IMI Hi-Torque Starter Setup Part I

I decided to go with a high torque mini starter primarily due to it’s compact size.  Since I’m not running high compression (about 9.5:1) starting even with a factory starter wouldn’t really be a problem.  The difference in size between the mini and stock starters is simply amazing.  Since I’m running headers, I figured I’d need as much clearance as I could get.  The aluminum body aides in heat dissipation better than the stock.


Ames Performance is a great supplier of Pontiac parts.  They actually restore cars so they have a good idea of what works and how the quality matches the original.  Since the IMI brand was the only mini starter Ames offered, I figured I would try it out.  This coupled with the fact that High Performance Pontiac magazine had featured an article on installing the very same starter.  The instructions are quite easy to follow.  There are two critical dimensions to check.  One is the distance from the face of the pinion teeth to the edge of flywheel teeth which should range from .040″ to .100″.  The second dimension is the backlash in the gear mesh.  The starter can be shimmed at two locations to adjust the dimensions accordingly.

When I first bolted up the starter to check for clearance between teeth, I was surprised to find that the clearance was almost twice what IMI recommends.  Instead of .040″ to .100″, I measured around 0.187″.  I called IMI and their representative recommended that I check the actual engagement of the teeth.  He said if it’s around 70% or more it should be fine.  He also informed me that the pinion is supposed to stick in the flywheel by design and not retract until the engine cranks.  In the event that there is less than 70% engagement, IMI offered to machine the aluminum mounting block.  I doubt seriously there’s enough variance between Pontiac blocks to be almost twice the recommended distance.  I’m curious to know how others have measured up.


Anyone replacing their stock starter with a IMI mini starter should be aware that it would be almost impossible to check the critical dimensions with the bellhousing on.  This could make for a big project since the transmission would have to come off as well and is not noted before you buy.  These dimensions could not be checked on the GTO and consequently chewed up the teeth on the flywheel.  Note, the assembly article on does not have the bellhousing installed.


10 Responses to “IMI Hi-Torque Starter Setup Part I”

  1. Ivan says:

    Yes I have a imi 908 with the same problem not sure wat to do as I live in new Zealand.

  2. Ivan says:

    Ivan says:
    June 7, 2013 at 3:30 am
    Yes I have a imi 908 with the same problem not sure what to do as I live in new Zealand.

  3. Zach says:

    Sorry to hear you’re having issues. You’re the first that I’ve heard with the same issue I had. Can you provide some info about the car? Make/model, manual/auto trans, stock trans, etc. Are you having backlash and engagement issues or is it one or the other? I would certainly send these guys an email. The shipping may be cumbersome since you’re in New Zealand but these guys were fairly easy to work with. They may even be willing to cover the shipping if you send them a link to the blog post given there have been multiple issues at this point. Their email is Definitely interested to hear how this one turns out. Keep me posted!

  4. Zach says:

    Not sure if you’ve seen the other two posts about the starter. There’s three in total that go into a little more detail. To summarize, I sent my starter back to IMI in California and they machined roughly 0.020″ from the top of the block and increased the bore depth about 0.125″ to correct my engagement and backlash issues. The starter is still running strong 3 years later.

  5. Zach says:


    Just curious about whether you got your starter problem fixed or what happened with it.



  6. Ivan says:

    Hi I had it machined and seems to get good depth to flywheel but I am not to sure on backlash as I can’t see so well with bellhousing on but looks ok somebody suggested to put some white out on the starter and give it a crank then view flywheel to see how it looks. I am waiting on my restoration tripower carbs to come back from the states should be here in the next couple of weeks so we will see.

    Cheers Ivan

  7. Zach says:

    I’m glad it seems to be worked out. Luckily my motor was out of the car when I set mine up. Thinking back I’m not sure how I would have checked all of that if it was installed in the car. I think white out would probably work ok. I think anything paint-like to let you see what’s going on with the contact pattern should do the trick.

    Nice choice on the 66 gto. That’s definitely one of my favorites. My dad has a 67 he restored a few years back. There are few pictures on the website under the “GTO Gallery” heading. Actually this car is why I was so particular on setting up my IMI starter for the Trans Am. The motor was already in this car much like your situation. Backlash and engagement was not really checked and it chewed up the flywheel. One of the projects this winter will probably be replacing the ring gear on the flywheel. The IMI starter was changed back to the stock starter. Sounds like there are rocks between the teeth every time it starts but it’s still limping along to all the cruise nights at the moment. I’m sure it’s destroying the starter pinion teeth as well but that will be replaced along with the ring gear.

    I’m glad to see the popularity of these cars abroad. I forget sometimes how easy we have it in the US with all the used and aftermarket parts just a few hours away at most. You guys are the true dedicated hobbyist. Would love to see some pictures of your project.


  8. steve h says:

    Having same issues with my starter looks like I need about .125 more for full engagement, and around. 040 to .050 removed off the top of block for back lash going to contact imi obviously a problem as much as I’ve been reading got lucky didn’t chew up flywheel to bad

  9. Zach says:

    Looks like almost exactly the same situation. They ended up machining 0.125″ out of the bore and 0.020″ off the top for me. I wrote that original post in 2009 and it’s been working great ever since. So at least they are getting it corrected when it comes up. I just wonder about all the people that have to find out about it the hard way. I’d also like to hear from anyone who installed without issue to know if the problem is in their machining process or parts combination or other. They machined it and got it back to me in a reasonable amount of time though.

    There are two other posts on this topic you may have not seen if you found this page from a Google search.

    Keep me posted on the details! What’s the starter going in anyway?

  10. What’s up,I read your new stuff named “IMI Hi-Torque Starter Setup Part I « Gerald’s GTO & Trans Am Restoration” daily.Your story-telling style is witty, keep up the good work! And you can look our website about proxy server list.

Leave a Comment