Rod side play.

[tminer]

Not a StageII, but steel caps, crank (Eagle) and rods (Oliver) so I thought y'all would be better informed. I can't reach the builder that is helping me and my machinist is waiting and he doesn't need another excuse to delay my work!

I don't know where I got my number, but I have 6-8 as proper rod side clearance. My machinist is pretty adamant that isn't enough. He wants 10-12. Rod bearing clearance is 2.2-2.6.

Thanks,
Tom

 

[LV GN]

Not a StageII, but steel caps, crank (Eagle) and rods (Oliver) so I thought y'all would be better informed. I can't reach the builder that is helping me and my machinist is waiting and he doesn't need another excuse to delay my work!

I don't know where I got my number, but I have 6-8 as proper rod side clearance. My machinist is pretty adamant that isn't enough. He wants 10-12. Rod bearing clearance is 2.2-2.6.

Thanks,
Tom

i did a search on this board and found this-------------
from what I've seen factory rod side clearance is usually outside the factory spec when tearing down a used engine. More often than not the side clearance is .015" +. With that said .050" is too much although the biggest problem you'll probably have is some extra noise. If your rod side clearance is somewhere between .010-.020" it will be fine.


I was asking this same question at one time & after alot of research (both on here & actually talking to a few extremely helpful Turbo Buick engine builders) went with .0015-.0018 on both mains & rods

 

[EightSecV6]

Not a StageII, but steel caps, crank (Eagle) and rods (Oliver) so I thought y'all would be better informed. I can't reach the builder that is helping me and my machinist is waiting and he doesn't need another excuse to delay my work!

I don't know where I got my number, but I have 6-8 as proper rod side clearance. My machinist is pretty adamant that isn't enough. He wants 10-12. Rod bearing clearance is 2.2-2.6.

Thanks,
Tom

Tom,
My opinion is that your builder is right on track with bearing and side clearances

 

[tminer]

Thanks.

I do pretty much trust him, but confirming opinions help me to sleep better.

Tom

 

[Camarosnake]

So what happens if you have 5 thou clearance ...........

 

[turbobitt]

I think the Buick power source says that .007 is optimum. Don't forget that this is not a typical even fire V8 engine with two rods per journal sharing the clearance. Another thing, two much clearance doesn't seem to hurt anything anyway. The bearing clearance is a much tighter clearance then the side clearance so the side clearance won't contribute to any significant oil pressure issues. Matter of fact, I here that some of the Cup guys center the rod on the piston end and have huge clearance between the rods. The only thing I would look for is if the oil hole and chamfer is completly covered by the rod bearing in any of its possible extream positions.
Allan G.

 

[Camarosnake]

Yeah, people seem to be saying a little loose is okay but what happens if it is tight like .005 I put a feeler guage in tonight and it seemed to accept a .008 snug so maybe it's not bad at all.....

Thanks for any help...

 

[BlownV6]

I agree with Anderson. But I will go on to say that that .030 wouldnt hurt anything!! Heres the deal your oil is both a lubricant and a coolant. Under normal low RPM and power the side clearance can be tight because the oil is not working hard and therefore does not need to be exchanged as quickly!!
However with higher RPM and/or power conditions the oil is working much harder and is subjected to more heat because of that load/friction on the bearing. So it is a good idea to have more and more side clearance as RPM and power goals are raised because it allows the oil to pass thru the bearing areas with less restriction. Less restriction means more oil , more oil means lower surface temps which means better bearing and crank surface life.
Hope that helps!! Mike

 

[Tweeked6]

It sounds funny, but one of my builders commented to me that you need at least 2 times what the thust is. So if .006 thrust is good you should have about .012 rod side clearance which falls into line what you guys are saying. Also one thing to look at is making sure the bearings do not bind in the radius of the newer cranks. Sometimes the wide race bearings cause the side clearance to look incorrect, but the bearing is what is holding everything up. Hope some of this helps also.

 

[LOT]

side play

With an off center, wouldn't more side play cause uneven rod bearing wear?

 

[BlownV6]

With an off center, wouldn't more side play cause uneven rod bearing wear?

And why would that be?? Mike

 

[LOT]

wear--Mike

On more than 1 stock eng. (off center) I have seen where the rod bearings wear on 1 side (hard to explain)--not on the edge but if you lay the bearing insert down with the business area looking @ you--the bearing surface will have uneven wear. IMO the more side clearance the greater the uneven wear. I assume all your stuff is on center.

 

[BlownV6]

On more than 1 stock eng. (off center) I have seen where the rod bearings wear on 1 side (hard to explain)--not on the edge but if you lay the bearing insert down with the business area looking @ you--the bearing surface will have uneven wear. IMO the more side clearance the greater the uneven wear. I assume all your stuff is on center.

The wear I think your seeing on the bearing is from the rod flexing (bowing sideways). This is common to high HP off-center motors and is the exact reason that the ON-center race block was developed!! This flexing will happen with whatever side clearance you have. I think I see where your coming from in that less side clearance will create a binding effect helping to keep the rod from bending , but this also will cause intense heat and try to gauld the rod to the crank and try to break the rod in the spinning direction.
Does that make any sense?? Yes all my motors are on-center. Mike

 

[LOT]

I agree

The wear I think your seeing on the bearing is from the rod flexing (bowing sideways). This is common to high HP off-center motors and is the exact reason that the ON-center race block was developed!! This flexing will happen with whatever side clearance you have. I think I see where your coming from in that less side clearance will create a binding effect helping to keep the rod from bending , but this also will cause intense heat and try to gauld the rod to the crank and try to break the rod in the spinning direction.
Does that make any sense?? Yes all my motors are on-center. Mike

There also comes a point where it can be too tight. The oil that has just lubed and cooled the rod bearing has to have ENOUGH room to escape. Our friend OC had some seize on him becase of tight side clearance. IMO .012-.014 should be close altho I once ran some @ .026.

 

[BlownV6]

There also comes a point where it can be too tight. The oil that has just lubed and cooled the rod bearing has to have ENOUGH room to escape. Our friend OC had some seize on him becase of tight side clearance. IMO .012-.014 should be close altho I once ran some @ .026.

Way back when I was running NHRA Super Street and was in the running for division points , I messed up a wide journal rod and didnt have one!! So we stuck in a narrow journal rod to make the last 2 races That had to have .065 side clearance (dont remember exactly) It ran perfect and everthing looked great when I tore it apart that winter , so I know first hand that lots of side clearance works. Of coarse I use a belt driven drysump pump so I dont have any oil pressure issues that could come into play. Later Mike