Rebuilt Engine Trouble

[Axlman]

Need your expert advice.
Rebuilt the 350 and installed.
Now have a wobble when it is in idle and running.
Shakes and wobbles badly.
Tried everything, new wires, new carb, adjusted timing, new plugs, and it stays the same.
I am thinking that the flexplate got bent but it was never at riskof any damage.
Also started to think maybe an issue because the flex-plate seems to have a counterweight and I think it shouldn't. But the trans and engine and flexplate are the same as before. No changes.
I am stumped.
Any thoughts or similar experiences?

[Mike S]

 When you say "wobble" are you referring to an engine balance/shake issue?
What work was with the engine rebuild? My initial hunch, if wobble is engine shake/balance, is to check the vibration damper to make sure the rubber is not damaged causing the outer weight to slip on the inner shaft bolted to the crank.

Mike

[CNorton]

350 short blocks are internally balanced.  Neither the damper nor the flex plate should have a counterweight.

c

[RonA]

Hi.  I assume that your 350 is a older one [ 2 piece rear main] then as stated it should not have any counterweights.  If by chance it is a newer one piece seal the balancing is different and the flex plate may be in the wrong position.

[69pace]

I assume you are noticing a rpm hit so you think its internal to the block, or is this an exterior vibration and maybe you have a loose or broken mount, crossmember, or something else free in the drivetrain  and or loose subframe bushings?

[Charley]

Have you triple checked that you don't have any plug wires mixed up ?

[miket1]

Did you install a different flex plate from previous,

[ko-lek-tor]

Did you install a different flex plate from previous,

"Also started to think maybe an issue because the flex-plate seems to have a counterweight and I think it shouldn't. But the trans and engine and flexplate are the same as before. No changes."

[Axlman]

Same flexplate.
Drove it on a trip and it ran terribly, used 7 tanks of gas and sputtered.
But it didnt shake and wobble really bad.
Now it is wobbling. Seems to be at the flexplate in my opinion.
you can see it shake and wobble at idle and it gets bad and is loud at high rpm.
But I have checked wires and plugs numerous times.
Going to try another new set of plugs today and see though.

[janobyte]

Let's see, ruled out plugs (one fouled plug will do it), wires( correctly routed/firing order), cap (hairline cracks, moisture), and rotor. Ignition.


Carb "sucking air" through the gaskets, base plate ? Vacuum leak: hose cracked, unattached, intake ports ?

Running rich? float level, needle and seats bad, o rings allowing fuel passage when closed?  Any recent backfires through the carb?

[KurtS]

Please explain what is wobbling.

[ss jim]

If it was a rather short trip and used 7 tanks of gas I would be looking at a bad needle and seat or choke partially closed. Don't ask how I know about the choke. Jim

[Axlman]

The wobble feels like it is at the flex plate and torque converter. It actually sounds like it is loose and shaking there between the seats while driving(all bolts are tight). (maybe torque converter is in wrong?)
I am going to try to change plugs today in about an hour. If there are no improvements after that I will pull tranny and flex plate maybe and see if it is cracked or warped maybe.
Could be running rich but i have put a Carter carb on as well as the rebuilt Rochester Quadrajet. Wobbles and shakes with both and when they are adjusted.

[BULLITT65]

May sound dumb, but firing order could be re-checked. What about drive shaft out of balance?
I understand most of the items are the same that came out of the car but stuff happens sometimes, and it is just a matter of tracking it down through a process of elimination.

[ko-lek-tor]

May sound dumb, but firing order could be re-checked. What about drive shaft out of balance?
I understand most of the items are the same that came out of the car but stuff happens sometimes, and it is just a matter of tracking it down through a process of elimination.

I kind of ruled out the drive shaft as OP said it was occurring at idle and the D. shaft would not be turning. Might want to check the pushrods and do a compression check before tearing into the trans. area to rule out the engine being sick. I am confident I could diagnose and repair if I were there. Hard to do so far away though.

[BULLITT65]

Good point on the drive shaft. I was thinking more about the excessive noise he referred to. But I agree start with the simple stuff like compression check, and easy items and go from there.
Being on site is totally different than trying to diagnose from someones description online. If he starts narrowing it down, he will figure it out.

[Axlman]

Checked compression and did leak down test on all cylinders. All checked out ok.
Went to get new plugs from NAPA and low and behold they went to give me different spark plugs.
Said the NKG 8177 plugs I had (and bought at NAPA I might add) were not correct for the 350 Camaro in 1967.
So they gave me Autolite N85 plugs.
I installed them and will try to set up and fire tomorrow morning.
I do not think that incorrect plugs can cause a woggle/shake like this? But thoughts out there?
I have checked firing order over and over.
What I am worried about is mayby not having set the balancer correctly at TDC when I assembled?
Or I did something else wrong on assembly to have timing off really bad?
Appreciate all of your thoughts even though it is far from all of you.

Thanks

[BULLITT65]

Glad the compression is good.
I am not sure you could have installed the (stock) balancer incorrectly unless you put it on backwards. There is a slot in the crank for the key, and the balancer has 1 has one slot as a key provision.
Spark plugs- I could see if they sold you to cold of a plug, and they fouled out that would cause a misfire shaking type response.
If your spark plug gap is not correct, and not all the plugs are firing correctly, that could also cause the issue.

So what did the end of plugs look like that you just removed? Black, white,  brown? 

[Axlman]

Plugs were very black and carboned up with some white burn on the ends.
Will try to set up the distributor and timing and fire tonight.

[BULLITT65]

Well perhaps they were to cold of plugs and fouled out right away. Good luck tonight, hopefully you will be in the clear.

[vtfb68]

Axlman,
 AC plugs have always performed better than any other brand in my chevrolets. Our local NAPAs in this area no longer stock AC parts but can order them, they will sell you what they have in stock if you let them. Is the camshaft degreeded properly ( the two timing chain gear dimples should be together).
     Good luck,
           VT

[ko-lek-tor]

Axlman,
 AC plugs have always performed better than any other brand in my chevrolets. Our local NAPAs in this area no longer stock AC parts but can order them, they will sell you what they have in stock if you let them. Is the camshaft degreeded properly ( the two timing chain gear dimples should be together).
     Good luck,
           VT

x2

[169INDY]

For what is worth.

I had lots of troubles when I left out that thin sheet metal heat passage tin gasket out (lack of installation) under the q-jet carb, 8$ part cause fouling and rough running if it moved at all.

Jim

[bcmiller]

You checked and the bolts for the engine mounts are installed, right?

And bolts are in the transmission mount and crossmember, right?

[BULLITT65]

You checked and the bolts for the engine mounts are installed, right?

And bolts are in the transmission mount and crossmember, right?

Remember it is doing it at idle, and unless you are doing a hole shot and putting a lot of torque on the drive train those mounts are not going to play a factor yet.

Always good to re-check those after putting a motor/trans back  in though.

[bcmiller]

Don't be so sure on that.

[BULLITT65]

Well I have driven cars with broken motor mounts and the only time they became a factor was when I would do a brake stand. Every so often the motor would torque over and the throttle would stick for a second or 2, but At idle or cruising down the road I never had any loud noises like the OP has mentioned.
I mistakenly mentioned the drive shaft being out of balance, but again just sitting at idle, it would be a non-factor.

So yes, you can re-check the mounts, but if it is sitting still and having issues I think it to be less likely...

[janobyte]

Still need addressed the increased fuel consumption. 7 tanks, what distance traveled?

Any un-burnt fuel finding it's way in the exhaust or puddles in the carb ?


Compression good-ignition: firing order/timing/quality of spark-carb: gasket leaks/adjustments/internals

Plug readings indicate engine running rich, all cylinders. Color of exhaust gasses ? Black smoke under initial load? (taking off/accelerating)

Oil contaminated with gasoline?

Same experience as Bullitt concerning engine mounts (more so my beaters when I was a teen  )

[bcmiller]

You checked and the bolts for the engine mounts are installed, right?
And bolts are in the transmission mount and cross member, right?

Come on guys.   Remember, check the things that are easy and don't involve any cost first.  Doing this will take a few minutes and if things are OK, then move on.  Process of elimination.

I actually think there is more than one issue, but without seeing this "wobble" in a video or in person, it will be hard to diagnose.

[BULLITT65]

Come on guys.   Remember, check the things that are easy and don't involve any cost first.  Doing this will take a few minutes and if things are OK, then move on.  Process of elimination.

I actually think there is more than one issue, but without seeing this "wobble" in a video or in person, it will be hard to diagnose.

X2

[ko-lek-tor]

You checked and the bolts for the engine mounts are installed, right?
And bolts are in the transmission mount and cross member, right?

Come on guys.   Remember, check the things that are easy and don't involve any cost first.  Doing this will take a few minutes and if things are OK, then move on.  Process of elimination.

I actually think there is more than one issue, but without seeing this "wobble" in a video or in person, it will be hard to diagnose.

Agree w/Bryon. When I learned OP used non AC plugs, that sent up a red flag to me. I used to think plug brand did not matter, I mean, a plug is a plug, right?  Well, I have had many instances where an engine just would not run or run right with certain brand(s) of plugs. Not even sure what it is that causes the problem, but I know it happens.
Couple of years ago, my cousin tuned up his '39 F20 Farmall (antique tractor). It would not fire,(hit a lick, if you are from Appalachia) so he calls me to bail him out. This is a hand crank magneto engine so patience goes away quick if there is no firing of the cylinders. I told him to put the old plugs back in and what you know, it starts. Autolites were the new plugs. I told him, they just will not work in that type engine. Made a believer out of him that day.

[Axlman]

Working on it tonight as last night date night with wife changed plans.
I suspect that the spark plugs were the issue and that the Autolite ones will correct with any luck.
But we shall see.
Much thanks go out to all on the advice and opinions.
I will post late this evening with results.

[crobjones2]

because I've done this before - assuming it is an automatic, do you have too much fluid in the transmission?

[BULLITT65]

now thats one I haven't done (yet?) .

What kind of response did you get with to much ? how much extra fluid did you have in there?

[crobjones2]

about two quarts - one heck of an out of balance at low end, smoothed out when accelerating. acted like I had lost a cylinder
everything I read said 9qts - but 7 puts it just under the full line - yes- completely empty with 1 qt in the converter

[Axlman]

Hello all.
Thanks again for all of the help and advice. I have to tell you it was not easy or completely clear what happened or the series of events at least.
While we have solved the problem we hope to have figured out the cause.
The issue, and it makes me a bit embarrassed not to have looked, was that the transmission and engine bolts were loose, two missing in fact. Now i am 100% sure that they were tightened.  Both of us know we tightened them. We did however miss putting in the one  bolt (small opening between firewall and has to go in before install).
Our theory is that the plugs were the wrong ones and were running cold and causing vibration.
This, coupled with the fact that I did not loosen the transmission when I tightened the flexplate led to the bolts backing off and increasing the vibration.
The second issue is that the Quadrajet carb was not tuned very well and the air mixture screws were worn  badly. This led to poor fuel consumption. Seems better with new screws and I still have some adjusting to do.
My failure to loosen transmission mount bolts led to  a gap between the engine and trans and when I tightened the flex plate it pulled the torque converter part way out of trans up against the flex plate.  Once i loosened the transmission mount the trans pulled up tight and everything fit well.
So it seems we have solved the dilemma. AT least for now.
All of you and your help are greatly appreciated.

[BULLITT65]

Awesome that you figured it out, and with (hopefully) very little damage.

A bunch of little items added up to a bunch of noise and a rough running car.

Enjoy your smooth ride!