ford 391 rods
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Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
ford 391 rods
are the rods used in a ford 391 the same as regular 390 rods? i have found a ford 391 engine all stock and want to use the crank,rods and block for a 390 build.
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Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
rusty,
i have no clue on the build, i found a ford 391ft enigine with np435 and pto in a field a year ago. i took the oil pan last year and never thought much about the engine until today. i am using that pan on my truck right now. i went out there and the engine was still there. so removed the heads and checked the bores and crank. it is a all original engine still has the fomoco bearings that say STD the bores still have the cross hatch on them. i plan on taking the np 435 ,block,rods,crank. i will skip the heads,manifold and pistons because they are useless for what i want. but the engine turns by hand and has compression.
i have no clue on the build, i found a ford 391ft enigine with np435 and pto in a field a year ago. i took the oil pan last year and never thought much about the engine until today. i am using that pan on my truck right now. i went out there and the engine was still there. so removed the heads and checked the bores and crank. it is a all original engine still has the fomoco bearings that say STD the bores still have the cross hatch on them. i plan on taking the np 435 ,block,rods,crank. i will skip the heads,manifold and pistons because they are useless for what i want. but the engine turns by hand and has compression.
Thread Starter
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Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
also is the 391 ft crank different in the rear? i know the front is but i plan on using the 391 cover pulley and balancer. i am just concerned about the rear. i also noticed dsc wants 275.00 for the crank and 500.00 for the block. why so much? i thought these were ultra common.
Posting Guru
Joined: Oct 2005
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here's a link with some ft info.. not much but a bit... i know very little about them
http://mustangandfords.com/techarticles/15999/
http://mustangandfords.com/techarticles/15999/
Post Fiend
Joined: Jan 2003
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From: Iowa
There has been some discussion on the 391 crank. Some say it's a little thicker at the rear, others say you can bolt up a standard FE flexplate / flywheel and it will work fine. Having never messed with one, I couldn't tell you.
The 391 block is extra reinforced, a true bulletproof piece. The crank, again, is bulletproof. Forged steel in an FE design; you're not going to break it. The regular FE cranks are known for being extremely strong, you can only imagine how the FT forged crank is...
If it was me, I'd build a blower motor out of it. Run, oh, a Paxton Novi 2000 centrifugal, methanol, forged pistons, Keith Craft ported heads with CJ valves, and lay the boost on thick!
The 391 block is extra reinforced, a true bulletproof piece. The crank, again, is bulletproof. Forged steel in an FE design; you're not going to break it. The regular FE cranks are known for being extremely strong, you can only imagine how the FT forged crank is...
If it was me, I'd build a blower motor out of it. Run, oh, a Paxton Novi 2000 centrifugal, methanol, forged pistons, Keith Craft ported heads with CJ valves, and lay the boost on thick!
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Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
ok well i had it sonic checked today. he said i can bore it to 4.13 if i wanted to. but i think i will only do a .020 over to clean it up
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Post Fiend
Joined: Jan 2003
Posts: 8,600
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From: Iowa
Possibly. My book doesn't list them. What you need to do is, measure the compression height and the dish volume. Then I can tell you real easy if they're good for anything. OBTW, are those the 3 ring or the 4 ring pistons? Some FT's had 3 compression rings and an oil ring.
Post Fiend
Joined: Jan 2003
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From: Iowa
Compression height is the distance between the centerline of the wrist pin and the top of the piston.
Probably the easiest way to do it, would be to temporarily install the crankshaft in the old main bearings, along with a rod and piston. Then you can directly measure how far the piston is below deck at TDC. Dish volume, you use the same setup, and calculate how much water would be in the cylinder with a flat top piston (easy). Then you subtract that from the measured amount, and viola, you've got the dish volume.
You know what, it's probably 1000% easier to just let the machinist do it.
Probably the easiest way to do it, would be to temporarily install the crankshaft in the old main bearings, along with a rod and piston. Then you can directly measure how far the piston is below deck at TDC. Dish volume, you use the same setup, and calculate how much water would be in the cylinder with a flat top piston (easy). Then you subtract that from the measured amount, and viola, you've got the dish volume.
You know what, it's probably 1000% easier to just let the machinist do it.