Vibration when I put car in gear

[JJbird]

I just rebuilt my engine 1965 Thunderbird it is a 390 and is stock. It runs great when it is in park and feels very smooth. The engine starts easily.

When I put it gear the engine vibrates and I get a squeal from one of the belts.

When I drive the car, the engine smooths out once it gets above idle. The transmission shift smoothly. When I slow down to an idle again it starts vibrating and a belt squeals.

When I removed the engine I pulled the torque converter out attached to the engine. I did not realize I was supposed to separate them.

The motor mounts are tight.

I am not sure what to check next.

Any suggestions?

[bird 60]

The next thing I would check is the Universal Joints. Also the Trans mounts.

Chris.....From OZ.

[simplyconnected]

If the engine is running, so is your torque converter so that is NOT the root cause. You say it runs smooth in Park. Is that at idle speed or elevated RPMs? Does the vibration start BEFORE the car is in motion? If so, U-joints aren't the root cause. Are you hearing engine noise, like piston slap or pinging?

How did you route your fan belts? Are any getting HOT? I'd like to see a few pictures. What happens if you remove all the belts except one that drives the water pump, then start the engine?

You may also have a vacuum leak in your intake manifold. Pull the car outside and use an UN-lit propane torch. Turn on the gas and wave it around your intake manifold. If engine speed increases, you have a vacuum leak.

Tell me how you set your distributor into the cam gear and how you timed the engine. Are all the plug wires in the correct distributor cap towers?

How did you adjust your carburetor's idle mixture screws?
You see, without a lot more information from you, this turns into a guessing game. All we have to go by is the few sentences you posted. - Dave

[stubbie]

What happens when you put car into reverse? Does the vibration go away?

[JJbird]

Thanks Chris and Dave for your input. You are right it is a guessing game, but you gave me some good tips and a starting point.

The engine runs smooth at any rpm. No noise from the engine.

As soon as I put the car in drive or reverse gear the engine starts vibrating (shaking).

Today I jack up the car and checked transmission mount. I could put a screw driver in part of the mount. I remove it and I can move the rubber part of the mount easily by hand. I assume the transmission mount should firm like the motor mounts.

I removed the a/c and power steering belt, it did not make a difference.

I put the distributor in before torquing down the manifold. I put the time chain on according to the manual and a video I watched. I put the cam in the block first then installed the crank and the timing gears and chain. After installing the pistons I checked to make sure the #1 piston was in the correct place with the timing gears. I marked the harmonic balancer at TDC and at 6 degrees BTDC so I could find the marks with the timing light. For the final distributor installation I made sure the engine was still at TDC and put the distributor in so the rotor pointed at #1. After I started the engine I set the timing with the timing light to 6 BTDC. I broke in the cam according to the manufacture instructions. All the plug wires are in the correct spot and on the correct spark plug.

I rotated the crank every time I installed a moving part to make sure everything was turning smoothly. The engine rotated smoothly before it went back in the car. I also rotated the engine while installing the rail rockers and only turn the bolts a small amount each time until they were torqued down. I tighten the bolts according to the shop manual sequence.

After breaking in the cam and checking the timing and dwell the engine was running rough. The air fuel mixture screws were doing nothing and we have terrible gas in California. The carb is about 5 years old and I use this car as my daily driver. I rebuilt the carb and that smoothed out the engine from idle to higher RPMs.

Thank you Dave for tip on how to check for a vacuum leak.

J.J.

[simplyconnected]

...The air fuel mixture screws were doing nothing and we have terrible gas in California...

If your idle screws are doing nothing, you have the throttle screw (not the idle mixture screws) turned down too far. That opens the butterflies past the idle ports, rendering the idle screws useless.

Start with the engine off, by turning the throttle screw so that the butterfly shaft barely opens. Then turn your idle adjustment screws all the way closed (by hand, don't force them), then turn each of them out 1-1/2 turns. This should give you a starting point for your idle mixture. Use your manifold vacuum for your distributor advance.

If the engine refuses to idle, back off your timing until you can idle, then continue adjusting the carb for the best idle. Then, bring your ignition timing back in tune. Pay attention to what's happening when you punch the gas. Are you getting two squirts? Don't stick your face over the carb. Instead, use a mirror (like a dentist's mirror on a stick). A new engine should respond immediately from an idle speed (like at a light) without bogging or coughing. Did you use a dashpot?

What cam did you use? Give me the duration and separation numbers.

It's easy to tell if your mounts are ok. If any are broken replace them. - Dave

[scumdog]

I just rebuilt my engine 1965 Thunderbird it is a 390 and is stock. It runs great when it is in park and feels very smooth. The engine starts easily.

When I put it gear the engine vibrates and I get a squeal from one of the belts.

When I drive the car, the engine smooths out once it gets above idle. The transmission shift smoothly. When I slow down to an idle again it starts vibrating and a belt squeals.

When I removed the engine I pulled the torque converter out attached to the engine. I did not realize I was supposed to separate them.

The motor mounts are tight.

I am not sure what to check next.

Any suggestions?

Is that ‘squeal’ actually a squeal as in mechanical - or is it the noise of a vacuum leak that may be linked to your engine revs dropping when you pull the car into gear?
(I’ve had vehicles that I could create such a noise by adjusting the idle speed)

As the motor seems otherwise sound I doubt the issue is directly linked to its mechanical integrity.

My 2-cents worth!

[JJbird]

My transmission mount was bad it has now been replaced.

I think I may have a vacuum leak, unfortunately I cannot find it.

I tried the propane method and the carburetor cleaner method, but I could not find a leak. I check all the way around the manifold, the carb, and the vacuum ports.

My door locks were not working which runs on vacuum ( the door locks worked before the rebuild). All the other vacuum options are working including the power brakes. I re-torqued the manifold and a couple bolts were a little loose, maybe a quarter of a turn. I torqued them to 35lbs and in sequence according to the service manual. When I put a vacuum gauge on a manifold port the vacuum fluctuates between 15 and 18. The fluctuations is at idle and at higher rpms. I test drove the car. When I put my foot on the brake the engine starts shaking. I have power brakes and when the booster is in use it requires vacuum. It seems like after I take my foot off the brake it builds up vacuum and the shaking goes away. I plugged the power booster port at the engine and it did decrease the shaking when I stop the car ( vacuum was not being used), but did not stop the shaking, so I do not think there is a vacuum leak in the brake booster and I replace brake boost vacuum line and clamps when I rebuilt the engine. I plugged all the vacuum ports and there was no difference, the engine still shakes.

I installed the intake manifold while the engine was out of the car. I used an engine hoist to help me drop it into place, and we also used some longer bolts to help guide it into the correct position before setting it all the way down. I used small amount of gasket sealer to glue the front and rear cork gasket down and they did not move when we dropped and torqued the manifold down. I also used gasket sealer around the manifold openings and ran it up above the gaskets in the front and rear.

The engine runs smooth and quite when it is out of gear.

Any suggestions of what to do next?

[simplyconnected]

Did you plug the vacuum line going to your transmission's vacuum modulator? Sounds feasible to me that things go wrong when you use the trans., but all I can do from this chair in Michigan is guess.

Is this trans a C4?
Was the trans set up properly?
Did you have the transmission rebuilt?
Were your pumps cleaned and re-assembled?

[jopizz]

When I put a vacuum gauge on a manifold port the vacuum fluctuates between 15 and 18. The fluctuations is at idle and at higher rpms.

I've found that a minor fluctuation like that is ignition related. I would check your point gap. Do you have a dwell meter. It may have nothing to do with the shaking but I would check it anyway. I would also check your plug gap.

John

[JJbird]

Thank you for your suggestions.

I could not find the vacuum leak, so I decided to look else where for the problem, before I started guessing and replacing parts.

I did a compression test and discovered that cylinder #4 did not have any compression. I pulled the head and will be taking it to the machine shop tomorrow.

[simplyconnected]

Wait a minute...
Explain what your engine overhaul included. I've never heard of one that produced a dead cylinder.

Did you also rebuild the heads? How do you know the head is bad? - Dave

[JJbird]

I had a machine shop clean the block and prepare it for rebuilding ( they bored it, honed, decked it, checked it for cracks) , they also rebuilt the heads. They put on the connecting rods and the rings on the pistons and I reassembled the rest.

When I install the pistons I made sure the compression rings where 180 degrees apart, I used a ring compressor, oil on the rings and the cylinder walls and wooden handle to knock the pistons in. Everything went in smooth and I turned the crank after I installed each piston. Everything rotated smoothly.

The machine shop thought I might have a bent valve. They told me to bring the head in. Today I did and they said it seemed to be fine, but they did some work on the head to make sure the valve seated better. The rods were all straight.

Should I pull the piston and see if there is a problem with the rings?

[jopizz]

Put the head back on and redo the compression test. If the cylinder is still dead pour some oil down the plug hole and redo the test. If compression starts to build then you have bad rings.

John

[simplyconnected]

Rings naturally rotate as the piston runs up and down. At times, all the gaps align, but momentarily. So, ring gap placement is only temporary.

First things first. I normally use a rubber mallet to smack the valve springs. All the intake valves should sound the same and all the exhaust valves should sound the same. A bent valve will hang, preventing the valve to 'pop' closed after the mallet hits it. So, a bad valve will sound different. I pour alcohol down the ports to check for valve leaks while the head is out.

I want to know about your CAMSHAFT. I asked about it before but didn't see your answer.

It is very important to pre-lube a dry engine before starting it. Oil needs to fill the lifter galleries, rocker arm shafts and lube the bearings before you fire plugs.

Did you watch the rocker arms go up and down before you replaced the valve covers? If #4 rocker arms aren't moving you better look at the valve train starting at the cam. Again, what cam is this? What pre-load is on your lifters?

If valves are opening, new pistons (even without rings) will produce some compression because there is about one-thousandth inch between the piston and bore. You may get oil but also some compression.

Sounds to me like your #4 valves are not opening at all. A visual check will confirm. Do these checks. Let's hear where you are. I have more depending on your results.

BTW, did you take lots of pictures as you assembled? - Dave