Cummins 4BT & Diesel Conversions Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
130 Posts
Discussion Starter #1
Im new to the sight and im getting ready to convert my 85 gmc half ton to a 4bt cummins. I am a machinest bytrade and was looking at making a bell housing adapter that will keep the engine and tranny in the upright position. My question to you guys is can anyone tell me why the gm bellhousing adapters are tilted at a 10 deg angle. Thanks for any help on this matter.
 

·
Registered
Joined
·
120 Posts
From what I have heard is that the adapter was tilted 10 deg to give more clearance in the bread vans. I'm guessing that at the time they were repowering enough vans to justify making a special adapter to tilt. Lots of people have been running them tilted if it doesn't interfere with anything. Personally I'm using a Dodge adapter, bellhousing and a GM nv4500 trans to keep it straight.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #3
From what I have heard is that the adapter was tilted 10 deg to give more clearance in the bread vans. I'm guessing that at the time they were repowering enough vans to justify making a special adapter to tilt. Lots of people have been running them tilted if it doesn't interfere with anything. Personally I'm using a Dodge adapter, bellhousing and a GM nv4500 trans to keep it straight.
Thanks for the info..I plotted out the stock adapter yesterday. I have it in a Cad system so after i got it all done i indexed it 10 deg to bring it back to level and i am a little concerned about the starter clearance now. Will that dodge adapter you used will it work with a GM m465?
 

·
Registered
Joined
·
120 Posts
Thanks for the info..I plotted out the stock adapter yesterday. I have it in a Cad system so after i got it all done i indexed it 10 deg to bring it back to level and i am a little concerned about the starter clearance now. Will that dodge adapter you used will it work with a GM m465?
I'm assuming that you are planning on cutting a new adapter on a CNC right? You will probably have to move the location of the starter hole since if you clock the adapter the starter hole will be in the block. That is guessing that you are moving the engine block mounting holes relative to the rest of the adapter. One thing I was thinking of doing before I went with a dodge setup was to mill down the rear face of the adapter (side attached to the trans) and makeup a ring that would either weld or bolt to the adapter and shift the trans holes 10 deg to level the trans.

I decided that was too much work plus I didn't want to spend alot of money on my 4L80E. So I went manual with the dodge BH and flywheel housing (engine adapter).

I don't think the bolt pattern for a gm sm465 will match the dodge. I'm using the dodge BH with a gm nv4500 because the 96 and later nv4500's all have the same bolt pattern to the BH and bearing retainer diameter.

I'm curious to see what you come up with!

Good luck :beer:
 

·
Registered
Joined
·
130 Posts
Discussion Starter #6
Gm

Thanks for the great info guys. Im glade to hear it is 8 deg. After i drew it up that is the off set i cam up with. I thought i had somthing wrong. I am going to cnc machine the adapter. I just need to figure out if the starter situation will be right. If all goes well i am going to do my adapter to work with the gm flywheel i have. And i will cut the face down on some so they will work with the ford flywheel setup. I have talked to Chris at rockey mountain cummins and he said if i can get them worked out he will sell them for guys wanting to do some convershions and keep a level setup.
 

·
Registered
Joined
·
126 Posts
Welcome Amwise,

definitely should be concerned about the starter as stated. Most installs involve trying to drop the tall-profile 4BT down between the frame rails quite a bit. If you bring the starter up (pass side) there is also the exhaust to contend with.

Here is an adapter made on CNC, not sure if they clocked out the 8 degrees or not. (I'm not affiliated with their company)

http://www.transmissioncenter.net/HPIM1714.JPG

Another design consideration would be for automatics (like mine, ha hah). It would be great to design-out the wave ring, basically bringing the Torque Converter closer to the Flexplate, (if the TC doesn't hit the Crank Spacer).

You could even machine a Flexplate with an annular ring the correct diameter (I belive a 10.5 in bolt circle rather than 11.5 in) so stock Torque Converters will bolt up which would also get rid of the Wave Ring.

Look forward to seeing your ideas.
Best Regards,
George
 

·
Registered
Joined
·
73 Posts
I index the transmission side of the adapter, therefore the starter location relative to the block does not change.
 

·
Registered
Joined
·
84 Posts
I just put one in my 1/2 ton chevy 1985 I used the bread van mounts and left it tilted the hood clears the water aftercooler by about 1/2 if you are running a water after cooler I dont know if you will have clearence if you put it in straight.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #10
Bell housing bolt

I looked at doing that. By doing so i think i will loose a bell housing bolt if my thinking is right. Some time it is not always right though i need to finish the drawing and extrude it as a solid to get the feel of it all. How did it work out for you. Did you loose a bell housing bolt? Does the bell housing have clearance for the starter nose?. Was there alot of other mods you had to do to make it work? Thanks all you guys are really good. Im glade i found this sight. It has been very helpful.
 

·
Registered
Joined
·
73 Posts
Assuming we are talking about the Chevrolet bolt pattern (not the Buick, Oldsmobile, Pontiac, Cadillac bolt pattern), either the top left bellhousing bolt or the adapter-to-block bolt immediately beneath it will have to be omitted, as they end up almost right on top of one another with both bolt patterns vertical. It is my thinking that this will be the case regardless of which bolt pattern is indexed. On adapters with no provision for bolts to the block above/external of the bellhousing pattern, I omit the bellhousing bolt. On adapters with the aforementioned provision, I have done either, with my preference being to omit the adapter-to-block bolt. I have not had any issues with either option. Starter nose clearance is fine. If you have access to a CNC mill, making an adapter from scratch should actually be faster and simpler (once you get it drawn and programmed) than modifying the OEM units as I have been doing, as it is a very time consuming and labor intensive undertaking. Unfortunately, this seems to be the only way (at the present, anyway) to get a vertical Chevy adapter. Good luck.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #12
Assuming we are talking about the Chevrolet bolt pattern (not the Buick, Oldsmobile, Pontiac, Cadillac bolt pattern), either the top left bellhousing bolt or the adapter-to-block bolt immediately beneath it will have to be omitted, as they end up almost right on top of one another with both bolt patterns vertical. It is my thinking that this will be the case regardless of which bolt pattern is indexed. On adapters with no provision for bolts to the block above/external of the bellhousing pattern, I omit the bellhousing bolt. On adapters with the aforementioned provision, I have done either, with my preference being to omit the adapter-to-block bolt. I have not had any issues with either option. Starter nose clearance is fine. If you have access to a CNC mill, making an adapter from scratch should actually be faster and simpler (once you get it drawn and programmed) than modifying the OEM units as I have been doing, as it is a very time consuming and labor intensive undertaking. Unfortunately, this seems to be the only way (at the present, anyway) to get a vertical Chevy adapter. Good luck.

Thanks for the good info. I am going to the junkyard today to get a bell housing. I will check it out this weekend i hope and maybe get ready to make one. If i get it all worked out i will post some pics so everyone can see. Thanks for all your help and input. Great sight..
 
1 - 12 of 12 Posts
Top