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Old 08-28-2011, 03:33 PM
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starter to flexplate gap gaining

Just picked up new flexplate from machine shop and got it installed and everything back together. Its a pioneer 168 tooth flexplate i had balanced/matched to the one that came off the motor originally. After i mounted the starter i was checking clearance from the starter shaft to the teeth on the flexplate. I checked it in a few different spots and saw some pretty big differences in the clearance. The gap i've heard to shoot for with this measurement is .125. As i rotated the motor over a few times and checked in different spots, i got measurements from .115 all the way up to .170. .055 sounds like a ton of variance and I'm wondering if that's at all normal and what to do about it? Will it work if i shim it so that the smallest gap is .125 making the largest gap .180? Thanks for the help.

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Old 09-01-2011, 07:05 AM
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I talked to the machine shop and they said that that amount of variance was to be expected with a stamped steel part like the teeth on a flexplate. He said to find the tightest spot and shim it so that it's correct there and it will be fine. I'm going to set it up and try it out this morning and post what happened for anybody who was looking at this.
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Old 09-01-2011, 08:57 AM
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I`m guessing you haven`t started the engine using the starter yet.
My best advice? Bolt it on without any shims. Make sure your using the correct starter bolts with a shoulder and a knurled section below the shoulder, no washers on the bolts. Install and torque the bolts to 35 ft lbs.
Then try the starter and see how it works. Chances are as long as it`s got a hot battery and a good ground it`ll fire right up without issue.
I`ve installed more starters than I can remember and I`ve never had to use shims. I`ve seen guys install starters with shims and it didn`t correct the problem, why was because there was no starter brace and they would only snug the bolts and not torque them. If the starter moves, even just the smallest fraction it binds, grinds, drags and sometimes breaks the nose. A starter brace fits on the opposite end of the drive and bolts on to the block. Since chevy starters are long and heavy they need the extra support and stabilization the brace offers, these can still be had from GM. However, I only use a brace if the engine is a high compression race engine or if I just happened to be changing one that still has the factory brace on it. On a low compression street engine as long as the correct bolts are used and they are torqued down the starter works just as well. I`m curious, what points did you make your measurements from?
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Old 09-07-2011, 09:14 AM
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I took those measurements from the shaft the bendix rides on out to the end of the teeth on the flexplate. I installed the starter w/o any shims and used a brace, cranked it over and it didn't sound good. Looked at it and the bendix was bottoming out on the flexplate teeth. I put in a full shim and cranked it, sounded better, looked at it and the bendix was now engaging towards the end of the teeth. So i ended up adding in a half shim on the outside bolt to get it into that happy medium. Everything is meshing well now. I also wired up a toggle switch that controls the power to the coil, so now i can get the motor cranked over and then light it up to keep the starter from moving around too much. Im running 20 degrees of initial timing and I think that is what aced my flexplate the first time around. I've started it up a lot since then, and it seems to be working well.
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Old 09-07-2011, 09:16 AM
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I don`t know what combo your using, or if it has vacuum advance, or if the engine has enough vacuum for vac advance, but if it does, you set the timing and let the vac advance handle the base timing, then it`ll crank over easily as there is no vac advance when starting the engine.
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