UPDATE ......... had my block checked the bellhousing mating surface to ensure perpendicular to the crankshaft bearing centerline bore.

Shop checked using the line bore fixture installed in the main bore and dial indicator off the bore bar ...... BBC 289 casting was .002 off so even if slight wiggle on guide as we rotated bar added say .002 can I assume Iam good to go ..... Jody ??

 

Parallel spec is +/-.001" or .002" TIR......you are good with the block.

You also need to measure the parallel alignment with the blocksaver plate and bellhousing installed with all bellhousing to engine block mounting bolts fully torqued to spec.

 

I can check the concentric at home done before but never did check the bell to be 90* to crank. Anyway now that I lmow to cjeck block first. Will do. And then install bell and check shim if needed Then move to the cincentric

 

Ok Jody. Tks. If I understand correctly so I should have shop check bell flange face on block and machine if needed. Then also check bell with block plate and shim if necessary or. Just square it all up using shims on bellhousing ?

 

Since you have the block at the machine shop, have them verify the bellhousing mating surface is perpendicular to the crankshaft bearing centerline bore.

You cannot believe how many blocks are not machined square once you have measured 100s of blocks.

 

You MUST check the parallel alignment and concentric alignment of every bellhousing in that order, parallel 1st, then the concentric 2nd.

You cannot believe how many bellhousing are out of parallel alignment as well as the block not on the same parallel plane of the crankshaft.

My original 396/350 L34 block was out .014" on the parallel machining measuring with a proven flat and parallel original bellhousing. My Dad had unusual transmission noises with warranty issues the dealership never found. Luckily with my machining background we have determined the root cause of the transmission noises was due to the bellhousing parallel mis-alignment.

We are happy to report that CarCraft Magazine just did an extensive "Bellhousing Parallel & Concentric Alignment" article at our location, soon to be in an up coming issue.

Here is what we use to correct the bellhousing parallel mis-alignment.

 

Your pbly right Tom. Im overthinking this Not even sure how the shop could check this. The more I think about it I will just check to ensure bell trans face is square to crank. And adjust with shims ??

 

I've never heard of one being off. Maybe because they're not or maybe because nobody checks.

Maybe you can start a trend, a new revenue stream for machine shops?

 

I assume you mean check the bellhousing flange for being 90degrees from the main bore. I allways check the bellhousing bore on a manual trans for being concentric with the crank center line and correct with offset dowel pins. Ive never checked a block like you describe