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Harmonic Balncer query here. My '77 F-150 has an original to it 351M and C-6 Automatic. D5AE-BA
Looking through my 400 stuff, taking stock, I look at it's balancr. D1AE-AA It came out of a '79 F-350 Wrecker with 4 speed. It weighs 9 pounds. I once looked them up on Damper Doc but that sight seems to have evaporated. I know that I had intended to use it, but now I wonder. It's not the fattest one, but it is a little thicker than the one on my 351M Auto.
Any issues or suggestions to track down whether I'll be OK using it?
I think the answer is yes.
I did find this statement.
Originally Posted by http://grantorinosport.org/bubbaf250/parts/parts04.html
Note: Both 351M and 400 engines have the same 28 oz-in crankshaft imbalance, so all M-block flywheels have the same balancing counterweight, and they can be interchanged without vibration or balance problems.
If you find one look the rubber over closely for any cracks. The rubber in them is so old now that I don't reuse them.
Thank you Sir .........
The one in my basement from the 400 has been in a cool dehumidified basement in a box up on a shelf the last 30 years, it looks fine, no cracking. I was just trying to confirm my recollection that I can use it with the C-6.
I don't know that I will need something different. I know what I have is a good one, and it's seal surface is really nice too. I know they both have that 28 oz counter weight.
I know that either will "fit" in place of the other, just wondering if there'll be any balance issues.
The one on the truck has always been on the truck. It may be that I'd be best off using it with the Auto flexplate. I think the 351M auto one is likely the 7.3 pound one as it is thinner than the 9 pound one that came with the 400, and I know therer is a really fat one that weighs 10.4 pounds.
Since my 351M with auto uses the overall lighter one with automatic, maybe that's the one I should run with the 400 in front of same automatic?
I agree you should be able to use it
Just get them both on the ground for an inspection and make sure the weight looks identical and in the same place
It should be, and you should be good to go
Good luck
Thank You Manimechanic007 ... I've compared them as best as I could laying on the ground, with the 9 pound one beside me, turning the engine with long ratchet, only difference I can see or detect is the 9 pound 400 HB has a thicker/heavier outer ring. The counter weight cast in is in the same place and is the same dimension. Below is a photo posted by "Filthy Beast" some time long ago along with his post then. I do not have the link. I have added some notes as to mine off to the side.
Originally Posted by Filthy Beast
...
A manual trans' engine rotating assembly consists of (from front to back) the balancer, crank (a 400 crank is heavier than a 351M, and I'm leaving out the con rods and pistons because the rods are the same and the piston weight difference is negligible), flywheel, clutch and pressure plate.
An auto's rotating assembly has the balancer, crank, flexplate and torque converter. All of which is lighter than the manual's rotating assembly. You probably know this from hefting the various parts in replacing 'em.
Ford engineers decided (I think) that the stick engine needs more overall weight on the balancer than an automatic to keep a smooth running engine because of the weight difference in rotating assemblies. They all have the same 28 oz external weight - on the balancers and flywheel or flexplate. The overall weight of the balancers are different depending on cubic inches, automatic trans or manual trans.
Using the 400's stick balancer's pound and some change (heavier) difference in an automatic set up makes the crank's snout heavier than engineered for an auto trans.
My opinion, yes, it makes a difference.
Makes sense to me. I guess what I find most odd is the one I have that I know came off of a 400 from a '79 F-350 wrecker with manual trans matches the one he showed for a 400 with automatic. I think it's just possible that the wrecker had been the recipient of a rebuilt 400 sometime in the past, my buddy whome gave it to me was not sure if his Dad had ever swapped it out before? If such be the case, then I have the correct HB for a future 351M to 400 auto swap already in my hand just by luck.
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