1970greenLS5

I am doing a frame off restoration on '70 big block. I rebuilt the motor. It and turbo400 are mounted on the chassis. I tried to start it, but the starter struggled and couldn't turn motor over. Battery and connections are good. I removed spark plugs. Starter then was able to crank motor, but with a harsh grinding sound between starter and ring gears. And the starter gear wouldn't retract out of flexplate gear when shut off. I shimmed starter, same problem. Tried another starter, same problem. Any ideas what might have gone wrong?

Steve2147

Flex plate backwards? Converter not in all the way and drive tangs on top of instead of over the pump drive tangs?

Steve g

1970greenLS5

Thanks for reply Steve. I checked before and after pictures of the flexplate. It looks like I put it on correct way as both pictures show the GM part number, a green paint mark, and the bump outs where the torque converter bolts all facing the torque converter.

When I looked up at the assembly from under chassis with flexplate cover off, it looked like the torque converter mounting tabs were up against the flexplate, but I will relook at that again today. Is there something else I can check to determine if the tangs are correctly engaging?

I am not sure, but I think the mechanical noise is the starter gear on the flexplate grear. Not only does the starter gear stick on the flexplate, but I also see some indication of the interference on the flexplate gear - its not chipped, but it looks shinny like something is wearing on surface. Any thoughts or ideas would be welcomed! Steve

njfl

Did you replace the starter or ring gear? Make sure you have them matching for the number of teeth on your ring gear.

CheezMoe

Depending on the machining of the starter and the block, it may just be too tight and in need of a few shims.

1970greenLS5

This is the my first attempt at starting the car, so I am not sure the original starter ever worked properly. When I bought the car, it had been sitting in someones garage for more than 25yrs without being started, and the gas tank and lines were clogged with varnished. That was one reason I am doing the restoration. The numbers on the starter that came with the car indicate it was for a small block for something like a '71 or '72. I bought another starter that had correct numbers for '70 BB and had it rebuilt. From the outside, both starters look the same. I did not replace the ring gear on flexplate.

I think I have a couple paths I can take. Add even more shims (there is a 1/64th shim in there that didn't help) between starter and block, buy a new starter at auto parts store, or separate the tranny from the block to see if that stops the binding. Any thoughts? Steve

Steve2147

When the converter is indexed into the pump on the trans properly you should be able to slide the converter to and from the flex plate at least 1/8th of an inch with the bolts out. If you can't move the converter back and forth, it's not in right.

Steve g

Peterbuilt

All the above advise is very good but you might want to try this to see how the gear on the starter aligns with the ring gear...
Disconnect the battery cable from the starter then jumper from the disconnected battery cable to the "S" terminal (small terminal on the solenoid closest to the block).
That will make the gear on the starter engage with the ring gear but the starter will not turn.
Make sure the gears mesh properly (in and out).
The space between the two gears is the thickness of a paper clip.

larrywalk

After you bolted the trans to the block, how much clearance was there between the flex plate and the torque converter?

Did the converter turn freely before it was bolted to the flexplate, or did it bind?

larrywalk

Did you use starter bolts or standard bolts?

Starter bolts have cross hatching just beyond the threads which cause them to register precisely. Regular bolts have too much slop and allow the starter to move somewhat - such movement will ruin flexplate/flywheel ring gears and starter pinions.

Roco71

Can you rotate the flex plate and torque converter by hand? If not my bet is the converter was not totally seated. The torque converter should spin freely before bolting it up to the flex plate if it hits part of the flex plate the converter is not seated. If this is the case you could have damaged the transmission pump or bent the flex plate

1970greenLS5

Wow - thanks for all the suggestions guys! I have tired a few things. I bought a rebuilt starter at local parts store. It turned motor over with no grinding noise with the plugs out. When I put them in, it didn't have enough power to crank the engine - same as the other starters. I took spark plugs out and valve covers off again, cranked engine and checked for - rockers all working properly, and that the flexplate didn't wobble. It looked fairly straight with little runnout. I tried turning crankbolt, it was very hard to turn, but that could have been because of bad access - car is on the ground, fan and radiator is in the way. I unbolted the 3 bolts from the flexplate to torque converter - it came off nicely and didn't look like anything was bound up. Torque converter moves in and out freely - seemed like a good 1/2". And it spins freely. While removing the 3 bolts, I was able to move the flywheel while using a combination wrench. But I did have to pull fairly hard to get it to turn. Couldn't get a torque wrench down there to see how hard I was pulling.

I have been using a heavy duty set of jumper cables to connect battery to the starter. I am wondering if I have a bad connections at the jumper ends and/or because all my bolts have been phosfated or painted. I will buy some short cables and bolt all the connections. If that doesn't work, something probably went wrong with my rebuild. Steve

larrywalk

Glad to hear that the converter is free. How much torque is required to turn the motor with the spark plugs out?

As a rough guess, the torque to turn with the pushrods removed is basically just ring and bearing drag - I'd guess 20-25 ft-lbs prior to initial run-in. With the pushrods installed and valves adjusted, the torque goes way up (unless a roller cam is installed) to turn the motor - I'd guess about 60 ft-lb prior to run-in.

Has the engine been pre-oiled? And the crank been turned 180 degrees to pre-oil again? (Recall that only the upper half of the main bearings have a groove, so to get oil to the rod bearings, the crank must be turned 180 degrees and pre-oiled twice.)

Has a lot of cam and lifter lube been used?

Rocker arms and pushrods lubed?

1970greenLS5

Yes - I pre-oiled with an old distributer and a drill. I did bump the starter a couple times and re-oiled. But I don't believe I turned it a full 180degrees. I have an oil gage plumbed in. It gets up to between 35 and 40PSI with the drill. I'll re-oil it before going further.

I did oil the main and rod bearings during assembly. And I used moly on lifters (new lifters and cam). Also dabbed some moly on ends of pushrods and rocker arms. I rebuilt the engine a year ago. Its been sitting inside my garage ever since. Not sure if that could cause any issues.

I don't know about the torque - I tried to get at it but access is limited with fan, crossmember, and radiator. I do know when I tried to torque the damper to crank bolt a year ago, I could not reach the final torque for the bolt without holding the flexpate teeth with a 2x4. So it was not at 85 ft-lbs. I will try checking that again tomorrow night before I try starting it with good battery cables.

scottw

Are all your clearances rigth from the starter to the Flexplate? If I remember right, from the starter to the flexplate there should be .04 to .1 inch of clearance. Once the starter is engaged into the flexplate there should be .02 clearance. Basically enough room for a paperclip to go inbetween the teeth.

When I replaced my engine, the first starter had all the right clearances but would not engage the flexplate correctly. When I returned it and got another one (same brand) it bolted right on and worked ever since.

1970greenLS5

I did remove the accessories in the front of the engine and got a torque wrench on the crank bolt - it takes somewhere between 55 and 60 foot pounds to turn the motor with the spark plugs removed. Does that sound reasonable for fresh rebuild?

I will check the clearance on the starter gear tomorrow. Is it ok to leave power to the solenoid for a couple minutes to get a clearance measurement between the starter and ring gear? Steve

larrywalk

Torque to turn (above) sounds ball park.

Are you using real starter bolts (post #10)?

Jumper cable clamps aren't going to do it! Use real battery and ground cables with the ring terminal on the end bolted to BARE metal. Also check that you have a GOOD ground strap from the engine block to the chassis - bolted to clean metal. Painted or dirty metal will cause enough extra resistance to hurt your cranking torque.

Power to the solenoid?... I wouldn't leave it connected for more than 30 seconds - and then give it time to cool. YMMV

1970greenLS5

Thanks Larry. Yes, I am using the original starter bolts with cross hatch pattern. The good battery cables worked - the starter now turns over quickly. Thanks for all the help.

Now the next problem is I can't get the engine started! I pre-oiled the motor. Set distributor in, and tried firing it up. It did catch and ran for a few seconds at a very fast idle. I was not able to get it restarted. I did smell gas, so I believe it flooded. And I saw a couple drops of gas seaping from the bottom of carb, passenger side, around the shaft that opens the primary. I had a heavy duty charger on the battery, but the battery lost too much charge and slowed down. Spark plugs tips were wet, so I bought some new ones and tried it again. No change - wouldn't start. I have battery charging overnight and will try again in the morning. Not sure if the points are set properly. What should the gap be if I set it manually before I start the car? And is there a way to make sure my coil is good? Steve

larrywalk

What is the condition of the carb? What kind is it? How long since it's been rebuilt?

Seeping gas sounds like the float/needle/seat is not doing its job.

It is also possible that a new fuel pump has too much pressure and is overpowering the ability of the float/needle/seat to stop fuel flow into the carb - therefore the gas level in the bowl goes too high and floods the motor.

1970greenLS5

Its a quatrajet. It was rebuilt by a carb shop thats been in business for a long time. The fuel pump is an NOS AC pump. New fuel tank and lines. Would letting it sit overnight allow any pooled gas in cylinders and in float boal to evaporate? I am thinking of trying it again now as the battery should be charged.