390 rebuild
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Senior User
Joined: Jan 2005
Posts: 176
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From: G-burg area in PA
390 rebuild
Ok, so heres the thing, im rebuilding my 390, its .030 over, and i got the pistons back in, yes, i used new over sized pistons, so now i try to turn the crank, and the mo fo is hard as heck to turn, real hard, everything is well oiled, so is this a bad thing? could this be any indication as to how much power or compression it will have?
thnx
thnx
Freshman User
Joined: Feb 2004
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I concur with the plasti guage idea. Did that when I rebuilt my MG 20-30 yrs ago. Plasti-guaged great, but hard as ---- to turn over. I had a hand crank and broke the ears off turning it over. All said and done, it ran great, for an MG ,when I finished.Happy Turning! JR
Elder User
Joined: Jan 2004
Posts: 867
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From: Eastern Pa
I would plastiguage and if the clearances are ok try it that way UNLESS you notice that it is harder to turn at one area of the rotation than the other. That could indicate a need for align boring.
Elder User
Joined: Jan 2004
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From: Eastern Pa
For the rest of your question, if you don't have the plugs in or even the heads on, your difficulty in turning has nothing to do with future power possibilities.
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Senior User
Joined: Mar 2004
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From: East TN.
do you have the heads on? if so, compression will make it harder to turn. if not as said before check clearances and possibly straightness of crank.
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Senior User
Joined: Jan 2005
Posts: 176
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From: G-burg area in PA
no heads on, clearances all good, everything lined up, i just figured that since there was so must resistance (only happened AFTER i got the pistons it) that it was a sign of possibly good compression
Elder User
Joined: Jan 2004
Posts: 867
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From: Eastern Pa
You won't have any signs of compression with the heads off. If you say it turned fine until you put the pistons in it may just be your feel compared to someone elses. I would however check you ring end gap and make sure they are not pushing out due to too little end gap.
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Joined: Jul 2003
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From: alaska
hard turning
a messy trick , that I learned was to dunk the pistons in a bucket of fresh oil prior to installing in the engine , very messy, but even with every thing tight and new the engine would still spin, and with the friction of the cylinder to piston minimalized , it was easier to pinpoint other potential problems, also made that first crank with the starter a quick one instead of hoping that enough oil would get to the cylinders before they got scored by the rings,my 2'c's 
