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I have a 1977 351W and two flywheels. One flywheel is out of a 1990 5.0 Mustang, and the other is out of a 1967 289 Cougar. Will either flywheel work on the 351W without rattling the engine to pieces? I'm not sure what counterweight is required for the '77. Anyone know?

Thanks.

Thespazardman
 

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Use the 289 flywheel. All 351's had 28.5 in./oz imbalance as did the 289's. 5.0 engines starting in 1986 were balanced at 50 in./oz.
 
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Some things to consider- Are you going to use the T-5 bellhousing? or the adaptor plate to use the original bell housing? I've heard negative things about the adaptor and proper alignments wearing out the pilot bushing and the front bearing on the tranny. If you go with the T-5 bellhousing, you will need the late model flywheel and have it rebalanced. BUT, one item of concern you should have here. The 351 can easily destroy a T-5. I was going to jump over to the 351 midway thru my project, but my oldest son, now 11, I'm sure will be driving the '66 one day. You know how you were at 16! If you start adding performance to that 351, you might want to think TKO.
 

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All 351W's use a 28 ounce balance flywheel or flex plate (auto). Consider using an 11" clutch assembly (flywheel, bell housing, etc.); a healthy 351W can really challange a 10" clutch. Also consider at least a Tremec 3550 for the same reasons.

http://pages.prodigy.net/opabear/_uimages/G1967TExhaust1b.jpg
 

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I must disagree with Scott on one point, a late model flywheel is not required if you run late model bellhousing. Assuming the bellhousing comes off a 5.0, you can run a standard 289 or early 302 flywheel (157 tooth ,28oz imbalance), you would also need the engine plate that goes between the block and the bellhousing. The only difference between a late model and early model 302 flywheels is the imbalance. I understand that a modern diaphram clutch will bolt up fine to an old flywheel (that would be my only concern).

You may consider a new steel or aluminum flywheel as they are stronger than stock cast units.

A 351 will exceed the torque ratings of the best T-5's if you get it to hook up. You might want to consider a Tremic 3550 or TKO.

11" clutches will require a 164 tooth flywheel & bellhousing.
 
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DOH!! You mean that I could have use the early flywheel with a late bellhousing?? I was told that the starter would not engage the teeth. Different diameters. Damned, I'm confused. Glad I have decided to just go with all 5.0 including the serpentine belt system.
 

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"I understand that a modern diaphram clutch will bolt up fine to an old flywheel (that would be my only concern)"

To use the late bell housing with the early flywheel means using the early long style clutch and pressure plate and adding a fulcrum spacer to the bell housing (See Windsor-Fox web site). The reason for this is the early flywheel is not drilled for the diaphragm clutch. You could have the early flywheel drilled to accept the diaphragm clutch however. There may be aftermarket diaphragm clutches that fit (e.g. Centerforce for early sb Ford).

The reason you're confused is there are several configurations that work and as many that don't. You just have to zero in on one approach and stick with it. You can buy a dual drilled flywheel from Ram Automotive and it will work with either. You can also select the correct balance for your engine (they make them to fit all sb Ford engines in any configuration)

WRT your 351w engine, the problem with using a T5 is the torque specifications are a mismatch. They work real well for 302 and smaller displacements because the torque ratings match the engine output. If you look at torque ratings for a group of 302 engines, from 200hp to 400hp what you see on the graphs is while the hp rating goes up, the torque rating stays fairly flat at somewhere near 300 ft-lbs. This is inside the T5-X or T5-Z's torque rating and hence the tranny holds up pretty well. What about your 351? Here's the problem. Your engine produces about 350 ft-lbs of torque minimum and goes up to about 380 ft-lbs in various horsepower ratings. This value is fairly constant over the hp AND rpm range. This means you will almost always exceed the T5-X/Z's torque rating at every stoplight. This in turn produces stress on the tranny and rapid wear. If you lauch hard, you're more likely than not to break it. My recommendation is you consider a better match for your five-speed requirement.

"I have a 1977 351W and two flywheels. One flywheel is out of a 1990 5.0 Mustang, and the other is out of a 1967 289 Cougar. Will either flywheel work on the 351W without rattling the engine to pieces? I'm not sure what counterweight is required for the '77. Anyone know?"

You need a 28 oz-in imbalance flywheel for your 351w. Here's a combination that I know works for your car. There are others, so this isn't the only way.

1. '69-'73 351w toploader bell housing (164 tooth)and matching block plate.
2. '69-'73 351w starter (nine gear starter for 164 tooth)
3. '69-'73 351w flywheel (28 oz-in - 164 tooth)
4. Adapter plate and cross member for the transmission you select. It differs with the transmission. Has to be 11 spline to fit clutch plates.
5. Pilot bearing for transmission input shaft (Tremec transmissions include T5 require needle bearing pilot).

This approach uses stock clutch linkage and clutch components up to 11" (10, 10.5 or 11").
 
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