Got a weird problem with my starter on the flathead. When the engine is cold, the starter works great, but when I shut the truck off after driving a while, the starter won't engage the flywheel. Here's the weird part.....it makes the same growling sound while cranking, like it's engaged, but the engine isn't turning!
If I let the engine cool off fully, it works fine again, so heat related?

I pulled the starter to check it out and found nothing out of order. On the bench it spins right over and the bendix works fine. I swapped in a new bendix with no change....

Gonna try a different starter next.

 

Could the ring gear be cracked? Maybe tight enough when cold but loosens as it heats?

 

Well now, that's a possibility I hadn't thought of. Makes sense though....if the ring gear is slipping on the flywheel, it would still sound like it's cranking over.

When I had the starter out I checked the ring gear teeth and none were chewed up or missing, but didn't think to look for a crack. Will check again...
Thanks Ross!

 

If that's what is going on, I'd guess the flywheel may have to be replaced. Not a fun job for sure!

 

I've spot welded the gear to the flywheel. A friend had a six cylinder Mopar PU where the gear was slipping on the flywheel. Nothing was cracked. We jacked it up, I crawled under it and put about four spots of weld around the perimeter. No more problems. Be sure to keep the ground on the flywheel to keep any current out of the bearings.

 

That thought occurred to me, Ray, did you use a special rod or anything? I guess all you need is to keep it from slipping, not a full-penetration weld.

 

No, not deep penetration. Just four spots, each probably 1/2". Going deep probably would not be an issue, lots of metal in the flywheel. What ever was in my mig set up at the time, nothing special.

 

Wouldn't they have to be evenly spaced (at 90 degree intervals) and of equal size to keep the flywheel close to in balance?

 

I like how you think .

 

I evenly spaced them as well as I could SWAG them. I considered this and marked the flywheel before performing what was definitely not brain surgery. Certainly not a significant amount of weight on a flywheel, clutch assembly that probably weights fifty-sixty pounds. The weld could not be over a couple grams each spot. Consider too, this engine would never see 4K rpm. End result, the truck runs fine, no more no start issues. Ed was happy, I was glad to be of help.
I would not hesitate to do it again.

 

Didn't find any cracks, but the ring gear does appear to be slipping. I was able to move it by prying with a screwdriver. Thought about welding it....also maybe "pinning" it by drilling and tapping the joint for some set screws? Welding might be simpler, but was wondering how well it would hold. Flywheel is cast iron, isn't it?

 

It is c.i. I'd be more afraid of splitting the ring gear by drilling than by adding some tack welds. (drilling is how you get them off in a hurry)

Do you have a spare flywheel? Which clutch are you using? I have spare flywheels drilled for 11" Long and for Merc B&B 10" clutches, let me know if you need one.

 

I have extra flywheels, thanks. Would like to keep this one as it is machined for the Astro clutch disc and balanced with my pressure plate. Will try welding......

 

There's a guy on the island named Frank. He drove a '47 dodge with a flathead six in high school back in the early 70s. It was of course his only form of transportation besides shoe leather. One day he threw a rod in it and his dad got under it and pulled the pan. He removed the offending piston and rod and put the pan back on and Frank drove it another year and a half until he graduated. I asked Frank if there was a loss of oil pressure after that with the open crank hole. He just shrugged and said he never looked. Just saying not everything is always totally balanced. I do love the idea of welding the ring to the flywheel. SO much easier than the customary replacement.

 

Well, I welded it....figured I had nothing to lose. I didn't remove the flywheel from the truck, just the tin cover so i could see things better. I took some measurements from an extra flywheel and laid out 4 equal marks turning the engine over by hand.
Dunno how long it will run that way, probably forever. No new vibrations so far, but I haven't driven it yet....