Click on image for the lowdown. 
====
| | | Forums66 Topics128,130 Posts1,056,717 Members48,454 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Oct 2021 Posts: 6,909 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,909 | What's the big hole in the bell housing for on the driver's side? Basically, it's a mirror image of the timing hole on the passenger side but slightly larger.
Last edited by Otto Skorzeny; 10/10/2026 9:43 PM.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: May 2015 Posts: 11,117 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,117 | It's there to make Otto ask questions. 
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: Feb 2004 Posts: 29,839 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,839 | Ventilation for clutch cooling, most likely- - - - -although it might be possible to add a pointer to time the engine on a cylinder different than #1.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jan 2022 Posts: 2,478 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,478 | It's used for the timing pointer south of the equator where the engines turn the opposite direction.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| | | | | Joined: Mar 2007 Posts: 3,433 Crusty Old Sarge | | Crusty Old Sarge Joined: Mar 2007 Posts: 3,433 | Do the GMC engines use the same Bellhousing? Could it be for timing marks on one of those?
~ Craig 1958 Viking 4400"The Book of Thor"Read the story in the DITY1960 Chevrolet C10"A Family Heirloom"Follow the story in the DITY Gallery'59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting) If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane | | | | | Joined: Mar 2010 Posts: 10,298 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,298 | Anyone know that there is a plug that is supposed to go in there? It is made of what appears to be rubber which would explain why they aren't found very often. Rubber does not last anywhere near 70 years.
I have one. It is black and has a crown on the exposed surface. Its density is similar to a hockey puck.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Jan 2022 Posts: 2,478 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,478 | Do the GMC engines use the same Bellhousing? Could it be for timing marks on one of those? GMC timing window is on the same (starter) side of the engine that Chevies are.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| | | | | Joined: Feb 2016 Posts: 1,993 'Bolter | | 'Bolter Joined: Feb 2016 Posts: 1,993 | I would believe that a reverse rotation stovebolt engine would exist. Marine, industrial, military, etc. would probably be customers.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
| | | | | Joined: May 2001 Posts: 1,907 'Bolter | | 'Bolter Joined: May 2001 Posts: 1,907 | I once used that hole for timing when I had a 235. Honest. It ran very, very poorly but I finally came to my senses.
1948 3/4-Ton 5-Window Flatbed Chevrolet 34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.
| | | | | Joined: Oct 2021 Posts: 6,909 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,909 | Did you paint a mark on the flywheel or something, Wally? And why not use the other hole that already has a pointer on it?
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: Oct 2021 Posts: 6,909 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,909 | Anyone know that there is a plug that is supposed to go in there? It is made of what appears to be rubber which would explain why they aren't found very often. Rubber does not last anywhere near 70 years.
I have one. It is black and has a crown on the exposed surface. Its density is similar to a hockey puck. I thought there might have been a rubber plug that was supposed to be there. That's what prompted me to ask the question in the first place. I have a bunch of rubber plugs left over from the Little Red project. I used one on the shift column. Maybe one will fit the flywheel hole.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: May 2001 Posts: 1,907 'Bolter | | 'Bolter Joined: May 2001 Posts: 1,907 | There was a bolt-hole on the flywheel.
Stupid me.
1948 3/4-Ton 5-Window Flatbed Chevrolet 34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.
| | | | | Joined: Oct 2021 Posts: 6,909 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,909 | Oh, are you saying you tried to set your timing using that whole by mistake?
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: May 2001 Posts: 1,907 'Bolter | | 'Bolter Joined: May 2001 Posts: 1,907 |
1948 3/4-Ton 5-Window Flatbed Chevrolet 34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.
| | | | | Joined: May 2015 Posts: 11,117 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,117 | I just took a quick look at the spare bell housing I have. The hole in question is machined, and MAY be lined up with the pocket for the clutch throwout arm pivot ball (I didn't look that closely.) That would be how that pocket was machined in the bell housing. If someone REALLY wants to know, I could go inspect more closely.
What prompted me to go look was the talk about a rubber plug for the hole. Why would GM machine a hole only to plug it up again?
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: Oct 2021 Posts: 6,909 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,909 | Again, that's why I ask all kinds of questions about innocuous things on these trucks , like the upside down coil. There are reasons for everything and I just like to know what they are.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: Oct 2021 Posts: 6,909 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,909 | That's funny. I did the same thing when I first got the truck running and wondered why there wasn't a BB. Then I saw the other hole.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | |
|
|
