Guys, Help! but be gentle.....
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From: G-burg area in PA
Guys, Help! but be gentle.....
I recently found the ID tag for my motor, which i thought to be a 390, but the tag says it's a 360! The pistons were stamped 390 when i pulled and replaced them with new ones. Do I have a 390? My machinists gave me the right parts and checked to see it was a 390, because thats what i told him it was, but he didnt specifically say if it was or not, but i did get 390 pistons. How can i be sure?
Thanks
Thanks
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From: Evanston, WY
Measure the stroke. It is the easiest way to make the determination. 3.5" = 360, 3.78" = 390. Also, with 390 pistons on a 360 crank and rods, the piston will stick out of the bore slightly at the top of the stroke.
-Scouder
-Scouder
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From: G-burg area in PA
ok, so i might have screwed myself here, i got the motor back together, so in order to measuer the stroke i have to take it back appart, i turned the motor a couple of times by hand before i put the heads on, and i thought clearance was ok, but now i cant get the motor to turn, i broke a breaker bar (thought it was because of high compression and cheap taiwan steel), but now i think i have the wrong pistons on the motor, f*#@ i just cant win with this truck, guess its gonna take more time and money, wouldnt my machinist know that the pistons were wrong for the motor? he did measure them, i gave him the original piston so that he would know which ones to get, is he partially at fault for this?
Lead Driver
Joined: Apr 2001
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From: Texas
You can measure thes stroke withot taking it apart. Simply use a rigid thin object to measure the stroke through the spark plug hole. Do a search in this forum for more detailed info. There's several ways to measure it. Maybe even in the FAQ at the top of the forum.
I'm guessing you do have a 390 that came later in the trucks life.
I'm guessing you do have a 390 that came later in the trucks life.
Posting Guru
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From: Evanston, WY
I just re-read your post. If you can't turn the engine over with the spark plugs out, using a breaker bar, you have a SERIOUS problem that DOES justify pulling it back apart. I could turn my 12:1 511ci engine over with a breaker bar with the plugs IN, if I let it bleed down for a few seconds.
Before you tear anything apart, calm down, and analyze the evidence you have at hand. Ask yourself questions like:
Does it turn partway then stop?
Is it difficult to turn no matter which direction?
Is it still difficult to turn if you remove the pushrods?
Did the engine turn freely before putting the heads on?
Generate some symptoms and it will be easier to build a logical box around the problem.
-Scouder
Before you tear anything apart, calm down, and analyze the evidence you have at hand. Ask yourself questions like:
Does it turn partway then stop?
Is it difficult to turn no matter which direction?
Is it still difficult to turn if you remove the pushrods?
Did the engine turn freely before putting the heads on?
Generate some symptoms and it will be easier to build a logical box around the problem.
-Scouder
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Elder User
Joined: Nov 2002
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From: USA
Could just pull the oil pan and check what #'s are on the crank. If you don't have Steve Christ's book on rebuilding the FE that lists all the part #'s, post the # you find on here and someone will tell you for sure.
Jordan
Jordan
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Senior User
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From: G-burg area in PA
Originally Posted by Scouder
I just re-read your post. If you can't turn the engine over with the spark plugs out, using a breaker bar, you have a SERIOUS problem that DOES justify pulling it back apart. I could turn my 12:1 511ci engine over with a breaker bar with the plugs IN, if I let it bleed down for a few seconds.
Before you tear anything apart, calm down, and analyze the evidence you have at hand. Ask yourself questions like:
Does it turn partway then stop?
Is it difficult to turn no matter which direction?
Is it still difficult to turn if you remove the pushrods?
Did the engine turn freely before putting the heads on?
Generate some symptoms and it will be easier to build a logical box around the problem.
-Scouder
Before you tear anything apart, calm down, and analyze the evidence you have at hand. Ask yourself questions like:
Does it turn partway then stop?
Is it difficult to turn no matter which direction?
Is it still difficult to turn if you remove the pushrods?
Did the engine turn freely before putting the heads on?
Generate some symptoms and it will be easier to build a logical box around the problem.
-Scouder
Posting Guru
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From: Evanston, WY
Originally Posted by novadragman2005
I could not get the motor to turn at all in either direction, it did turn with the heads off, i did not try to the the motor with the pushrods out, if this helps give you an idea at all
-Scouder
Postmaster
Joined: Nov 2002
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From: Littleton, CO
Originally Posted by Scouder
Before you tear anything apart, calm down, and analyze the evidence you have at hand. Ask yourself questions like:
-Scouder
-Scouder
--Mike
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From: Evanston, WY
Originally Posted by Mike G
Ditto... Take a deep breath and step back. Also, is the motor back in the vehicle or is it on the stand still? If you put 390 pistons in a 360, your not having clearance issues as the 360 has a shorter stroke and the 390 pistons have a shorter compression height (than 360's). There is something bound up in there that occurred after you put the heads on. Start with the rocker assembly and work backwards, checking for freedom of movement with each step. Report back, we'll help nail it down.
--Mike
--Mike
My bad. I was thinking of 360 rods on a 390 crank causing the piston to protrude above the deck.
That leaves valvetrain as the likely culprit.
-Scouder
Postmaster
Joined: Nov 2002
Posts: 3,447
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From: Littleton, CO
Originally Posted by Scouder
Mike,
My bad. I was thinking of 360 rods on a 390 crank causing the piston to protrude above the deck.
That leaves valvetrain as the likely culprit.
-Scouder
My bad. I was thinking of 360 rods on a 390 crank causing the piston to protrude above the deck.
That leaves valvetrain as the likely culprit.
-Scouder
Not meant to correct, just to calm the DragMan down a little...
That could very well have been happening, I was just analysing what was presented. DragMan, were the pistons coming to or over the top of the block when it was rotating freely? If so, then depending on how far, you can compensate by adding a .020 copper shim gasket to your .040 FelPros to fix the issue.
--Mike