Side Rod Clearance Question

[BigBlueOvalFan]

I have a couple different stock 427 Steel cranks that measure 1.757 to 1.759 rod journal width and my factory LeMans rods measure .862 to .867, most in the .862 range.  This gives me a .030 to .035 total clearance.  It's been awhile but I seem to remember .025 being a max number for total clearance.  Building a couple hot street 427's and I'd like to stay with factory parts (replacing hardware of course).

Can any of the pro builders comment ? 

[blykins]

It will be fine there.  I have ran everywhere from .012-.035" on rod side/side clearance and have not seen any appreciable difference in any of them.  If it's a flat tappet cam, you could even argue that more side/side clearance will sling more oil up on the lobes. 

[1968galaxie]

Many of the high rpm/high dollar builds are now using piston guided rods. The crankshaft big end side clearances are large.
See interesting article: https://www.enginelabs.com/engine-tech/the-great-rod-side-clearance-imbroglio-clearing-up-the-confusion/
Cool picture below.

Oil loss is determined by bearing clearance, not the side clearance (unless side clearance is too tight).



My stroker 385 series engine ended up with over 100 thou side clearance (offset ground crank and + .400" BBC connecting rods) Not a problem at all in 15 years.

[GerryP]

That crankshaft is as much art as it is a crankshaft.

[BigBlueOvalFan]

Thanks for the replies guys, I truly appreciate it.

[Stangman]

That’s a lot of work on that crank I’d hate to get it dirty. I’d like to put it on the coffee table so I could just look at it although I don’t think the wife would appreciate it.

[dozz302]

I always thought that a wide side clearance would bleed off more oil or oil pressure. Mostly only being a slight problem at causing a lower oil pressure at idle.

[blykins]

I always thought that a wide side clearance would bleed off more oil or oil pressure. Mostly only being a slight problem at causing a lower oil pressure at idle.

I have never seen evidence of that and I have ran some pretty loose side/side clearances. 

The perfect theatre for this to happen in would be a piston guided rod setup and oil pressure is never discussed around those combinations of parts.

[Rory428]

It has been quite a few years since I used leMans rods, but I seem to recall unlike other stock FE rods, the LeMans rods are lacking the oil squirt notches at the big end, so the Lemans rods were a bit narrower, with more side clearance. Also, many years ago, I helped a local racer with his Super Stock 396 Camaro, and he spun rods bearings 2 weekends in a row, and the problem was excessively loose rod side clearance. Once he replaced the crank and rods, he never had another such issue.

[Keith Stevens]

I haven't seen a set of rod bearings in the last ten years that have the notch in the bearing shell. I wouldn't think it would be relevant to failures?
I sold my Le Mans rods with the last build. They're excessively heavy, 60 years old and prone to bolt failure.  With the current cost of rods I wouldn't risk a build with the current expenses involved. I came in at .012 with the Eagle I beams.

[cammerfe]

That’s a lot of work on that crank I’d hate to get it dirty. I’d like to put it on the coffee table so I could just look at it although I don’t think the wife would appreciate it.

I 've noticed that wives seem to have very little understanding of such verities. On the other hand, they often can fully appreciate six or eight hours at a stretch of Hallmark movies.

KS

[machoneman]

That’s a lot of work on that crank I’d hate to get it dirty. I’d like to put it on the coffee table so I could just look at it although I don’t think the wife would appreciate it.

I 've noticed that wives seem to have very little understanding of such verities. On the other hand, they often can fully appreciate six or eight hours at a stretch of Hallmark movies.

KS

Hah! Love the Hallmark note. My sister-in-law could not wait until they started running the Christmas specials with back-to-back episodes 24 hours at a stretch! Funny indeed.

[cammerfe]

That’s a lot of work on that crank I’d hate to get it dirty. I’d like to put it on the coffee table so I could just look at it although I don’t think the wife would appreciate it.

I 've noticed that wives seem to have very little understanding of such verities. On the other hand, they often can fully appreciate six or eight hours at a stretch of Hallmark movies.

KS

Hah! Love the Hallmark note. My sister-in-law could not wait until they started running the Christmas specials with back-to-back episodes 24 hours at a stretch! Funny indeed.

 
I've been married 49 years to this one. I've been able to watch LOTS of Hallmark movies.

KS

[turbohunter]

Ahhh the Christmas Hallmark season and the wife. Makes me chuckle. Ho ho ho.

[Stangman]

Alot of nice Ford F-100 pickups on Hallmark. At least its got something for us.