I've got a quick question about align boring and honing main journals for you machinists. I was checking the main bearing clearances on my 455 for the Firebird, and they seemed to close up at #3 to .0010 or so. #1 and #5 were around .0030, and #2 and #4 were about .0020. These were being checked with a dial bore guage which reads to .0005, and compared on a dial caliper that reads to .001. I know, I should have some mics, but I don't have anything over a 1-2 at the moment. Anyway, I pulled the bearings back out, and torqued the caps back down to specs, to check with the dial bore guage again. I set the pointer on 0 on the front journal, and moved back. #2 read -.0015, #3 read -.0025, #4 read -.0020, and #5 read +.0005. I also pulled the caps and dressed them with a file, as I had some risers at the dowel pin holes on a couple of them. Nothing changed on the clearances. So I take the block back to the machine shop to have it fixed. My machinist says this can and does happen when guys just hone the whole thing at once and think it's done. BTW, his shop didn't do the work initially. Another shop had done it, and the engine lasted about 800 miles before the forged pistons were scored bad, and crank journals were shot. Luckily, I bought the project cheap, damage done.

So my question is, is this just careless machine work? Or is there something else I should be looking at for a cause? My machinist says after the outer journals show a good hone, they should be loosened up so the inner caps can catch up to them in size, and then bolt them all back down to take the last .001" or so out together. Sounds like a good procedure, just want to verify. I'm just slightly put out that I had asked him to check the mains when I dropped it off last month. He commented that it appeared they had been honed, so he obviously didn't check them. :rolleyes: Other than that oversight, I've had nothing but good work come out of that shop. Thanks for any input, guys.

Originally posted by Cameano:
I've got a quick question about align boring and honing main journals for you machinists. I was checking the main bearing clearances on my 455 for the Firebird, and they seemed to close up at #3 to .0010 or so. #1 and #5 were around .0030, and #2 and #4 were about .0020. These were being checked with a dial bore guage which reads to .0005, and compared on a dial caliper that reads to .001. I know, I should have some mics, but I don't have anything over a 1-2 at the moment. Anyway, I pulled the bearings back out, and torqued the caps back down to specs, to check with the dial bore guage again. I set the pointer on 0 on the front journal, and moved back. #2 read -.0015, #3 read -.0025, #4 read -.0020, and #5 read +.0005.

So my question is, is this just careless machine work? Or is there something else I should be looking at for a cause? My machinist says after the outer journals show a good hone, they should be loosened up so the inner caps can catch up to them in size, and then bolt them all back down to take the last .001" or so out together. Sounds like a good procedure, just want to verify. I'm just slightly put out that I had asked him to check the mains when I dropped it off last month. He commented that it appeared they had been honed, so he obviously didn't check them. :rolleyes: Other than that oversight, I've had nothing but good work come out of that shop. Thanks for any input, guys. The caps should be cut .003 to .004 tight and lined honed from there. When we line hone a block we take the caps off with a .001 left to come out and retorque the caps to see if they repeat, Line hone it to size and take the caps of one more time to check for repeatability.

Line honeing is an art and not everybody can do it and have it come out right. I have seen this from time to time. You should never have too loosen caps to let the other caps catch up.

We ship blocks all over the coutry to shops and engine builders and so far we have had no complaints on our main line work as we install billet caps on most of the blocks we ship.

Infact even on the new blocks we prepare we remove the caps and 99% of the time we useally have to line hone to the high side.

Originally posted by CNC BLOCKS N/E:
Line honeing is an art and not everybody can do it and have it come out right. I have seen this from time to time. You should never have too loosen caps to let the other caps catch up.Thanks for the reply, Carl. I just wanted to doublecheck that this was indeed what most likely happened with the motor. Obviously, whoever built it the first time should look into another line of work, IMO. I saw the receipts for the parts and machine labor myself when my buddy bought the engine from the seller. He was going to put it back in his Granville, but he picked up another project, needed space. He did have a '65 Chevelle project in the garage too, and a 427 with a 6-71 on it sitting next to it, so he's definitely a gearhead. Just hope he's found a better machine shop by now.

Well, I got the block back today. My machinist says he had quite the time with it. Got it fixed right, but took awhile. He wasn't too happy, seems like. He's wondering who did it the first time himself. Now I guess I'll look into a short timing chain for it, if one is available. I know they are for Chevys, but that's not promising much. Time to get'er done. ;)

And it continues to be a painful build. I got to work on it this morning, fitting the bearings, taking clearances, etc. Well, now everything's tight except the rear bearing, at .0020", which is just about perfect. The rest are between .0005"-.0012", too tight. Being that I got the bearings from the machine shop, and they cut the crank and did the align hone, I put the crank in, torqued it down, verified that it is indeed too tight (can't turn it by hand without a ratchet on the snout), I called the machine shop, and took it down to have it fixed. The machinist was cool about it, he knows he's got to fix it for free, since everything involved was paid for already, so it should fit. I'm just wondering why, because I've never had a problem with them before. They've machined all of my engines in the past 10 years or so, and all have been fine, until now. This is aggrivating. :mad: I guess it goes to show, as said many times, it's the builder's responsibility to check everything. Don't just believe it's good because you paid for it. Good thing is, I shouldn't have to touch it once it comes back, except for installing the rear seal. I'm going to pick up the neoprene seal vs. the rope seal that was in there, so I shouldn't have to pull the crank to get it in.

Darren,
I have had problems with a couple of Pontiacs in this manner. I dont know if the caps distort when you put the bearings in and tighten them or what. What we have started doing on almost every engine we are building ourselves is to check the crank and figure what size it will need to be turned to. Then align hone the block, get the bearings and torque them in place. Then I get the guy that grinds our cranks for us to bring his micrometer with him when he picks the crank up to grind it. We set up our bore gauge using his micrometer, then figure out where to grind the crank to get the clearances we want. So far this method has worked great.
By the way, you will probably still have to pull the crank if you are going to go to a rubber seal. The blocks vary too much and you usually have to trim the seal some when you install it. We have been using the 500 cuin Caddy seals, I think that is what everyone sells as the "special" rubber replacement seal for the 455's.

Bill, I've found info at Bruce Fulper's site (Rock 'n Roll Engineering) on this, and he's basically saying the same thing, cut the crank last. My machinist is figuring the same thing. Funny thing is, I can get a reading of .0005" difference from one side of the bearing to the other (front to back) with the bore guage on a couple of them. Kinda frustrating, but I guess in the future, we'll lay down the procedure in advance, to forego anymore additional work. Thanks for the tip on the Caddy seal, I was going to go searching for it, my friend thought it might be an Olds piece.