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Discussion Starter · #1 ·
I live in the UK and am very fortunate to have a lovely 1965 Mustang Coupe and a new 2016 Mustang GT. I'll post an intro soon with some pics.

But first I'm seeking some advice: My '65 looks and drives great, but it's always had a nasty vibration from the engine, which really resonates at speed. It has a 347ci stroker engine based on a 1987 302 block (E7TE), mated to an AOD transmission, and I'm wondering if a previous owner may have used an incorrectly balanced flex-plate or damper.

The flex plate is marked EOSP-AA, which I believe is a 164 tooth flex plate with a 50oz imbalance. But the damper is marked D2TE-6316-DA, which I believe could be a 28oz imbalance (as D2 means 1972 and I think that all 302’s prior to 1982 were 28oz). Clearly this doesn't seem right!

If I can identify the crank I can find out if it is supposed to have a neutral balance, a 28oz balance or a 50oz balance. Then I can change out the damper or flex-plate and hopefully stop the car rattling my teeth as I drive along!

I pulled the oil pan to look at the crank, but the only numbers I could see are 'USA M88 266' and 'C20 EB'. It's supposed to be an Eagle crank, but I can't find anything that matches these numbers. The counterweights are quite big with four deep holes drilled at each end.

Can anyone offer any suggestions as to what this crank might be, and whether my belief that the damper might be a 28oz unit is correct?

Thanks,

Adam.
 

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Welcome! Your '65 sounds like a sweet car. I can't help, but I'm sure someone will soon.

Post up some pics of your rides when you get time.
 

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I'm betting that you have a cast crank which requires a 28oz balance and means you need a different flexplate. If it's a forged crank it could be zero balanced, but you mentioned that you know that you have a 28oz damper and the offset damper/flexplate combo. on a zero balanced crank would knock the fillings out of your teeth.
 

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Discussion Starter · #4 ·
I agree - in theory. I figured that the engine builder would have been unlikely to mismatch the crank and damper, but someone could have changed the transmission at a later date and used the wrong balance flexplate. The problem is that I really need to prove this one way or another so I can figure out what needs changing.

According to Eagle's website, cranks for 302's could be either 28oz, 50oz or zero/neutral balance: Eagle Specialty Products, Inc.. But it look like there are only two listed for a 3.4" stroke (as needed to get 347ci). These are both 28oz (part no.'s: 103023400 and 103023402).

How can I identify the crank, given that I only have the following reference numbers: 'USA M88 266' and 'C20 EB'? I'm guessing the EB probably means external balance, which at least rules out it being a zero balance crank.

Any thoughts would be gratefully accepted.
 

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Just call the manufacturer. They should be able to verify your number in short order.
 

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The good thing is a 50oz flex plate can be lightened to 28oz. if it hasn't already been done.
 

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Discussion Starter · #7 ·
I emailed Ray at Eagle Specialty Products, Inc., but he said that the numbers I gave him didn't match anything he had, and the photos of the crank didn't help.

I've attached the photos here just in case anyone can ID the crank, but I suspect I will have to pull the oil pan again and look a bit harder for a number. Ray said the number will be on the 1st counterweight, so I probably need to turn the engine if it's not showing.
 

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The number will be on the front counter weight by the oil pump. Usually on the flat side facing forward. The rods are common Chinese imports. Often the bolts will say something besides ARP 8640. SCAT and Eagle usually out their name on the end of the bolt. That would be another clue.
Randy
 

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Discussion Starter · #9 ·
Thanks Randy. I guess I'll have to pull the oil pan again and take a better look. Maybe a job for the weekend.
 

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Discussion Starter · #10 ·
Okay, I’ve now found the part number on the first counterweight. It is: 30234005400-0. It also shows 5-09-05-090 underneath and has 2421 stamped on the edge of the counterweight.

I believe that this is an internal balance crank. So the question is, what are the correct damper and flexplate to use with this setup?

The car currently has a 50oz flexplate and what seems to be a 28oz damper. Could this combination ever be right - it seems very odd. Or should I replace both of these with neutral balance units?
 

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That part number is quite similar to what SCAT uses for their 4340 forged cranks. I would check with them as well. Regardless, the crank manufacturer should know what all the numbers stamped on the crank mean, not just the part numbers... :|
 

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Discussion Starter · #12 ·
Ray from Eagle has now confirmed that this could be either a 4340 which is internal balance or a cast crank which is 28oz balance.The problem is I need to know which it is, and I really don't want to have to pull the oil pan off yet again to look for more numbers.

If it is a 28oz balance do the harmonic damper and flexplate BOTH have to be 28oz balance too? Or can any other combinations ever be valid, e.g. 28oz crank and damper with 50oz flexplate?

If it is internal balance what damper and flexplate do I need? Do these both need to be neutrally balanced, or again is any other combo valid?


 

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Ray from Eagle has now confirmed that this could be either a 4340 which is internal balance or a cast crank which is 28oz balance.The problem is I need to know which it is, and I really don't want to have to pull the oil pan off yet again to look for more numbers.

If it is a 28oz balance do the harmonic damper and flexplate BOTH have to be 28oz balance too? Or can any other combinations ever be valid, e.g. 28oz crank and damper with 50oz flexplate?

If it is internal balance what damper and flexplate do I need? Do these both need to be neutrally balanced, or again is any other combo valid?
Ray's confirmation just made my head hurt. How could a company put identical numbers on two very dissimilar cranks? If it is the cast crank, both the damper and flexplate need to be 28oz.
 

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Discussion Starter · #14 ·
Yeah, me too. I really thought I'd nailed it when I found the part number, but according to Ray at Eagle, if it has a 4340 stamp on it it's internally balanced and if it has a 'C' after the part number it's a cast crank that is a 28oz balance.

The numbers I listed above were all that I could see. I don’t remember seeing anything after the part # (30234005400-0) unless I mistook the -0 for -C?

I have noticed that the part numbers listed on various websites all start with a 4 – e.g. 430234705400. However there definitely wasn’t a 4 at the start of mine.

If anyone can offer any advice as to how I figure out if it's a forged internal balance 4340 crank or a cast 28oz crank it would be much appreciated. Otherwise I guess I'll just have to buy various damper/flexplate combinations and keep swapping them out until the vibrations stop - a very expensive and time consuming way to do it!

I do have some photos I took of the crank in situ when I last had the oil pan off. Perhaps it can be visually identified to determine if it's cast or forged?
 

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I think you need to closely inspect that crank looking for traces of parting lines. Finding them, it'll be a cast. Good Luck.....
 

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From your three pictures it looks "to me" like a cast crank. The numbers are also more like a "CAT" or RPM International brand crank. They are usually 28oz.
 

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Discussion Starter · #17 ·
Thanks. Eagle is stamped on the counterweight, so it's definitely an Eagle crank. I just need to determine whether it's cast or forged to work out if it's internally balanced or 28oz.

I also think it's probably a cast crank as these are more common, so I'm probably going to try swapping the flexplate for a 28oz (and probably buying a new 28oz damper too just to be sure). The current flexplate certainly seems to be a 50oz one from the part number, so hopefully this will do the trick!
 

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"I" would do the flex plate first as it seems the likely suspect. If you do both at once you can't be sure which one caused the problem.
 
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