Dialing in a Bellhousing ================================================= The "dialing in" is only necessary when you use a different block or bellhousing upon reinstallation.. Your Engine-bellhousing pair was "dialed in" at the factory and then the two dowel (alingment) pins were installed to assure that "alignment", for so long as, THAT PARTICULAR bellhousing/engine are used with one (each) another. Even tho you seperate them to effect removal the dowel pins will assure that they go back in proper alignment when it comes time to mate them again. Studebob July 2003 =================================================== --------------- Not a question of 'tilt' really, you are assuming the bellhousing mounting surface of the block and the bellhousing surfaces are all 'flat' or parallel with respect to each other. What you are dial indicating is the 'offset' of the horizontal centerline of the bellhousing with respect to the centerline of the crank. If you pull up the bellhousing to the engine without any pins you will note that you can move around the bellhousing up and down and sideways slightly with respect to the engine (due to the slop in the bellhousing bolt holes); and thus the centerline of the bellhousing might not be quite pointed down the centerline of the crank. This centerline offset of the bellhousing is what you are adjusting to not be an offset........ ----------------- What you need to do is: Pull out the existing dowel pins Mount the belhousing (loosely} to the block Mount your magnetic base dial indicator to the snout of the crankshaft so that as you turn the crankshaft, the indicater measures the inside flange of the hole in the bellhousing. I use a leather mallet to "nudge" the bellhousing in whatever direction the dial indicator tells me to. Once centered.. bolt the bellhousing down securely Re-drill the holes with an undersize drill bit, and use the reamer (by hand) to ream the hole to the appropriate size. I install the dowel pins, and "stake" them into the engine block with a punch. They should slip on the bellhousing, but stay in the engine block. I wish I had time to do my Truck engine bellhousing... and take photos of the process. This will eventually be another page on the NCSDC Tech-pages when the website is back up (soon guys...soon!) ----------------- If your bell housing is off, you usually don't have to machine it. Just pull the pins and lightly tighten the bell housing to the engine. Dial indicate it and tap it into alignment with a hammer. When its true, tighten the mounting bolts and re-dial the pins for a larger size or re-drill in another location for new locating pins. Alex M --------------- 26May03 > >I got a magnetic base to hold the gauge, but in thinking about it, and >after talking to Ron yesterday I'm not sure that will do it. How do you >know if the gauge is actually in the center? If you mount it on the crank flange and rotate the crank in the main bearings then it (the indicator) will be spinning around the center you are interested in. You position the indicator tip to "indicate" the bellhousing pilot hole, relative to the crank centerlin, with the indicator part-way thru its travel. >I seem to remember someone >showing a plan for a bracket to hold a gauge but I can't find it back >(and Ron said he couldn't either). > If the engine is in the car, so the crank is horizontal, the indicator "bracket sag" due to gravity must be >>measured<<, and taken into acccount. Typically a perfectly aligned bellhousing would have readings of 0.004 to 0.020 inch due to bracket sag. If the block with crank can be stood up vertical then bracket sag due to gravity can be ignored. ---------- If you are using a good mag base and indicator post, the sag would be minimal. When I aligned the bell housing on my 37, I made an indicator mounting post. It was a 1/2 rod that fit the crank center,with a piece of flat stock welded on. The flat stock had two holes drilled in it to bolt to the crankshaft. This was done with the flywheel off. Then an indicator was attached and run around the transmission bore. The bellhousing was then tapped around to true it up. Once this was done, it was tightened down rechecked and new dowels installed. Then everything was taken apart, cleaned and re-assembled and checked again. This seems to have worked just fine. Mike -------- /////>If you are using a good mag base and indicator post, the sag would be minimal. My dial indicator experience has been the opposite. Its based on many machinery alignments (when 0.001 inch counts) and a few precision machine tool housing bore alignment checks (when 0.0001 inch counts). If I did not check for bracket sag, The first clue that I should be suspicious of my results would be if the bell housing must be lowered on the block. I respectfully offer 3 items for your review. (1) Send google on a search for "indicator bracket sag" and check out a few of the first references which are specifically for procedures using dial indicators on various brackets for checking and correcting machinery alignment. Here's a quote from one of the first search results (http://www.reliabilitydirect.com/appnotes/rdia.html) "Many commercially available reverse dial indicator alignment kits have modular bracketry which can encompass the majority of applications. However, some applications will require a custom bracket. Regardless of the type of bracket used, the amount of bracket or bar sag should be documented so that this information is available to be included in the calculations." " (2) go here ------- http://www.dow.com/styron/design/guide/beam.htm ----- and plug a few numbers in for your set up. ------ "I" for a round rod is .049 X DIA ^4. For a 1/2 inch dia rod 'I" = .0031 -----E= 30,000,000 psi for all steel alloys regrdless of hardness. ----- L = length in inches P = indicator weight in pounds The rod weight could be added. (3) One of the ancient physic/mechanics-of-materials guys said something like " don't waste your time calculating what can be easily measured." I like to double check any machine work I have done, even by the good guys. I have found valve springs set to coil bind at full lift, severely (0.020) eccentric valve faces, cranks freshly ground with taper exceeding Plymouth's wear spec (looser than most) and journal radius that bind the rod bearing wiith zero clearance, and disk brakes machined 0.010 inch thickness variation (yes, the brakes locked up) The link mentioned above saysat first link say"Bar sag can be easily documented by installing the bracket and dial indicator, in the identical arrangement to be used on the machine, onto a pipe. Zero the indicator while it is on top of the pipe. Now rotate the pipe 180 so that the indicator is at the bottom position. The indicator will now display twice the amount of bar sag." If the engine is on an engine stand I could sweep the bellhousing once with the engine oil pan straight down, then rotate the entire engine 180 (oil pan up) and repeat the sweep. Because the crank would be lying in the top of bearings, the rotating center sould shift 0.001 or 0.002, but anything greater than that would be the result of my bracket sag. --------- >how would one measure the bracket sag, considering that the bell >housing is suspected of being off center? > The link mentioned above says "Bar sag can be easily documented by installing the bracket and dial indicator, in the identical arrangement to be used on the machine, onto a pipe. Zero the indicator while it is on top of the pipe. Now rotate the pipe 180 so that the indicator is at the bottom position. The indicator will now display twice the amount of bar sag." If the engine is on an engine stand I could sweep the bellhousing once with the engine oil pan straight down, then rotate the entire engine 180 (oil pan up) and repeat the sweep. Because the crank would be lying in the top of bearings, the rotating center sould shift 0.001 or 0.002, but anything greater than that would be the result of my bracket sag. ----- Hi Jeff, if you have a dial indicator with a magnetic base, you don't have to get the base in the center of the crankshaft flange. You could just put it to the outside edge of the flange and turn the crank. The needle can then be adjusted to ride on the inside circumference of the bellhousing bore. As the crank is turned, the dial will let you know if the bore is out of alignment and therefore you can use offset dowel pins to line everything up. Hope this helps, if not, I may have some pics i can email you so that you can "rig" it up to dial it in. Nimesh =================== May 2004 it definitely should be done 'if' the bellhousing you are using is not the one that came on the vehicle. The procedure is not too hard. What you need to do is fabricate (or find the correct J-tool) and hook up a dial indicator to 'read' both the flat surface the trans bolts to, and the inside edge of the hole in the bellhousing that the trans input shaft cover rides in. I think the spec (my service manual is out in the shop) says .006" allowable on the flat surface, and .004" runout allowable on the hole. What you do is set up the dial indicator on the jig so it's pointer is contacting the edge of the bellhousing and you rotate the crankshaft. Stop every inch or so and jot down the numbers. If it varies more than .004", then you remove the bellhousing, and using a punch, drive out the 2 locating pins. Bolt the bellhousing back up and snug up some of the bolts and try it again. Using a rubber mallet, you can whack the bellhousing around until you get it within .004". Then tighten the bolts. You remove the two bolts 'next to' the holes with the pins, and you drill them out with a 3/8" drill bit and drive in two 3/8" dowel pins. Then you drill out the holes where the original pins were and install new through bolts. Then your bellhousing is centered on the crank centerline and the pilot bearing won't get beat out. I can scan the service manual pages and e-mail them to you if you need, and I am sure there is a faq page on this somewhere... Hope it helps... Jeff =================== See the Sept 2001 issue of Truning Wheels, pages 18/19 ----------- The best setup, and universal, too, is to mount the indicator on a magnetic base and stick it on the end of the crank, or anywhere on the flywheel, if it is mounted, and adjust the indicator so that it is on the inner diameter of the bell housing. turn the crank 180 degrees and tap gently on the bell housing until the dial is half way back . Rotate 90 and repeat, again until there is no run-out. But the crank should be vertical for this to be truly accurate.