Flex Plate to Converter Gap

[PlumCraZRT]

Hi all,

Today I installed a 440-Source flex plate onto my 440-Source 400-->451 stroker, then test fitted the Coan converter (alone, without fluid) to verify the hole alignment, spacing, etc.  What I found was a 1/16" gap between the flex plate and the screw bosses welded to the converter.  Without taking dial guage measurements to check, I suspect the pilot on the converter is bottoming out in the crankshaft pilot hole/pocket.

Is this a problem, or do I just use the screws to pull the flex plate onto the converter?  Seems like it would take quite a bit of force to move it.

If this is a problem, are there measurements I can take to inspect correct fabrication of the converter, flex plate, crankshaft?

Thanks,
Evan

[Katfish]

I would think you want it flush, converter should be pulled into flex plate with bolts.

[Skunkworks Challenger]

would think you want it flush, converter should be pulled into flex plate with bolts.

I agree.  The converter floats on the splines to a degree and is positioned by the flex plate.

[anlauto]

Let's get the dumb questions out of the way first.....

Are you sure the flex plate is not installed backwards ?

[PlumCraZRT]

Let's get the dumb questions out of the way first.....

Are you sure the flex plate is not installed backwards ?

Not a totally dumb question, since I was trying to install it backwards... the crank bolt spacing isn't even, so the flexplate only installs one direction and in a single clocking.

Additionally, the flex plate is shaped away from the torque converter, such that if I flipped it, the pilot may not be long enough to engage the crankshaft.

[PlumCraZRT]

I spoke with a tech from Coan who said that it should be fine to 'flex' the flexplate ~1/16" to bolt it up to the converter.  As I mentioned earlier, it looks like the forward-most part of the converter pilot is bottoming in the pilot hole of the crank.  The tech also gave me a number of dimensions to check to ensure my crank and converter are in-spec; everything checks out.

My next step is to temporarily bolt up the transmission with converter onto the housing and check for the 1/8" to 3/16" play they require.  I would like to find a flexplate spacer/shim to reduce/remove the gap between the flexplate and converter, but haven't had any luck.  Conceivably, the spacer would be necessary for reducing excess play of the converter (which I hope I don't have).

Thanks for all the input,
Evan

[burdar]

You need to test fit it with the transmission installed.  There was just a post about converter engagement a couple weeks ago on Moparts.  I didn't know this before but there is a spec for converter pump engagement.  With the trans installed and the converter pushed all the way into the trans, there should be no more than 3/16" between the flex plate and the converter.  If there is more gap then that, a washer should be used between the flex plate and the converter.  This is to make sure the converter is engaged into the pump the correct depth.  You might not need the converter all the way seated into the back of the crank.

Also, check the length of the converter bolts.  You don't want the bolts hitting the converter body before they are tight.

[anlauto]

If I'm reading this right....The converter hits the back of the crank before it hits the flex plate. The depth inside the transmission has not even come into play yet.
Do converters "seat" into the crank ? I never knew that 

[burdar]

If I'm reading this right....The converter hits the back of the crank before it hits the flex plate. The depth inside the transmission has not even come into play yet.

Exactly, that's why it might not even be an issue.  You have to test fit it with the trans installed.  If there is more than 3/16" gap between the converter and the flex plate, when you tighten up the converter, it will be pulled too far out of the pump.  The drive lugs on the converter won't be engaging the pump enough.  If you put a washer between the flex plate and the converter to correct that issue, the converter will no longer extend as far into the back of the crank.  If no washer is needed, then I would look into taking some material off of the converter snout so you don't have to "bend" the flex plate to get the converter tight.

Check the other gap first.  If that is OK, then address why the converter bottoms out on the crank too soon.

[PlumCraZRT]

If I'm reading this right....The converter hits the back of the crank before it hits the flex plate. The depth inside the transmission has not even come into play yet.
Do converters "seat" into the crank ? I never knew that 

Correct.  The converter hits before touching the flexplate.

If there is more than 3/16" gap between the converter and the flex plate, when you tighten up the converter, it will be pulled too far out of the pump.  The drive lugs on the converter won't be engaging the pump enough.  If you put a washer between the flex plate and the converter to correct that issue, the converter will no longer extend as far into the back of the crank.  If no washer is needed, then I would look into taking some material off of the converter snout so you don't have to "bend" the flex plate to get the converter tight.

Check the other gap first.  If that is OK, then address why the converter bottoms out on the crank too soon.

Because the snout is contacting the crank, the gap between the converter and flex doesn't matter.  Fastening the flex plate will not move the converter relative to the transmission.  In terms of engaging the pump, only the amount of travel it has matters.  I agree though, that if there is excess travel adding washers should be sufficient to correct it.

So we dry-installed the converter into the transmission and bolted the transmission up.  Currently there is 5/32" of converter travel between the converter being pushed into the transmission and then the pilot snout bottoming in the crank.  In that sense, we are right on the money between the 1/8" and 3/16" spec provided by Coan.

Since it was bolted up, we took a feeler gauge to more precisely measure the gap between the flexplate and converter bosses.  While pulling the converter forward, I could get the gap down to ~0.042".  My plan forward is to install 0.03" washers to reduce the gap and then install the bolts.  Local hardware shops didn't have any washers under 0.065" thick, so the 0.03" washers have been ordered. 

[burdar]

Maybe I didn't explain it very well, but you are doing exactly what I said. With those washers in place, the converter snout will no longer bottom out in the crank...and the pump drive lugs will be inserted into the pump the correct distance.