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Discussion Starter #1
Hi
Are the clutch pressure plate mounting holes the same on a 289 28 oz and a 302 50 oz flywheel ?
Thanks
 

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No. You need to use a conversion or crossover wheel to do that.
 

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Discussion Starter #3
Thanks
I thought maybe they were the same as I am looking at a clutch set that says it fits a 289 and 302. Perhaps the listing is wrong.
 

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The difference is a 302 can be from 1968 through to 1981 with 28 oz imbalance.

The 302 50 imbalance carries you through to present.

That is why a clutch can be listed for both 289 and 302 and still not be correct for you.
 

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Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
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That's why a lot of parts vendors will refer to the post 1981 engines only as "5.0's", to help avoid this type confusion.
All 5.0's (be they 255's or actual 302's) use the 50 ounce imbalance. All 260/289/302's and 351/5.8 Windsors use 28 ounce imbalances.
 

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All 5.0's (be they 255's or actual 302's) use the 50 ounce imbalance.
No, because Ford started calling the 302 a 5.0 in 1978 but did not switch to 50 oz imbalance until 1982.
 

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Discussion Starter #7
Ok so pre '82 289 and 302 pressure plates will interchange but post '82 302 pressure plates have a different hole ctrs ?
 

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Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
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Ford started using the 50 ounce imbalance in 1980 along with the debut of the marvelous 255 cubic inch engine they called a "5.0". Started. We don't want to get into exactly which and what. There's evidence that "leftover" 28 ounce 302's were used in trucks up into early 1982.
The practical side of this is if you are working a late '79 to early '82 302/5.0 and need a flywheel you have to just ignore what is "supposed" to be in there and match up to what you actually have. I'm old enough to remember when that was a big deal because even the Ford parts counter guys couldn't tell you which engine you were supposed to have well into the '80's.
What Ford called the engines in 1978 is immaterial to me, in 1980 thay called that awful 255/4.2 a 5.0 too. In 1978 it was one of the 1968-81 302's. If you look up stuff on Autozone.com you'll see they refer to all 302 engines 5.0's all they way back to 1968. Up to the customer to know that though both engines have the same displacement they are somewhat different. Knowing is the actual key, other than that it's really a "you say tomato, I say tomahto" sort of thing. Post 1980 I say 5.0. Mostly.
 

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DONT PUT A 50oz flywheel on a 28oz Engine or vise versa.

Just had to say that :)
 

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Gypsy, are you saying the 5.0 was a50 oz imbalance in 1980 or the switch to 50 oz imbalance first first done on the 255?

I have never heard of the 255 being called a 5.0.
 

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Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
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The 50 ounce changeover began in 1980 and most vehicles changed, like Mustangs for example. But there were drag alongs like some full-sized Fords and trucks in particular that didn't get swapped. Kind of like how Ford used up the rest of the 289's in 1968 before everything got 302's.
Back in the day many a proud owner of 1980-to early 1982 "5.0" Mustang was disapointed and a bit ticked to discover their Ford-termed 5.0 was in fact a 4.2.
 

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Hate to be dumb but can someone explain what exactly the "imbalance" is??
Sure! The smallblock Ford crankshaft was so compact they couldn't get it to balance, so the needed weight was added at each end to the harmonic damper and flywheel. For many years this extra weight was 28 oz. In the early 80's, the crank was reconfigured, and the weight increased to 50 oz.



 

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Sure! The smallblock Ford crankshaft was so compact they couldn't get it to balance, so the needed weight was added at each end to the harmonic damper and flywheel. For many years this extra weight was 28 oz. In the early 80's, the crank was reconfigured, and the weight increased to 50 oz.



Thanks a million - makes perfect sense!!
 

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That is cool info. I didn't know that. I always 'assumed' the balance switch happened in 1982
 
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