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Got my 327/300 back from the rebuilder and while putting the flywheel, clutch and bellhousing on, I looked inside at the pilot bearing. It didn't look like it was new. The builder said he was going to put a new one in.
Attached is a picture of the bearing as best as i could photograph it. I need a second opinion as to whether or not it's new and if it's not, after a total rebuild, should I replace it.
Of course the next question is how to replace it. Any help is really appreciated.
A new bushing is something that should always be done 'while you're in there' so time for a new one. You probably already know this but do make sure to install the bronze non-magnetic type bushing. If in doubt when shopping for one, take a magnet. Available from most parts houses and maybe still from GM like the one I replaced a few years ago.
Mike T - Prescott AZ
Not much left of it. It's egg shaped and it's shot.
Took the pic with my cell phone and a flashlight. Tough to get any detail but you're right: it's egg-shaped. How do I get it out and how to put a new one in? Thanks 65.
A new bushing is something that should always be done 'while you're in there' so time for a new one. You probably already know this but do make sure to install the bronze non-magnetic type bushing. If in doubt when shopping for one, take a magnet. Available from most parts houses and maybe still from GM like the one I replaced a few years ago.
Mike T - Prescott AZ
I was told by the shop it was going to be done. Now what?
Ask the shop if they did it and send them the picture you posted here - give them the chance to come clean. Was there a detailed invoice with all the parts listed? (of course my problem now is - if they 'overlooked' this, what else did they possibly 'overlook").
Pilot bearings are cheap and not hard to replace - I would rather do that job than return an engine. Just get a metal or wood rod that fits closely into the pilot bearing (but not an interference fit), pack the bearing center full of dense grease, place the rod into the bearing center and whack it good with a BFW, the pilot bearing will pop right out.
From what's in your pic, you have bigger problems than just the pilot bushing. The bushing is stuck to the trans input shaft and came out of the crank pilot bore. Sure sign of some serious crank/transmission misalignment. Plan to check both bellhousing bore centering w/ the crank and crank axis being aligned with the transmission main shaft axis (both off centering and tilt). It's a PITA to check but it will save you worlds of headaches later on.
Alex - A better pic might be needed here. If you're not sure what's there or not, pull the clutch parts back out and get us a better pic. Easier to deal with it now.
Mike T - Prescott AZ
From what's in your pic, you have bigger problems than just the pilot bushing. The bushing is stuck to the trans input shaft and came out of the crank pilot bore. Sure sign of some serious crank/transmission misalignment. Plan to check both bellhousing bore centering w/ the crank and crank axis being aligned with the transmission main shaft axis (both off centering and tilt). It's a PITA to check but it will save you worlds of headaches later on.
When I put the trans on the engine after the rebuild, lining the shaft up once I had the splines matched wasn't that difficult. Getting it to seat flush with the bell was. But after wiggling things around, it went in all the way without bolt assist. As to checking the component geometry you mention, I wouldn't begin to know how to do it. How?
Alex - A better pic might be needed here. If you're not sure what's there or not, pull the clutch parts back out and get us a better pic. Easier to deal with it now.
Mike T - Prescott AZ
Hey Mike! Nice to hear from you. Got Permatex red thread locker on the PP and FW. Not looking forward to that.
Ask the shop if they did it and send them the picture you posted here - give them the chance to come clean. Was there a detailed invoice with all the parts listed? (of course my problem now is - if they 'overlooked' this, what else did they possibly 'overlook").
Pilot bearings are cheap and not hard to replace - I would rather do that job than return an engine. Just get a metal or wood rod that fits closely into the pilot bearing (but not an interference fit), pack the bearing center full of dense grease, place the rod into the bearing center and whack it good with a BFW, the pilot bearing will pop right out.
Alex - The flywheel won't need to be removed but it's going to be a bit tight trying to remove the old bushing and install the new one with the clutch disc in place. By the way, I gotta ask...if you had the trans already installed, what made you think about the pilot bushing now?
By the way, you've got my email address, any time you have those questions to ask about Prescott, fire away.
Mike T - Prescott AZ
There are several ways to get the bushing out. One is to tap it and thread in a large bolt that you can then use to pull it out with. Another way is to take a grease gun and pump the cavity and center or the bushing full of grease. Take a short socket that just barely will fit in the bushing hole and insert a short extension in it from the socket side. Stick it in the bushing hole and rap the end of the extension with a mallet and the hydraulic force of the grease will push the bushing out. Sounds hokey but I've done it and it was amazing how easily it popped out.
To check the bell housing alignment you need a dial indicator and a magnetic base. With the clutch removed and the bell housing in place, the mag base goes inside, attached to the center of the flywheel. Position the dial indicator so that it rides on the inside of the bell housing opening as the crank is rotated (much easier said than done). Mark the rear of the bell housing opening at 90 deg intervals and read the gage at each mark as you rotate the engine 360 degrees - you don't have to zero it. If your measurements starting from the 12 o'clock position and going clockwise are .110, .106, .104 and .106 - your bell housing is centered vertically to .000 inches but has horizontal run out of (.110 - .104)/2 = .003, which would be well within the given standard of .005 inch.
However, GM bell housing have a reputation for usually being within spec. so it's kind of up to you as to if you think you should go through the trouble. It does make for an interesting exercise.
There are several ways to get the bushing out. One is to tap it and thread in a large bolt that you can then use to pull it out with. Another way is to take a grease gun and pump the cavity and center or the bushing full of grease. Take a short socket that just barely will fit in the bushing hole and insert a short extension in it from the socket side. Stick it in the bushing hole and rap the end of the extension with a mallet and the hydraulic force of the grease will push the bushing out. Sounds hokey but I've done it and it was amazing how easily it popped out.
To check the bell housing alignment you need a dial indicator and a magnetic base. With the clutch removed and the bell housing in place, the mag base goes inside, attached to the center of the flywheel. Position the dial indicator so that it rides on the inside of the bell housing opening as the crank is rotated (much easier said than done). Mark the rear of the bell housing opening at 90 deg intervals and read the gage at each mark as you rotate the engine 360 degrees - you don't have to zero it. If your measurements starting from the 12 o'clock position and going clockwise are .110, .106, .104 and .106 - your bell housing is centered vertically to .000 inches but has horizontal run out of (.110 - .104)/2 = .003, which would be well within the given standard of .005 inch.
However, GM bell housing have a reputation for usually being within spec. so it's kind of up to you as to if you think you should go through the trouble. It does make for an interesting exercise.
I'm gonna like so pass on this exercise. I've neither the tools or the space to do it let alone the expertise. I would hope the machine shop did this. Yeah...I know. So I gets the old one out using grease or bread. Then how do I gets the new one back in?
Alex - The flywheel won't need to be removed but it's going to be a bit tight trying to remove the old bushing and install the new one with the clutch disc in place. By the way, I gotta ask...if you had the trans already installed, what made you think about the pilot bushing now?
By the way, you've got my email address, any time you have those questions to ask about Prescott, fire away.
Mike T - Prescott AZ
I looked at it when I initially assembled it and thought no way would he have not put a new one in. I didn't know what new ones were supposed to look like or what tolerances were. Then I was reading some posts here about clutches, TO bearings and the related components (another post of mine) and someone gave a link to an article that said how important the bushing is and how often it's overlooked. I had to take the bell off to change the stud- another article and afterthought- and took a closer look at the bushing. I gotta say, I'm annoyed.
Be sure that you or your mechanic dress the pilot shaft and polish it. I suspect that it's got ridges in it at this time. As mentioned previously, be SURE to use a BRONZE OILITE bushing (non magnetic) many of them are bronze/iron mixed sintered metal. These will score your pilot shaft in short order.
Your mechanic should have a bushing removal tool which is a slide hammer with a double hook attachment, but that bushing is almost worn to the crank in two places, so it should be easy to deform/break and pull out. If the pilot shaft needs a lot of cleanup, then you might need an oversized bushing because shaft/bushing clearance should not be more than about 3 thou. The shaft hole in a new bushing gets smaller once it's driven into the crank, so measuring it before installation is not accurate, but it will shrink by a thou or two.
As mentioned, check your bellhousing alignment, and check it for cracks as well.
Last edited by 65tripleblack; 07-02-2015 at 09:53 AM.
I'm gonna like so pass on this exercise. I've neither the tools or the space to do it let alone the expertise. I would hope the machine shop did this. Yeah...I know. So I gets the old one out using grease or bread. Then how do I gets the new one back in?
Excellent question - take the new bushing and put it in your coldest deep freeze for a day. Get everything prepared - clean out the crank recess, determine what you are going to use to set it with - the bottom end of a large socket works or a large wooden dowel. The chamfer on the bushing hole goes to the outside when installed. Very lightly lube the crank recess, pull the bushing out of the deep freeze, and as quickly as possible drive it into the end of the crank. It should go in without a lot of effort but make sure it's seated all the way in.
It's always a good idea to check the alignment of the bellhousing but from my limited experience and what I've read on here, the GM factory bellhousing is usually dialed in reasonably close. With a bushing it's not as critical. If you were planning to run a pilot bearing in the end of the crank it would pretty much be mandatory to dial it in.
Last edited by DansYellow66; 07-02-2015 at 08:26 AM.
07-01-2015, 06:08 PM
Trans pilot bearing
