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Overbore question

754 Views 8 Replies 4 Participants Last post by  LSG
Just got done mic'n my 84 Windsor block. It's definitely 0.040" over... most of the hole are at 4.0405 to 4.0413 and one a little tight at 4.0395. Just wondering if that's an issue. Can't find specs of max cylinder to piston clearance... Probably just looking in the wrong places. I want to go 393 or 408 stroker for my 66 F250. TIA.
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Piston to cylinder wall clearance depends upon the piston type- forged, cast, hypereutectic, etc.
My intent is to go forged.
My intent is to go forged.
Check the website of the piston manufacturer you prefer and see what they recommend.
Tweet, that tighter hole is going to have to be homed larger to match the rest. Do you have the pistons yet ? if you have .040 pistons already, and you actually NEED .041 or .042 or .043 pistons, you can do that without customs, and no, I don't mean knurling. Whatcha got ? LSG
LSG, don't have any of the rotating assembly yet. Shopping different kits at the moment. Since I'm not looking for anything past 450hp and gobs of torque (it is a 5000lb truck after all) I'm limiting myself to a cast crank, longer rod combo. I have a set of redone TFS High Ports to go up top, Edlebrock RPM, & link bar lifters for roller cam (still need to pick one). Biggest issue I'm running into now is finding a machine shop around me to go through the block, do balancing or just check stuff out.... They're dropping like flies and the few that are left are looking for exorbitant money for minor work. Took a finished 289 in four can bearings and they wanted $300 plus I had to wait 4/6 weeks.
As long as the cylinder out-of-round (eccentricity or "egg shape") is less than .005" and the taper (from top to bottom) is less than .010" then hone it and go, as long as the dimensions after a final hone don't exceed 4.042". Select a piston that will provide the required piston-to-cylinder-wall clearance needed for the piston being used.
Woodchuck, that's the info I was going for. When I mic'd the cylinders I checked in 3 locations at three different angles (9 readings total) and all are consistent with no taper. They just vary cylinder to cylinder. I know it was a rebuilt engine from Jasper put in a few years back. Still has the warranty stamping numbers and overheating tag on it. It came out of my uncle's old van and barely did 10K since installed.
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Tweet, are you saying the engine RAN with the bores so wildly different ? ! If thats the case, EVERY measurement on the work Jasper did is suspect. I wouldn't trust any of it. And forget about 'kits' - there really isn't any such thing. If you are trying to stay within a limited budget, you should get new ARP bolts for the 351W rods and get a 3.85 crank and look for 302 pistons that will give the compression you want. when you have your new pistons IN YOUR HANDS, the machinist can measure them, THEN the block can be honed. LSG
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