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Diputado 06-28-2013 12:39 PM

390 flywheel on 289..??
Here's a "head-scratcher"...I was told by the PO who built the 289 in my '65 that he used a flywheel off a 1968 model 390. He said he did so because the current transmission (a Toploader version RUG-AE2 which was originally behind a 428 CJ) was one he pulled out of a '68 Mustang with a 390, and he used that same 390 flywheel on the 289. The 289 engine also has a 50-oz harmonic balancer off a 5.0 engine. I asked him how the hell this was balanced, and he says he had the rotating assembly "balanced" by a local machine shop.

My this guy full of s***, or is it possible to use a 390 flywheel with a '65 289 crankshaft AND late-model 5.0 balancer??? I was told by a local engine builder that the bolt patterns were different, and the 390 flywheel won't fit on the 289 crank. Whatever he did...the engine actually runs fine with no noticeable vibration.

2+2GT 06-28-2013 05:52 PM

I'm gonna go out on a limb and favor BS. The 390 wheel is bigger than the 289 and 302 wheel. Not gonna fit inside a smallblock bell.

As for the balancer, how many bolts are holding the pulley on the balancer, 3 or 4?

Diputado 06-29-2013 02:16 PM

The drive belt pulley is attached with 4 bolts. The part # on the balancer is E4TE-A3A. Because of this, I at first thought the engine was a 302 (or at least a 302 crank,etc.). But the block and heads are DEFINITELY a 1965 289. I know because I have changed the intake, and seen the casting numbers. I specifically asked the PO if he dropped in a 302 crank, and he swears that it is all 289, top to bottom. Any insights based on that balancer?

67mustang302 06-29-2013 02:54 PM

Does it vibrate?

While I suppose you COULD get the crank balanced with a different's ill advised. Balancing deals with inertia in the locations of mass....but there are still harmonics. I'm not sure I'd trust that harmonics aren't present in a cockamamie ass setup like that.

If it's true.

Diputado 06-30-2013 03:41 PM

Man, that's part of the mystery...damn thing runs noticeable vibration at all, even up past 5,000 rpm. Ahh...but there's more to the story. You see...I bought the car back in October from a guy about 70 years old who said he bought it about 2 years ago at an antique car show because he "liked the way it sounded". Then, after driving it a few times, he claimed he was "scared of it" (too much hp, he said) and decided to sell. Well, I later went to the Motor Vehicle Dept. to try and track down who HE bought it from, to find out what had been done to the engine,etc. Found out that the car had been bought and sold a couple times previous! I FINALLY tracked down the "original" PO (who built the car), and paid him a visit. He told me he built the engine about 7 or 8 years ago, and drove it mainly on weekends for a couple years before selling it. SO....if there was a serious imbalance issue, you would think the engine would've blown apart by now. I have NO idea how many miles have been put on it after the rebuild, but when I changed the intake and valve covers right after buying it, the lifter valley and rocker arms were all clean as a crud....just a lot of scale and corrosion in the old intake (a Holley Street Dom.) from all the other POs running straight water with no additives.

67mustang302 06-30-2013 06:11 PM

Harmonic destruction will occur at a certain rpm/load scenario. You could drive a car 100,000 miles and never reach that scenario....then at the track one time, boom. Imbalance isn't quite like a time bomb, it doesn't eventually happen. If there's a harmonic imbalance in the engine under a certain condition, then it'll destroy the engine if the conditions are met (load, rpm, duration). It'll either hit the harmonic or it won't. If it vibrates it may destroy other stuff sooner, but a lack of vibration doesn't necessarily mean a lack of harmonic imbalance.

Honestly, I've seen so much crazy **** from so many places, that I'm skeptical of anyone who can't say specifically what part was used (which was correct for the application). Any of the "we did this to make that work" stuff is cause for alarm much of the time.

You'd be amazed how many "professional" engine builders and mechanics, don't have the slightest clue what their dealing with.

Diputado 07-01-2013 07:14 AM

Hmmm...interesting. Never thought about "harmonic imbalance". Makes sense, though. Well...whatever the engine has on the inside, let's hope I never hit that "magic combination". I don't intend to run it on the track, this car is strictly a weekend street rod, so I'm not going to be "dogging it", as we would say back home in Tennessee! Maybe my luck will hold.

Yeah, you're right about the crap that folks will force together to "make it work". In fact, I'm in the process right now of changing the entire front disc brake system because the PO who built the engine also did a "conversion" to front discs using rear rotors off a '96 Mustang and calipers off an Oldsmobile. The pads only make contact with one side of the rotors, and the calipers were actually welded to the spindles!! The car also has leaf springs off a late 60's Chevy Nova. They actually seem to work pretty good, being stiffer (5 leaves) than the originals (4 leaves). Yeah...this ride will keep me busy for a while...!

2+2GT 07-02-2013 09:39 AM


Originally Posted by Diputado (Post 8240715)
The car also has leaf springs off a late 60's Chevy Nova. They actually seem to work pretty good, being stiffer (5 leaves) than the originals (4 leaves). Yeah...this ride will keep me busy for a while...!

You may want to check the front sway bar for the same reason…

Diputado 07-03-2013 06:57 AM

Did's got a 11/16" bar on the front. Appears to be original. Am just about to replace the bushings on it with some brand new Prothane bushings. In fact...will also be replacing EVERYTHING in the front suspension, brakes, and steering linkage. Was only going to do the disc brakes at first, but everything else is so worn, rusted and sloppy I decided to just "bite the bullet" and rip it all out and start over with all new components.

Diputado 07-03-2013 07:01 AM

Quick asked if there were 3 or 4 bolts on that balancer/pulley combo. It has 4. What does this tell you?

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