bellhoushing

Greg Reimer 7376 · 03-13-2019, 02:23 PM

A machinist I knew, one of those guys who must stay up nights thinking about new ideas and stuff, took a very accurately machined,decked, squared, line honed and ready to go block, and just for something else to do, decided to check and see if the rear mating surface of the block was accurate, in this, he meant 90 degrees perpendicular to the center line of the main saddles. He put a ready to go crank in it, then a flywheel which he properly torqued, and checked for run out,it was perfect, but when he checked the distance from the rear face of the flywheel to the surface of the block, it wasn't 90 degrees from the crankshaft c/l. In other words, the bell housing flange wasn't the least bit flat, or accurately machined.Now,dealing with a cast iron block that came from the furnace and was originally machined at the OEM engine plant long before it ever was a seasoned casting, that makes sense. I remember cars when I worked in dealers in the mid-late '70s once in a while you would get one with a cracked flex plate. If it's absorbing run out every revolution,how long can you expect it to last? You 4 speed racers, and I love seeing them, trying to get an accurate result using offset dowel pins and God knows what else it might take to achieve an accurate result from a hydroformed or stamped part like that scatter shield,could have a whole host of inaccuracies to deal with. In short, has anybody ever had clutch and flywheel issues due to inaccurate machining of the rear face of the block on back? I'll bet we have,and don't know it!!

Dwight Southerland · 03-13-2019, 03:27 PM

Quote:

Originally Posted by Greg Reimer 7376

. . . In other words, the bell housing flange wasn't the least bit flat, or accurately machined.. . .

X2!

Jim Caughlin · 03-13-2019, 03:27 PM

Quote:

Originally Posted by Greg Reimer 7376

A machinist I knew, one of those guys who must stay up nights thinking about new ideas and stuff, took a very accurately machined,decked, squared, line honed and ready to go block, and just for something else to do, decided to check and see if the rear mating surface of the block was accurate, in this, he meant 90 degrees perpendicular to the center line of the main saddles. He put a ready to go crank in it, then a flywheel which he properly torqued, and checked for run out,it was perfect, but when he checked the distance from the rear face of the flywheel to the surface of the block, it wasn't 90 degrees from the crankshaft c/l. In other words, the bell housing flange wasn't the least bit flat, or accurately machined.Now,dealing with a cast iron block that came from the furnace and was originally machined at the OEM engine plant long before it ever was a seasoned casting, that makes sense. I remember cars when I worked in dealers in the mid-late '70s once in a while you would get one with a cracked flex plate. If it's absorbing run out every revolution,how long can you expect it to last? You 4 speed racers, and I love seeing them, trying to get an accurate result using offset dowel pins and God knows what else it might take to achieve an accurate result from a hydroformed or stamped part like that scatter shield,could have a whole host of inaccuracies to deal with. In short, has anybody ever had clutch and flywheel issues due to inaccurate machining of the rear face of the block on back? I'll bet we have,and don't know it!!

Totally correct, you have to check for parallel before you start checking for run out, I've seen this problem also.

On another note regarding Quicktime, thank you very much for changing the flange bolt pattern and not saying anything. I use a small block Ford bellhousing from Quicktime which bolts to an adapter plate (that I fabricated) to fit my 2.3 Ford motor. I bought a new 'duplicate' bellhousing from them last year and the entire flange arrangement had been changed. I had to rework my adapter plate along with the chassis cross member to make everything fit. As a general rule, I like the Quicktime quality but sure wasn't happy about the unnecessary redesign. Also, their prices went through the roof when they got bought out a few years back.

Chevy55 · 03-14-2019, 04:11 PM

As a old IH truck mechanic we were required to make three checks when there was a clutch disengagement problem.

1. flywheel parallel to the block (dial indicator on block, turn crank to check flywheel face)

2. face of Bellhousing parallel to the flywheel (dial indicator on flywheel, check bellhousing face when turning crank)

3. center hole in the bell matching the centerline of the crank.

03-13-2019, 02:23 PM	#1
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,139 Likes: 172 Liked 727 Times in 221 Posts	Re: bellhoushing A machinist I knew, one of those guys who must stay up nights thinking about new ideas and stuff, took a very accurately machined,decked, squared, line honed and ready to go block, and just for something else to do, decided to check and see if the rear mating surface of the block was accurate, in this, he meant 90 degrees perpendicular to the center line of the main saddles. He put a ready to go crank in it, then a flywheel which he properly torqued, and checked for run out,it was perfect, but when he checked the distance from the rear face of the flywheel to the surface of the block, it wasn't 90 degrees from the crankshaft c/l. In other words, the bell housing flange wasn't the least bit flat, or accurately machined.Now,dealing with a cast iron block that came from the furnace and was originally machined at the OEM engine plant long before it ever was a seasoned casting, that makes sense. I remember cars when I worked in dealers in the mid-late '70s once in a while you would get one with a cracked flex plate. If it's absorbing run out every revolution,how long can you expect it to last? You 4 speed racers, and I love seeing them, trying to get an accurate result using offset dowel pins and God knows what else it might take to achieve an accurate result from a hydroformed or stamped part like that scatter shield,could have a whole host of inaccuracies to deal with. In short, has anybody ever had clutch and flywheel issues due to inaccurate machining of the rear face of the block on back? I'll bet we have,and don't know it!!

03-14-2019, 04:11 PM	#4
Chevy55 Banned Join Date: Nov 2014 Posts: 324 Likes: 625 Liked 179 Times in 89 Posts	Re: bellhoushing As a old IH truck mechanic we were required to make three checks when there was a clutch disengagement problem. 1. flywheel parallel to the block (dial indicator on block, turn crank to check flywheel face) 2. face of Bellhousing parallel to the flywheel (dial indicator on flywheel, check bellhousing face when turning crank) 3. center hole in the bell matching the centerline of the crank.