Hi, thanks for the membership. I’m posting for a buddy (a computer hater) who has recently bought a '68 Cougar he’s fixing up. It came to him with a bagged 289 that someone had shoehorned in there. He knew about that.
Well long story short, buddy bought a nice reman 302 for 6 grand and then encountered the 157 tooth versus 164 tooth flex plate compatibility debacle. The new 302’s supplied 164 tooth (50 oz.externally balanced) flex plate won’t work with the bell housing/starter mounts he has on his C4… So surprise surprise, it appears that the previous owner swapped both the engine AND tranny for older versions. (probably together)
So learning this, buddy thought he is now facing the cost of a new compatible C4 with the later starter location. But I see there are ads up for 157 tooth 50 oz. flex plates, leading to my question: Can buddy just buy one of these 157 tooth 50 oz. aftermarket flex plates, and have a starting, smooth running 302 mated to the earlier 289’s C4?
Thanks, sorry for the ramble.
No and the 157 tooth flex plates are available pretty much anywhere and everywhere so I am unsure why he thinks he has this problem. The earlier 289 / 302 was balanced at 28 OZ so the later trans will not work at all.
Is the ENGINE 50 oz. balanced? Just because it came with a 50 oz flexplate doesn’t prove anything. But if it is, then a 50 oz, 157 tooth flexplate should solve the issue. If not use the (presumably) 28 oz balanced 157 tooth flexplate he already has.
No the 1967 - 78 289, 302 and 351 are all 28 OZ imbalance factor so they will not work with any 50 OZ imbalance factor items at all.
RE: the current engine, Any Ford product with a 302 built for the 1979 or later model year will be 50 OZ imbalance factor. To balance one of those it needs the correct harmonic balancer and flywheel / flexplate. Changing the balancer means the earlier pulleys and brackets won’t work either. And then there are problems with the engine front cover and water pump and fan. Lots to consider. Do you know the casting date or casting number on the block?
Hi, thanks for the responses.
The new crate engine (non roller) came supplied with a 164 tooth 50 oz. flex plate, the engine builder expecting he was supplying a direct replacement for the stock '68 J code 302 4v that should have been in there.
Buddy did assemble it with the 289’s 28 oz. flex plate at first, and the engine vibrated when driven. My thought would be that this means the engine builder wants a 50 oz weight flex plate on there like the FRA-214 he supplied, and that a 157 tooth flywheel with a 50 oz. weight should both be in proper balance and allow the starter to bolt up and work with the existing 289 bell housing he already has. I know there are still ring gear offset considerations to meet.
Is there something I’m overlooking?
Thanks all.
You will still need the harmonic balancer for the 50 oz imbalance plus any pulleys that drive any accessories. This will make any of the existing accessory components not fit, including the front cover, brackets, water pump etc. All of it needs to be compatible with the harmonic balancer.
With the earlier style balancer it will shake like crazy.
I hear what you’re saying, but since the new crate engine is made for the stated '68 302 and was shipped with a 50 oz. flex plate, isn’t that a properly balanced set? (unless the crate engine builder/seller was incompetent)
It did shake like crazy with the old 28 oz flex plate, the very reason the old flex plate on the new motor was found to be obviously a wrong combo. 
I’m rationalizing that if the motor is set up for and needs a 50 oz plate and it gets a 50 oz plate (just not the one the crate engine builder shipped with the motor) shouldn’t that fit and work? Thanks
You are skipping the part about the harmonic balancer. It has to match the flex plate.
My thinking is based on he point that that the builder of the crate motor supplied it with a 50 oz. flex plate, FRA-214, it was all strapped on the same skid. The flex plate wasn’t mounted on the motor surely as a measure to protect it from damage during shipping.
The harmonic balancer the builder put on there pretty much has to match the flex plate that he also supplied unless we believe the builder of the crate motor screwed up and supplied it with mismatched parts…It’s certain that the builder wants that 50 oz plate on there, with whatever harmonic balancer that he also fitted…
What’s not quite certain is whether a 164 tooth 50 oz. flex plate is the same as a 157 tooth 50 oz.flex plate, balance wise. My gut says it should be but there are plenty of things I wouldn’t bet on, presuming the answer.
My hope is that someone who’s been there will say, “Of course, I did that very swap and it works just fine.” Buddy of course hopes he doesn’t have to buy a new tranny now too.:
Sure the 50 oz 157 tooth flex plate will work with the early transmission. You are setting your self up for a nightmare with pulleys and accessories. Have fun.
If in doubt call an engine balancing shop. They are a wealth of information and deal with this kind of thing all the time. You can they sleep well at night and not worry if you will have to pull everything apart again.
Thanks PopsOtto. At this point there’s little doubt it has to come apart again as it’s got a 28 oz flex plate in there and all research shows it needs a 50 oz plate.(Like the engine builder supplied. Imagine!) Learning is uncomfortable but essential.
That’s a good idea, ask a balance shop.
You can take the 28oz flex plate to a machine shop and have them balance it to 50oz. This is not expensive or difficult for a competent machine shop.
In all honesty, the charge from the labor might be as much as a new flexplate with the proper balance though. A lot of people probably have one of these sitting around. I know I do.
It was about $65 the last time that I had this done, but that was pre-COVID pricing.
Thanks for the positive suggestions guys. Buddy bought a 289 compatible 157 tooth flex plate that has a 50 oz balance weight, and we slid it in there. Works perfectly and the engine is smooth and strong. All the pulleys and accessories work perfectly because they were simply transferred from the old block to the new one. She’s a good runner now. Thanks again.