Who can draw CAD? Looking for solution to offsetting bellhousing on V6

[vlad01]

Hi all,

In my main build thread I talk about all my bellhousings being off alignment. There is no offset dowels in existence for these engines.

I have not really found anyone that can sort it, Dandy engine can give it a crack but the min cost they estimate is $650 and it might not be right, apparently they enlarge the holes, plug them with an alloy slug and re-machine them to the original size but with the offset correction. To me it sounds like a lot more steps where error can creep in that other potential methods.


No general machine shop/engineer want to do such one off small jobs, at least all the ones I tried and precision is key here. And the worst part is poor turn around, I don't have much time left as the property has virtually sold (probably will be by tomorrow or so after) and the family including me, needs to get their shit out of there, the quicker the better. So stuck in an awkward place where stuff up after stuff up and delays from 3rd part people have delayed my car from being on the road for probably 1-2 years more than it should have been.

So I had the idea of looking at quick turn around CNC services and many are available, especially in China. Where cost and turn around is good and most are ISO certified, so you know it should be right.

I was thinking either I have offset dowels custom made or offset sleeves made that go into the bell housing location holes provided they are accurately enlarged on center.

But I have bugger all CAD experience (only 2D cad and some cardboard package design cad experience, of little benefit here), so I am wondering if this route is viable but I need a hand if anyone can draw up a file to make X offset part, and I can sent it off and get it made.


I was also looking at the idea of drilling new dowel holes else where as suggested by Duggan Balancing, but I can't get any tools into that space in situ to do that. I am also not even sure if the existing dowels are removable, I talked to someone who had tried and couldn't get them out. So it sounds like a risky move to try and remove them without making things worse. So the sleeve idea might work best? But I'll still need a machine shop to fit them.


But if anyone else knows a machine shop with the skills that isn't going to toss it in the "in 6 months pile", with quick turn around and not going to stuff it up, I am all ears, ideally someone with experience in correcting bell housings, that I would prefer than going the route of getting custom offsets made overseas and seeing if it works or not.

[antus]

Im not sure I fully understand what you are trying to do. But I have seen shops cut the ends off two transmissions and tig the end from one box on to the other to adapt the box. Not sure if that is an option for you, and still need a shop that can do it.

[pman92]

Can you post up dimensions/ drawing of exactly what you need?

I have a lathe and can probably machine them for you (if it's only a few).
Otherwise I can draw them in CAD for you

[immortality]

Why not take out the OEM dowels, clock the bellhousing and true it up, bolt it on tight and then drill in some new dowels or overside the old dowel holes to suit.

[vlad01]

Why not take out the OEM dowels, clock the bellhousing and true it up, bolt it on tight and then drill in some new dowels or overside the old dowel holes to suit.

Yeah this is what Duggan Balancing suggested, issue is I can't get any tools in there. I would just do that if I could. There might be one spot but I need two spots really.

[vlad01]

Im not sure I fully understand what you are trying to do. But I have seen shops cut the ends off two transmissions and tig the end from one box on to the other to adapt the box. Not sure if that is an option for you, and still need a shop that can do it.

This should help make sense.

https://www.holley.com/blog/post/how_to ... utch_life/

All my factory bellhousing are way out of spec, but my issue is the offset dowels normally sold for this task, don't exist for the V6 or any GM engine for the matter of fact that uses the GM metric bellhousing pattern. So it's not unique to the V6.

And the dowels are extremely difficult to remove anyway as they are massive (18.5mm dia) and are in deep (about 22mm length with about 9mm sticking out). Using an easy out may work, but I better damn sure I have dowels on hand to take their place.

So as an alternative given that and that the engine is already installed, modifying the housing itself is likely the best path, maybe?

[vlad01]

Can you post up dimensions/ drawing of exactly what you need?

I have a lathe and can probably machine them for you (if it's only a few).
Otherwise I can draw them in CAD for you

How precise can you machine? It would be just two of the same, either hollow offset dowels, or rings/sleeves with the inner diameter offset. In either case, the offset is 0.17mm.

I might pick up a micrometer ($45 from total tools) and measure up the outer diameter of the dowel, so we can know what tolerances we are playing with for either option.

[pman92]

Can you post up dimensions/ drawing of exactly what you need?

I have a lathe and can probably machine them for you (if it's only a few).
Otherwise I can draw them in CAD for you

How precise can you machine? It would be just two of the same, either hollow offset dowels, or rings/sleeves with the inner diameter offset. In either case, the offset is 0.17mm.

I might pick up a micrometer ($45 from total tools) and measure up the outer diameter of the dowel, so we can know what tolerances we are playing with for either option.

+/- 0.02mm if I take care.
A sleeve would be easy assuming the ID is big enough. Whats the OD and ID of this sleeve and how long would it have to be?

[vlad01]

The ID would be a tad over 18.5 (dowel appears to be exactly 18.5mm) and I think the best OD would be a tad under 20mm since 20mm is a common end mill most machine shops should have. A slightly larger size of 21mm would be better, but that mill size appears uncommon, same with 22mm. So I want to make it as full proof as possible for the actual housing machining.

The length I think would be 8mm as only about 7mm of the dowel actually engages if you discount the chamfer on the dowel. What it also would need is the end slotted like many of the offset dowels out there. That allows you to see the axis of offset and a means of turning it to point in the direction required.

If that is something in the too hard bin, a CAD file will be best and I can palm it off to one of these online CNC services in China. They state an accuracy of 0.005mm and the one I was looking at has EDM and precision CNC grinding capability. So I'd imagine a pair of rings to those dimensions should be easy for them and quick turn around.

So in the case of a CAD file, maybe an ID of 18.51mm and an OD of 19.98mm should work? I'll have to confirm the actual dowel OD with a micrometer, as if these are made from steel, they might interfere if the tolerance is wrong. Ideally if the holes are milled to the 20mm, then a slight gap of 0.02ish mm I'd imagine will allow them to slip in assuming exactly a 20mm bore and still be loose enough to turn via the slots to adjust their direction. I'm not super versed in tolerances for slip fit, press fit etc... But I feel like these are in the ball park?

[VK_3800]

You wouldn't use an end mill to size, the holes need to be reamed for an accurate fit (or possibly bored).

Should be pretty easy to make some offset dowels of the right size (if you had to create a CAD file this is easy too, just two cylinders), certainly easier than re-drilling and doesn't require access to any other parts to make them. If you did then maybe make a few different offsets at once so you have some options. The slot on the ends isn't hugely important, you could just attack them with an angle grinder and clean them up afterwards.

The straight sleeve idea is maybe an option to use smaller off-the-shelf offset dowels but adds to possible tolerance errors. Installing an offset sleeve would be a real pain as it would be near impossible to turn. Unless you have a suitable reamer and way to fixture it square I wouldn't be over-sizing the bell housing holes.

If it were me I'd take pman92 up on the offer of making a couple of new dowels with the appropriate offset - should be easy enough to machine and least room for error as long as you measure the OD correctly. Make sure you remember to halve the measured offset so you don't end up the same distance out in the other direction.