Hit the wall again... I ended up needing to shim the caps on my engine. Shimmed the first, second and third and the crank spins just fine. I had been fighting this but did make progress until I got to the rear main cap.
The bearing is tight going onto the crank, even with the crank on blocks on the bench. But the crank spins ok in the block with the top rear main bearing in place and the other three torqued.
I did torque the cap on to see what happened and when removed there were only marks on the edges where the bearings meet. Nowhere else.
Thoughts?
1954 3600 Stakebed non-original engine out of a '55 passenger car with powerglide
Are the shims overlapping the ends of the bearing shells, like they're supposed to do? What does the bearing inside diameter measure with the cap torqued down- - - -without the crankshaft in place? That dimension, compared to the crankshaft journal diameter, is what will tell you what the actual clearance really is. Any other method of measuring clearance, including Plastigauge, is just an educated guess. Has the crankshaft been reground recently? 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!
Unfortunately my measuring tools are limited to a decent vernier caliper but I'd say the the rear main journal is about .001 too big. Shims are not even in the conversation at this point, with the crank on stands, on the bench with the bearing in the cap will not go onto the crank without forcing it, there is NO clearence. Oddly, as I mentioned, with the other three caps installed, shimmed and torqued the crank spins fine. The rear cap (lower) bearing is the hold out.
And NO, the neither the crank nor the block has seen a machine shop during my ownership. But based on what I found during dissassembly a fast moving rebuild shop was the last to be inside the engine. Just a quick review of how I got to this point.
1. All this started in my attempt to replace the rear main seal. When I removed the cap I found that the bearing was wiped, see the pic 2. Then there ws the problem with the doweled bearings. You and I spoke on the phone about that and I dissasembled the short block and notched the block for the tabs. 3. Tried to install the crank. Beginning at the front bearing I shimmed the caps using plastiguage and got in the ballpark, with the crank able to spin freely after installing each of the first three caps. When I got to the rear main that's where I saw that fitment of the rear lower cap was an issue.
What has me mostly puzzled is that with the rear main upper bearing in place and the other three caps torqued it spins. At the same time the rear main lower won't go over the crank all by itself away from the block and on the bench.
I think I know what the solutin is and I'm pretty sure I won't like it but just wanted some input before I take the next steps. Thanks!
1954 3600 Stakebed non-original engine out of a '55 passenger car with powerglide
Measure the bearing at each end and in the middle to find the thickness at all three locationsl. Do the same with the upper half and one of the middle bearings for comparison. This is to rule out a odd sized bearing, they all should measure the same.
Bearings before installed should be wider than the openings in the block and cap, when installing they need a slight compression it fit tight. How does yours fit?
Measure the block opening at the mating seam in the cap and block best you can.
Install the bearing in the block and cap then measure across the seam again, subtract the bearing thickness from both ends and you should have the block width.
If the measurements don't come out, look closely at the bearing tang and how it fits the groove of the block. Swap upper and lower bearings, how's the crank fit?
The last post about the rear crank journal being tapers would make me take it to get checked, .0015" is not enough clearance and if you shim it, the other end will be out of spec causing oil pressure loss. The bad bearing in picture shows the taper of the crank, your new bearings will not last either as long as the crank is tapered.
Did you replace ONLY the rear main? Any chance it is a undersized bearing and the crank is std?
'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.
Call again- - - -I can loan you the right measuring tools to do the job accurately. Also, it's possible you have one bearing shell that's incorrect- - - - -slightly undersize. Don't be afraid to "shoeshine" the crankshaft a little with a long strip of cloth-backed sandpaper if necessary, but only after getting an accurate measurement. Dial or digital calipers just don't make the cut!
Edit: Is the engine still in the frame, or have you done enough disassembly to get an inside diameter measurement of the main bearing bore, the bearing ID, and the crankshaft? Trying to do accurate measurements with the crank still in the block will be difficult, if not impossible. The block bore specification for the #4 main is 2.969"-2.970". 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!
Well I took the measurements that Joe H reccomended and addresses Bills question and put them into a spreadsheet hoping it would make sense to you guys.
And please remember that My measurement tools are limited but I do feel that while the numbers may not be 100% they do show a pattern that indicates what the problem might be. I have a hunch but would rather not cloud your thoughts with my opinion. Probably better to go in with an open mind.
Jerry, thanks for the offer, very generous. Take a look at what's here and maybe it will make sense to you. I may give you a call tomorrow. Thanks all!
You've already tried "easy"- - - - -that's why you still have a problem. Just like the slogan Sun Electric used to put on all their test equipment- - - - -"We Test Not Guess!" Works every time! Every time I've tried shortcuts on the race engines I've built, I ended up with some VERY expensive scrap iron! That was back in the dark ages when a good round track engine only cost around $15K- - - - -and lasted about half a season. An engine with 1K miles on it was an antique! 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!
To me it looks like maybe the cap was damaged during the rebuild and they swapped for a diffirent one. The block and bearings seem fine. Looks like a line bore is coming your way along with a crank polish for good measure.
Since the main bearing bores on a stovebolt engine are four different diameters, line boring can be a real challenge. I have home-brewed a few machining fixtures to allow me to narrow the thrust faces of the #3 main bearing web on a 216 engine so I can install a 235 crankshaft. That same setup could be used to guide a small rigid cylinder hone in the rear main bearing bore to adjust the diameter, while maintaining sufficient alignment with the other bearing bores. It would be a tricky, but doable procedure, I believe.
I have a portable line bore setup that could be used to do a conventional boring procedure, but that would require doing four separate cutter diameter settings. The fit of the timing gears between the crankshaft and the cam is also a critical measurement because the centerline of the crankshaft is moved slightly in the process. Most of the material must be removed from the bearing caps, while little or no material is removed from the block.
I'm planning to add this small diameter rigid hone setup to my line bore fixture to use on stovebolt blocks:
"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!
