Wits end.....Please help

[Doug Comer]

ISome of you may know that I have had a pretty tough time with flywheel ring gears this year. Well I just broke six teeth off the one I installed less than three weeks ago. Per the starter builders suggestion I have checked the following:

The timing. He suggested I check it and that it should be know more than 16 degrees advanced initially and around 32-34 @ 3000rpm. Upon inspection it was found to be around 24 degrees initial.

The motor plate. I had two of these so I measured the hole that locates the starter and used the tighter of the two which was well within his recommendations.

Distance from the ring gear to the starter. I checked the distance between these two to see if it was egaging too far. All was within his specs.

Pressurized each cylinder at the bottom of the stroke with the rocker arm shaft removed so the valves were closed. I was checking for a possible crack in the block that could be hydro locking my motor at start up. No bubbles in the radiator.

For those that don't know I have a 1970 F250 4x4 with a built 410. I have destroyed 5 of the gears this year. Every time I think I fix it it breaks a couple weeks later.
Thanks
Doug

[Doug Comer]

Also used a mag base and dail indicator to check runout of flywheel. Looks good.

Anyone???

All the gears have been purchased at Autozone and been Pioneer brand.

[bluef250]

Try another brand as you cannot be sure of the origin of the part.

[BobbyFord]

It's definitely a strange situation.

[ScreaminZ]

The timing. He suggested I check it and that it should be know more than 16 degrees advanced initially and around 32-34 @ 3000rpm. Upon inspection it was found to be around 24 degrees initial.

Is that 24 degrees with or without vacuum advance? If that is true base timing, that is way too much! You must have one hell of a starter if it can even turn the engine with that much timing. My 460 loves that kind of timing, but I have to get it with the vacuum advance hooked to the manifold so that the extra advance comes in after the engine's running. Otherwise, it just acts like the battery's going dead and the battery cables get hot and the solenoid starts smoking!

[Doug Comer]

I have a RobbMc starter. Running a MSD distributor with no vacuam advance. The guy who built my engine said not to worry about the base timing. Needless to say I haven't asked him for any more help.

[BobbyFord]

Have you tried a stock starter?

[Doug Comer]

No Bobbyford. I haven't tried a stock one. I started out 10 years ago with a power master and it gave up the bgining of this year. I always TRY to upgrade when replacing and heard good things about the RobbMc. I am wondering if it (the starter) doesn't have too much torque and just rips the teeth off?

[Doug Comer]

Thanks for the replies Bobbyford. I have sent my starter back for rebuild two of the times. It shattered the starter gear one time. Robb said he had never seen that kind of damage. That wasn't very reassuring.

[Tirehead72]

Not sure what "built" is meant to describe..to some its an intake and cam,To others its titanium rods, custom pistons and flowbenched heads with matched cam and valvetrain. The 24* of initial timing seems like alot to work against..If the battery is stout and the starter motor really has balls-somethings gonna show up as the weak link..I guess my reply is more a comment. Ive seen more than alot of guys crank up the initial to cover up poor idle due to too much duration in the cam,huge poorly calibrated carbs sittin on a single plane intake, stock (too tight) torque converters, or a combination of all mentioned. Too much initial just leads to too much total...If theres 1 to 25 degrees availible (just as an example) in the mechanical advance of the distributor -If the curve is quick,that could mean 48* as soon as 3000. Ive seen bent rods and melted piston releifs from bad detonation. Usually from too much advance too soon on low octane fuel. With no vacumm advance,that things gotta drink fuel like no tommorow! Im curious as to why not use one? After so much hassle with flywheels -Id suggest Less intital timing,get idle circiuts richened up on carb, and gettin distibutor curved..A good ditributor guy will ask you a million questions bout your setup and fuel you use...Its definitley worth it in fuel savings and throttle response...Just my penny and a half worth

[brownac1983]

I fixed a 460 for a friend that was having the same kind of problem. The starter hole in his motor plate was too big. Your starter should have different size holes in the top and bottom. The top hole is the right size for the 3/8 bolt that goes through it. The bottom hole also uses a 3/8 bolt, but the hole is oversized to allow the starter to pivot a little. The only thing that positively locates the starter in relation to the flywheel is the motor plate. When you place your starter into the hole in the motor plate and insert the top bolt finger tight, can you still move the starter from side to side? If you can, the hole is not properly holding the starter. The way I fixed my friend's was to plug the bottom hole with a piece of 1/2" aluminum dowel and drill it with a 3/8" hole in the correct spot. This forces the bolts to hold the starter in place. The only sure way to check for proper starter engagement is to paint the starter gear with Prussian Blue or valve dye and install the starter. Spin it over a few times and remove the starter. You should have a good contact pattern at the middle or bottom of the starter teeth. If the pattern is only on the edges, your gear is not properly engaging. I'd check that first, hope it helps.

[Doug Comer]

Wondering about the dowel pins that align the bell housing to the motor. Has anyone heard of these going bad? I figure if the bolts were loose it would cuase wear on the pins. I will probably tear into this today as I am on vacation this week. Concerning the advice about redrilling the holes, I have checked three motor plates that I have around here and installed the one with the smallest starter locating hole. I am using ARP bolts to hold the starter in. I can't see a reason that the bolt would cuase a problem, what do you all think? Thanks for all your input.
Doug

[averagef250]

re: bellhousing alignment- Clean the bellhousing, bolt an indicator to the crank flange, turn the engine and watch for runout on the bellhousing center hole.

I think you need to fix your timing to start. 24 initial is a bit over the top. 12-14 with a proper curve sounds good to me.

[Doug Comer]

Average250 I think I mis-typed my statement. I checked the timing last time the teeth broke off following another persons recomendation. I found that it was at 24 degrees at idle. I then brought it to 16 (I can still go more) and recurved my dristributor so I should be at 32 degrees at 3000 rpm. I Like your idea about checking the bell housing. I will report back what I find. Thanks agian for the help
Doug

[Doug Comer]

Just got done tearing it apart. I used a magntetic base stuck to the flywheel bolts and checked the runout of the bell housing at the area where the transmission slides in. If you were to sit under the truck facing forward and draw and imaginary clock at the bellhousing opening where the transmision slides in, this is what I got:
12 o'clock position .099
3 o'clock position .088
6 o'clock position .073
9 o'clock position .081
The greatest difference is .026. Is this within range? Sounds a bit off to me. How do I cure it? I tried baring it over while tightening and could get much. Should I try another bell housing? Thanks for your help.
Doug