Loose bearing clearances

[chilly460]

Continued putting the 352 project together, this was an old circle track motor from the mid 60s running LeMans rods. 

I didn't have much experience running a bore gauge before so wasn't sure of my measurements, but had my uncle verify the measurements and they're accurate.  I'm getting  .003-.0035" on the rods, and .003'-.0032" on the mains.  I was doubting the rod measurements before but it makes sense being a short track motor that they'd use some extra rod clearance. 

My question is 1) clearance is obviously on the high side but I assume it'll be ok with a HV pump?  This thing is never going to see many miles.  2) I'm running Morel lifters which suggest 10w-30, but as I recall they state 10w-40 can be used max.  Anyone seeing any issues running 40w with Morels?

This motor is just an effort to get it running, so there are some "that's close enough" calls being made. 

[blykins]

Run it.  I set up a lot of stock rod journal FE's exactly like that.  An HV or B pump will be fine.  I would not run 10W40 with the Morel stuff. 

[chilly460]

Got it, thanks!

[My427stang]

I don't love looser rods, mains I couldn't care less, but as Brent says, it'll be fine.  As they say, "loose, nobody knows, tight, everyone knows"

BTW some bearing P/Ns are tighter than others, which do you have?  There is a 427 part number that is getting harder to find, I don't have it here with me, but it adds clearance.  Worth keeping on the shelf if you don't need the clearance

I also agree with the pump and oil recommendation, but I'd push to the HV, only because of idle oil pressure with the bigger gears, off idle there is nearly no difference.

[blykins]

Got it, thanks!

Yeah, a stock rod is more flimsy than a new Molnar/Scat rod so there should be some consideration there.

Using the rule of thumb, you should be at least at .0025" for rod bearing clearances and I like to run a hair more than that. 

I just looked back at build notes for the last four stock journal FE builds that I did and they were all between .003-.0035". 

My old 352 dyno mule had the exact same clearances as yours on the rods and mains and I ran a B pump with it as well.  It's worth a few ponies in itself according to Bill Conley's testing.

[gregaba]

Showing my age here but in the 60's and 70's it was common practice for us to run our circle track engine's with looser rod and main clearance.
The theory was the looser clearance allowed more rpm and faster run up coming out of the corner's.
Also note we normally rebuilt our engines 2 or 3 times a year unless they blew up.
Greg

[blykins]

I don't even consider those clearances "loose". 

The general rule of thumb is .001" of clearance for every inch of journal diameter.  That's my minimum.  For an FE main journal, it would be .0028".  For a factory FE rod journal, it would be .0025".  Those would be my minimums for a mild street engine.  In an application where things flex and move around more (like using factory rods or an application where a crank would flex), I would increase the clearances past that.  It's not a rotating assembly acceleration type of thing, it's just more clearance so that things won't get pinched when parts deflect and distort. 

Now, if someone said that they were running .005" on the mains and rods....that would be loose LOL

OR....if you were to make a bonehead mistake like someone I knew (it was me) who put standard bearings on a crank that was cut .010" and ended up with about .012" main bearing clearance, THAT IS LOOSE LOL  BTW, the only way I knew something was wrong there was that the oil pressure didn't recover as quickly as I'm used to seeing at the end of a dyno pull. 

[chilly460]

My dad crewed on the car in the mid to late 60s.  As the story goes, it ran ok in qualifying heats but in the longer mains they'd hurt a rod bearing or blow it up often.  They were basically taking stock 352s, throwing in a cam and intake and running them.   Eventually they had a shop build it, ran the LeMans rods, and it was more reliable.  The block has basic oiling mods, and they had a homemade pan with kickouts that I'm guessing helped keep it alive. 

My father passed away last year, my uncle came down this week and said the engine was in the car in 1972 when the driver won the late model class at Lancaster speedway in NY, my dad moved away by then.