Chevy Tri Five Forum banner

Bellhousing Alignment SBC W/ 4spd Muncie

8K views 17 replies 12 participants last post by  Old Buzzard 
#1 ·
I have searched threads and online regarding bellhousing alignment for manual transmissions and also watched a couple of You Tube videos on how to perform.
All of the articles deal with aftermarket bellhousings, and don't offer much on the original bellhousing. So I am going to put it out here for discussion. My setup is a mildly modified SBC with less than 400 Hp, plan on using the original bellhousing (with starter mounting) with front stock motor mounts and a newly rebuilt M20 Muncie transmission.
Is it necessary to check bellhousing alignment for this setup?
How did the factory ensure bellhousing alignment on the 60's muscle cars?
The problem that I am experiencing the setup of the dial indicator and trying to configure the dial indicator to check the readings . I am using this type of dial indicator. (Which was recommended on the Summit You Tube).
Hopefully someone has used this setup and can shed some light for me, this my first time attempting left me quite frustrated but today is a new day!!


Thanks,

Tony
 

Attachments

See less See more
1
#2 ·
I've done this application many times without complications. The alignment pins that are standard on the block is all you should need. If everything is in alignment the four speed should slide completely in the pilot bearing without having to draw up using the four bolts into the bellhousing
 
#9 ·
Agree.

I have a 56 Belair 2 dr HT. I removed the 265 ci engine and 3 speed manual and installed a 61 348 Tri-power stroker. The original cast iron bell housing, 168 tooth flywheel, clutch and pressure plate, starter and a M-21 Muncie all bolted right up to the engine. Everything was aligned, no pressure required to stab the tranny. I bought engine front side mounts, which positioned the engine/bell housing in the original position. I had to change only the worn-out pilot bushing and adapt the clutch cross shaft tube mounting on the engine, a simple 1" alum plate. :anim_25: Chuck
 
#7 · (Edited)
I've used both the dial indicator and the Browell tool. Personally I prefer the indicator. So it can go either way.

Just because the factory didn't use a dial indicator doesn't make it right. They relied on whatever tolerances were in machining the individual parts. And there was some kind of quality inspection on the parts, maybe not 100% though. You're not talking just the bellhousing, it's the block and the crankshaft too.

The reason that indicator checking of the assembly became common for hot rodders was because Lakewood bellhousings are so much worse than stock bellhousings due to the way they are manufactured. Factory bellhousings have all the holes 100% machined - a Lakewood housing does not! The big hole is just a precision flame cut, but that precision flame cut is far from the accuracy of a boring bar in a milling machine.

Years ago when Detroit Diesel was part of GM, I was involved as a customer on a run of several dozen bellhousings on new engines that were far beyond GM specs. Also found out that GM specs were not as tight as SAE specs. GM and the DD dealer fixed them all at their expense - but they didn't pay for the broken hydraulic pump gearboxes their problems caused. Luckily we found the problem in time to limit that to a half dozen. So GM doesn't/didn't always make and check things to their specs all the time.
 
#8 · (Edited)
Well with a little help from a friend we managed to get the dial indicator setup and took the following readings.
We first made a couple of trial readings and we found that at 11' o clock was our negative reading and we set the Dial to zero and made that our starting point. 2 o'clock reading was 23 thousandths, 5 o'clock read 54 thousandths
and 8 o'clock read 28 thousandths.
Besides the readings here is what I found, the one bellhousing pin was damaged. Even though the damage is on the tapered end of the pin, it appears that it is deformed. I am thinking this might be causing me my problems. I am first going to try and get a OEM replacement pin and re-do the readings.
I have no idea why this pin was damaged or how it happened, and I am a little disappointed that I wasn't informed by the engine builder who did not point this out to me.
 

Attachments

#10 · (Edited)
Zman57, if your indicator reading are positive, then your bellhousing is .027" too high on the 11 o'clock to 5 o'clock axis, and it's to the right by .0025" in the 2 o'clock to 8 o'clock axis.

Given how your driver side dowel pin looks, I would replace it with another straight one and make the measurements again.

.021" is the biggest offset I can find quickly. Hopefully a new straight pin will show that you can fix it with an .021" or less offset pin.
 
#11 ·
ALLLLLLLLLLLLLLLL my cars with a Muncie(5), have a pure bone stock Chevy bell housing (both iron and alum) and good dowel pins on the rear of the block.
My 51 Chevy was the first car to get a Muncie (1968). I put it together with a 55-57 style bell housing. I absolutely DO NOT DISPUTE making the effort to align a bell housing. BUT, I have never had any issues with GM/Chevy parts for a manual transmission installation.
I have one Olds that is a FACTORY 5sp car (I ordered it new). The original small Olds V8 was replaced with an Olds 455 in 87, and the puny factory 5sp replaced with a Richmond Street 5sp, then the 455 was rebuilt to W30 specs in 2013. The bone stock Olds alum bell housing was used with the Richmond street 5sp tranny and it has performed flawlessly ever since.
So when it comes to bolting a bone stock Chevy bell housing to a Chevy engine and the bolting a manual tranny to the Chevy housing without taking the effort to index the engine/housing/tranny, I'm a believer.
Now, one exception to the above. My 23 T-bucket has a scattershield, which was on the car when I bought it several years ago. I have no clue if it was indexed. But the Muncie behind it works fine.
Have I just been lucky over the years? Maybe so, but if it ain't broke, I ain't fixin' it!
 
#13 ·
I have always used guide pins on the bellhousing to install the transmission. If the trans goes in with nothing more then a little wiggle of the output shaft to align the clutch splines, then I am good to go. Lakewood scatter shields can be a bit of a challenge sometimes, but not always. I do the same thing, if the trans does not just slide in on the guide pins, then I will dial in the bell housing (which really dislike doing and is a big giant pain in my opinion.) I will have to try one of those tools instead of dial indicator. Seems like an less frustrating method.
 
#14 ·
Well a little update , I started off tonight with replacing the bad bellhousing alignment dowel with a new Moroso dowel. The Moroso dowels were not the stock length but the longer dowels. I thought that I was receiving the stock length from the local auto store that I ordered them from but ended up with the longer dowels.
The readings became better but still not within tolerance. With nothing to lose I replaced the other pin as well hoping for a little luck that we would be in tolerance but we are still out. My last set of readings with two new pins are, 12 o clock 0 , 9 o clock 4 thousandths,
6 o clock 30 thousandths and 3 o clock 28 thousandths.
If I am understanding this correctly, I need a pack of 0.14 Offset pins to go in the 10 o clock position.
 
#17 ·
Sorry for the delay on my response but I had a short vacation that interrupted my project. However I want to put closure on this thread so that people searching this topic out could read it and know that it worked.

I used a set of Lakewood .014 offset dowel pins and after 9 attempts I was able to get my final readings within .005 of an inch. I read on an another thread to make small adjustments were required and that is what it took in the end to get it right. To say the least this was a frustrating process and you need patience to do this. I would recommend using the dial indicator and if you are not used to setting one up by the time you go through the this process you will be very familiar with the adjustments needed as I did.
Thanks for all of the replies to the thread.

Tony Z
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top