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Crank Mods

sunalp

sunalp

Diamond Level Sponsor
OK, I'm at the point in my rebuild of the 1725 where I have to decide to do, or not do the crank mods for better oiling. For those that don't know, you are supposed to groove the third main journal .060 to match the groove in the bearing. Also you are supposed to drill all the way through the crank.

Has anyone done this, and does it really help. On paper it makes sense. just want to know if anyone has any real world experience with it.

Thanks!
Cheers!
Steve
 
jumpinjan

jumpinjan

Bronze Level Sponsor
I wouldn't do ANY of that work. Its not a solution that I have heard of and it will be detrimental if anything.
What is the problem that you are trying to solve? Getting more oil to rod #3?
Jan
 
sunalp

sunalp

Diamond Level Sponsor
Jan, this was an old piece of information that was entitled "building a bullit proof Alpine" from someone named Milo Muterspaugh from Colorado Springs. I'm not sure of the date but he also included Jarrids oil pressure relief valve mod to go with it. According to the article it gets more oil to #3 bearing. I'd never heard of that either so I figured I'd ask about it. I did notice that when Jim E rebuilt the 1725 a few months ago, it was never mentioned. I figured if it was something to be done to prolong the life of the engine, nows the time to do it. One of my concerns was that if I did, I'd probably have to have the crank ground, right? My crank is in great shape & the bearings were hardly worn, so I'd just as soon no cut the crank if at all possible.
Thanks for your input!
Cheers!
Steve
 
sunbeam74

sunbeam74

Silver Level Sponsor
Milo was one of the last, if not the last, to seriously be racing an Alpine in the SCCA. (maybe 1970's to the mid-late 80's) Somewhere I have his notes on modifying the Alpine engine. He was running a chevy rod based 1725 at that time.

BTW< on the black Alpine race car's engine we just finished... the Main journals were grooved. Not sure if it really helped... the bearing shells already have a channel... but it was certainly interesting.

It wasn't uncommon on Alfa motors to do this type of mods.

Steve
 
sunalp

sunalp

Diamond Level Sponsor
Thanks for the info, as usual, Steve! I figured that it must have had some racing history to it and like I said it does sound good on paper, just don't know if I need/should do it for a street engine.
Thanks again!
Steve
 
jumpinjan

jumpinjan

Bronze Level Sponsor
Jim E said:
Jan you ever drill the one oil passage in the block like is sugested?
Click to expand...
Yes, I do that on every 1725 engine that I rebuild. That modification, I would approve.
Steve - Don't forget to blueprint your oil pump. Get in there with a rotary tool and debur & smooth the edges...Right?
Jan
 
sunalp

sunalp

Diamond Level Sponsor
OK, which oil passage do you drill? I haven't heard about that one & the block will be back from the machinist next week. Is it something that can be done in the home shop or shoul I let the machine shop do it?
Thanks !
Steve

Jan, I wasn't sure what they were getting at about the oil pump.
 
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