Hot Rod Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
43 Posts
Discussion Starter · #1 ·
Hey yall, im posting because recently i was asked to help complete an already mostly built project car. The car is an 1987 Mazda Rx7, with a SBC 350 and 4 speed auto. When they first bought the car, im pretty sure it had a 305, because when i ran the numbers for the trans, it comes back as a 200-4r from 84 based on the date code. There's a few other signs that point to the original engine having been a 305, im guessing whoever built this car first, probably pulled the engine/trans combo from a G-body monte carlo or something alike.

The engine the car came with blew up, so they sourced out a 350 from a 1996 Chevy Tahoe ( Casting No. 10243880) and installed it. This is where they asked me to come help finish the project. The flexplate is new, not sure of the brand but it's from a local parts store, for the 96 Tahoe. The starter is a summit racing brand high torque mini starter, i can't get the exact part number right now because somethings up with summits site.

The first issue, is that the starter bendix is constantly engaged against the flexplate and by a good amount.

Second, the bolts for the 200-4r torque converter are a fair amount smaller than the diameter of the reliefs in the flexplate, after some quick research the 4l60/700-4r the tahoe would have came with, would have had larger diameter bolts for it's torque converter.

Lastly, the gap between TC and flexplate is almost at what i would call the limit. The TC cannot seat all the way against the flexplate because it hits the crankshaft hub/ bolts. There's slightly less than the thickness of a box wrench, with even what i would say is the standard spacer, it would be as thick as said wrench. That seems excessive to me.

I would really appreciate some input on this, not sure what direction i should go from here with this huge mix-match of components.
IMG-0474.jpg
 

Attachments

·
Registered
Joined
·
512 Posts
20b or 26b will give you better power.

But dealing with what ya have the torque converter can use a spacer but sounds more like a mismatch of parts? Too bad as that is a fantastic handling car with outstanding brakes. Take out the starter as a bendix is easy to replace. Take it with you to the parts store.
 

·
Registered
Joined
·
43 Posts
Discussion Starter · #3 ·
20b or 26b will give you better power.

But dealing with what ya have the torque converter can use a spacer but sounds more like a mismatch of parts? Too bad as that is a fantastic handling car with outstanding brakes. Take out the starter as a bendix is easy to replace. Take it with you to the parts store.
I should have mentioned i tested the starter bendix and it appears to be working fine, i don't think its partially engaged or sticking at all. Also the starters a summit brand mini starter, local parts stores can barley help with basic stuff anymore, this would be beyond them lol.
 

·
More for Less Racer
Joined
·
20,571 Posts
When the starter was new in the box from Summit, it would have had several circular shims made to go between the starter motor and the aluminum adapter plate that mounts it to a chevy block.
They were used to set the at-rest position of the starter gear and bendix. They would shim the starter gear back toward the front on the car, fixing your constant mesh problem.

You may have to search, but IIRC you can get that shim package separately.
and I'm not talking about the ordinary long and flat starter mounting pad shims.



In regards to the flexplate and torque converter, are the raised pads around the torque converter bolt holes facing to the rear of the car, towards the converter??.
Hard to tell from just the one pic, but the flexplate may be on backwards. If so, it will be almost an 1/8" difference

It will also affect the starter depth if the flexplate is backwards on the crank.
 

·
Registered
Joined
·
14,742 Posts
More from Speedway

The starter gear on a Chevy is engaged using a solenoid that is mounted atop the starter. This solenoid is actually doing a couple functions when you hit the start switch. It moves the pinion gear into the ring gear and engages the contractor that switches the heavy current that supplies the motor.

When the key or switch is released the magnetic field that engaged the solenoid collapses at which point a spring the solenoid collapsed is released and moves the solenoid piston back to its rest position taking the pinion gear out of ring gear engagement and opens the high current contactor stopping the motor.

If the pinion is not retracting and if the motor continues to run then some possibilities are:

Electrical
  • The ignition start switch is not cutting power to the solenoid.
  • There is a sneak circuit either in the switching or the wiring or the solenoid keeping the solenoid charged.
  • The contactor points are welding hanging up the solenoid piston.
Mechanical
  • The motor nose is not properly dimensioned either not fitting the install mounts properly or the pinion engagement is off because of problems with the solenoid and or the pinion engagement fork or linkage.
  • The mounting bots are an improper type not providing sufficient rigidity. Here you need to deal with GM’s partial pregnancy between USS bolt threads and Metric as well as shank fit in the starter’s mounting holes, this should be a slight interference fit, not a drops right through nor a press fit.

One early determination is to see if the motor shuts electrically off. If it’s not electrically engaged then it’s a mechanical problem. A bench test may help at least it isolate the wiring issue to not the solenoid and and gives a glimmer of hope that mechanically it can retract the pinion gear. This doesn’t eliminate installation issues be they electrical or mechanical.

Bogie
 

·
Registered
Joined
·
43 Posts
Discussion Starter · #9 ·
Eric thank you, i'm remembering now i had to setup the starter on my olds 403 the same way.

49' Coupe, i checked and they do have the flexplate installed correctly, counterweight towards engine, raised reliefs towards TC. Flex plate is right for this engine, but not exactly right for the TC. This Flexplate does have a dual pattern, 3 holes spaced farther out, and 3 more to accommodate a smaller TC like the one that's currently in the car or so it seems.

BogiesAnnex, i actually pulled and bench tested the starter, it's working correctly. This particular one uses an external solenoid btw, it's mounted on the firewall like an old ford haha. Electrically everythings working in the car. I think the issue comes down to this starter not being shimmed correctly for this setup. This flexplate may also be somewhat of a mismatch for this TC as well i believe.
 
1 - 12 of 12 Posts
Top