Engine shakes BADLY!!

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Weird. All brand new. I hope that's not the issue.

Something else I noticed is that the shake gets worse after a drive/cruise, and when I put it in park the Rpm raises more then normal/vacuum reading is higher then normal and it's really shaking to the point i can feel it.

Almost like a lean issue but my AFR is 12.6 -13 at this time
 
That motor was brand new too, we think somebody bumped the crank when installing the motor. Hopefully that not your problem though.
 
Ok so I just finished fooling around with the car, and no matter what I did with the carb it still shakes a lot. So then I checked everywhere for vacuum leaks one again and nothing...... While messing around with my curb idle I noticed the car shakes so horrible at 1000-1100 rpm. And of course when the engine makes more vacuum. If I get more rpm then 1200 it smoothens out. I went for a little rip with my idle set a little higher (1000) and I seriously thought the car was gonna shake it's self apart. My fillings in my teeth were falling out! Once back on the gas smooth.
My buddie got ahold of scatt and they gave me a part # for a balancer/damper I should be using.
My engine builder said they used the same damper from my 340 which was internally balanced by them. Below I've posted a picture o what my current damper looks like. I found a part number but can't fine any info on it.
Part# 128668 current damper
The back looks like this picture
 

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So I found that the part number is a oem 340 damper....that I believe is neutral/internal balanced.
If that's correct this balancer should work?right?....I have no idea where else to look
 
340Duster247 said:
Okay guys!!
Have a new set up. Internal balanced scat 408 stroker. Same heads. Lunati 60405 (degreed correctly).
AFR is 12.5-13 at idle. Checked for vacuum leaks everywhere with nothing.

Still shaking. Especially when decelerating back down to an idle (1200 rpm) shakes a lot.
Locked my timing out at 34. Still shakes at idle. Haven't driven it locked out yet.

Only thing I'm looking into now is if the damper is wrong.
I'm going insane trying to figure this out haha.
Click to expand...
So whole different engine and still got the shakes ?
 
So you are using the same balancer.
And still no confirmation that the TDC mark was ever proved with the piston stop method.
What was the definition of insanity again? Oh I remember, doing the same thing over and over and expecting a different result.
Having said that, I must admit, I don't think you have a serious timing issue.
You have a serious A/F issue on the low speed circuit.

Here's what I would do;
1) Defeat the vacuum advance circuit and crank the dizzy 'til the engine idles as smooth as it gets and lock it down.Make sure the PCV system is functional.
2)yank the carb off, flip it over and set the T-port sync with the idle speed screw.The transfer slot should look like a little square,to slightly rectangular, below the throttle plate. After this do not move it.
3) flip it upright,remove the front float bowl and the power valve. Install a power valve plug, thereby eliminating that circuit. Put it back together and re-install it.
4) set the mixture screws to 1.5 turns from lightly seated.
5)fire it up. If the idle is too slow,use the secondary cracking screw to make changes.Adjust the mixture screws as may be required.
6) put a vacuum gauge on it. If you are still below the previously stated 5 inches(?), I would suspect an intake valve issue. Time for a leakdown test to see if they are fully closing.
7) when all tests are completed and the idle issue is resolved,you will need to re-install the PV or replace it, and fix the timing. This is an idle/low speed tuning test only.You can drive it like this,but it won't go very fast, and it wont take much throttle before hiccuping.

Or you could just do the leakdown test first. But it's a lot cheaper to buy a PV plug than an LD tester
 
AJ/FormS said:
So you are using the same balancer.
And still no confirmation that the TDC mark was ever proved with the piston stop method.
What was the definition of insanity again? Oh I remember, doing the same thing over and over and expecting a different result.
Having said that, I must admit, I don't think you have a serious timing issue.
You have a serious A/F issue on the low speed circuit.

Here's what I would do;
1) Defeat the vacuum advance circuit and crank the dizzy 'til the engine idles as smooth as it gets and lock it down.Make sure the PCV system is functional.
2)yank the carb off, flip it over and set the T-port sync with the idle speed screw.The transfer slot should look like a little square,to slightly rectangular, below the throttle plate. After this do not move it.
3) flip it upright,remove the front float bowl and the power valve. Install a power valve plug, thereby eliminating that circuit. Put it back together and re-install it.
4) set the mixture screws to 1.5 turns from lightly seated.
5)fire it up. If the idle is too slow,use the secondary cracking screw to make changes.Adjust the mixture screws as may be required.
6) put a vacuum gauge on it. If you are still below the previously stated 5 inches(?), I would suspect an intake valve issue. Time for a leakdown test to see if they are fully closing.
7) when all tests are completed and the idle issue is resolved,you will need to re-install the PV or replace it, and fix the timing. This is an idle/low speed tuning test only.You can drive it like this,but it won't go very fast, and it wont take much throttle before hiccuping.

Or you could just do the leakdown test first. But it's a lot cheaper to buy a PV plug than an LD tester
Click to expand...

Sorry forgot to answer you. Yes TDC is correct with a stop. I've already done all your 5 points except eliminate power valve. I have a 3.5 in there now. As for the new engine setup it's producing more vacuum now then the old.

I double checked all ignition this evening. Nothing is wrong there. The only things that have not been changed since the last engine that could be an issue as far as I know is the damper( which I just found out today that it was the same) and the engine mounts.

I've actually done your points twice to double check everything. No change. Like I stated earlier in other posts. I have a AFR innovate gauge and have the AFR dialed in good.
 
Well, that just leaves the leakdown test,and the converter/flexplate...................I think.
Tight or leaking intakes will really suck the idle vacuum down,and then the engine hates a load.
Is it still the same converter on there? And is it a neutral balance?

Well, there is one more thing, I guess; The converter stator clutch, or the tranny forward clutch.
Since you say putting it into gear drags the engine down, I suppose it could be a stator. If the stator was bad, off-the-line torque could be sluggish. A stall test would probably rule it out .
If the forward clutch was out of balance (hard to imagine), that could do it.I can't think of a test to prove the forward clutch.
 
340Duster247 said:
Yyeeeeeeeeeeeesssssss
Click to expand...
How bad is the shakes ? It's not a Bentley after all , they do shake a bit , if you got a big cam especially . Do you have rubber stock motor mounts or poly locs , the poly locs tend to transmit a bit more vibration to the car .
 
jerry6 said:
How bad is the shakes ? It's not a Bentley after all , they do shake a bit , if you got a big cam especially . Do you have rubber stock motor mounts or poly locs , the poly locs tend to transmit a bit more vibration to the car .
Click to expand...

Bad At 1100 rpm it's brutal. I'll try and take a video
 
AJ/FormS said:
Well, that just leaves the leakdown test,and the converter/flexplate...................I think.
Tight or leaking intakes will really suck the idle vacuum down.And the engine hates a load at idle.
Is it still the same converter on there? And is it a neutral balance?

Well, there is one more thing, I guess; The converter stator clutch, or the tranny forward clutch.
Since you say putting it into gear drags the engine down, I suppose it could be a stator. If the stator was bad, off-the-line torque could be sluggish. A stall test would probably rule it out .
If the forward clutch was out of balance (hard to imagine), that could do it.I can't think of a test to prove the forward clutch.
Click to expand...

Yah. I'm at a loss just as much as you guy are trying to help me. I have rubber mounts with the Schumaker or whatever torqe strap. The flexplate is neutral balance for internal balance. The converter is fairly new 3500 stall.
I haven't looked to much into the tranny yet.
I guess I could do a leak down next.
 
The higher I can get the vacuum at idle....the worse it shakes. Idling at 1000rpm around 9.5-10" vacume it's a paint shaker.
 
340Duster247 said:
So I found that the part number is a oem 340 damper....that I believe is neutral/internal balanced.
If that's correct this balancer should work?right?....I have no idea where else to look
Click to expand...
128668? OEM PN would be 7 digits.... mid'72 or earlier OEM 340 damper would be internally balanced. Sounds right but not 100% sure of that PN.
 
I feel that it is either a couple cylinders are not good or leaking intake manifold.
 
340Duster247 said:
Yah. I'm at a loss just as much as you guy are trying to help me. I have rubber mounts with the Schumaker or whatever torqe strap. The flexplate is neutral balance for internal balance. The converter is fairly new 3500 stall.
I haven't looked to much into the tranny yet.
I guess I could do a leak down next.
Click to expand...

Oddly enough my Purolator guy just went through this on his 350 Chev in his Camarrow. He chased it for months and months changing balancers, carbs, timing chain etc....

It turned out to be his Torque Converter. Food for thought. J.Rob
 
I'm pretty sure when I did my first engine (340) and that engine shook tooI had a different 2500 stall converter, I switched to the new tci 3500 with no cure.
 
This is strange , did you ever run the engine on a dyno ? If so did it shake there as well ? Wish you could narrow it down to an engine or transmission torque converter problem . Is it worse with the second engine or the same ?
 
340Duster247 said:
Yyeeeeeeeeeeeesssssss
Click to expand...

Okay...let me get this straight, new engine, still shaking?


Then I'm gonna venture to guess that it is NOT your engine that is the problem. I had a 408 do the exact same thing, especially in reverse. It ended up being a slightly warp flex plate...btw, it was a brand new, neutral balanced B&M plate..............................

this will sound crazy, but unhook the trans, slide it back, support the rear of the engine and fire the engine up, see if it still shakes, if not, you know its in the trans/flexplate/converter.
 
Are you absolutely 100% sure that the firing order is correct. I know you went over this already, a long time ago, but.............
One time I had a bad shake on a 4-banger,that turned out to be a cracked sparkplug porcelain insulator.It was all but impossible to see, and sparked perfectly in open air. I swapped the plug around to a different cylinder and saw the problem follow the plug. Bingo! Under the magnifier, I spotted what I thought was a very thin carbon track, but was in fact a crack.
I suppose you have not been able to source the shake to a particular cylinder? In which case a leakdown test, might at least rule out multi-valve leakage.
 
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