clearances on rods and mains

ronbuick

Active Member
Joined
Jun 12, 2001
I got the motor to the machine shop for a rebuild and was talking
to the engine builder about clearance on the rods and mains,
he said he would set the rods at .0015 and the mains at .002,is that too much clearance for the mains, the rods sound right, but
I'm thinking that that .002 is too much for the mains, what do
you engine builders out there think??, thank you, Ron
 
I would prefer . 0015 on both....002 is the absolute max in my opinion for an engine that will not see more than 6000 rpm. Seems like .0018 was the factory max? I did not go look it up so I may be wrong. Lot's of guys here that think that .002 is great...

I just look at how well the factory engines lasted and they were seldom near the max clearances from what I have seen. I think it is a chevy mentality that makes people want to go larger.
 
You are right Steve, the factory says .0003-.0018, that is why I'm
asking the guru's of engine building out there for there opinion
on this, and it will not see anywhere 6000 rpm, Ron
 
Don't allow him to open it up that much.

I consistently set up stock block/crank/rod combinations at .0015 - .0016 on both the rods and mains. I have done 6 or 7 of these shortblocks, and all are in 11.50 - 10.30 cars. None have ever had spun bearings, and have run these that fast year after year.

Too large of a clearance in these areas is directly responsible for at least 75% of pissed-off rebuild customers these days who went to a machine shop that operates on the old "Set 'er up like a Chevy" mentality.

g'luck
 
We do 0.020 on rods and mains even for strip/street motors. Oil pressure is fine with proper flow.

From the V-8 Buick experiences, rods do not, or actually should not, be less than that. Race V-8's with their bigger journal diameter live better at 0.030.
 
LOL

Don't do that...what will I do if I have no one to argue with!?

I was a bit worried because I saw yesterday that Jack M was for tighter clearances...:)
 
Thanks for all the replys, I will ask him to set the rods and mains
to tight .015, thanks, Steve Y for that info you you sent me on
this, Ron
 
Originally posted by Nick Micale
We do 0.020 on rods and mains even for strip/street motors. Oil pressure is fine with proper flow.

From the V-8 Buick experiences, rods do not, or actually should not, be less than that. Race V-8's with their bigger journal diameter live better at 0.030.


WHOA!!!
I'm pretty sure you have a typo but .020 & .030 is a plug gap..lol...
I think you mean
rods: .002 NOT .02..

:D
ks
 
Originally posted by KEVINS
WHOA!!!
I'm pretty sure you have a typo but .020 & .030 is a plug gap..lol...
I think you mean rods: .002 NOT .02..:D ks

Ok, I was off a decimal point!

I should NOT do complicated math early in the AM:confused:
 
I sent off an email this morning that I had to resend... IT WAS WAY TO EARLY!!:D
 
Clearances

I set mine all at .002 as I run the hi vol. pump, the cam brg redrill and reclock. I keep the rod side clearance at .012 to a MAX of .015. w/ the .012 being the target.
Trying to get to oddball clearances such as .0018, etc is HARD to do, unless the crank is polished so a .001 under brg 1/2 can be used w/ a std 1/2, etc.
If the crank is going to be ground under, now is the time to see what the REAL rod/ main clearances are w/ new brgs in the rods and block.

back under my rock....:D :D :D
 
Rod side clearance is seldom mentioned...

I finally got something out of GMHTP....the second article on Jack M's engine....it actually mentioned rod side clearance, gave the number for the wider Felpro bearings, and mentioned that the oil holes needed to be opened up to the bearings to take the load off the hv pumps...

Of interest, was the clicking noise that sounded like valvetrain if the rod clearance was in excess of .015.

It made me wonder if that was TurboSam's problem when his engine warmed up.

Sam are you out there? :)

Chuck, you need to write a book on engine building. On every page, you can say but Nick disagrees with this part, and Kendall disagrees with that and Cairns/Wood don't agree with anything. :)

One of these days, I am going to take a digital camera and photagraph every piece I screw up so we will have some pictures to guide people with on simple things such as which slot the crank sensor goes, or how to degree a cam, etc...

The other day when I was changing shocks and holding the air ratchet with a two foot extension on it would have made a great picture. Particularly when it jumped out of my hand when it got tight but my fingers were still on the trigger...it bounced off the side of my head about 15 times before I realized I had to quit cursing like Porky Pig and get off the trigger...looked like Bozo the clown with a lemon stuck under the fringe of hair on the side of his head. I should of quit when the long box end slipped off of one of the drop bolts and hit me in the bridge of the nose...I did not realize until I went into the house to inspect the side of my head that I had split my nose open as well. Some days just go that way.
That would have made a good photo session on how not to hold wrenches...:D
 
Originally posted by Steve Wood
Chuck, you need to write a book on engine building. On every page, you can say but Nick disagrees with this part, and Kendall disagrees with that and Cairns/Wood don't agree with anything. :)


God I laughed when I read the above. One of the funniest things you've ever written Steve....and also true.

I've often thought that a compilation of collective knowledge from here and the list would be fantastic....but who would have the balls to do the compiling with all the differing opinions and thoughts being offered.

Ah well, it would just be stolen and sold on Ebay anyway. :)
 
FOTOS OF SCREWUPS!!

Steve, I had a particularly painful experience as you did.
Mine was w/ a 1/2" drill. I was drilling holes in the frame of my dually for running boards. I passed the drill to my helper and got the cord wrapped on the trigger, and the drill body wedged between my chest and the floor of the truck. The bit grabbed my shirt and twisted my tit up in the wad. I couldn't let go, couldn't shut it off!! FINALLY, when my helper quit laffing hysterically, he unplugged it!!

As for the book.. THAT would be a real entertainer!!

Doubt it would be a best seller. I'd rather write a book on wheel/tire combos and Grainger valves.:D :D :D :D

Back to gettin ready to BBQ some horsemeat!!;)
 
Yeah, I read that too Steve. Its a possibility. I am getting the car out again today to mess with it so we'll see.
 
Top