1978 Chrysler 85HP Powerhead Swap

topgun3690

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Got the torque value, thanks. The lapping procedure is in the manual.....you draw 3 pencil lines 120* apart on the crank taper, then slide your flywheel on and with light pressure spin it around one time. Check the marks and see how much got rubbed away. The book says if 80 percent of the pencil lines are gone then it is making good contact and is good. If not, put some valve grinding compound on the crank taper, put flywheel on an work it in different directions. Then check it again. Mine seemed ok but I did it anyway just to be sure. When I bought the PH from Franz he said I should do this since I was putting my old FW on a different PH to make sure the tapers were contacting good. Probably overkill but I said wtf....lol
 

topgun3690

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Was there a lot of rust build-up caused by the key?
No, there was no rust on the key or flywheel.....the rebuilt PH taper and key slot looked good too. Franz recommended the lapping and checking to make sure the tapers were making good contact. Probably overkill but now I know it fits right. Might help to prevent a sheared key.
 

topgun3690

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Today I completed steps 1-6 of the link and sync.....the LU is off so couldn't try to start it yet......will be installing new water pump and repairing at least one stripped bolt hole, the seventh "hidden" bolt under the exhaust snout. Got a heli coil kit to fix it, and any others I find.
For a "first start" on a rebuilt PH....any advice or warnings would be greatly appreciated. Was planning on using the break-in procedure outlined in my Chrysler manual (for a new motor) but am open to other suggestions or ideas. (y)
 

jerryjerry05

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The "hidden" bolt hole repair.
Just go the next size bolt.
Or get a longer bolt?? Or, Drill then tap and get a stainless bolt.
 

topgun3690

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F6294492.jpg87817778A1.jpg

My old PH used the thermo switch on the right, it screws in the cylinder head cover next to the top plug. The rebuilt PH came off a 1986 Force and had the one on the left, which was mounted in a special hole in the top left cylinder head and held in with a retainer clip with it's own wire that reached around to the terminal block. Is one better than the other? The old style switch(on the right) is more expensive and I had just replaced it last year. And I could use either one which is why I was asking.
 

topgun3690

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You'll get the same results.
Ok.......now, what if you used both of them.....I realize that if one goes off and the other doesn't, then the buzzer won't come on. But if the buzzer comes on....then you have 2 separate switches telling you that it is getting too hot? Not a good idea? Just thinking out loud here......
 

The Force power

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Ok.......now, what if you used both of them.....I realize that if one goes off and the other doesn't, then the buzzer won't come on. But if the buzzer comes on....then you have 2 separate switches telling you that it is getting too hot? Not a good idea? Just thinking out loud here......
Sure, but don't hook them up in series because then a faulty one will not close the circuit (ground path)
You would have to split the wire & run one to each sensor
 

topgun3690

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Sure, but don't hook them up in series because then a faulty one will not close the circuit (ground path)
You would have to split the wire & run one to each sensor
Thanks Force P.....each switch would have it's own wire hooked into the terminal block for the overheat circuit. (orange). The old style switch uses an orange wire coming out of the harness....the new style has it's own wire that goes directly to the terminal block. Would this work? Even if one of them was faulty, as long as one activated and provided a ground path, then the buzzer would work, right?
 

The Force power

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Thanks Force P.....each switch would have it's own wire hooked into the terminal block for the overheat circuit. (orange). The old style switch uses an orange wire coming out of the harness....the new style has it's own wire that goes directly to the terminal block. Would this work? Even if one of them was faulty, as long as one activated and provided a ground path, then the buzzer would work, right?
Yes, it will
 

topgun3690

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The "hidden" bolt hole repair.
Just go the next size bolt.
Or get a longer bolt?? Or, Drill then tap and get a stainless bolt.
Went ahead and tried out the heli coil kit I bought on that "hidden" bolt.....worked really well and put in a new SS bolt. LU is back on with new impeller and gasket.....will have to tweak on the gear shift rod a little to get it adjusted right, then see if she will fire up.
 

topgun3690

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Update......Today I hit the key and she fired right up. After a 30 minute run on the hose I shut it off, let it cool down, then retorqued the head bolts, pulled the plugs and checked them.....then ran it again for 30 mins. Seems to be running very well so far. Just to be sure will check compression/spark tomorrow....and if that checks out will take it to the lake next week and resume the break-in.
 

racerone

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Lapping.-----Done with valve grinding compound on the flywheel and crank tapers.----Rotate them together to get a matched fit.------As you know the flywheel key locates the flywheel for proper ignition timing.----The flywheel is DRIVEN by the locking tapers.----Hence the importance of torque on the nut.
 

Redbarron%%

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Dec 7, 2017
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A clean taper and and a wee drop of oil and they will pull down tight. Not too much oil!
Make sure you have it clean after lapping.
 

topgun3690

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Lapping.-----Done with valve grinding compound on the flywheel and crank tapers.----Rotate them together to get a matched fit.------As you know the flywheel key locates the flywheel for proper ignition timing.----The flywheel is DRIVEN by the locking tapers.----Hence the importance of torque on the nut.
I did the lapping racer.....since I was putting my old flywheel onto a rebuilt PH, just to be sure it fit right. After running for an hour, think I will check the torque on FW nut too.
 
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