Need help with vibration in 67 mustang
 

A friend of mine purchased a 67 mustang with an unknown history. There is a major vibration near the rear of the engine, it is so bad that you think a cylinder is misfiring at first but when you check all are firing. I think that someone has installed a 302 and not changed the flex plate (3 speed automatic) to suit. The flex plate has 2 very small balance wieghts. Any Ideas as to how to find out the correct combination?

Thanks
Micro

Well first off i just wanted to congrats you on ur choice of big block stang. NEWAY

When does the rattleing occur. Mine did this awhile back when i was going 50 or faster. WHen i put it in neutral or turned it off it just started to viberate. It was the driveshaft. Check both U joints if you think that it could be comming from the tranny.. But if it is the engine i can't help you there. But try to see what your doing when it happens. And go from there.

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1967 mustang gt, coupe, dark moss green, black interior, s-code, 4 speed toploader ( only 1546 mustang gt,s-code,coupes with 4 speed toloader ever made in 67) ... Now it currently has a 302 (for daily driving, i am only 16) an edlebrock 600 cfm 4v carb - wanting dual quads - with a comp cam, pop up dome pistons, headers, msd electronic ignition. 3.00 with a ford 9" gears - wanting 3.50 posi gears. Recently accuaired a 390 from a 69/70 ford truck which is being moddified for some seriouse power

I recomend the same thing 67 says. I was going 30 mph and the car statred to shake but when I let off the gas it dissapeared. It was the rear U-joint not properly seated into yolk or whatever you call that thingy with U-Bolts.

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66 Mustang Black W/ Black
289 Hi-Po 65'heads, MSD
Lunati High lift Cam
750CFM Carb Heddman Headers

Check the tires for roundness (not balance)
Check the drive shaft
I replaced the wheels and tires and installed a new driveshaft and all the vibration went away.

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66 burgandy convertible; 306 (289 bored .03 and 302 crank) edelbrock: Performer intake,4v carb; hurst 4 spd; 2.8:1 rear;Classic Auto Air perfect fit AC; Pertronix ignitor, 17x7 American Eagle 211's w/ 22545zr17 Toyo proxes

Pre 1980 motors had a 28.2 ounce flex plate and harmonic balancer to match.

Post 1980 have 50 ounce flex plate.

When you look at a 50 ouncer plate,the weight is about 3/4 around the plate.

The 50 harmonic balancer weight covers a litle more than half,around the balancer.

Rule of thumb, it looks like the 50 oncer has twice the mass as a 28.2 ouncer.

Not putting on the right balance will kill your rear main bearings or worse, if your lucky.

Alot of people swap in a AOD but bring the heavy plate too. Thats fine if you rebalance the plate to 28.2 ounces. That is if you have a older motor.

Thanks for all the replys. This is not a universal or driveshaft vibration. Vibration is there with engine idling and vehicle in park. When you increase the rpm the vibration gets much worse.

Thanks MustangII460 for the years and wieghts information. The harmonic balancer is likely the early one as the wieght goes only about 1/3 of the way around. I would guess the flex plate is the original 289 one as it only has two very small wieghts both about 1 inch square and thin.

Thanks again for the good information

Micro