I was going to mention too that the number six cylinder looks like the piston to wall clearance was too tight, that's probably the reason for the pin galling.
383 rebuild - kinda whimpy on the dyno?
- Thread starter JAndrea
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See more details of my project where I have more details of the build.
All of my mains were between .0015 and .002”.
Connecting rods were: .0015”, .0016”, .0016”, .0016”
Crank endplay: .005”
fratzog lover
Well-Known Member
That is ok by Chrysler standards, but on the tight end.
Yeah... finding that out.
fratzog lover
Well-Known Member
That is the Chrysler minimum. Stay at .002 on your rebuild. You might want to investigate 0w40 synthetic for after the break in. Just for giggles, what was the ambient temps this engine was broken in/operated in? For instance, it is 100 today in New Jersey.
It was about 106 heat index here in Mnpls yest... just brutal.
The day I broke it in it was about 80.
I like the idea of .002” next time. My manual says .001” a .002” for the 4 barrel, so I thought I was fine.
When going with conventional SAE or multi weight oils of 30 and heavier, there is a rule of thumb that is safe that says for every inch of material diameter to allow for .001 inch of oil clearance. That being said, .0024 on the rods and .0027 on the mains is usually good on a B engine with a good high volume oil system. Sometimes to achieve the proper thickness it takes .0005 under sizes bearings mixed with standard bearings with the thicker o.s. shells in the top of the rods and in the main caps.
fratzog lover
Well-Known Member
Wow. .001 doesn't leave much room for error.
One of the disadvantages of closer bearing clearances is that it can raise both bearing and oil temperatures. That’s no problem as long as the bearings and oil can handle the heat, but if they can’t it increases the risk of lubrication breakdown and bearing failure. The tighter the clearance, the more critical perfect machining has to be. Perfectly round, straight and smooth journals. That’s why high quality synthetic motor oil is the norm if you are building an engine with tighter than normal clearances. Don't be afraid to use an oil that starts with a zero.
One of the disadvantages of closer bearing clearances is that it can raise both bearing and oil temperatures. That’s no problem as long as the bearings and oil can handle the heat, but if they can’t it increases the risk of lubrication breakdown and bearing failure. The tighter the clearance, the more critical perfect machining has to be. Perfectly round, straight and smooth journals. That’s why high quality synthetic motor oil is the norm if you are building an engine with tighter than normal clearances. Don't be afraid to use an oil that starts with a zero.
aaronk785
Well-Known Member
You have something wrong somewhere. 0015 is a little tight but would not cause what I see. I've ran as tight as .001 on stock cranks and never had a bearing problem, but had some easy break in time after cam break in. If I have a crank turned I shoot for .002 to .0025 on rods and mains. A lot of them old speed pros call for clear down to .001 clearance. No way I would go under .003 even if it called for it to be .001to.002. I had built an engine with .001 and it locked up after cam break in. Just to much heat on break in. Scuffed the walls pretty good.
fratzog lover
Well-Known Member
That must be infuriating after all the money a build costs. What did the re do entail cost and time wise?
aaronk785
Well-Known Member
Tear down and a new set of rings. My machinist honed it out for .003 clearance and luckily it cleaned up the walls. I was young and didn't tell him my intentions for the motor so he set them on the close side. which is apparently to close for any build. Yes it sucked. car was down for a couple weeks.
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