long story!! ok here goes. My original engine in my 79 bronco was dying fast (351M). It was way gone for a normal rebuilt so I bought another engine (M) this one was bad also so did the deal with the rebuid. The dampner for the bought engine looked real bad so we matched it with the one from the original engine looked the same so we put it on, the dampner on the bought engine wasn't on the engine it just came with it (used). We used the fly wheel from the bought engine. The dampner has a big weight on it and the fly wheel doesn't. The fly wheel from the original engine has a weigth on it. I've been told thiers 6 different dampners for the 351's and at least 2 maybe 3 for the M engines. We've done the junk yard and got another dampner but no way would it fit on the engine. It vibrates wicked bad!! My question is how do I figure out which dampner to use with this fly wheel or are the dampners/fly wheels a matched thing?? Since the dampner has a weight on it does the fly wheel have to also?? or can I change the dampner to match the fly wheel and how do I figure that out???? Need help bad!!

 

I would think all 351m's would have the same dampner. The 400 on the other hand would have a different one. Could you have a 400? At any rate I would be surprised if there were any other differences except for the engine size.

1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

 

chilinetc,

The best way to make sure you have the correct balancer is to determine if the engine is a 351M or 400. The only way to do that is to find the crankshaft casting number on the first throw or counterweight of the crankshaft (toward the front of the engine). You have to at least drop the oil pan to do that. Once you know which engine you have, you can determine the correct balancer.

A 400 crankshaft should have the casting code "5M" on it. A 351M crankshaft should have the casting code "1K" on it.

Ford lists part #D5AZ-6316-A for the 351M balancer, and I believe it is still in production. The 400 balancer is part #D2AZ-6316-C and it is obsolete, but you can still get them from some obsolete parts dealers like Green Sales. There was also a truck balancer part #D7TE-6316-A, or -BA, but I can't find the specific application (351M or 400) for it. That part is obsolete as well.

If you clean the outer metal part of the balancer, you should find a stamped part number, probably only the first four characters and the revision code (e.g., D5AE-A). That will identify the part you have. You can also identify a junkyard balancer the same way if you're looking for one.

All M-blocks (351M/400) used the same flywheel (original part #D7TE-6375-A, or updated part #E5TZ-6375-H) and the same flex plate (part #D1AZ-6375-A).

BubbaF250

1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.

 

Not all 351m's have the same dampner. I was told by the ford dealer himself.... It is a 351m we just rebuilt it. If it was a 400 i think we would have known that. Any ideas on my question about the dampner/flywheel thing???

 

[font size="1" color="#FF0000"]LAST EDITED ON 02-Jun-01 AT 08:22 PM (EST)[/font][p]Dealers have been known to be wrong. They hire the same "parts monkeys" as everyone else. Look at it another way, why would a motor which had virtually no changes to it during it's entire production run have different dampers?

I believe bubba answered your question, sorry you didn't like it...

 

It is a 351m we just rebuilt it. If it was a 400 I think I would have known. I was told the 351's have 6 different dampners from a repitbal ford dealer. So any thoughts on my dampner/fly wheel relationship??

 

chilinetc,

I guess I couldn't quite follow your long story and I didn't understand your question. Let me try again.

Since you know you have a 351M, I suggest you check the part numbers on the flywheel and harmonic balancer you have now. Your flywheel should be either #D7TE-6375-A or #E5TZ-6375-H. If it is any other number, you probably have the wrong flywheel.

Check your harmonic balancer number also, using the technique I suggested above. According to my Ford parts reference sources, there are only two possible 351M harmonic balancers, #D5AZ-6316-A and the #D7TE-A (or D7TE-BA). I know the D5AZ number is correct, and it is still available from Ford, unless it was recently obsoleted (like in the last 3 months).

I can think of only three reasons you would have a balance problem:

1. There is an internal balance problem inside the engine (e.g., a bad crank, piston, or rod), which would require opening up the engine to find and correct.

2. You have the incorrect flywheel or balancer, which you can verify by checking the part numbers.

3. You have a defective harmonic balancer, which you can find by checking for movement between the inner and outer metal parts of the balancer.

I can't explain why a dealer would tell you there are 6 different balancers for the 351, unless he was referring to all three different 351 engines (351W, 351C, 351M), which all use different balancers.

Check the part numbers on the flywheels and harmonic balancers you have and post them here. I'll look up any numbers you have that I haven't listed.

Good luck.

BubbaF250

 

Thankyou...... I didn't mean to offend anyone but I was told by two different people about the dampners. I understand what your saying about the 'parts monkeys' But I was also told by a well known engine rebuilder in the area. I will look for the part numbers. I take it I have to take the fly wheel out to get the part number on it??? Thier shouldn't be any internal damage considering it's only been back on the road for a couple of months from the rebuilt?? Thanks again and I'm sorry if I offended anyone...
chilin

 

I wanted to say thankyou for all your info! I checked the fly wheel from the original engine and the numbers didn't match up. They were painted on and I didn't find any others. Will they be painted or stamped. Had planned on taking the damper off that's on the engine to determine if that's right,but got side tracked onto another vehicle with problems, then I was just going to buy the right fly wheel and put it in hoping that would solve the problem. do you know anything about the weights on the damper/flywheel.?? the damper has a weight and the fly wheel doens't. But the fly wheel I took off the origanal engine has a weight?? Thanks again I probally won't be getting back to it till next weekend so I wanted to let you know I apprieciated the info!!!
chilin

 

>I checked the fly wheel from
>the original engine and the
>numbers didn't match up.
>They were painted on and
>I didn't find any others.
> Will they be painted
>or stamped.

chilinetc,

The flywheel part numbers are raised numbers in the unfinished casting surface, just like on the engine block, manifolds, and other cast parts. They are on the non-machined side, opposite the clutch, on the side facing the back of the engine block. You'll have to dismount the flywheel from the engine to find the number.

>Had planned on taking the damper off
>that's on the engine to
>determine if that's right

The harmonic balancer part numbers are stamped into the outer ring of the part, just like the timing marks. You don't have to remove it from the engine to see the part number. Every M-block balancer I've seen has just the application-specific codes (e.g., D5AE-A), not the complete number. The part number is usually located just to the side of the timing marks.

>do you know anything about the
>weights on the damper/flywheel.??
>the damper has a weight
>and the fly wheel doens't.

Flywheel counter weights are visible on the non-machined side facing the engine. They appear as thicker and thinner areas (raised and lowered surfaces) on the casting. There are may be shallow drilled out spots in the flywheel from balancing.

All M-block flywheels have weights because the engines were all externally balanced.

Post any part numbers you find if you have any question about their application.

BubbaF250

 

Ok here goes another long story I hope you dont' mind. This is from my dad. We are trying to figure this out.... with your help!!
Original engine in bronco went south. It had a flexplate with a weight attached and a front pully also with a weight as part of the pully/dampner.
The engine we bought came out of a stake body truck. The flexplate did not have any wieght attached to it. The front pully was missing. Someone in the salvage yard placed a pully on top of the engine so it would be complete. The pulley was the same as the one on the original 351m.
If there wasn't any weight on the flexplate could the engine have a different crankshaft?? Could it be "internally" balanced and not require weights on the flexplate and pully??
Thanks for patience on this matter we are at a loss!!
chilin

 

chilinetc,

All M-block engines (351M/400) are externally balanced.

I suspect that the engine you got from the salvage yard had either the wrong flex plate or the wrong harmonic balancer, or both. Those could have been switched from the original parts at some time prior to your acquisition. It is also possible that the flex plate on the salvage engine was damaged or had the weight broken off.

Unless you had balance problems with the original engine in your Bronco, you should be able to just re-use the flex plate and harmonic balancer from the Bronco engine on the rebuilt engine, especially if you know they are both 351Ms.

Good luck.

BubbaF250

 

Bubba
Ok I finally got a chance to take off the dampner. This is what is on it...... on the side etched into it is D5AF-BA with a long space then it says B9, cast into it is 6316 on the top of the dampner and RE casted onto the bottom. We started the truck to see if the vibration was more or less .... It was more big time!!!! The only thing we seem to come up with is to use the flex plate that is matched with the dampner both off the original engine..... the flex plate that is on it came with it. Their was no swapping it, it was taken out of the truck so it hadn't been changed.... We're trying to not have to do the hardest thing to make it stop vibrating but it seems like we're gonna have to!! Thanks for the info.....
chilin