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Discussion Starter #1
I have installed a 1990 5.0 HO that I got from a reputable junkyard saying it was a good running motor. This motor came out of a Mark VII. I installed this into my 68 Mustang with a T-5 transmission. I had to buy a flywheel. I have already had an issue with the parts house giving me the wrong starter and now I want to make sure I have the right flywheel. The car is idling with a bad vibration and it also has a terrible metal on metal knocking sound. Could these 2 be related or are they seperate issues?
I am not sure if the weight on the flywheel is 50oz or 28oz and can not find anything conclussive on the internet. I am trying to get out of pulling the motor again but it is looking like I will have to.

The flywheel has this info on it:
RF-E1ZR6380-A2A and EZ6-AA
I have read that the E1 represents 1981 meaning it could be a 28oz or 50oz but I may be wrong. It is a 157 tooth flywheel

The harmonic balancer is part # E4TE-A3A

I am hoping both of these are 50oz.

Here is a link of the motor running. It is from a Droid phone so not the best quality but the video sonds the same as real life. The smoke is from oil and crap on the exhaust headers.

The sound did go away for a little while and then came back, the vibration never went away and at one point, it sounded like a rattle can (like the metal was moving around inside, maybe a foreing object?)

What is that metal knocking sound - YouTube

Thanks for any advice. I am trying to get my stepdad to come listen to it but they live an hour and a half away and I am trying to diagnose it first if possible

Premium Member
34,853 Posts
Take the dang engine out.

The flywheel may be wrong.. 50 ounce versus 28 ounce... Plus it might be on backwards or bolts too long or yadda yadda yadda, there should be no banging or hitting metal noise! EEEEEK!

And it's hitting SOMETHING, so git it out and identified, the 50 oz balanced flywheel has a larger 50 ounce counterweight and the 28 has .... 28 ounces on it....

Here is a pic of each.

Now go check out his article about engine building mistakes and you'll have something to attack with.
Engine Building Mistakes - Mustang & Fords Magazine
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