Run-Out Vs. TIR; bellhousing alignment

[TheMonkey]

i need to align my scattershield. i test fit it with straight dowels. the indicator dial has a total delta of 0.020 where i need to shift my bellhousing toward 10:30 position. offset pins come in .007, .014, & .021.

i need an offset of .010 to line up the centre of the circle from shield & centre of the crankshaft. if i use the .007, i can get my indicator dial to a total delta of .006, but the centre of the circle will be within .003.

Tremec requires run-out to be within '.005'. i thought run-out was the same as TIR (total indicator reading), but if that is the case, then i can't get within tolerance - there wouldn't be any offset dowels available! so.... for anyone that was actually in an engineering classroom.... is 'Run-Out' the difference between the centre of the circles, or is it synonymous with TIR?

i ASSume that run-out is actually difference in the centre of the circles because of the choices of dowels - as long as .005 is a standard tolerance?



by the way... i know, i know.... i can enlarge the existing holes and weld on washers, but this is a question of definitions rather than what my options are.

on another note.... i had a heck of a time pulling out my straight dowels with the usual vice grips method. so, i drilled a hole all the way through the dowel, tapped for a zerk fitting, and pumped grease through to the back of the dowel and pushed it out. first time i've used that method, worked great!

[SDMAN]

Pitch the offset dowels. PITA. Get a Browell bellhousing alignment tool (~$140). It attaches to the crankshaft. There is a sleeve that will slide onto this tool. This sleeve has an ID of the tool, and an OD of the registration hole in your bellhousing (-.005"). Drill the dowel holes in your bellhousing to a larger size so the bellhousing will slide around some. Get a set of .5" long sleeves with an ID that will snugly fit the straight dowels. Bolt the tool to the crank. Lay the bellhousing on the back of the block. Slide the sleeve down the tool and into the registration hole of the bellhousing. It is now aligned. Place the 2, .5" long sleeves over the dowels and weld them to the bellhousing. Done.

[TheMonkey]

i seen that Browell tool. very slick.

i read about it here: http://www.camaros.org/bellhousings.shtml

in that article, they say that the OD of the sleeve is .0025 smaller than the ID of the register. that tolerance would be .0025 difference of the centers of the circles, or .005 TIR. so, if that's the case, the tolerance of that tool seems tighter than the options of the offset pins (if you were to use them). furthers the confusion.

anyhow, seems that i should just get it as close as i can and be happy with it, but i really am curious about the definition of run-out vs. TIR.

thx for the suggestion.

[CarlC]

The proper term should be TIR. The term runout can be misinterpreted. Any machininst should understand TIR. If not, run away, quickly.

[Bigblue73]

Following is a breif explanation of the Bell housing alignment procedures for the installation of our kits. Please note that the bolt sizes may be different for your application. I hope this provides an explanation of what you are looking for.


Bore Runout – Clutch Housing to Crank Shaft Centerline Alignment

When performing adjustments or repairs that involve removing the clutch housing, it will be necessary to check transmission mounting bore runout and squareness to the crankshaft when reassembling.

Note: If your engine has been line bored as part of a rebuild, this step can be omitted.
If you are using a Lakewood Scattershield, follow the manufacturer’s recommendations and instructions.

1.) Replace one flywheel to crankshaft bolt with a bolt that is about 3 inches long. Mount a dial indicator on this bolt with a “C” clamp. If you have a magnetic base for the dial indicator, this can be used in place of the bolt and “C” clamp arrangement.

2.) Rotate the engine clockwise, using a socket wrench on the vibration dampener bolt at the front of the crankshaft while noting dial indicator needle deflection. Bore out of round must not exceed .005 inch of maximum total indicator reading. (.0025 one-half total indicator reading)

3.) Excess bore runout must be corrected by installing correct size offset dowels. These dowels are available in three offset sizes and must be installed in pairs of the same size. Mopar Performance and Lakewood each sell these offset dowel pin kits. The offset dowels are in size of .007, .014 and .021 inch offsets.

4.) To illustrate the recommended correction procedure, assume the total indicator reading is .020 in a direction that indicates 2 o’clock on the engine block.

In this case, the clutch housing or scattershield is off crankshaft centerline by .010 inch (one-half of the total indicator reading) which is .008 inch greater than the allowable limit of .0025 (one-half total indicator reading).

In the case under consideration, installation of two (2) .007 inch offset dowels will bring the runout within the allowable limits of .0025 inch. .009 minus .007 inch offset dowels equals.002 inches of runout.

The amount of eccentricity of the dowel will produce a total indicator reading change of double the dowel eccentricity, therefore, select a pair of dowels to the nearest to one-half the total indicator runout.

For runout (total indicator reading) of .009 in. through .020 in., use a .007 in. offset dowel set.
For .021 through .034 in., use a .014 offset dowel set.
For .035 through .050 in., use a .021 inch dowel set.


To install the dowels, remove the clutch housing and old dowels from the rear face of the engine block.

Install both dowels with the slots parallel and aligned in the direction to correct the bore runout. The slot in the top of the dowel indicated the most of amount of offset. Make sure that both dowels are installed up to the shoulders of the offset.

5.) Install the clutch housing onto the engine block using the bolts that were removed. Tighten the bolts to the recommended torque specifications. 7/16 bolts tighten to 50 ft lbs. 3/8 bolts tighten to 30 ft. lbs.

6.) Recheck the runout by repeating steps 1 and 2. If the bore runout is within the acceptable limits, the clutch housing to engine alignment is complete.

[TheMonkey]

... Bore out of round must not exceed .005 inch of maximum total indicator reading. (.0025 one-half total indicator reading)
...

Tony- thanks for clarifying your required tolerance.

few questions, that i was not able to find answers:
1) with the tolerance you indicate; if your TIR is out by 0.020 with straight dowels, it seems that the closest you will be able to get the alignment with offset dowels will still not be within tolerance (0.010 - 0.007 = 0.003). your example above started with 0.010, but in the final calculation for tolerance, 0.009 starting point was used. should a guy be happy with netting 0.003, and warranty will be in tact?

2) where should the indicator dial readings be taken for the bell face squareness? at the tranny bolt holes, or just outside the register ring? what is required tolerance at these points where the readings are taken. also, same question as original, does the tolerance refer to TIR?

3) to correct for any bell face squareness, i have read that < 0.020 can be corrected with shims, anymore should have the bell face machined. should the shims be installed at tranny bolt holes on bell face, or should the shims go between bell & rear of block at bolt holes & alignment dowels?

thanks for the help, Scott.

[Bigblue73]

Scott - Those are good questions. I'll be talking to my local engine builder to gather his input. I looked at a couple of chassis manuals and your subject isn't even addressed. I'll post what I find out.

Tony

[TheMonkey]

thanks Tony, look forward to hearing a response.

offset dowels went in, and my concentric TIR is within 001 throughout the bottom of the circle! weird though, the top of the circle must be kind of egg shaped, because TIR was at 004 at the top. this is without register ring. oh well, it is very tight so i found my way into the tightest tolerance requirements.

i just need to shim the squarness. i figure it's either 007ish at the tranny mount, or about 2x that at the bell to block. i was thinking that i could just use 1/64" caster/camber shims at the dowel and a couple bell mounting bolts on the side that i need pushed out.

hopefully will shift like buddah.

Scott.

[TheMonkey]

Tony-

I dumped a 1/64 wheel alignment shim around the dowel that i needed the space. worked perfect. TIR on squareness is 000. now.... just don't sneeze

[Bigblue73]

Excellent job, Scott.

I spoke with a few folks regarding your out of parallelism situation and I got to thinking of how in the world could that be measured on the block. It can't....at least with the tools that I have access to. I'm in the process of modifiying a small block mopar lakewood bell housing to accept a Viper T56 and just when I was about to pull it off the machine center, I ran the set-up to verify the points and used a dial indicator to check for parallelism. If it still gives you trouble, check with your local machine shop or anyone in a QC department that has a granite surface plate.