my iPhone using The H.A.M.B. mobile app
I've had several worn out flatheads with low compression and they all ran fine. The difference is all the cylinders were in the 65- 75 range on compression. Used a little oil but started and ran fine. Where you have three cylinders that were rusty and then honed, the difference in compression could cause problems. I wouldn't even consider boring three cylinders, bound to screw up the balance.
I would get the truck driveable and roadworthy, then drive it awhile to see just how badly that rust affected things, and if it is not good enough, then pull it and build it right.
Flatheads are tough. Get em cleaned up, put it back together see if it'll run...you might be surprised.
Years ago I knew a mechanic who ran into the same problem during WW2. New cars and trucks were impossible to buy. Even parts were in short supply. He had the job of putting an International truck back in commission, that had been left with the head off long enough to rust the cylinders. He did as you are planning to do, tore the engine down, honed the cylinders and put it back together with new rings. He said it ran well but smoked a bit for the first thousand miles then settled down and stopped burning oil. Several years later he had it apart for a valve job. All the pits in the cylinders were filled with carbon and polished smooth. He ground the valves and the truck ran for years after that. If you were building a race car or a Bonneville record car I would say bore the cylinders and put in new pistons, but for your use, honing the cylinders with a bottle brush hone and installing new rings should be fine. Note that 2 stroke engines have large holes in the cylinders and run fine. If the pits are small they will not harm the rings.
How you build an engine depends on several things 1) how are you going to use your engine 2) what kind of shape your engine is in and, 3) how much do you have to spend. Different answers to these questions will give you different methods to approach your peculiar engine. To answer your question as to if you could just bore only three cylinders to save money... yes you can. I have torn down engines in my career that had different bores and different sizes on the bearings. They were all high mileage engines that ran fine prior to reaching the point of needing repair. Some were claimed to have came from the factory with overbores on one or more cylinders or an undersized crankpin. But that was “ claimed” not proven. Sometimes you just gotta do what you gotta do! Edit: before you elect to bore only three cylinders, check to see if you can buy only the rings you need, or will have to buy two complete sets of rings. Bones
You say this needs to be low budget. How bad is the rust in the cylinders. Is it possible you could crank each piston below the rust line and ball hone each, lubricate well and put the heads back on. Fire it up and see how it works out. Give it a little time, if it doesn't make the grade you have lost nothing but a pair of head gaskets and you are back to boring as many cylinders as need be. BTW boring only three cylinders will affect the balance little to nothing at all. Again, nothing to lose and you might save your buddy a pile of money.
You have it turning over now? Pull the all the pistons out. Hone the cyls. Make sure the rings are not stuck in the pistons. Put it back together and run. If it uses a quart of oil every 500 miles who cares. If your friend puts 3000 miles a year on it it will be $30 or so for the 6 quarts of oil. That is a lot cheaper than a full rebuild.
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