[inzane]

not sure I'm following Joel. You're saying the converter is simply not 'seating' completely to the flexplate?, and if removing some from the converter snout will allow the converter to fully seat? Or when all bolted up tight the converter is not seated far enough into the flexplate/crank pilot hole? That may simply be an '8HP' thing...but why would it have manifest with the 727...with a totally different converter?

You have a 'new' stroker crankshaft right...so the 727 'problem' should not have transferred to the stroker...?

...I'm sorry could you please repeat the question?

It acts like the face of the converter hub is bottoming in the bore of the crank. Prior to this '90 engine which I installed in 2014 I had an '82 360 bolted to the same 727 and converter for years without issue. I dropped the '90 engine in it just before leaving for our meetup in Moab. On the way home we turned south at Cortez on 491 and few miles past the state line it started the tin can rattle of something hitting the dust cover. I pulled the cover and the flexplate had cracked. I hammered the bit sticking out back down, threw the dust cover in the back and we came home with no further issue. I then replaced the flexplate with a new one and thought no more about it.

Fast forward to 2022 when I pulled the engine and again found the flexplate had cracks is a couple of the webs. Thinking that odd I inspected things a bit closer and found a shiny area on the face of the hub and in the bottom of the crank bore. I assumed it was an issue with the '90 crank not being machined deep enough, and since I wasn't going to reuse it....meh.

Since I was still driving at the time I started tinkering with the 8HP, I bought a junk '78 360 block from a local machine shop, dropped the brand new Scat stroker crank in it and mocked up the flexplate/trans. I took pictures of the converter showing measurements both fully seated in the trans and clearly faced up flat on the flexplate. Some 5/32" of travel I believe it is.

Now that crank is in the '90 block and the converter has a bit of stand off from the flexplate, as if the hub on the 8HP is bottomed in the bore like the 727 was. I don't have an exact measurement, but it is a noticeable amount when the converter bolts are loosened. The flexplate relaxes toward the block, away from the converter. It did not do that when the crank was in the '78 block.

That simply makes no sense.......unless....and this just occurred to me after all of this pontification......maybe the mounting face of the '90 block is not square with the crank and what I'm seeing is actually an angular issue between the converter and flexplate. But it would have to be ridiculously out of square. I'm going to sweep the face of the block with an indicator to find out.

Man would that suck. Have to tear the engine down and get it machined if that's the case. That in turn would affect running depth of the converter in the trans, maybe enough to be an issue depending on how much had to be shaved off the mounting face. Have to add a spacer between the block and trans.

Other than that I got nothin' as to what's going on. Think of any other possibilities?

 

[Mad Max]

if it is out of square...you could machine the tranny instead of pulling the engine back apart. Not sure that's really any better but maybe. Gotta be something else tho right - that'd be pretty unusual...

 

[SuperBurban]

Could just be the centerline of th engine and trans are not in line. That is usually the biggest cause of flexplate breakage.

 

[inzane]

if it is out of square...you could machine the tranny instead of pulling the engine back apart. Not sure that's really any better but maybe. Gotta be something else tho right - that'd be pretty unusual...

Yeah.....I don't think I'd want to go that route. Trying to keep things as boneyard friendly as I can in case broken/fried parts. The flexplate I'm using is definitely not a boneyard piece so I need to get a handle on this cracking thing.

I'll get out in the shop tomorrow and run an indicator on things and see what I can see. I semi retired this past Monday so I should finally have time to get this thing going.

 

[inzane]

Could just be the centerline of th engine and trans are not in line. That is usually the biggest cause of flexplate breakage.

That's a possibility too but it mates up very easily, basically just falls into place. This engine has always had an RPM relative vibration in it, or did with the previous crank/converter. I put a new balancer on it back in '14.

Going to be indicating things tomorrow and will check it. Be great if some offset dowels would do the trick. This engine was originally paired with a 435 and I still have that bellhousing, may use it to check center. Be easier to sweep.

 

[Canadian country boy]

Are you running a factory flexplate or something aftermarket like a B&M? I know the B&M is much stronger. Also if the flexplate is springing back towards the block then could you have thicker mounts welded to the torque converter where it bolts to the flexplate?

 

[inzane]

Are you running a factory flexplate or something aftermarket like a B&M? I know the B&M is much stronger. Also if the flexplate is springing back towards the block then could you have thicker mounts welded to the torque converter where it bolts to the flexplate? View attachment 637234

It's a modified ATI Chevy trans to Mopar engine swap piece. There were no flexplates available when I had this hairbrained idea of putting an 2015 5.7 Hemi 8HP70 8 spd behind an LA small block.

JVX Racing supposedly now has flexplates for LA, Magnum with a tone ring and big block kits. Only a couple years late to the party.

 

[Canadian country boy]

It's a modified ATI Chevy trans to Mopar engine swap piece. There were no flexplates available when I had this hairbrained idea of putting an 2015 5.7 Hemi 8HP70 8 spd behind an LA small block.

JVX Racing supposedly now has flexplates for LA, Magnum with a tone ring and big block kits. Only a couple years late to the party.

View attachment 637239

Oh crazy, I never knew that.

 

[inzane]

Just to bust up the monotony of build pics, here's one from last year. It hadn't rained here in Odessa for months but the Davis Mountains to the southwest had been getting some pretty consistently. Being tired of blowing dust and seeing the clouds far off in the distance I decided to just jump in 'ol Bumpy and take a drive to see some rain. Only 150 miles one way lol.

This was taken at the north end of Wild Rose Pass or Lympia Canyon, it has been called both. It's in between Balmorhea {pronounced bal/more/ray} and Ft Davis. A lot of interesting history in that part of Texas. Pretty country.

And yes, I finally got to test the spherical rod end linkage I built for the wipers. Blades were a bit dry rotted but the linkage worked great.

 

[inzane]

Boring video, quit any time you like, but I wanted to show you guys how quiet the Ramcharger is inside now even with the soft top, side exit exhaust and noisy tires. Most of the noise you hear is the A/C, the VintageAir isn't exactly quiet. Has a bit of a squeak somewhere in the cage too, not surprising since it's welded to the frame. But it's a really nice driver for a 37 year truck that was a beaten down old turd just a couple years ago. The 2500 rpm at 60 gets a bit monotonous on the highway but the 8HP will cure that.

See that screw hole in the top of the dash? That's where an 8" tall plastic gold eagle resided when I bought the truck 15 years ago. Si' habla espanol. Throwing it in the trash was the first mod I did.

Anyhow, this is the south or upper end of Wild Rose Pass, just a nice relaxing drive. Road gets too twisty a bit farther on to video with a cell phone.

 

[Canadian country boy]

If you hold your phone sideways you get a bigger panoramic view. 👍

 

[KurtfromLaQuinta]

Just to bust up the monotony of build pics, here's one from last year. It hadn't rained here in Odessa for months but the Davis Mountains to the southwest had been getting some pretty consistently. Being tired of blowing dust and seeing the clouds far off in the distance I decided to just jump in 'ol Bumpy and take a drive to see some rain. Only 150 miles one way lol.

I thought I was the only one who would pull that stunt. ☺
Love the rain!

 

[KurtfromLaQuinta]

Boring video, quit any time you like, but I wanted to show you guys how quiet the Ramcharger is inside now even with the soft top, side exit exhaust and noisy tires. Most of the noise you hear is the A/C, the VintageAir isn't exactly quiet. Has a bit of a squeak somewhere in the cage too, not surprising since it's welded to the frame. But it's a really nice driver for a 37 year truck that was a beaten down old turd just a couple years ago. The 2500 rpm at 60 gets a bit monotonous on the highway but the 8HP will cure that.

See that screw hole in the top of the dash? That's where an 8" tall plastic gold eagle resided when I bought the truck 15 years ago. Si' habla espanol. Throwing it in the trash was the first mod I did.

Anyhow, this is the south or upper end of Wild Rose Pass, just a nice relaxing drive. Road gets too twisty a bit farther on to video with a cell phone.

Pretty country!

 

[inzane]

I thought I was the only one who would pull that stunt. ☺
Love the rain!

Only desert dwellers get it. Odessalation is a few miles from the edge of a caprock to the west/southwest. That generally means that most rain clouds which make it this far go around to the north or south. Not unusual for there to be no appreciable rain for 2-3 years. Dirt blowing today as a matter of fact, wind gusts topping 70mph......I love it here.

 

[inzane]

Well... back to the 8HP.

I still have no clear answer as to why the 727 cracked two flexplates when mated to this engine. I ran an indicator on things today and can find no boogers, The block face is within .002" total. I bolted a manual trans bellhousing on and swept the bore, runout is .010" total. Probably enough slack between the two dowel pin holes to allow the .005" off center, and there's probably a bit of indicator sag in that. Runout with this flexplate is also good.

Which brings us to the converter. I can find no major boogers there either. Measuring from the flexplate face to the bottom of the crank bore, 5/8". Measuring from the converter face to the hub face, 5/8". Granted those measurements were made with a steel scale and much eyeballing but it's close.
I pulled the converter out of the trans and mated it by hand {don't go there} to the engine, and there is indeed a bit of a gap between the converter and flexplate. The hub is bottomed in the crank bore. Can't precisely say how much because trying to hold the converter square with one hand while measuring with the other is almost impossible. My eyecrometer says .030", maybe a bit less.

So here's a question. Should the hub be bottomed in the bore with a tiny amount of preload in the flexplate to prevent endplay/float in the converter, or be allowed to float in the bore with the flexplate controlling endplay? I have no idea if torque converters actually generate a thrust. I would think that with pressurized fluid the tendency would be to thrust towards the engine, in which case the hub being lightly bottomed in the crank would be a good thing.

 

[KurtfromLaQuinta]

Well... back to the 8HP.

I still have no clear answer as to why the 727 cracked two flexplates when mated to this engine. I ran an indicator on things today and can find no boogers, The block face is within .002" total. I bolted a manual trans bellhousing on and swept the bore, runout is .010" total. Probably enough slack between the two dowel pin holes to allow the .005" off center, and there's probably a bit of indicator sag in that. Runout with this flexplate is also good.

Which brings us to the converter. I can find no major boogers there either. Measuring from the flexplate face to the bottom of the crank bore, 5/8". Measuring from the converter face to the hub face, 5/8". Granted those measurements were made with a steel scale and much eyeballing but it's close.
I pulled the converter out of the trans and mated it by hand {don't go there} to the engine, and there is indeed a bit of a gap between the converter and flexplate. The hub is bottomed in the crank bore. Can't precisely say how much because trying to hold the converter square with one hand while measuring with the other is almost impossible. My eyecrometer says .030", maybe a bit less.

So here's a question. Should the hub be bottomed in the bore with a tiny amount of preload in the flexplate to prevent endplay/float in the converter, or be allowed to float in the bore with the flexplate controlling endplay? I have no idea if torque converters actually generate a thrust. I would think that with pressurized fluid the tendency would be to thrust towards the engine, in which case the hub being lightly bottomed in the crank would be a good thing.

I'm sorry... I will look back some. What's your converter "brand".
Might be a question for an actual torque converter builder?

 

[SuperBurban]

A quick search, I cannot find any specs for the depth of the hole. My take, is the diameter is important, but the depth is not. The fore and aft movement of the torque convertor is managed by the flexplate, and the torque convertor should not bottom out in the crank.

They do make spacers to shim the flexplate/ flywheel rearward, that may be the easy answer, just need to make sure you are not bottoming the torque convertor in the trans.

You might find these two threads interesting.

Can I use a 67 904 on a 72 225 or is the crankshaft register hole size a problem?

I've opened this discussion up on a "wanted" thread (because I may need a new flexplate) but I thought I'd post it here also. I'd appreciate any advice from people who have done it! I have a rebuilt 904 from a 67 slant (I think it's a 170). I need to put it on my 72 225. I've been reading...

www.forabodiesonly.com

Can I use a 67 904 on a 72 225 or is the crankshaft register hole size a problem?

I've opened this discussion up on a "wanted" thread (because I may need a new flexplate) but I thought I'd post it here also. I'd appreciate any advice from people who have done it! I have a rebuilt 904 from a 67 slant (I think it's a 170). I need to put it on my 72 225. I've been reading...

www.forabodiesonly.com

 

[inzane]

I'm sorry... I will look back some. What's your converter "brand".
Might be a question for an actual torque converter builder?

It's the factory issue converter for the 8HP.

 

[inzane]

A quick search, I cannot find any specs for the depth of the hole. My take, is the diameter is important, but the depth is not. The fore and aft movement of the torque convertor is managed by the flexplate, and the torque convertor should not bottom out in the crank.

They do make spacers to shim the flexplate/ flywheel rearward, that may be the easy answer, just need to make sure you are not bottoming the torque convertor in the trans.

You might find these two threads interesting.

Can I use a 67 904 on a 72 225 or is the crankshaft register hole size a problem?

I've opened this discussion up on a "wanted" thread (because I may need a new flexplate) but I thought I'd post it here also. I'd appreciate any advice from people who have done it! I have a rebuilt 904 from a 67 slant (I think it's a 170). I need to put it on my 72 225. I've been reading...

www.forabodiesonly.com

Can I use a 67 904 on a 72 225 or is the crankshaft register hole size a problem?

I've opened this discussion up on a "wanted" thread (because I may need a new flexplate) but I thought I'd post it here also. I'd appreciate any advice from people who have done it! I have a rebuilt 904 from a 67 slant (I think it's a 170). I need to put it on my 72 225. I've been reading...

www.forabodiesonly.com

So free floating more or less. OK, that's what I'll do.

The earlier years of the 8HP like mine have a smaller diameter hub which requires the use of a bushing in the crank on the factory Hemi setup. The Mopar part # is 0473 6283 AA, which I have installed in the LA crank. Not sure why they went that route initially, 2019 and later I believe, have a larger diameter hub and do not require the bushing in the crank.

From what I've read the crank flange stand off in relation to the block face is about .090" more on the LA than the late Hemi. But all the info concerning that relates to mating a 727 to a Hemi. I don't know what the specified running depth of the converter is for the 8HP, but it isn't bottomed in the trans, having 5/32" movement.
There is an O ring on the input which I assume is for the lockup clutch in the converter. How wide the land is that it seals to inside the converter or how critical converter position is in relation to it I can't say. Basically I'm just going to hope for the best on that bit. It can't be too far out of whack.

Given that I only have 5/32" rearward to play with, the .090" added length of the crank and one off flexplate I'm thinking that shaving about .060" off the face of the hub would be preferable to spacing the converter back any further. Not bottomed in either direction is as good as it can get in this case.

 

[inzane]

Shifter mounted. Tape measure says the location is right but I have it tacked to the bracket until it's been checked in the truck. Lengthened the linkage two inches.