Bad Vibration at 2000-3000RPM

Rona · Apr 16, 2022

Ok I’m stumped. 1995 mustang v6 car converted to 5.0 I pulled the block this fall and took it down to the bare block. Got it bored .030 over, like honed, new plugs, cam bearings decked the block and got a scat street/strip 347 stroker kit installed. Here’s the rest…

347 stroker
Ford F303 Cam
Windsor sr heads 62cc combustion chamber
(9.5:1 compression according to scat with 62cc)
Running 93 pump gas
1.6 roller rockers
Summit racing 750CFM carb 4 barrel mechanical secondaries
Shorty headers
Bbk x pipe
Flowmaster 40s with tailpipes
MSD Coil
MSD Billet Distributor (no weights or springs?!?!!)
*** was told before it’s locked at 30 degrees***
Mallory 685 ignition box
Ford racing 9mm wires with autolite copper plugs gapped at .050

OK SO with that out of the way the problem i am having is in any gear from 2000-3000 RPM the whole car shakes like a bastard. The stroker kit was balanced and is a 28oz balance. I have the flywheel and balancer both 28oz that were balanced with the crank. All my engine mount bolts are tight. Tranny mount bolts are tight. I have aluminum driveshaft and I checked the u joints before putting it back in the car. I’ve played with timing from 30-34 degrees. Timing doesn’t change from idle to 2500rpm. I’ve adjusted the carb idle air on both sides and both accelerator pumps. I just can not get this problem solved! I’ve also read other similar posts on here and seems no one can find the fix. Any help would be greatly appreciated!!!

PS: Sorry for the long post!! LOL

Noobz347 · Apr 16, 2022

Does it shake when it's not in gear?

Rona · Apr 17, 2022

Noobz347 said:
Does it shake when it's not in gear?

Yes if I set timing at 2500 in neutral it shakes the whole time at 2500

Rona · Apr 17, 2022

Noobz347 said:
Does it shake when it's not in gear?

Do you think maybe it’s getting too much fuel at that rpm range? Or could one or two cylinders be misfiring at that rpm range? Or should I even try that VP Racing Octane booster and see if it doesn’t like 93 octane? These are things I’ve been trying to look into. Just don’t know if I should spend more time and money if it could be something else

General karthief · Apr 17, 2022

What is your static timing set at (idle)
What firing order are you using?
Octane is not going to cause a vibration.
I doubt the carb is the cause either.
You didn't answer the question above ^^^ does it shake when not in gear? (Sitting still, 2500-3000 rpms)
I would run a compression test.

Rona · Apr 17, 2022

General karthief said:
What is your static timing set at (idle)
What firing order are you using?
Octane is not going to cause a vibration.
I doubt the carb is the cause either.
You didn't answer the question above ^^^ does it shake when not in gear? (Sitting still, 2500-3000 rpms)
I would run a compression test.

Yeah sorry I did I replied twice though. Yes at 2500 setting timing it vibrates the whole time. My timing at idle is 32 degrees. There is no change from idle to 2500 for some reason. I’ve tested it multiple times. I don’t understand the setup. I bought the car with that ignition setup. Firing order for f303 cam is 13726548

limp · Apr 17, 2022

Rona said:
Do you think maybe it’s getting too much fuel at that rpm range? Or could one or two cylinders be misfiring at that rpm range? Or should I even try that VP Racing Octane booster and see if it doesn’t like 93 octane? These are things I’ve been trying to look into. Just don’t know if I should spend more time and money if it could be something else

I would have the clutch checked for balance.
Not your shaking problem but your Carb is too big..... People think by "jetting" it they can fix a " too large" carb......

Rona · Apr 17, 2022

limp said:
I would have the clutch checked for balance.
Not your shaking problem but your Carb is too big..... People think by "jetting" it they can fix a " too large" carb......

I was unaware that the clutch needed to be balanced. Or is there a specific way to mount the pressure plate and I missed that?

Noobz347 · Apr 17, 2022

I'm having difficulty understanding your reponses.

I think Limp might be onto something though. Double and Triple check that your flywheel is the correct flywheel for your application. The OEM flywheel has a 50oz. imbalance.

You need to determine what the imbalance is for your new rotating assembly and ensure that the flywheel is a proper match.

Other flywheel imbalance possibilities are 0 imbalance and 28oz imbalance.

My suspicion is that yours is mismatched but again... I may not be interpreting your responses correctly either

Rona · Apr 17, 2022

Noobz347 said:
I'm having difficulty understanding your reponses.

I think Limp might be onto something though. Double and Triple check that your flywheel is the correct flywheel for your application. The OEM flywheel has a 50oz. imbalance.

You need to determine what the imbalance is for your new rotating assembly and ensure that the flywheel is a proper match.

Other flywheel imbalance possibilities are 0 imbalance and 28oz imbalance.

My suspicion is that yours is mismatched but again... I may not be interpreting your responses correctly either

Yes I have a 28oz harmonic balancer and 28oz flywheel which is what the stroker kit calls for. They were balanced with the crank

General karthief · Apr 17, 2022

30* of timing at idle is too much unless you're using a timing light that sets advance reading at idle, I believe it's called a 'dial back timing light' (?) The timing should be between 10-16* at idle, the advance mechanism takes care of the rest.
The clutch could be the cause but lets check all the boxes before dropping the trans.
To answer the question about the flywheel/clutch position, the flywheel should have pins that position the clutch assembly in the right place.
I figure the stroker kit listed the correct firing order, oh wait, B cam so your firing order is correct.

General karthief · Apr 17, 2022

I will add that the 750 carb can be 'tuned' to run on that combination but as I said I doubt the carb is the issue right now.

limp · Apr 17, 2022

General karthief said:
I will add that the 750 carb can be 'tuned' to run on that combination but as I said I doubt the carb is the issue right now.

Depending on what he is doing with the car.. Driver? Too big a carb.....It will run OK, but your driveability would improve with a smaller carb..

limp · Apr 17, 2022

Rona said:
Yes I have a 28oz harmonic balancer and 28oz flywheel which is what the stroker kit calls for. They were balanced with the crank

which is why I suggested the clutch.....
You are getting the vibration by just revving the engine in neutral? Engine.... You have had the crank assembly balanced by the machinist? so the only thing that leaves is the clutch, in my opinion...... The only other thing could be a problem in the transmission?????
I would guess something in the " rotating assembly".........

General karthief · Apr 17, 2022

limp said:
I would guess something in the " rotating assembly".......

I would agree for the most part.
I'll add that it would be easier to tune 'up' a 650 carb than tune 'down' a bigger one. But it can be done.

limp · Apr 17, 2022

General karthief said:
I would agree for the most part.
I'll add that it would be easier to tune 'up' a 650 carb than tune 'down' a bigger one. But it can be done.

My engine is a 030 over Explorer engine with a TF 1 cam and new valve springs, so no comparison, but I am installing a 500CFM 4 barrel on it... Back to is it a street car" Drag car? or a track car?
My Carb knowledge is old, but all we ever did was OVER carb our drivers with help from HOT ROD mag and the local speed shop.....

General karthief · Apr 17, 2022

Back to the vibration issue.
Can you do a compression test?

Rona · Apr 21, 2022

limp said:
which is why I suggested the clutch.....
You are getting the vibration by just revving the engine in neutral? Engine.... You have had the crank assembly balanced by the machinist? so the only thing that leaves is the clutch, in my opinion...... The only other thing could be a problem in the transmission?????
I would guess something in the " rotating assembly".........

The crank, flywheel, balancer all went to machine shop for balance yes. And if it’s clutch then wouldn’t it not shake if you push the clutch in? Cuz it does

Rona · Apr 21, 2022

General karthief said:
Back to the vibration issue.
Can you do a compression test?

I can. But I think I’d know it a cylinder wasn’t firing.

Rona · Apr 21, 2022

limp said:
Depending on what he is doing with the car.. Driver? Too big a carb.....It will run OK, but your driveability would improve with a smaller carb..

It’s a street car. But I know how to drive lmao

Bad Vibration at 2000-3000RPM

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wonder how much it would cost to ship you a pair

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wrap a little cheese around it and its a done

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Stangnet Facilities Maint Tech... Er... Janitor

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wonder how much it would cost to ship you a pair

wonder how much it would cost to ship you a pair

wrap a little cheese around it and its a done

wrap a little cheese around it and its a done

wonder how much it would cost to ship you a pair

wrap a little cheese around it and its a done

wonder how much it would cost to ship you a pair

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