Well after having my neck fused and rehabbing after I have gotten back around to my deserted LT1.

I am trying to finish a NA 355 . 3.48 STROKE/6.0 h BEAM EAGLE ROD, 4340 eagle crank.

To make a long story short I was trying to get' r done before my surgery. That didnt happen. I had remembered several hiccups had hindered me from that, and one in particular was a tighter than I want rod bearing clearance.

I have searched and read until my eyes have emitted drops of blood. I am also very experienced mechanically, and I have my own thoughts and opinions about it. However, this is the first time I have used the Clevite H series Coated bearings.

From my research I have gathered what I already assumed. The bearings are thicker. How much so, I don't know............thats a question there if someone knows the answer.

I am old school and typically like the .0025- .0030 clearance on my rod bearings in a High Performance application. I try to keep it closer to .0025.
The rods are all new and all the same size and weight. So imagine my surprise when I saw .0019!

The literature I have found says that is ok, especially with the new synthetic oils.......thoughts/opinions very welcomed here.

I have come to the conclusion that I have 3 options:
Resize the rods
Change the bearings to non coated
split the bearings with race shells (use half undersize half standard)

or........run it with what I got.........

Again I am open to idea's thoughts and opinions. Thanks for the help in advance

 

Maybe a slight polish on the crank?

 

http://www.carcraft.com/techarticles...ance_tips.html

However, if all the journals are measuring larger than normal, I would consider like Rob mentioned and bring them down to spec.

 

Thanks for the link, I have read that one many times and saved it to favorites. I am thinking about splitting the shells to get to .0025. I am still awaiting several responses that I have sent out concerning this and if I do come up with an answer I will repost. It seems that this is a perplexing question that not many have or dare to answer

 

What is the specific application for the motor?

.019" is perfect in most cases. If you need a little more, the crank can be polished .0002" and remain straight, and the rod housing bore could be opened to the high spec.

 

It will be cruiser/bruiser street/strip and some autocross. The track time will be limited, just a e few events here and there and then shows and cruising. It should perform all around and it will be quite a nasty lil booger. I was erring on the side of caution and looking towards .0025.......6800 will be max RPM's. I am expecting 450ish to the rears out of it. Custom heads and cam. The majority of its life will be below 2500 RPM, to and from work which is a 40 mile commute on open Highway.......thats why I am undecided lol

 

Like the guy said, it's fine. I had the same .002 rod clearances with the same Clevite coated bearings and it runs great.

 

If I recall, my new ones were right on top of 0.002 as well.

 

For what you're doing, that clearance will be fine - especially with a strong rod. You do need to be precise with the measurements though, I assume you measured the crank journals for taper and transfered that number to a dial bore gauge to check the rods with?

 

Yes sir!

 

Then you're good - remember the coating is a sacrificial layer that arguably really is not to be accounted for when doing clearances...had I paid attention to your original post and see that you were talking about coated bearings, I would have said that even .0016" would be acceptable with a coated bearing as long as your measurement dial bore gauge has a tension adjustment like a Sunnen so that you're not poking through the coating when taking your measurement so that you know that's the true number, Mitutoyo dial bore gauges have a lot of tension on them and you need to be careful when taking bearing measurements...

A quote from Bill McKnight at Clevite.

"A question comes to mind about bearing clearances. If you apply a coating, won't that decrease bearing clearance? The TriArmor(TM)bearing's coating is 0.0003-inch thick. This reduces the clearance by about half of one thousandth of an inch. McKnight explained that most engine builders find this slightly tighter clearance will not affect performance or engine life, especially in view of the reduced friction.Of course, if the engine builder has a particular preference, he can ask the crank grinder to make any size adjustment he feels is necessary."


Clear as mud?

 

^I love that saying lol I use it all the time. I had another poster reference that as well. I think I am gonna go with what I got. Without the coating I would be where I wanted so......

I really appreciate all the answers and suggestions. I cannot express how much I have delved into the topic and nothing like this ever came up in any of the other forums or online sooooo.......next time that someone looks for the same or similar they can and will find it right here. Good stuff!