Zf swap
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Joined: Sep 2019
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Zf swap
Hello all, new member here. Not sure if this has been settled, but here is my question. I have a 78 f250 supercab with a 460 and C6. I picked up a ZF s5-42 out of an 89 f250 with 460 from the local U-Pull&Pay for a ridiculous low price. I have the flywheel from the 89, but all the local machine shops want $300+ dollars to machine it to neutral balance for my 78 460. I also have a 390 flywheel, which from my understanding will bolt up to my 460. The 390 flywheel has 184 teeth, whereas the 89 460 flywheel has 180. Can I put an 180 toothed ring gear on the 390 flywheel to avoid starter issues and use the 89 starter? Also, what clutch? I was really hoping to get the 89 flywheel machined so I could just use that clutch and starter with now issues. Comments? Suggestions? Tia
Laughing Gas
Joined: Dec 2004
Posts: 754
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From: Idaho
I may be wrong but isn't a 78 460 externally balanced and if it is then the 390 flywheel wont do you any good as it is internally balanced. look at your balancer and behind it, if it is external there will be a spacer with a fly weight on it, if not the fly weight won't be there just a spacer.
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Mid year '79 is when "most" 460's went to the external balance. I've checked my block numbers and for the flyweight on the harmonic balancer space and mine is definitely internally balanced. Still trying to find a machine shop to machine and balance the '89 flywheel. Especially as how the 390 flywheel I have seems to be about 15 lbs. Lighter than the 460 flywheel. It'd probably rev faster, but I'm thinking the weight would be good for slow speed work.
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Yes, that's what I thought about the revving faster, but with torque loss. I'm going to try a few more machine shops and see if I can find cheaper. They keep telling me they can't just turn and balance the flywheel by itself, that they have to have a crankshaft and all the Bob weights and so forth to do it. Seems they should be able to turn the flywheel by itself, but I am only an amateur when it comes to machining. I will keep posting updates as I go. Eventually my plan for the truck is to swap in a Cummins 4bt and convert it to 4wd. Going to box the frame and see if I can use the stock coil buckets on the frame, chop the 2wd crossmember out, fab in a new crossmember and sling some f350 Superduty disc brake axles under it. But getting the 5-speed in there is definitely happening as soon as I get all the parts together. I have everything but the flywheel issue, and a pedal swingset.
Laughing Gas
Joined: Dec 2004
Posts: 754
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From: Idaho
NO they don't!! my guy does it all the time without the crank. all they have to do is take the weight out on the flywheel there is a triangle weight machine it out and balance it or drill the thing and balance it I have had it done many times by the same guy with no problems!!!!! at all. find a real machinist! it would probly be be better with the crank but like i said no problems and 19 conversions to 460's
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