Early Hemi to LA Mopar Bellhousing Adapter

I'm wondering about the thickness of the adapter plate....in this thread it is mentioned that the original plate is around 3/4" thick but every one I have measured is 1-1/8" thick???

 

It could be practically any thickness over 5/8" which is the difference between early and late crankshaft lengths. If the trans adapter is thicker, then the crankshaft spacer/adapter must be thicker as well to keep the torque converter in the right position.

At 5/8", you will need a very custom flexplate that I don't think is available. I have one but it has no manufacturer markings. I think mine was custom made by someone who is no longer with us to confirm that.

If the trans adapter is 3/4" thick or thicker, you can use an off-the-shelf 8-bolt flexplate as used on the 426 Hemi.

A 3/4" thick adapter uses a 1/8" thick crankshaft spacer/adapter.

A 1-1/8" thick trans adapter needs a 1/2" thick crank spacer/adapter.

Basically, trans adapter thickness minus crankshaft spacer/adapter must equal 5/8" or bad things will happen.

 

OK thanks. So does this same approach apply for a manual trans/flywheel?

 

Yep.

5/8" is the difference between crankshafts, regardless of what type of trans is behind it. I just assumed you would be running a 727.

 

i have never had good luck with a alum. flywheel. they sound great at a idle and the idea of less rotating weight is always a tempting thing. the problem is they are too light. to get the car going takes more rpm. you will realize this the first time down the street. remember if less weight makes a engine rpm faster it will also slow it down just as fast. thats why they work so well on circle track cars where you are on and off the gas all the time. on a street car or drag car the steel works much better. all that stored energy makes the car leave from a stop so much smoother regardless if it is a street car or drag car. it also keeps the rpms up between shifts. i learned the hard way. i had a steel flywheel and replaced it with a alum. wheel. then went back to steel. the difference between the two is night and day. the steel is not coming out again. with your skills it shouldn't be a problem making a steel one. if you do let us know how it drives with each one.

 

How did anything get done before CNC and CAD?

 

You got it. Look at this picture and in the top right the text explains that you take the thickness of the bellhousing adapter and subtract .600 from that to get the thickness of the crank adapter.

 

great work there, monc. $53.88 is a darned good price on that aluminum.

'course it's been more than a week since I put an HH adapter on my 331 to 727, but was thinkin' those crank-flange mounting holes were 29/64 and the bolts 7/16-20....in fact I just saw some of them the other day. They have a round head with a flat on one side.
When using the flex plate for the 727, these are replaced with Gr 8 hex-heads and Nyloc nuts.

The HH adapter is full circle (pressure?) cast aluminum. I really don't see the need for it to be that way....in fact, there's much better access to the hex-head bolts for the TC in that narrow space without it; as you have done.

For those who use or intend to use one of the commercial adapters, I found that with a little work, there are 2 more hole locations (which are tapped 7/16-14) on the 727 that can be modified slightly and the adapter drilled/tapped 3/8-16 to provide much more needed support. These holes are almost inline with the crank center; so it's much better than only the 4 that HH uses. I should contact HH about them.
I think I might have a sketch somewhere of what was done.

 

A rhetorical question no doubt... But we do owe a lot to the pioneers of the day.







.

 

Yeah....I can't say I am completely comfortable with the adapters that are half, or even less than half, circle. An LA Mopar even uses steel struts to help the lower half of the bellhousing attach to the block. I know guys run the half-moon adapters with no apparent problems but I still have to wonder if there are some un-apparent issues that arise?

I looked at my Hemi block and unlike an LA, there are no convenient bosses to attach a strut to or that would be an easy solution.

 

There are no structural bolt bosses below the transmission centerline. The struts used by MaMopar were mostly found in vans and pickups and they can be adapted to a Hemi block/pan rail if needed.

.

 

Guys same goes for early 241 hemi to LA bellhousing and a 1963 Dodge T10 borg warner tranny?

 

there's the 61 & earlier & the 62 & later bell patterns, so yup.

 

There really is no need for the adapter to full circle the bell housing. It only gets in the way.

 

With an aftermarket bell housing that is full circle, such as a Lakewood or a Quick Time, there is no real benefit to a half circle adapter....it really offers no improved access to anything that matters...or am I forgetting something?

Again, I know guys run half circle adapters...I just wonder what a true analysis of the stresses would tell us? The stock adapter has several decent sized bolts below 9 and 3 o'clock that are eliminated with a half circle adapter....that must have some effect someplace.

 

I've used QEC 's (73RR) horseshoe type adaptors w/o a problem. Bob Walker has said his (HH) full circle style is intended to be bolted up with the flex plate & everything else done before the oil pan goes on the engine. That would mean if you can't drop the pan you'd have to pull the engine & tranny for a problem usually requiring just pulling the engine or dropping the tranny.

 

There were hemis that did not use lower braces and there were factory adapters. What difference does it make if the adapter or the transmission only bolted the top 1/2 of the circle.

 

The difference is that the factory adapter transfers any loads on the bottom half of the trans to the engine block. It's not an ideal arrangement, but it's undeniable that it occurs. With the factory adapter, the lower half of the trans bell is given some support and damping.

We could label the half-circle adapter value of clamping/damping as 'zero' on the lower bolt holes. Then, we could state that the factory adapter provides over 100 million times that value...even if the amount it provides is small, it's still a massive
percentage increase over zero.

I don't know if the contribution is meaningful or not - I want to make that clear - but I suspect it does 'something' and I wish we had some insight as to what that is.

 

Take a look at just about any modern engine block and see how many bolts you can find that are significantly below the crank centerline.

Bellhousings and auto trans cases wrap around the bottom in order to cover the clutch or the converter and simply do not attach to the block below centerline.
Yes, from a structural design standpoint having fasteners below the centerline adds tremendously to the ability to span the distance but it just isn't required in 99.9999% of the applications.

As Tom said, too much adapter just gets in the way.

.

 

Great thread, thanks for the useful info and all the dimensions.

So It look like if I welded a 2.150" o.d. ring to the center of the crankshaft flange, I could just slap a 426 Hemi flywheel on there and use a 5/8" thick plate between the block and the belhousing, right?

 

cool follow up....

 

Just reread this post and enjoyed it more than the first time.
Thank You

 

I would say YES if it is a 727 application.

For a stick, it may depend on the flywheel. Did all 426 hemis use a direct drive starter? Did they all have the ring gear in the same place? Would a direct drive starter even work on an early hemi & late trans adapter application? I think it would work if the 426 hemi flywheel is compatible with the chrysler gear reduction starter.

Your 2.150 ring idea would work, but the starter needs to be considered.

Also be sure to consider the pilot bearing type and area it will be installed at. Some fit inside the crank, some inside the flywheel bore, some are thick, some are thin...

 

As mentioned, you would need to verify the fore-aft location of the ring gear relative to the starter pinion. Your block plate thickness could be adjusted to correct any concerns.
Also keep in mind that post-62 A engine bellhousings will either be 130 or 143 tooth count and the flywheel must be the same as there is significant difference in the o.d.

With minor fussing, you could also just install a pre-62 146 tooth wheel and the a 143 tooth bellhousing and skip the crank work...

.

 

i use a dakota starter on a quick time bell. most after market bell housings are drilled for both flywheel sizes. there are a few old lakewoods out there still that only have one pattern. if i remember right they all use the same lower bolt hole. its the upper that has two holes. the holes just tip the starter in or out to match the flywheel. it would be no big deal to drill a second one if you found a older single pattern bell.

 

Unless it is a truck crankshaft, there will not be enough depth for the pilot shaft.
Trust me when I say, that in the last 60 years, all these ideas have been tried at least once.

 

73RR,

Cool pics,,what engine assembly line is in the middle pic?
Any clue to the year and location of the plant?
That auto tranny looks trick as well,,,looks like it would rival todays stuff !

Tommy