Technical Help - SBC - Horrible Vibration - Wrong Harmonic Balancer?

I'm so close to getting my 49 Ford Sedan on the road, but....

It has a HORRIBLE vibration in the engine.

I thought it might be timing, a short, etc.

The engine is a mid eighties 305, and seems to run great, it just shakes like hell.

Anyway, one thing that I have noticed, is the harmonic balancer is notched, not smooth all the way around.

Here's a pic....

 

Is it a harmonic balancer off a sbc 400? Kinda has the look

 

From the searching that I have done, this harmonic balancer appears to be for an externally balanced 400 SBC.

Could it possibly be the correct balancer for this engine?

Or is this the source of my engine shake?

Thanks,
Rich

 

I should have one in the garage. I 'll go look after I eat dinner

Just saw the gear head down the street has a 283 bal on his 350 , Doh !

 

check the crank snout with a dial indicator to see if its bent,

 

It should have a neutral balanced damper on it. The 305 damper was smaller in diameter than the 350, but a 350 will work.

That does look like a 400 damper, someone probably needs it a lot worse than you.

 

My 283 had a terrible vibration too. I checked the flywheel/clutch for balance, ignition for possible misfire and a million other things. Had a bad feeling so I pulled the motor out and apart. Turns out the crank was drilled for lighter pistons and rods at some point and I didn't catch it on the first go around.

Hope your fix is easier.

 

yep,a 400 which is different from all other SBC and like they said,is externally balanced.Also might need to check the flywheel / flexplate.

 

400 balancer will rattle er loose.

 

OK, I went out and looked at my 305 balancer.

No it doesnt have a notch or counter weighted. It is neutral balanced , 'bout 6 3/4" diameter.

The '80 350 balancer layin' in my garage is 8"diameter

Looks like you got the wrong balancer on there


.

 

Grind the notch off. Do it with the engine running, will be easier to make it look pretty.

 

I bought the engine as a rebuilt, "good running", 305 from a mid-eighties monte carlo.

Why would it have this balancer on it?

 

Pick a reason, it's a guessing anyway.

I got screaming deal on a 71 Chevy truck that had issues.
The starter went BAzzzingching 90 % of the time and if it did catch the motor shook like hell. Dude had wrong balancer and flywheel on a 400. Maybe this guy worked on yours and switched the parts around.

That's a reason right ?

 

Cause there are idiots in this world

From what I read 305 heads are prone to cracks too. Maybe just some years with thin casting, '80s cheap ass thin casting

 

Pull the balancer off and start it.....for a second or two

 

That is absolutely a 400 external balancer. Any other small block balancer will work fine. The next question is does the motor have a 400 flywheel/flexplate on it too? If so that will need to be changed too.

 

Could put JB weld to fill in the notch

That'll fix it ....


.

 

As many said--400 item--better ck flexplate too

 

334 stroker kit for a 305 uses a 400 balancer

 

Not exactly every other SBC. Everything after they went to a one-piece rear main seal is externally balanced. All of those engines have the weight that once resided on the crank flange, moved to the flywheel/flexplate, to make way for the seal.

 

I had a pickup with a 350 but a 400 flex plate. I took the torque converter cover off, found the bat-shaped weight on it, and pried it off. Smoothed it out, and I didn't have to pull the trams or replace the flex plate.

 

Does that mean ill have problems when I try my 307 crank in a 2001 roller block ?

 

not for you , you have a grinder and a welder and know how to use them ,,

 

Says who ?

 

Depending on how long the engine has had the "wrong" dampener on it, the main bearings could be trashed, so better pull the pan and check. Like others have said, that IS a 400 dampener, so check the flex plate/flywheel also, everything on that year 305 needs to be neutral balanced. Many years ago, I bought a "balanced" 305 to 334 stroker kit; the entire rotating assemble. Then I found out my 305 block had trashed main bearing bores/caps. Put the rotating assembly on the shelf, and even more years later, a good 305 block fell into my lap. After the block was bored/prepped for clearance, I assembled it. Sat on an engine stand for a couple of years destined for one of my Sedan Deliveries. I even took the "400" flex plate into a machine shop, with my Dual Range Hydro fly wheel to have it balanced to the engine/flex plate. Then the 350 in my truck dropped an exhaust valve, so I put the stroker 305/334 in the truck; it would not run right. Idled fine, but any more than an idle and it would vibrate, and driving the truck it felt like King Kong had a hold of the rear bumper. I could not figure out what was wrong, I'd paid for the balance job, had the "right dampener and flex plate on it, and I even changed out the cam (was't a street friendly grind). Then one day in a magazine I read an article on SBC/BBC flywheels/flex plates; that 400 flex plate does't look like mine. IT had a 454 flex plate on it! Thank you California Discount Warehouse. They sure were't going to do anything about it, it had been many years since I bought the kit. Swapped out the flex plate, pulled the pan and checked the main bearings, and they were fine. Fired the truck up, ran fine, still runs fine; amazing what a properly balanced engine runs like. There you go, Butch/56sedandelivery.

 

I pulled the pan and checked a couple of the mains after I bought it, they looked good.

The oil pressure is good also.

Rich

 

That's the plan at this point.

Thanks,
Rich

 

What's this gonna show you ?
You have a improperly balanced engine now, take the balancer off and you now have a differently improper balanced engine.

 

Yes. You will need one of these:

http://www.jegs.com/i/Moroso/710/38315/10002/-1?parentProductId=745554



This allows a 1986-earlier crank to be bolted into an 1987-later block. Then you you would use the balancer and flywheel/flexplate that goes with that crank.

 

Oh yeah! , then there's no problem thanks !