Early Hemi to LA Mopar Bellhousing Adapter

Just thought I would post this info up for anyone that is looking. The picture below shows the measurements for making a small block Mopar transmission work on an early Hemi. The measurements where taken from a 1955 Dodge 270 starter plate and block, a 1967 318 LA block, and a Lakewood LA pattern bell housing. I also used some reference info I found on the HAMB and on a couple web sites.

Attached is an image of the bolt and dowel locations for the bellhousing spacer. I will also post up a print of the crankshaft to flywheel (or flex plate) adapter after I get all the specs and get it drawn. But for now I can tell you the measurements I have.

LA engine; block to crankshaft flange face = 0.590, flywheel/flex plate center mount = 2.155, big center crank hole (where the torque converter center hub would rest) = 1.815
270 Hemi; block to crankshaft flange face = 1.190, crankshaft flange OD = 4.810

When making the crankshaft flange you have to take into account the thickness of the bellhousing adapter. The difference between the LA and Hemi block to crank flange face is 0.600. So let’s say you make your bellhousing adapter 1.00" thick. That reduces your block to crank flange from 1.190 to 0.190. Now to make sure the LA flywheel is in the correct location it need to be spaced 0.590" form the block so doing the math (0.590 - 0.190) the crankshaft adapter must move the flywheel back 0.400".

Now when I started looking at using an LA trans on an early hemi I placed an LA Lakewood bell on the back of the hemi block and thought ok if I space the bellhousing back why do I need a crankshaft to flywheel adapter. I was thinking I could just use a 426 Hemi flywheel. After I found the Hemi tech on the HAMB I found my answer.

I pulled the info below from the Hemi Tech that explains why you need a crank to flywheel adapter (thanks to Wilcap).

• The early Hemi crankshafts all share a common 8 bolt pattern with one bolt hole offset.
• All used 7/16" non threaded bolts to attach the flywheel. The holes are drilled to a few thousands over the tap drill size for 1/2-20 NF.
• All use the outside diameter of the flange to register the flywheel.
• The 426 Hemi flywheel has the correct bolt pattern but uses the inside flange of the crank to register the flywheel.

Note: The early Hemi crank doesn't have the inside flange it is machined flat.
So all LA, B & RB Mopars center the flywheel on the center of the crank flange. All early Hemis center on the outside of the crank flange. So your crank adapter isn't just a spacer it has to center on the outside of the hemi crank flange and have a center flange made into it for flywheel/flex plate to center on.


Hope this helps out fellow rodders like me that can't afford to buy an adapter but have access to the machines to make the stuff. This sure was fun.

 

0.400", not 0.410", but one hundredth of an inch probably doesn't matter on this particular measurement..

 

Nice, any pics of your adaptor and a report on how it is working? I will file this information in the someday file . . .

 

Yes, let us know the total cost of materials (because not everyone has a 14" x 18" plate of 1 inch aluminum or steel under their workbench), the total of labor hours involved with CAD and machining your plate AND center hub (because not many have free access to a cnc machining center and lathe), and of course, how it fits. Thanks.

 

I read it over 3 times and still missed that. Thanks I'll fix it.

 

This is true. I'll keep you posted on costs and estimated hours of labor as I go. I have to go buy the plate today or tomorrow. I will start the crankshaft adapter today sometime as I already have that material.

I'm tying to decide on steel or aluminum? If I use aluminum I think I will make it half moon with just a hole in the middle for the crankshaft & if steel I will cut it out like a horse shoe.

 

Do I sence sarcasm?

 

You do have to consider how much the hours of your life are worth. Nice to say you made something if there's considerable savings, but sometimes I see things people made & can't see why, of course adaptors aren't exactly cheap....

 

Stopped at Alro Steel on my way home last night and looked thru their 6061 aluminum drop bin & found a nice piece 1 x 11 x 24. Had the guy weigh it for me and it came out to $66 + tax. I didn't buy it yet because I'm still not sure if I'm going aluminum or steel. They also had about 6 7/8 x 12 x 19 give or take 1/2". These were about $52 + tax each.

The steel bin didn't have any drops the correct size so I'll check back later.

 

No sarcasm. It will save the OP from having to answer all of those same questions after he is done his project.

 

x2.
...also might want to include the time for each trip to the s**** yard and all the rest of the time where you 'sit and ponder' what comes next, or 'how do I handle this' since it is part of the money saving programme...

.

 

I've seen this done before but never had any dimensions...Thanks for the research...

 

Ok I've decided to go with 6061 aluminum. I figure if the the original starter plate was .750 cast aluminum then .750 to 1.000 6061 should do the trick. I picked up a nice piece of 6061 drop .875 12x16 at Alro Metal Supply for $53.88 out the door.

As far as figuring in driving time and gas, I could do that but I try not to make special trips into town just for this stuff. When I stopped at Alro on Saturday I was doing a number of differant things. I guess if you want to figure in the 15 min I was in the store I could add that to the time.

The time to 'sit and ponder' about how things are going to work, I guess I could add time for that also but hopefully threads like this will drastically reduce that time for fellow street rodders. Thats why I started this thread in the first place.

 

Guy's It is not so much the cost but the accomplishment . The reward is in doing it and having success. I would love to have these kind of skills.

 

Agreed - ^^^^

I also think when I hear the argument "You have to figure what your time is worth" that if I am barely making ends meet and spending my time on this is how I get it accomplished, then I didn't have to take on a 2nd (or 3rd) job to pay for someone else's work and in the process I learned something.

 

Here is the drawing for the crankshaft to flywheel / flexplate adapter. I made mine already and will post some pics when I get a chance to take them.

 

You sir amaze me.
Thank's for sharing.

 

Pics of my crank adapter set on the crank and with my quarter master 7.25 clutch housing.

 

Pics of the bellhousing adapter in the making. Took me a bit longer because I was machining inbetween other jobs but I got it done in about 3 hours from programming the prototrak to removing it from the mill. I still have to tapper some of the holes and edges but all the hard work is done. I took notes on mill speeds and feed rates if anyone needs them.

The first pic is the drawing on the prototrak.
The next pic is a trick I learned from my old instructor to put a marker in the mill head and do a test run. I'm glad I did because the test run was 2 close to the bolt holes because I forgot to figure in the width of the tool.
The next is drilling holes.
Then making chips.
Last the plate removed from the mill.

Next project is the blower intake manifold........

 

very nice work!

7.25" clutch????!!! about the same size as the one I just changed in a Ford Focus!

 

Yes but the Quarter Master is 3 stacked clutch discs. Holds up to 700 TQ. Way more than I'll ever need with the Hemi. I wanted it because it was 8 bolt and light about half the weight as the original flywheel.

 

so how did this come out for you?

 

All the parts are made and everythings lines up but it will be a while before the road test. I have to build the rest of the car.

 

So, another week or so?!

 

Sure x 10 and thats wishfull thinking. Never enought money or time.

 

great to see.

I like to see a guy have a go, of course the off the shelf adaptors sold by some here are a great thing as for the average guy, they don't have access to the equipment to do what your doing, but I enjoy seeing people who have acess making the most of it.

the posters who are saying about factoring in your time are just reflecting on the fact that if your doing it for yourself most people forget to factor in certian parts of the equation, and say 'I built this for $X' but if someone asked them to start manufacturing them to sell, then you would find that the cost would be 3-4 times the build cost. And thats ok.

I have a couple of Hemi's and I still can't decide on what trans to put behind them. they are slated for projects but the adaption of a manual box is what I would like but it just seems easier to go auto, but then easy isn't always satisfying is it...

 

Unless I missed something in the OP he's doing a one-off for himself. I didn't see where he was implying that this was anything but for him or that he'd be infringing on anybodys business or anything like that. As far as keeping track of the costs of things, sure that would be interesting to know but not so much as a business angle. Relax guys, he's got more time than money. Others will still be buying your stuff including me.

 

Really not much difference between an auto and a manual if you are talking about Mopar transmissions. Using a GM manual, for example, causes you to spend major money on a custom flywheel whereas a Mopar has several options using OEM wheels. Similar deal with the flexplate for autos.

Speaking only for myself, my curosity was simply to get an idea of what 'somebody' would be spending (time wise) to make a one-off. Just good reference information to p*** along to others who ask the question...and it does get asked.

.

 

Thanks

You said it. I don't always have more time than money, sometimes I don't have either one!

I totally understand the point of your questions I think allot of guys that don't have experience making this stuff think it is as easy as blowing out a frame support bracket with a plasma torch. Many things to consider when fabricating these things; time, cost and safety are the biggest ones. Nothing wrong with pointing that out.


I would say my total time into this project was about 10-12 hours, finding measurements, drawing parts, double checking measurements, setting up the tools, programming, then running the parts. If I had to do it again which I might, for my dads coupester and a buddies rail, that time should lower some to just setup and cutting time. IMHO for the first timer for a one off part 10 to 14 hours and about $75 in cost, maybe add $20 in tooling if you don't have the correct tools.

Again hope this helps.

 

what did u use for the inside and outside radius?