VCCA Home Forums TECHNICAL - 1945 AND NEWER 1946-1948 very tight motor

Hello All, I have what I think is a big problem.
I recently had my motor reconditioned, which included new pistons, new rings, new camshaft. Also I had all the babbit bearings replaced with slipper bearings. The problem I have is that the motor is now very hard to turn over. Without the head and rockers attached, I can turn it over with some effort, however when the head and rockers were attached and bolted down, it takes a lot of force to turn it by hand and only then by using a lot of leverage.
Before I attempt to start the motor normally, I want to make sure that this tightness is "normal". Personally, I don't think it is normal to be so tight but then again, I am no mechanic.
So please, can someone offer me some advise?
Many thanks
Ron

That is perfently normal. If the starter does not turn it over very fast jump it with 12 volts to get it going. I would suggest pouring abouut an ounce of a light oil into each spark plug opening. This oil lubricate the cylinder walls and help it to turn over faster.
Once it is running get it up to a fst idle so oil get thrown around. Some kind of camshaft break-in oil should be used to break-in the cam and lifters properly along with a "thin" oil.

Leave the spark plugs out and see if you can turn it over with the 6-volt battery. If not, use a 12-volt jump and turn the engine over many times. Should get easier each time you try it.

And continuing to be even more cautious, you can remove the two rocker shafts along with the rockers. Since the spark plugs are removed, it won't hurt to have no valve movement. Essentially what this will do is remove a "huge" force that is required to open and close all valves while the engine is turning over.

You should be able to turn the engine with a 6 volt battery with the rocker arms removed (and oil in the plug holes). Do this long enough that you feel that it's turning freely.

Don't let the starter get too hot.

Once you feel it's turning okay, then reinstall the rocker shafts and set the valves "close enough". With the plugs till out - now turn the engine over again. It may sound a tad stiffer but it should still turn over. Do this for a while again until you think that it's "free".

Finally, set the values fairly close to accurate (But remember that this is only a cold adjustment) and install the spark plugs. Now turn the engine over. This should be your last test before trying to start it. If it's turning okay now, then you can turn the ignition key on and try to start it.

Lots of good advise above. I would also disconnect the fuel pump supply hose otherwise your going to flood the motor with excess fuel and wash the cylinder walls of the oil. Once you have it turning over and your ready to start it then connect the fuel hose back up. Good Luck Don

The fuel pump should not need disconnected! the needle valve will stop the flow of gas to the carb. when full.

Ron,

Do the things suggested as far as loosening the engine up. Reinstall the spark plugs, adjust the valves, and make sure the carburetor is getting petrol (gasoline). In other words, have the engine in running order.

After you have done all this get a length of 3/8th chain and thread it through about 8 feet of pump pipe. Hook it up to your mate's (buddy) pickup and pull the car down the road at 35 KPH for about 5 miles with it in high (drive) gear. Start off slow and increase the speed for the first mile.

After you have done this, for the five miles run, give it a little gas and then switch the ignition on. It will start running . Stop and unhook the chain. Drive it back to the shop and readjust the valves.

Note: If, when you start off pulling it down the road, the right rear tire drags then you can assume that it is indeed too tight. Stop. You probably forgot to put oil into it.

The above used to be the preferred method of restarting an overhauled engine in North Carolina. Was too! Saves the starter and no need for no stinking 12 volt battery.

You are most welcome.

Charlie

I keep hearing stories here of tight rebuilt motors...I find it odd that all the motors I've ever had rebuilt never had such issues...They've always turned over about as easily as the "worn" out ones...Makes me wonder...As a machinist I believe if the crank bearings have the proper clearance...There shouldn't be such tightness and the new ring clearance shouldn't cause that much "friction"...Personally, I would be a bit worried that a shop would let such an engine out their door...In the past I just sent out the various parts to be machined and reassembled everything in my shop...Only to notice the slightest new tightness...Hmmm

If the rings and cylinder walls are a bit rough (like they should be for new or honed parts) then there will be some resistance even when well oiled. Once those parts wear in a bit (seat) then the resistance is reduced. Same for the crankshaft and babbitt bearings. They are normally set a bit on the tight side so they can be burnished and run in during the early stages of rebuild and startup. I have found that if everything is set right then a strong 6 volt starter with proper battery cables will not have a problem turning over a freshly rebuilt engine.

Agree with the above....at least that was the way it worked when the cars were a few years old. I suppose after everything is 60 or 70 years old things change a little.(like the starter power, etc)
But it still is normal for the engine being very difficult to turn over by hand for the first 100 miles or so.
We had one mechanic in the shop that always set up everything in his overhaul jobs too tight. They did have to get the car out on the street and push it with the wrecker to get it to turn over. This was from before the advent of the 12 volt battery.

Thank you everyone for your advice. I certainly feel a bit better about the tight motor being normal and nothing to be too worried about . I will let you know in due course How I went.
Thanks again,
Ron

sounds to me like you need some shims in your main beirings and maybe your rods. if they are too tight on your crank when the engine heats up after running everything will expand from the heat and gald your babits and lock up the engine,in other words ruin it.this is a very technical part of a car or truck and should be done by a professional.you might cost youself a whole lot of money if you don't do this right.

jeff korner
south east indiana

He hasn't even started the engine yet....give the engine a chance to run under power.

No one has mentioned the fact that the rope seal on the rear main will initially be a cause of significant drag on the engine. Takes a few minutes to get it smoothed up to the rotating crankshaft and develop its own natural clearance.

I agree!!!

As do I

I had a problem when I first rebuilt my motor. I didn't have the crank checked and just reinstalled with new brings. When I had all the main caps bolted and torqued the motor was very tight. I continued to complete the build and install in my car well ended up completely wiping out my new bearings to the copper and wiping out the crank. Come to find out the crank was different thickness and caused the crank to bind. I ended up pulling the motor back out and having the crank built back up and balanced by a shop. Once that was done I re-assembled and it was nice and smooth. Hope this helps.

Thats why the main bearings are adjusted before the pistons are installed. With the mains properly adjusted the carnk sould turn freely. With the rods properly adjusted as per the manual the same, should turn over easily. With new rings on honed ctlinders the drag will be considerable, even with correct ring gaps, etc. This is due to the pressure of the ring against the cylinder wall. For the same reason you can not just take the piston and shove shove it down the cylinder to install the connecting rod cap. The common method is to take the handle end of a hammer had tap it down.....especially with expander type rings. Now multiply this drag by six when turning over the engine.

Well, it's been a while since I first posted my problem, but here' an update.
I had a hell of a time turning the motor so I had to resort to a 12 volt battery. Disconnected all the appropriate electricals and turned it over and it started on the first go. Without going into all the details, I have driven it twice using the 12 volt battery with no problems. I have now installed a 6 volt battery and the motor will start after a bit of coaxing but, I am sure that with a bit of driving the motor will become a little looser and starting will become easier.
Now to iron out all the small problems I have encountered.
Thanks again to everyone for your advice
Ron

'Glad it is finally going your way.

Now that you've got it turning, you might make sure your timing isn't a bit too high. That obviously wasn't your initial problem but timing can make 'em hard for the starter to turn.

Good luck