Well I figured that... But when looking at a 6 bolt they dont have a girdle and yet dont have any main bearing problems.
I was shown a post on NABR about a guy making a girdle for the 6 bolts because of them "swinging/dancing" under high cylinder pressure.
[RANT]If your going to flame me for posting it up here, then dont even respond. NABR has such shit rules about "stealing info" its retarded. Why would someone get so pissed if all they use the info for was to help someone! Its like their own little cult. I know some of you are on NABR and will probably go back and post this just like how I got banned... Seriously, grow up, we are all trying to do the same thing and gain knowledge, why keep everything a "secret"?!?[/RANT]
Sorry... Ok here is the post:
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After seeing some nasty fretting where the main caps bolt to the block, I decided to make a main girdle. The caps on a 6-bolt dance around at high cylinder pressures, where the 7-bolt has a nice integral girdle. I wanted the larger rod journals the 6-bolt has, but with better structural integrity.
I'm considering making some of these and I wanted to gauge interest. The price I'm shooting for, if I can get enough people interested, is $125 on the initial run. There are a couple bosses for the rear cover bolts that need to be ground away and the oil pan lightly interferes with the ARP studs at the rear of the motor (nothing a ball peen can't easily fix). Both these things are pretty minor to work around.
The part is designed to clear crower rods on a stroker motor. It will easily clear everything on a 2.0L. I don't know about other rods because this combo is all I have.
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Another poster:
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Honestly, though, the first thing I thought when I saw the topic was "crankwalk." The girdle is the major difference between 7-bolts and 6-bolts that hasn't been investigated with regards to crankwalk.
Also, how would this keep the caps from dancing around? Just the friction of the girdle to the caps? Is the problem that you are trying to solve cap movement or the mains moving around with respect to one another?
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Original poster :
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The problem I was having with the main caps was fretting due to them flexing at the axis the 2 bolts per cap makes. This was the worst on the center main as it isn't tied into any others in OEM form. Basically, the front and rear edges of the main cap and mating block surface become fretted and pitted. The goal of this part was to stabilize the top of the cap so they can't do this swinging dance anymore.
From what I've seen, I don't think the caps are moving around due to bolt strength or preload. I didn't really improve the main cap fretting when I upped the torque from OEM spec to 50ft-lbs with moly lube. Unfortunately, I don't think this will work well with OEM bolts. They have larger heads than the ARP's and will get into the oil pan worse. It would probably take a decent bit more beating on the pan to get them to clear.
I installed the pan on my race engine tonight. The last 2 studs only interfere by about 1mm. I set the pan on the block and smacked it with a deadblow hammer until the nuts formed large enough dents in the pan that the pan bolt holes all lined up.
I don't see any reason this would require a line hone. Its not changing the clamp load on the caps or their alignment in any way. I wouldn't be scared to drop the pan and just slap it on an otherwise existing engine.
Actually, I've never line honed a mitsu engine. They always seem to rotate nice and freely with new bearings and I've never seen a wear pattern in the mains that indicated any axial misalignment. Maybe I've just been lucky though, I don't know.
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I was just shown this and I dont know what to think... Anyone else feel the need to comment?