MG MGB and MGB GT Tech Talk
I have installed new rocker arm bushings, hand reamed them to a tight size and finished them off by honing them to proper size using pin gages to get the correct size. Now that they are correct (.6255-.6260") some of the bronze is gone, through to the silver (steel backing ??) . Has this occurred to anyone ? I am very pleased with the fit, but am apprehensive about running them, should I rebush them again and hope that the layer of bronze is thicker?? Thanks
I have not had that problem, how much shaft to bushing clearence did you end up with.
It sounds like you may have reamed them well off-center. Either that or you got cheap bushings or you have an oversized shaft?
B-racer Wrote:
I have a worn set on the bench that are at .623". There's still a ton of bushing left, and its a solid bronze bushing with no lead, steel, or other layers of materials.
ALL PARTS CAME FROM MOSS MOTORS, SHAFT (.6250" O.D.) AND BUSHINGS WHICH AFTER HONING .6260" PIN GAGE FITS AND .6265" GAGE DOES NOT FIT. THEREFORE BUSHING TO SHAFT CLEARANCE IS .001". I AM GOING WITH MANUAL SPEC. FOR 18G / 18GA UNDER GENERAL DATA SECTION. SPECS. SHOW SHAFT O.D. .624 - .625...............AND BUSHING I.D .6255 - .6260.
THANK YOU FOR THE RESPONSE !!!
I suggest you give Moss a jingle and let them make it better. In my experience, they really do want to give you the best part for the best price and they may have been "sold" a bill of goods too.
THE POSSIBILITY OF REAMING WAY OFF CENTER IS ALWAYS A FACTOR ALTHOUGH I DID IT SEEMINGLY CAREFUL BY HAND . NOW IF YOU HAVE A SET OF WORN (OVERSIZE ....? ) BUSHING THAT ARE MEASURING .6230 ???? MY INFO SAYS THEY WOULD NEVER FIT ONTO A NEW SPEC SHAFT .624 - .625 , NOT TO MENTION ROTATE ??? I WILL BE RE-ORDERING BUSHINGS AND STARTING OVER AGAIN, DO YOU HAVE A RECOMMENDATION FOR HIGH QUALITY BUSHINGS??
ALL INFO. IS MUCH APPRECIATED, THANKS
67mgbrich Wrote:
Nah. Common thing to type in all caps.
Rich, turn it down a little, eh?
Try Mini Mania if Moss can't give you satisfaction, but I'd try Moss first.
My guess is that you just got some cheap bushings. I know the distributor shaft bushings Moss sells are extremely porous and problematic. If the rocker shaft bushings are made by the same company, I'd try a different supplier. Even if you were off center, it shouldn't matter. There shouldn't be a layered bearing in the rockers.
Rich,
YOU ARE NOT CRAZY, YOU REALLY DID GET CRAPPY PARTS!
A friend of ours rebuilds Healey's and has had a hard time getting good bushings for the last several rebuilds. Same problem you had and no difference if he hand reamed them or took them to his machinist and his Sunnen hone. The bushings are poorly made. He started out with Moss and moved on to a couple of other suppliers, same problem. He finally got some from a place in Maryland I think that are correct and have a lot of bronze material in them after they have been reamed to fit.
Things like these bushings get into the supply chain and since a lot of parts houses are buying from the same manufacturer they all end up selling the same bad part and then they don't know where to get better stuff. There was a situation with Ford pilot bushings many years ago that was similar. Folks started getting extreme wear on the nose of the input shaft after a clutch job. Turns out the bushings had so much iron in them you could pick them up with a magnet and they would machine off the nose of the input shaft for you in short order. It took a long time for all of those to work their way out of the supply chain.
Joe
Try Gordon Strickland at the B Hive, maybe he sources his bushings from a another source, I've never had a problem with his, if all else fails go to McMaster Carr and source you own bushing material and make your own, that what I do when I convert press fit connecting rods to floating, I use alloy bronze, its a good wearing material.
I feel the need to apologize to several people, specifically B Racer and Speed Racer. I am a "hunt and peck" typist. As mjamgb mentioned, all caps can be common. Thanks for covering me on that. I typed my original question in upper and lower case because I had the time. When I am pushed for time, I put on the Caps Lock and fire away, as was the case when I responded to your replies. I did not realize the etiquette involved until my wife explained that all caps with multiple question marks and exclamation points can be considered yelling (or bad attitude). Multiple question marks simply indicated areas of confusion on my behalf. My sincerest apologies to all. Many of your responses have helped me re-evaluate sources for bushing material.
Thanks again.
Rich
67mgbrich Wrote:
Takes a big man to apologize. While I was not involved in this thread I think I can say you have earned respect by your actions. There are others here that still insist on using all caps even though they have been asked repeatedly to do otherwise. I know that there are some who will not respond to their inquiries because of the attitude displayed by their insistence in using all caps. Thank you.
My opinion mirror's Gerry's, but ther ewas no offense taken by typing in caps. Its harder to read, but the same point is still taken. I, in no way, take capital letters to mean yelling and utlize the hunt-and-peck method of typing myself.
If its something that would be used, appreciated, and utlized by the MGE members, I'd be happy to spec out the rocker bushigns and have them manufactured by the same company who does my distributor shaft bushings. They'd probably cost about the same as Moss's bushings, but be of a significantly better material and more consistent fit.
Jeff, think you could make them so that they would not need to be reamed after pressing in? Do all rocker arms ID spec follow pretty close specs or do the wander around like everything else. Reaming them is the PITA to me. Just no way to do it right with a jig to hold them square. I have though about making a jig to hold them in my lathe but it has just been easier to farm that job out
Yes, I think you could get them VERY close to perfect. The company that's making my bushings has no issues with staying within .0005" tolerance range. The real trick is getting them press fit without too much distortion. If you push them in a bit crooked at first, you'll always need to ream or hone them slightly. I know I can get them very, very close, to where you'll be honing only .00025" here or there as opposed to agressively reaming them out to fit. I'd make them to a +.0005/ -.0000" ID tolerance so they'll always fit.
Does anyone know the exact OD of a new rocker shaft? I'm wondering if they're accurate to the old ones since old ones are all I have to measure at the moment.