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Discussion Starter #1
I have never been able to properly identify what my engine was made of. I know 2 things :
  • The engine was rebuilt in 08 by the PO. I had a receipt that detailed it, but at that time didn't know how to properly read it, so I gave it to my mechanic, who never gave it back to me.
  • A few years ago, the car needed a new flexplate. I gave it to that same mechanic who told me he had to get a custom flexplate done. He also said the engine was original and had a bunch of non-stock parts. I recall him saying something about a high compression ratio and a mild cam. How I wish I had known what that meant then...
I've moved since and haven't been able to reach the guy, so I unfortunately don't have much to go on with.

I'm getting ready to do my T5 swap and the only parts I haven't ordered yet are the flywheel and a clutch kit to go with it. The reason is that I removed the inspection plate the other day to get a look at the flywheel and the counterweight was BIG. It was spread over roughly a quarter of the flywheel. I was not expecting this. I assumed I'd see a small 28oz counterweight.

I know that pre-1981 302s had 28oz flexplates, 1981+ and aftermarket ones had 50oz ones. Is it possible that an aftermarket 302 crank that requires a 50oz imbalance flexplate was put in my 289 during the rebuild?

Thanks,

Leo
 

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That "imbalance" doesn't denote how BIG the balance weight actually is but, rather, the correction of non-sinusoidal vibration measured in oz-in. that determines where and how much weight needs to be added.

Is it possible a 50oz 5.0 crankshaft was installed? Sure, if the block was machined to accept the one-piece-rear-main seal and retainer...but why would someone WANT to?
 

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Just about anything is possible. I have a 28 oz crank going in a 93 block which has a 1 piece rear main seal which is the opposite of your situation (maybe). The crank company said that the crank would work in a 2 piece or 1 piece seal block with no modification needed.

You should be able to have the balance verified on your flexplate at a machine shop.
Some eons of time ago I remember talk about just cutting the back lip off the 50 oz cranks to go in a 2 piece rear main seal block. It was relatively cheap for a machine shop to do but I am not even sure now that this was actually required from looking at my crank and my old versus my new block. Maybe it was.
 

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The lip thing is apparently some sort of oil slinger. It may be the other way around. Cutting the lip off an early crank to go in a later model block with a 1 piece seal. I can't remember, sorry.
 

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The lip thing is apparently some sort of oil slinger. It may be the other way around. Cutting the lip off an early crank to go in a later model block with a 1 piece seal. I can't remember, sorry.
yep. the cranks with a 2 piece seal had the oil slinger, and it gets machined off to put it in a one piece seal block.
 

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Discussion Starter #6
Is there any way to tell which crank is in there from the outside? Assuming I remove the transmission and flexplate of course.
 

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Is there any way to tell which crank is in there from the outside?
You can measure stroke thru the spark plug hole to determine if you have a 289 (2.87 stroke) or 302 (3.00 stroke). Assuming you have a factory crank all 289s were 28 in-oz. All factory 302 cranks before 1981 were 28 in-oz. All 302 cranks 1981+ were 50 in-oz. One piece main seal was incorporated in 302 cranks/blocks starting Dec 1 1982.

Keep in mind that a 289 converted to a 302 would need the '2M' 302 (3.00 stroke) crank and 302 length rods (5.090).

Good luck
Paul
 
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You could have the flexplate match balanced. I have done this before. But you need a good machine shop. You could also fill the internals of the engine with 50oz pieces, but this wouldn't be the right way to choose parts . . .building an engine just to use a certain flexplate.
 

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Discussion Starter #10
You can measure stroke thru the spark plug hole to determine if you have a 289 (2.87 stroke) or 302 (3.00 stroke).
What tool should I use to do that?

check your crank damper to see if it is 28 or 50 oz.
IIRC the weight is on the back on the damper, does that mean it needs to be removed to check the imbalance?
 
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A small piece of dowel, or a pencil.

if you have some artist paint brushes, the opposite end works. Just something narrow that won't damage anything.
 

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What tool should I use to do that?
Keep in mind that the difference in stroke between a 289 and a 302 is only 1/8th of an inch so it must be measure carefully. But it can be measured if you take your time.

1. Remove all the spark plugs (makes cranking the engine over by hand easier) and disconnect the battery negative cable (makes killing yourself less easy by preventing the engine from cranking thru the starter).
2. Insert a small (ie 1/4") wooden dowel or similar into a spark plug hole until it rests on the piston. Be sure its long enough so some sticks out of the hole by several inches.
3. Slowly crank the engine clockwise by the crankshaft bolt until the dowel moves down to its lowest point. This is a bit of a trial/error procedure but you should be able to determine within a very small margin. Have a friend help if needed.
4. Mark the dowel with a pencil at a reference point near the spark plug hole (a machined edge, etc). Now crank the engine by hand clockwise until the dowel is a its highest point (should be 1/2 turn). Mark to the same reference point/edge.
5. Remove the dowel and measure between points. That is the stroke.

289 stroke = 2.87
302 stroke = 3.00

Like I said previously 302 cranks can be 28 oz (68-80) or 50 oz (81+).


IIRC the weight is on the back on the damper, does that mean it needs to be removed to check the imbalance?
Pic below: 28 oz on L, 50 oz on R. Note the thickness of the outer ring (thicker on 50 oz). If you get under your engine and look between the damper and the oil pan you should be able to see the back of the damper to compare.


Good luck
Paul
 

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Discussion Starter #13
Thanks for the info, I'll take a look at all this over the week end. I'll post a picture of the damper if I'm still not sure which one I have.
 

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Discussion Starter #15
Last night I manually turned the crank and got a few pictures. First, the flywheel counterweight :



It looks pretty big for a 28oz, doesn't it?

I also took pictures of what I assumed was the balancer, although it looks nothing like the ones in Paul's picture. I assume it's aftermarket. I did my best to show the size of the weight by getting 2 angles. The weight takes exactly half of the balancer (it's a half circle) and is bolted on by 2 bolts.



So it seems to me this is the sort of balancer I have :



Which is a 50oz imbalance balancer. Aside from the size of the weight which is similar, mine also has the 2 small holes (top left of the picture). The 28oz one has 4 and looks like this :



I have yet to measure the stroke, but in the meantime, thoughts?
 

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Assuming your engine was not vibrating before, the only way to know for sure is to take your flywheel? or is it a flexplate?,,,regardless, take whatever it is to a machine shop that can tell you what the balance is on it. You need to call around and find one that can do this. Some machine shops do not balance assemblys and some do. They can tell you what it is and then you know what you need to get. If it is something other than 28 or 50, they can also match the balance of your new flywheel to what your old "whatever it is that you have" is balanced to. The only way it would be other than 28 or 50(not discussing internal balance), would be if what you are running was custom balanced at some point and they wound up having to adjust the thing on the back. You mentioned both flexplate and flywheel in your posts so I don't know what it is that you have. It doesn't matter with regard to this balance issue though.
 

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Discussion Starter #17
I finally took out the flexplate :



I haven't found a shop that could tell me what the imbalance was. Is there any way I can do it myself? Looks to me it's 50oz, but I can't be sure.

Also, when putting the new flywheel in, do I have to bolt it on with the weight at the same location it was when I took the flexplate out?
 

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Look at the back of the block. Does it have a one-piece rear main seal retainer? If not, you can be reasonably sure it's 28.8 oz/in. It's kind of hard to add the lip to a 5.0 crank.
 

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I finally took out the flexplate :



I haven't found a shop that could tell me what the imbalance was. Is there any way I can do it myself? Looks to me it's 50oz, but I can't be sure.

Also, when putting the new flywheel in, do I have to bolt it on with the weight at the same location it was when I took the flexplate out?
You wont be able to tell by just *looking* at it. The inbalance is in in-oz which is a function of both the amount of weight and the distance it is from the rotational center.

Flexplate/flywheel can only go on one way. One of the 6 holes in the flex/fly and crank is not symmetrical.

Paul
 

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Look at the back of the block. Does it have a one-piece rear main seal retainer? If not, you can be reasonably sure it's 28.8 oz/in. It's kind of hard to add the lip to a 5.0 crank.
Have to disagree with you again Bartl. Ford changed from 28 to 50 in-oz on 302/5.0L for 1981. The one piece seal was instituted on Dec 1 1982. So engines made from ~9/81 - 12/82 were 50 oz with 2 piece seal.

Paul
 
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