Anyone been here ? Gear Reduction Starter Fitment

[lezesig1]

Re: IMI starter assembly sold by our favored vendors.

Mounted on the 850/903cc block. Notice the riding condition
on the electrical stud/nut which has been expressed by MANY, repeat
MANY people who have fitted this starter.

I'm not happy with the riding condition. (Even)
with the protective silicone cap squished against
the cast iron of the block acting as insulation.

Vibration, fatigue, and degradation of the elastomer boot comes to mind.

What I have done to help mitigate the riding condition is
reduced the height of the interferring electrical stud by 4mm,
and trimmed the height of flanged hexnut on that stud by 3mm.
Clamping force has still been maintained on that stud. It is now
at its barest minimum though.

Still fitting too tight to the block for my liking after the stud/nut trimming.

One vendor has recommended to relieve (locally grind) the block
in that area to reduce this riding condition. This seems a good
course of action providing that we don't thin it too much in that area
and create stress risers.

Anyone relieved the block in that area ? How much material is available there ?


Thanks upfront into any insight on this one.

lezesig
'72 850

 

[lookforjoe]

Relieving the block sounds like a bad idea, without knowing exactly how thick the casting is in that specific area - is there oil or water galley there? It seems reducing the stud & securing nut as you have is the safest procedure. Perhaps a clamp around the battery cable to prevent vibration of the cable at the fitting? As long as it's not touching the block, and the cable is secured so it can't work loose from vibration, I would feel comfortable, personally.

 

[Dan Sarandrea (Phila)]

Re: IMI starter assembly sold by our favored vendors.

Mounted on the 850/903cc block. Notice the riding condition
on the electrical stud/nut which has been expressed by MANY, repeat
MANY people who have fitted this starter.

I'm not happy with the riding condition. (Even)
with the protective silicone cap squished against
the cast iron of the block acting as insulation.

Vibration, fatigue, and degradation of the elastomer boot comes to mind.

What I have done to help mitigate the riding condition is
reduced the height of the interferring electrical stud by 4mm,
and trimmed the height of flanged hexnut on that stud by 3mm.
Clamping force has still been maintained on that stud. It is now
at its barest minimum though.

Still fitting too tight to the block for my liking after the stud/nut trimming.

One vendor has recommended to relieve (locally grind) the block
in that area to reduce this riding condition. This seems a good
course of action providing that we don't thin it too much in that area
and create stress risers.

Anyone relieved the block in that area ? How much material is available there ?


Thanks upfront into any insight on this one.

lezesig
'72 850

Vendor claims this fits?

Yeah like a screen door fits on a submarine.

It does NOT.

Return for refund, vendor pays shipping both ways since they claimed their item fits your application but it does NOT.

 

[dnudelman]

Hi Les,
Seems that gear reduction starters are the rage right now with good reason. But really how many times a week do any of us start and 850? A good working stock starter would seem more than adequate. Just my 2 cents.

If you can't or don't return the starter, maybe you could epoxy a small patch of insulating material to the block.

 

[Dr.Jeff]

I'm not familiar with this particular starter for that particular engine. But in general gear reduction starters can be "clocked" with lots of mounting positions possible by rotating the motor portion on the gear reduction housing. I'm sure that has already been considered, but just in case it hasn't - will clocking it differently help? I know on the X1/9 with a gear reduction starter it makes a huge difference for such clearance.

 

[dnudelman]

Hi Les,
I pinged Marshall, 850EV who does a youtube channel on 850's. Here is his reply:

dnudelman said:
Hi Marshall
Congrats on the 124.
One of the board members put a gear reduction starter on his 903 block. The positive terminal is riding on the side of the block.
Did you have that problem and how did you solve it?
Thanks
David

I was able to use the boot that came with it to keep it from touching. I went out and got my own and doubled it up as extra insurance. Haven’t had a problem since.

 

[Lowtechprime]

I had this issue with my 128. I put an 1/8th" thick piece of rubber between the block and silicone boot for added peace of mind....

 

[kmead]

I think mine was clocked differently so the stud was in a different but not a much better spot. I will have to look.

Bolting mine down was a painful experience

 

[Daniel Gibson]

On the one I bought, I had to ream two of the mounting holes just a smidge, and then it bolted right up and worked with no issues.

 

[ramona300]

Reclock the mounts. This is mine.

 

[Frank L. Di Gioia]

I think mine was clocked differently so the stud was in a different but not a much better spot. I will have to look.

Bolting mine down was a painful experience

Karl, I have a "special 13mm open end wrench just for my reduction starter center stud. I shortened the length and narrowed the jaws to be able to move the nut enough to eventually tighten it down. As per regular practice chase the stud threads so as to be able to finger tighten it most og the way. Pulling the radiator also helps....being on a motor stand is best! On a hot day it's worth the previous effort.

 

[lezesig1]

Re: IMI starter assembly sold by our favored vendors.

Mounted on the 850/903cc block. Notice the riding condition
on the electrical stud/nut which has been expressed by MANY, repeat
MANY people who have fitted this starter.

I'm not happy with the riding condition. (Even)
with the protective silicone cap squished against
the cast iron of the block acting as insulation.

Vibration, fatigue, and degradation of the elastomer boot comes to mind.

What I have done to help mitigate the riding condition is
reduced the height of the interferring electrical stud by 4mm,
and trimmed the height of flanged hexnut on that stud by 3mm.
Clamping force has still been maintained on that stud. It is now
at its barest minimum though.

Still fitting too tight to the block for my liking after the stud/nut trimming.

One vendor has recommended to relieve (locally grind) the block
in that area to reduce this riding condition. This seems a good
course of action providing that we don't thin it too much in that area
and create stress risers.

Anyone relieved the block in that area ? How much material is available there ?


Thanks upfront into any insight on this one.

lezesig
'72 850

Firstoff, thanks for all the replies on this one. Much appreciated.

We're narrowing in on a solution to this manufacturing produced issue.

The design is good, and the general attitude of the assembly to the
block is GENERALLY good....but they missed it by "that" much.

I suspect that the slope of the block was not taken into account
at the interface. Modeling a plumb, perpendicular line would
yield what we are seeing.

Throw the slope of the block in there at the interface....this is
what we have as a result. A riding condition. Slight, but nevertheless,
there.

- Relieving the block is still feasible if I knew the material thickness
there in that region. I lack the non-destructive testing equipment to
evaluate that area to determine thickness. I really dont want to
gouge a spare block and ruin it just to determine thickness there.

- Not going to return it because it does not fitup without issue.
Tempted to, but no. As you know, sometimes (often) replacement parts
require the caveat "some tweaking required" for installation. Common.
Acceptable....for this application. Does present some unacceptable difficulty
for certain customers though. Can't dismiss that point.

- Have two known good stock starters but opted for the newer
design just because. Who know's, I might switch back. Starters are
not that difficult to rebuild. Faults are easily found and our vendors still
stock all of the replacement pieces.

- Reclocking this particular starter cannot be accomplished with an
adjustable index plate. It is not supplied with it. I have read that the other
models have this adjustable plate as an option. That would be slick.

- Adding an additional insulative barrier between the block and
the supplied boot. Now we are adding a preload to the mounting studs,
and also adding additional compressive force to that barrier. It'll
probably work! I hope it does for the many who have chosen this route.

- Bolting the starter down is without trouble. Maybe three minutes total
time to accomplish this. No special tools, no special technique.
Accomplished on a bare block without any restrictive interference from
ancillary components, wiring, plumbing, belts, etc. Swapping in situ....
I can see the headache.....bigtime. Specialized(modified) tooling would
be the key. A couple of extensions with a wobbly would catch the inboard
stud. On a good day. With the lighting just right. One shoe untied. Salt
over the shoulder, and so on. (Chuckle)

Could someone just take a sledgehammer and break the block in that area
to show the material thickness there.

Just joking of course. Really. Unless someone has a completely useless
block just setting around and is crazed enough to try it. One posted picture
and a measurement of thickness in that area would help all future carvers
fitting this starter motor to the 903 block. That pic should be posted to the
Xweb wiki and credit given where due. It would benefit future many.

I am now inclined to oval the mounting holes to allow for slight reclocking of the starter. The hexnuts will touch the milled slots after this modification, and I will loose the ability to use full sized washers in three areas. That'll probably be the tradeoff.

.....the quest continues


lezesig
'72spi

 

[lezesig1]

Reclock the mounts. This is mine.

Thanks for the snapshot ramona300

Did you reclock by slotting the three mounting holes?
I suspect that the attitude of your starter is now parallel to the bell housing
shown in this attached picture. Can you confirm ?

 

[ng_randolph]

I am now inclined to oval the mounting holes to allow for slight reclocking of the starter. The hexnuts will touch the milled slots after this modification, and I will loose the ability to use full sized washers in three areas. That'll probably be the tradeoff.

Rather than slotting the holes, perhaps you could drill them over-size with a slight radial offset. Then install bushings to get the right size bolt hole.

 

[ramona300]

Thanks for the snapshot ramona300

Did you reclock by slotting the three mounting holes?
I suspect that the attitude of your starter is now parallel to the bell housing
shown in this attached picture. Can you confirm ?

I just bolted it in! In this photo, it looks to be parallel to the flange. I will check later.

 

[Jeff Stich]

Could someone just take a sledgehammer and break the block in that area to show the material thickness there. Just joking of course. Really. Unless someone has a completely useless block just setting around and is crazed enough to try it. One posted picture and a measurement of thickness in that area would help all future carvers fitting this starter motor to the 903 block. That pic should be posted to the Xweb wiki and credit given where due. It would benefit future many.

I have a scrap 903 block that I could sacrifice for this. I also have an IMI 850 starter & an 850 bellhousing, & could mount all 3 together on an engine stand for a little further r&d work.

Who knows, maybe we could use these findings to get the manufacturer to tweak their set-up, so all future product installations would be more "consumer-friendly"? The place they're made (Whittier, CA area) is only about 30 miles away from me. I could toss the block/bellhousing/starter set-up in the back of my truck to physically show them the problem that buyers of their product are having to deal with. Hopefully they'd be receptive to feedback...

 

[lezesig1]

Hello Jeff,

Having an IMI 850 starter implies that you might fit it someday?

Perhaps for curiosity....maybe see if you are experiencing the same thing ?
If it is worth your time.

The very easiest fix for the manufacturer would be to move the counterbored holes on the same circle *150 thousandths or so.
Please reference the attached pic.

That would effectively make the electrical stud/nut on the starter parallel to the block surface
and help provide the required clearance.

*Geometry would prove out the math as well
as just slapping a starter on and witnessing
the rotational requirement for clearance.



Makes me wonder now if there is a couple versions of this drilled mounting block out there.
One that I have and perhaps some that have motor mounting holes in a different location. Hmmmm

lezesig
'72spi

 

[lezesig1]

Rather than slotting the holes, perhaps you could drill them over-size with a slight radial offset. Then install bushings to get the right size bolt hole.

Hello ng_randolph

Thanks for the idea.

Given, correction to what we have supplied versus changing the root cause, yours
is a NICE solution IMO.

I can see what you have proposed.

(And) a step further. Make that bushing tapered with its base on the forwardside surface. Or easier yet, make the bushing stepped with its base on the forwardside surface. All this to prevent bushing pullout during starter fitment and final torque applied.

A straight-sided bushing would also work and pullout being prevented from the flat washer span. A few choices here.

We run the risk with slotting, or bushing use, of having to hogout the aftside surface to allow for hexnut/flatwasher placement. The current allowance in that area doesn't leave much room for hole center movement.

We also run the slight risk of breakout. Although there seems to be plenty of margin there to accommodate a greater hole diameter.

Yes, your solution, drilled/milled to tight tolerance would ensure great ring-pinion engagement !

....the quest continues


lezesig
'72spi

 

[Jeff Stich]

Relieving the block sounds like a bad idea, without knowing exactly how thick the casting is in that specific area - is there oil or water galley there?

This side of the engine block has the main coolant jacket right behind it. The basic wall thickness is just under 5.5mm, except for the thicker freeze plug port surrounds & support webs. The spot where the starter motor side stud's blue silicone cover makes contact with the wall is marked with a white paint splotch in this photo, to the right of the cast-in "S":



Wall thickness was measured by drilling a hole in the side of the block & inserting a measuring probe.



This wall thickness doesn't leave much room for error if relieving the block, or really provide much extra clearance for the starter side stud.

It seems reducing the stud & securing nut as you have is the safest procedure.

I agree. I gained a little over 2mm of clearance just by replacing the supplied nut/washer on the starter stud with a shorter-profile nut & washer. Grinding off the now-exposed end of the stud would net that same amount of clearance between the tip of the stud & the engine block wall.

Perhaps a clamp around the battery cable to prevent vibration of the cable at the fitting?

No need to worry, as this short stud is only for the power cable that connects the (lower) starter body & the (upper) solenoid unit. The battery cable gets attached to a different stud on the opposite side of the starter motor body, shown on the right here:

 

[Jeff Stich]

Vendor claims this fits? Yeah like a screen door fits on a submarine. It does NOT. Return for refund, vendor pays shipping both ways since they claimed their item fits your application but it does NOT.

You might want to have at least an inkling of actual experience with the item & the issue being discussed here before going off on a tirade against the part &/or the vendors supplying it. I have 2 of these IMI 850 starters, & have had 3 others in the past, & they ALL fit just fine. The issue being noted (close proximity of the solenoid cable stud end to the block) does NOT prevent the starter from being mounted, & it does NOT prevent the starter from working as intended.

Could the manufacturer modify the starter further to help alleviate buyers' concerns in this area? Most definitely. Simply changing the thickness of the hardware used would go a long way. Axially re-clocking the 2 main starter body-to-base bolt holes (&/or the 3 stud holes) might help a little more, but may also introduce unwanted access/interference issues with the 3 starter mounting studs (mainly the upper right one). It's highly unlikely that the manufacturer gets much customer feedback on this starter motor, let alone any improvement suggestions. This may be an opportunity for us as 850 Owners to do both.