Have a 52' chevy 3100 I've owned and driven for a few years now so I just installed a sbc 383 that I had built locally had the engine dyno'd by the same shop 385 hp 439 tq. All good, brought engine home installed it got it runnin but seemed to have a mis. engine shook rather violently at idle so checked out plugs wires couldn't get it right so I called the builder and realized I installed the wrong flex plate. It needed a weighted one so I had it towed over and he installed the correct one. I also had him tune the motor to his satisfaction. Well now I have the truck home. in park it idles fine,fires right up runs cool. But.... Rev the engine it vibrates violently put it gear it vibrates the shifter badly, does smooth out a bit but I'm really un comfortable with this . Just wondering if a bad torque converter would make it vibrate like this has 2600 stall . Ideas ?... Thanks
You are running a 400 harmonic balancer, aren't you? Balancer and flex plate should match. I've seen this happen to many 383's because of engine being out of balance.
Hard to believe, because he towed it to the shop who built the motor and they tuned it after they replaced the flex? How could an engine shop let it go, if it was vibrating? Hey, call me silly for asking, but is it all cammed to heck? and that is what you feel if it smooths out? ,
Unless the builder did the engine as an "internally" balanced rotating assembly you will need the 400SBC harmonic balancer and flex plate. Look at the harmonic balancer and if it is for a 400 there will be a section of the casting that looks thicker than the rest, like a counterweight on the engine side. A regular 350 type looks like symmetrical casting. I build mine internally so it doesn't matter if I go standard trans with clutch and flywheel or auto.
we need video...so we can try to get some idea of what you're complaining about. Vibration and rough running can feel similar.
400 balancer on the right in both photos. Check that yours has the depressed area around the circumference like the one on the right.
Just from an "Old" mans opinion....You need a new machine shop...one that knows how to balance all types of engines,,,which obviously yours does not.
CHILWIL86.....Aaggie is correct on the balance..We called it "Independent" or "dependant" when we balanced any engine,,,On "dependant" type engines,It is necessary to add the front harmonic and the Flywheel to your crank before spinning on the balance machine..We NEVER believed in this method. We always added "heavy metal" to the stock cranks then balance them..So if in fact you need a different harmonic balancer later or flywheel.those items can be balanced as a single unit and added to your engine without disturbing your balance job,,,Many early Buick nailheads were of the "dependant" type. this is my reasonimg for saying your balancer man does not what he is doing. I feel your pain..
Did your "builder" install the harmonic damper, or did you? If they did, then they definitely don't know what they are doing, but I'm thinking since you mentioned that you installed the flex plate then maybe you put the damper on as well. If so, chalk it up to a rookie mistake, you'll know better next time. Report back on what you find regarding the damper. If it's got the correct one on it, next step would be to remove the belts and do a quick running check to see if anything changes.
Builder is flatbeddin the truck back too his shop to figure this out, so we'll see hes seems to be a dtand up dude sooooo we'll see
Good for you, having the smarts shut it down. You definitely have a mismatch of parts or balance guy screwed it up big time. Happened to me 1x, majority of my racing engines, dyno ran and ready to run, would freshen myself as needed, last Sprint car 410 engine I bought, was assembled by a very reputable shop, his assembly tech was a local hero, but their dyno was down, pick up engine, go racing, ran OK, but wouldn't pull your hat off on a windy day. Shop owner comes over and asked about engine, repeated my comment (hat, windy day) and told him they F***ED up. He walked away pissed off, Keep in mind, I worked for a famous engine builder at one time, by trade a Tool & Die Maker, had my own shop, measuring tools and I know how to use them and built many engines, was so busy at my shop, just did'nt take the time. So..... start checking things, pull 1 head off and the dome was milled off, at 13+to1, dome does not get touched other than cleaning sharp edges off dome area, pull engine, cc cyl at TDC ,do the math 10 to 1 comp., on engine stand and checked cam timing, summers gear drive, 1 tooth off, cam retarded 9 degree, Had shop owner come over to see his mess. So... as someone said, even the best shops can have a comedy of errors, not that I appreciated the humor
Well I'm glad to say that it was just the wrong flex plate. The weight was in the wrong place. A big thanx too all that contributed.
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