350 Starter holes drilled incorrectly?

[Gibson]

Been working on this problem for a week, and I'm stumped. Sorry such a long post, but I figured I'd go ahead and list what I've done already. This has all my local small block buddies stumped too.

The short story is: when I install starters, the bendix is too far from the flexplate when at full throw - not the intermesh, but the actual throw on the bendix. As a result, only about a 1/16 to 1/8 of the tip of the starter gear engages the flexplate so it chews the tips of the teeth off.

Here are the things I've checked:

• This is a new build on a block built out by a local machine shop - they also supplied my new transmission (700r4)
• I've gone from a TH350 to a 700r4, but the converter and flexplate are new (converter came with new tranny)
• The flexplate is not on backwards (see photos)
• This block is a 2 piece RMS made between 1968-1979 according to the casting numbers.
• I have the correct flexplate (168 tooth neutral balance)
• I have tried several starters (angled bolt pattern standard type and universal 153/168 tooth straight across mini high torque - specifically a Powermaster 9600x)
• No body shims were installed on any of the starters
• The flexplate appears to be flush to the crank (see photos)
• The bellhousing appears flush to the block as it should be
• With the torque converter bolts out, the converter spins freely and has clearance from the flexplate
• The bolt holes on the block are not cracked

I'm seriously about to rip my hair out. I've read a couple of places that there are blocks out there where the starter holes were accidentally set back too far, but I have no idea if that is true.

Any ideas?

Pictures below (full album at: https://plus.google.com/photos/10266...61803719973329 )

Starter gear fully deployed:


Stater gear not deployed:


Crank to flexplate (flush):


Flexplate orientation:

[4x4k30]

is this a new engine that hasn't been ran yet? or have you had it running before you had the starter problem? I think your flywheel is backwards

[Gibson]

Yep, we've run it a good bit (before the starter teeth got chewed). The flexplate is on correctly (see pictures) - that was my first thought too, but unfortunately it wasn't that simple.

[buddy_1]

Where did you get the flywheel? It looks like it is too far away from the block. In the one pic, it looks like it is real close to the bell housing. I found this pic http://www.oreillyauto.com/site/c/de...=at+flexplate# and the center looks like it is recessed to make the ring gear closer to the block. My opinion is that it is the wrong application flywheel.

[Gibson]

The flywheel was selected by the engine builder (who also helped with the transmission swap). The flexplate I have does have that recess - I'll post a pic.

Also, I believe the only stock variations for a 168 tooth flexplate for a small block would be weighted (for 1 piece RMS) and neutrally balanced (for 2 piece RMS, which is my application).

[Gibson]

I just mounted up the mini high torque starter to another small block I had sitting outside to see if the edge of the starter and the edge of the block had the same offset that they do on the engine in the truck. They do, so I think the "misdrilled starter holes" idea is out unless I just happen to have two faulty blocks.

[buddy_1]

Originally Posted by Gibson

I just mounted up the mini high torque starter to another small block I had sitting outside to see if the edge of the starter and the edge of the block had the same offset that they do on the engine in the truck. They do, so I think the "misdrilled starter holes" idea is out unless I just happen to have two faulty blocks.

I agree with you on that. If that were the problem it would have been found some thirty years ago. Do you still have your old flywheel? Put it on your other engine and compare the distance between the ring gear and block on both.

[Mr.Chevy4x4]

Everything looks right. Have you tried another starter? I'm thinking that maybe the bendix on the mini might not have enough travel. Maybe a manufacture flaw with it? It's not a Summit brand is it? I had one of those cheapies on my race car for a little while, complete piece of junk. Finally broke down and bought a good one....never had another problem (with the starter anyway).

Mike

[Gibson]

This is the only flywheel this engine has had on this build (so far). My previous engine and tranny were sold off when I got my new one. I did buy a new flexplate, just in case, but measurement wise it looks identical. If possible, I'd love to avoid having to swap the plate.

I'm starting to wonder about the starter too - although I've checked three: two minis and a standard, but now I'm wondering if I should try another standard just in case it was a fluke. The two minis I tried were both Powermaster 9600x models, which are on the cheap-I end of things.

What mini did you end up going with?

[Mr.Chevy4x4]

CSR - best $300 I ever spent. Spun over the big block with ease, and never any grinding.

Mike

[buddy_1]

The reviews from Summit customers seem to agree with the starter theory. Look here http://www.summitracing.com/parts/pwm-9600 and 2 out of 3 say they had the same problems.

[ron350]

Ok the gap between the back face of the block and the face of the flywheel teeth is 0.470 to 0.477.
This is measured at the oil filter side with the oil filter removed on a stock 1975 350 block and flywheel.

Now you need some one else to confirm this measurement.

[Gibson]

Originally Posted by buddy_1

The reviews from Summit customers seem to agree with the starter theory. Look here http://www.summitracing.com/parts/pwm-9600 and 2 out of 3 say they had the same problems.

Well I'll be a monkey's uncle. I didn't even think to look on there - thanks buddy! Oddly, mine looks a lot different from that one especially the mounting block but mine is a 9600x, so maybe that is why. The body and the bendix both look like they do on that one though.

I'll measure that gap - thanks ron! I'm assuming that measurement is with the torque converter bolts in, correct (since that flexes the plate a bit)?

[buddy_1]

I'll measure that gap - thanks ron! I'm assuming that measurement is with the torque converter bolts in, correct (since that flexes the plate a bit)?[/QUOTE]

The bolts shouldn't flex the flywheel. Did the crankshaft have a pilot bushing in the end of it from a previous standard trans application?

[ron350]

Yep that is with the torque converter still bolted to the flywheel.

I only measured in two places close to 180* apart.

Makes me wonder what the tolerances are for that measurement?

[Gibson]

Hey Buddy,
It was a brand new crank, so no bushings would have been in it - at least, I can't imagine why there would have been.

There is supposed to be gap (between .060" and .187") between the flexplate and converter. Too little gap, and you'll wear out the pump. Too much, and it could disengage from the pump.

I picked up a new standard starter to try while I'm under there measuring. Anyone happen to know the torque specs for the flexplate-to-converter bolts for a 700r4? I searched but couldn't find any.

[buddy_1]

Anyone happen to know the torque specs for the flexplate-to-converter bolts for a 700r4?

I think it's around 35 lb ft.

[Mr.Chevy4x4]

35 lb.ft. and I always put a dab of loctite on them for good measure.


Mike

[Desert1957]

Most "Quality" mini starters come with an installation kit as pictured below. On my race engines the solenoid must be removed and the shim (shown below) must be installed.

This shim allows more stoke on the shift fork arm inside the starter, allowing more stoke. allowing a more positive engagement with the flywheel.



Desert

[Gibson]

Wait so that shim INCREASES throw? In my instruction sheet it indicated the opposite - maybe I misunderstood. I'll try putting that body shim in tonight and see if I get more throw out of it. Thanks!

[Desert1957]

Originally Posted by Gibson

Wait so that shim INCREASES throw? In my instruction sheet it indicated the opposite - maybe I misunderstood. I'll try putting that body shim in tonight and see if I get more throw out of it. Thanks!

In my applications it does, think of it this way. The solenoid pulls back, causing the shift arm to move the starter drive in the opposite direction. If that starting point is spaced back to begin with , the starter drive will travel further.

The round shim supplied is only used if the drive is too close to the flywheel in its off position.

You can remove the starter motor and check all this on the bench , just measure the distance the drive will come out off the mounting area. check it with and without the shim. It will be easier with the solenoid and spring removed for measuring stroke distance.

Desert

[Gibson]

Well as it turns out mine has only the round shim (for moving things back) but that would be a pretty easy thing to fab up. I'll do some experimentation. Thanks!

[Desert1957]

I have seen some starters that come with three shims in the installation kit, I'm sure you can purchase one on line. Maybe a forum member might have one or two they would give you.

Give a shout out....

Desert

[Gibson]

Cool - I'm going to do one last set of measurements tonight after I get the converter bolted back up and torqued down just so I have the block-to-flexplate gap documented. I measured it last night with the flexplate free, and it was right around .5 - so already a bit too far out based on ron's measurements. That is only going to get farther when torqued down, so I'm a bit worried already. We shall see!

[Gibson]

Ok, got off the phone with Powermaster (really nice folks) the model I have looks to be a white label version of one of their starters - possibly an older model. At any rate, they helped me anyway which I thought was cool.

They have seen this issue before on sbc's and confirmed that it is very possibly just a case of stacking tolerances. So my block is off a fraction, the crank might be off a fraction, etc. All those add up to "too much gap between the starter mounting holes and flexplate". The tech said that on a gear reduction starter, you really only want the teeth to engage about half of the width of the flexplate, so I don't need a ton more throw really. Unfortunately there is no shim of the type Desert mentioned available for this starter.

What I'm thinking of doing instead is modifying the pinion gear on the starter. On the one I have, there is at least a half inch of smooth bushing area on the tip of the gear. You can see that in the pictures - it is pretty large. I'm going to precisely cut a thin disc of that away and move it to the back side of the gear, effectively moving the teeth forward about 3/16. Whats the worst that could happen, right?