IgorT.455/406

Hey guys. My 383 is running ok (fresh), but it shakes at idle, and throughout the RPM range. Checked my valvetrain (solid roller) 3 times, perfect each time. Plugs were too hot for my heads (Victor Junior), about 14 steps hotter then what Edelbrock recommends (11:1 CR), changed them but went to change the HEI to a pro billit, got 1/2 way done and had to go out of town for work.

Now, my hot plugs were black when I pulled them (not oil) with white tips. I know that is not good, but this vibration I got didn't seem like it was ignition. Motor ran ok, was responsive, wanted to rev, etc.

Its a 1 pc rear main seal block that was internally balanced. I got a small flexplate but the counter weight has been removed (good).

I bought a powerbond neutral balance balancer, but when I got it back, someone elses name was on the box. To me, the thing looks like there is a counterweight on it, which suggest external balance. I think that the engine shop gave me back the wrong balancer, one for external balance when my motor is neutral blanced.

Could this bs cause my motor to shake the way I describe it. At idle, my dash and the nose of the car shake. As it revs up, you can still feel it. I didn't rev it higher then 3k in gear, only drove it to the exhaust shop and back (could really feel it after the exhaust got built, open headers fooled me, thought that was it). Does anyone know what kind of vibration would a wrong balancer like this cause. Thanks for any input, I need to get this solved so my nice 383 does not blow up right away. Thanks.

jzajac1

The vibration you describe could be caused by a incorrect flywheel but you said your plugs were black. If your running a carb make sure the float needle is not stuck open and constantly dumping fuel into the intake. Sounds very much also like a ignition issue. Take your time and double check the spark wires are in their correct place.

jzajac1

I missed in your sig you have a MAF. Did you happen to buy too big injectors? You need to hook up a T1 and scan your 02 and see if it's running rich all the time. Are you using stock programming or did you already go aftermarket?

IgorT.455/406

Yes, I am running a 750 DP. The MAF is for the other car, the 383 is in the '88 bird and is carburated.

I am going to finish my MSD ignitoin wirng when I get home and all the new stuff I got, but I belive the balancer is wrong. Called the shop today, there was "Steve" written on my balancer box for some reason, turns out they did a 383 for a "steve" that was a late model block as well, same brand balancers, so its very possible that they mixed up the boxes going from the balance shop to the machine shop. So, I'll check that too. Thanks for your input. Igor.

angel71rs

For sure. I hope your bearings didn't get damaged. How is the oil pressure?

The shop should own up to the error if there is any problem resulting from this.

Stephen 87 IROC

So what shop did your balancing? I currently have a rotating assembly at Hole Shot getting balanced. Ron's custom balancing in Balzac just isn't convienient for me.

IgorT.455/406

Big S, but Ron balanced it. He also balanced a motor for some Steve guy, and the box from the balancer I got back says Steve on it, so chances are I got a wrong balancer. I'll check when I get to Calgary, gonna pull it and see, and finsih wiring my MSD distributor and see how it goes. I honestly think its a counterbalance balancer. We'll see.

What are you doing, 500+ inch motor? I still got that 10" converter, works good. Built a new th350 though, it also works good. I even got a built 700 on the shelf, but no converter yet, plus gonna keep the th350 until something in it lets go.

Stephen 87 IROC

I spun a main bearing in my 2 year old engine. Ripped it down during the big National Open weekend and called it a very short season. Just building another 469 (454 +.070) but the new one will be about 850 hp when done. Should easily push me into the 9's since I was running mid 10's with a 600hp engine at altitude All depends on if I can get traction or not on a 10.5 slick.

I still don't have enough money to go all out and build a 540. Just too much to change for an engine that big. It's those $1500 USD headers that I would really need.

90rocz

Sounds like ignition related to me..Black pugs, vibration thru the rpm range...
Maybe a weak coil, leaking plug wire, fouled plugs??
I put a brand new set of plugs in a fresh long block once, and fouled them just a little starting it up and getting it to run right, but I didn't think that was it. But after exhausting all othe possibilities, I replaced them and it smoothed out immediately after firing it back up...worth a shot...
Then there was the time I crossed 2 plug wires, it ran pretty good, just had a rough idle, like a cam, and stumbled just a little accelerating...
Just my take...good luck!

HiTech5

It definately sounds like the balancer. It is so important that the crank be balanced with the flexplate and harmonic balancer on it.

My advice is not to run the car until you resolve the problem or you will wind up tearing it down again to replace bearings.

On the condition of your plugs, you may have a dual problem where you are rich at idle and lean at higher rpm. I had a 383, 11.5-1, solid cam etc. I ran AC Delco FR3LS plugs.

www.geocities.com/dzperf