Searched and couldn't find this easily available. Did some research and some drawing and made the following, these are the standard dimensions for a Chevrolet bellhousing dowel/locating pins and bolt pattern. If anyone sees mistakes, let me know and I'll correct, this is probably good information to have for someone. I'm going to be using this to make an adaptor plate for my seagrave engine. ps.. if you right click on the image you can open in a new window or tab and get the full 8.5 by 11.00 drawing, not to scale but the numbers are much easier to read.
Put your cursor on the red X. Then right click, then select "properties", the do "copy" of the URL, then paste in your browser. It's a PDF file, not a pic, so it won't show here.
I do know chev pont olds buick all have the dowel pins and the lower set of holes in the same place >>>>.
That's what I thought to, but the drawings I got from Chevrolet engineering show the dowels .11" closer to the crank
My Sunnen line boring machine will fit all of those G.M. engines as far as dowels and crank center lines >>>>.
Well I like it. Thanks a lot. I put a block on the machine and made a drawing in '99 when I put the Nissan engine in Jacks streamliner. But then I lost it. Now they are all over this thread
Looks like that drawing from Chev eng appears to be wrong as far as that .11 dimension, should be half of that .055". (15.49-15.38 = .11, but that is total, not one side only, so divide .11 by 2 = .055.) His new drawing appears to be ok if he is copying the chevy dwg, other than the .11 dimension. But what if the 15.38 or 15.49 dimensions are wrong and the .11 is correct, something isn't right on that drawing from Chevy!!!!!!!!!! Now this post has me curious, think I will look at my Chevy bell housing and check it out.
That is a broad variety of engine bell patterns for that statement. Perhaps you meant BOP and Chevy (mentioned in this post) have the dowels and lower set of holes aligned? Doesn't seem to be the case in the Chevy drawing, or even the OP version.
I dont care about any drawings. I know the line boring machine will bolt on the blocks I listed and the centerline of the crank and the dowels are all in the same places >>>>.
Some may care about accurate drawings for the purpose of adapter plates used to adapt engine to other transmissions.
Or, accurate drawings simply give a workable idea of the bulk of a component. If like me one likes to set everything out in advance and be able to pick up any component collisions while things are still floating around in the abstract, all bits of accurate dimensional information help. One can say that things can be set out on a garage floor, and any conflicts resolved when one gets to them, but that means committing to a basic configuration before all the data is in. And that configuration might end up not making any sense at all if certain changes are necessary to keep things from hitting. It'd be better to start again from a different approach: a lot of hassle that could have been avoided. All useful: thanks Rob.
Engine Pro, Yes, I'm digging up an old thread...but... To clarify what you said: The dowel pins on the Chevy are the same location as BOP, and the lowest pair of holes is in the same place on the Chevy as the BOP...correct? Your line boring tool lines up on those points. The bellhousing adaptors use those as reference points as well. Did anybody ever verify which dimension(s) were correct/wrong?
The dowel centers are not in line with the two bolts centers. the offset is .110 Starting at crank centerline as X0/Y0 and starting on the left going CCW BOLT X -7.800 Y .440 DOWEL X -7.690 Y 2.320 BOLT X -7.800 Y 4.200 BOLT X -4.100 Y 7.020 BOLT X 0.00 Y 9.220 BOLT X 4.100 Y 7.020 BOLT X 7.800 Y 4.200 DOWEL X 7.690 Y 2.320 BOLT X 7.800 Y .440
I've had at least three different adapter plates over the past 25 years for swapping transmissions on GM rigs and the Chevy, Olds and Cad 500 all have the same dowel pin dimensions including spread and height as centered on the cranks shaft. I'm pretty sure that the bottom two bolts on all of them will bolt up also and it's the upper four that have different locations.
Thank you Dreracecar, That's what I needed. Whoever did those other drawings forgot to add the .110 to the other side.
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