My friend is building a motor for the first time and Im trying to give him as much help as I can from the motor builders on this board. He plastigauged (sp???) the front main at .004 which sounds extremely loose to me, I have yet to ask if he had the block's mains align bored, hopefully they did that for him. with bearing clearances like that he would need atleast strait 50wt oil wouldnt he? I mean this is replacing his 305 in his 84 z28 and the block has now been REbuilt 2 times and its .06 over on the bore right now. Why would they be so large anyways and how do you set the clearance, by honing the mains individually untill they are where you want???? I just dont want it to mess up with all the work he is putting into it hes already ignored my recommendation to wash the block, which I was told if its been dipped at the machige shop its ok. Any input?

 

Tell him to buy a book....

Why would you NOT wash the block? I don't care who dipped it.

You can set the clearance with .001 smaller bearings, called a .001X, if the crank was turned down or polished you could use .001+ If it gets too big then you are going to have to resort to thick oil.

It sounds like a disaster waiting to happen to me, .060 over (any idea of the wall thickness?), no washing, crazy high bearing clearances.

Bret

 

I agree why not wash it???? Especially considering Im not sure he even cleaned the backs of the mains before installing the bearings and all I saw him do is wipe the bearings off with a blue shop towel (linty). Also no idea on the wall thickness. Ive already given him advice before but him and his brother shrug it off like I dont know what im talking about or they dont care or get an "im sure it will be fine" attitude... btw he only checked the front bearing clearance which was approaching top fuel motor clearances, he just put white lithium chassis grease on the bearings and slapped the crank on and said "Im sure it will work"... on top of that he just wants to use 5w30 or 10w30 oil despite the oil advice I give him about clearances. I just dont understand how you can care so much and spend all this money on somethign like this and almost refuse to do the proper research or learn what you need and ignore advice. He bought a book called how to build a small block chevy and is going off of that I really hope this is a fluke and runs at all... you think it will? Ok done ranting sorry

Also about chosing those bearings are you supposed to have a few sets then find the set that provides teh best clearance and go with it or should the machine shop know exactly what set you need. I guess Im wondering how you know if you ordered parts from across the internet that your clearances are correct?

 

the rod and main journals should be checked with a micrometer to see the actual size , you can then order bearings to set the proper clearance, they don't all have to be the same size

 

Double check and see if the main cap saddles have been switched around. I loaned a good crank( that I had recorded measurements of) to a friend and he reported the same wild clearances. Turns out the stampings were real faint and he switched two of the caps which in turn did not register perfectly, giving the inflated clearances.

 

I wish I could go make him double check things but the crank is in and I doubt i can convince him to take it apart....

 

Sounds like it might come apart all by itself...

 

Sounds to me like the guy is convinced there is nothing wrong. I suggest simply watching him finish up this motor, let him sink a few more hundred in getting it in the car and running, and then stand at the ready with an "I told ya so".

Some lessons are best learned the hard way for the hard-headed out there.

Dave C.

 

Great post Nate!

I wish we could rate posts around here.

Bret

 

I'd love to watch this thing consume itself upon start up, but I've got a feeling he may be allright, at least for a while. It seems like Murphys law only applies to those that take the time and effort to do things half way right. This guy sounds stupid enough to be immune.

 

I wouldnt say stupid I would say stubborn and ignorant as hell though... I have a feeling it will run OK for a little bit but not for long from what ive been told and when I tell them what went wrong he'll go to someone else with some quack idea and think that was the problem. Its funny how he almost never takes my advice but will hear something somewhere from some guy and take it whole heartedly. I usually have the good technical knowledge and he has the hands on, if he would just listen I think we would make a great team...but nay.

 

I feel you there..... You could be dead nuts right on it and it's like your opinion doesn't matter. Don't feel bad it happens to me sometimes too, just let them learn the hard way. I would, I hate seeing people fail but when they do it wrong and have the help up front and ignore it, it's worth the entertainment then.

Bret

 

never ever plasti-frigen-gauge an engine that matters. save that crap for bus engines and other diesels that oil clearances arn't the biggest engine concern. with a gas engine, specifically one intended for high out put, always mic. it. more importatly, your friend is going at this all wrong. if he wants to be too "stubborn"to do it right, then let him do it on his own. no reason to try and help someone who doesn't really want your help. none the less, without proper oil clearances, it will never work. with that much oil slop comin from the crank, he'll starve the top of his engine. i give it 3 hours running before it burns up, tops.

 

yeah he got the block and crank for 50 bucks, its non roller so it will probably wipe the lobes and destroy itself faster, and to top off the cheap block is about 2000+ dollars worth of edelbrock aluminum heads/cam and all the necessary parts.... If I cant convince him Ill try to get it on video...

 

please do, it's always good to see an engine go on film. the problem is it will be a slow death. meaning no spectacular fire ball, but what the hell, i can watch a motor fade out for thirty minutes. i have nothing better to do with my time. see if you can get it, or at least convince him that he needs help. there is no reason for this engine not to work well if he just puts the time in to do it right.