Drilling a 460 ZF5

[Bashby]

I have a ZF5 with the 460 bolt pattern to put in my IDI. The trans is disassembled and I have new sychros and bearings to put in it, so I can stand the case upright to work on it. I have an adapter plate off of my old engine to use as a template. The 2 top holes needed to be opened up for the bolts to fit, so I did that then bolted the adapter plate to the trans case to use as a template. I am thinking that the holes for the dowels need to be pretty exact as to not put a side load on the input shaft/ pilot bearing. With the bolts backed out 1/2 turn, I can move the adapter plate around a little in relation to the case. At the dowel holes I can get about 1/4" variation on the spot to drill. Should I just center it up, take a leap of faith, drill it and hope for the best or is there a better way? Any other input for this conversion greatly appreciated.

 

[G. Mann]

QUESTION:
We have several folks who have drilled the 460 ZF trans to fit the 6.9 adapter plate, I have a 460 ZF trans [fresh rebuild, setting in reserve] so I have "skin in the game".

Has anyone tried a 460 adapter plate against the back of the 6.9 Diesel engine? Is it possible, the bolt up to the block is the same pattern on both engines?... I have to ask, I've never tried it.. If the trans is being done.. clutch and flywheel almost always come off, so great time to just change the adapter plate... maybe?? There are a ton of scrapped 460's around so should be a "supply" of plates?

Inquiring minds want to know.. anyone have one of both to lay side by side and measure the hole pattern?

 

[Bashby]

460 doesnt have an adapter plate, The trans bolts directly to the block.

 

[riotwarrior]

LOOK in the tech section there is a picture in a thread that shows what needs to happen.

DON"T drill...use a four flute end mill and then mill the hole larger as the drill will always attempt to wander off due to not fully engaging the material and the tapered point which forces it sideways.

Four flute end mill will work well and allow you to drill/mill straight down properly!

JM2CW

 

[Bashby]

I know what you mean by the drill bit walking. They way I see it, as long as the dowels are RIGHT and the bolts will start it should work. using the adapter plate as a guide and some pilot point bits I should be fine. After looking at the article in the tech section again, I can see the 2 holes that intersect with the original holes. I think if I eyeball those and get them even it should be close enough.

 

[riotwarrior]

I know what you mean by the drill bit walking. They way I see it, as long as the dowels are RIGHT and the bolts will start it should work. using the adapter plate as a guide and some pilot point bits I should be fine. After looking at the article in the tech section again, I can see the 2 holes that intersect with the original holes. I think if I eyeball those and get them even it should be close enough.

Well walking is not good and may cause issues when bolting the case to the block. Would hate to see the case crack from weakening which is what happens and having a really oblong hole cause the drill bit walked.

Close enough eh?

I see only one issue with doing this to a 460 case and it's that exact issue...alignment of transmission mainshaft centerline to crank's centerline...off a bit can/will cause undue wear on input shaft, pilot bushing, and mainshaft support bearings...

I've thought long and hard about this procedure and though I'd do it I would not expect it to last however many have had great success with it so can't knock that fact!!!!

 

[icanfixall]

Gosh.. Get the right end mill and do it right once. Close enough isn't going to fix it down the road. Once you drill it off center thats it. You fubared the housing. you have the right idea about using the adapter plate but please don't use a pilot drill. An end mill is designed to cut in on an edge or flat face metals. They have a cutter on the bottoms of them. Some don't so know what your buying before some counter guy sells you the wrong cutter. Any metal working store or metal supply yard will have these. They are cheap for what they are.

 

[franklin2]

Gosh.. Get the right end mill and do it right once. Close enough isn't going to fix it down the road. Once you drill it off center thats it. You fubared the housing. you have the right idea about using the adapter plate but please don't use a pilot drill. An end mill is designed to cut in on an edge or flat face metals. They have a cutter on the bottoms of them. Some don't so know what your buying before some counter guy sells you the wrong cutter. Any metal working store or metal supply yard will have these. They are cheap for what they are.

No one has still answered his original question; How is he going to know what is centered when he can move the plate around? A end mill will do no good if you don't know where to put the hole in the first place. Unless you have a milling machine or a very heavy duty drill press, the accuracy of the end mill will probably not matter anyway.

I wonder if the distance from each 460 dowel hole to the centerline of the crank are the same distance? If that were true, you could then use those holes as a reference, making sure the new diesel dowel holes were exactly the same distance from the 460 dowel holes on each side.

 

[riotwarrior]

No one has still answered his original question; How is he going to know what is centered when he can move the plate around? A end mill will do no good if you don't know where to put the hole in the first place.

B I N G O !!!!!!

Hence my concern with just drillimg it out.

in essense and i could be incorrect.....not ever having done this procedure....I would suspect you ensure the two top holes are centered PRIOR to milling through those two to increase their diameter to 1/2"....bolt plate in place tightly and it becomes the mill guide for the next set of holes bolt those down n do next set n so on....

However dont quote me cause i havent done this...

 

[Wicked97]

You don't mill the top two holes you use a tapered ream and ream them out from 7/16 to half. Then you bolt the adapter on and mill the other holes except the dowl pins which you can drill.
Then You simply center your bolts in the top two holes you reamed out.
A 1/2 in bolt will fit loose in those top holes. That's normal on a diesel zf or c6 from the factory.
To get it centered wrap the bolt in a very tight wrap of electrical tape until it is snug in said hole.
That will center it close enough to perfect to not have problems down the road.

 

[Wicked97]

A couple other notes.
Weakening the case is not a factor here as the factory cast the case the same for a as or diesel so there is plenty of meat there for extra holes.
Also I don't think standing it up in a drill press will work unless its bolted to the press. A much better option is a bench top press modified to bolt to the trans or a mag drill. End mills put alot of side load and a drill press isn't made for that so keep it close to the press.

 

[typ4]

I have the steel plates to use as a guide, they are available, a member used them to go this way, they are made to drill a diesel for a 460.
When I did it I took a 1/2 bit and blunted the end and it worked great, but you need drill guides for this. Also the top holes are not a good locator but it is all there is in your instance.

 

[Wicked97]

Those guides would be far better to use.
How much is rent on those?

 

[riotwarrior]

End mills put alot of side load and a drill press isn't made for that

Huh....HUH? If used vertically only and proper cutting speed, there is no side load. It is not like you are milling across a face just in essence boring a hole vertically so I don't see how side loading comes into effect.

JM2CW

And thanks for the info on the tapered ream and such...good to know!

 

[Wicked97]

Take your end mill chuck in a hand drill and tell me how much it pulls to the side. Also a cheap press with side to side play doesn't make a round hole.
There is a lot of sidways force from that cutter. Its a lot different than a drill bit.