Small Block Duster
Well-Known Member
Hi guys. You guys have been a lot of help and I appreciate it very much. I don't like starting another post so quickly but I need your advice.
I began to do the initial blueprint to my 360 such as mock-up and checking bearing clearances and the first thing I found was the machine shop had pressed my pistons onto the rods backwards. I understand mistakes happen but this is a pretty amateur mistake and it makes me wonder what else they may have missed. So I took them to another machine shop to have them pressed off and assembled correctly. And hopefully not destroy my pins or my pistons in the process.
Anyway, the main bearing clearance is coming up as high as .0026" on the rear main, #3 and 4 were about 2.4, and the tightest being number 2 main at 2.0 to 2.1. The #2 main bearings showed a little tracking after turning the crank with the caps torqued up. We switched bearing shells from the #2 main to the #1 main and vice versa. #1 main went from 2.3 or 2.4 down to 2.1 or 2.2 and #2 main still close to the same at 2.1 or 2.0. This is after measuring at different ambient temperatures and several times. Also, both get about .0001 smaller from front back on each main. I have full groove p-series main bearings. The thrust is about 3.5 and the crank seems to turn smoothly. I'll know the rod clearance when I get them back. This engine is going to red line at approximately 6500 rpm, mostly street driving and a little racing.
This is a 10 to 1 compression motor. Any information you want to know about it I would be glad to answer. I haven't listed it here to save space.
Back to my question. Everything except the rear main seems awfully tight to me. If it was a small-block Chevy I would probably not run it. But as I have been told, this is a Mopar and I need to think of it in those terms. In your experience, can 360s be run this tight given my operating range and engine set up? I'm still thinking about a high-volume oil pump, but maybe thinner oil than I normally run. Maybe 10w30. I don't know what the rod clearances are yet. I will when I get them back. I don't think they make 9 thousandths under bearings for Mopars. Do you guys think this is an acceptable spec in this case? If not, what do you recommend? Would getting Federal-Mogul bearings and mixing them with the Clevites possibly help change the clearances a little. I've heard that polishing the crank to slightly open up the clearance may not keep the crank journals round. The crank has been freshly machined .010/.010 under and the front 4 main bearing journals are miking out exactly the same.
The machine shop said the crankshaft line bore was good. Do you think it's time to take this to another machine shop and have it line bored and put studs in the same time?
Have you had a successful engine in the past with clearances like mine?
I began to do the initial blueprint to my 360 such as mock-up and checking bearing clearances and the first thing I found was the machine shop had pressed my pistons onto the rods backwards. I understand mistakes happen but this is a pretty amateur mistake and it makes me wonder what else they may have missed. So I took them to another machine shop to have them pressed off and assembled correctly. And hopefully not destroy my pins or my pistons in the process.
Anyway, the main bearing clearance is coming up as high as .0026" on the rear main, #3 and 4 were about 2.4, and the tightest being number 2 main at 2.0 to 2.1. The #2 main bearings showed a little tracking after turning the crank with the caps torqued up. We switched bearing shells from the #2 main to the #1 main and vice versa. #1 main went from 2.3 or 2.4 down to 2.1 or 2.2 and #2 main still close to the same at 2.1 or 2.0. This is after measuring at different ambient temperatures and several times. Also, both get about .0001 smaller from front back on each main. I have full groove p-series main bearings. The thrust is about 3.5 and the crank seems to turn smoothly. I'll know the rod clearance when I get them back. This engine is going to red line at approximately 6500 rpm, mostly street driving and a little racing.
This is a 10 to 1 compression motor. Any information you want to know about it I would be glad to answer. I haven't listed it here to save space.
Back to my question. Everything except the rear main seems awfully tight to me. If it was a small-block Chevy I would probably not run it. But as I have been told, this is a Mopar and I need to think of it in those terms. In your experience, can 360s be run this tight given my operating range and engine set up? I'm still thinking about a high-volume oil pump, but maybe thinner oil than I normally run. Maybe 10w30. I don't know what the rod clearances are yet. I will when I get them back. I don't think they make 9 thousandths under bearings for Mopars. Do you guys think this is an acceptable spec in this case? If not, what do you recommend? Would getting Federal-Mogul bearings and mixing them with the Clevites possibly help change the clearances a little. I've heard that polishing the crank to slightly open up the clearance may not keep the crank journals round. The crank has been freshly machined .010/.010 under and the front 4 main bearing journals are miking out exactly the same.
The machine shop said the crankshaft line bore was good. Do you think it's time to take this to another machine shop and have it line bored and put studs in the same time?
Have you had a successful engine in the past with clearances like mine?
