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460 Rod Bearing Clearance

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460 Rod Bearing Clearance Empty 460 Rod Bearing Clearance

Post  bbfguy1 on December 17th 2019, 8:58 am

This is a very mild, cast piston, stock truck rod (resized with ARP bolts) 460 I'm assembling for a driver Torino. My main clearance seems livable, ranging from .0027-.0003. The rod clearances give me some concern. I have measured multiple times, just to confirm what I'm getting. Are the figures below too large for a 100% street driven engine? The crank is .010 on the rod journals and .020 on the mains. Rod bearing is Speed Pro 7185CH. Measurements taken using Mitutoyo dial bore and Mitutoyo outside mic. I'm measuring crank journal and then setting (0) dial bore to crank specs. I even took #1 rod and tried a set of new .010 Clevite bearings and got the the same .0033. Any thoughts?


#1-.0033
#2-.0028
#3-.0027
#4-.0031
#5-.0030
#6-.0034
#7-.0029
#8-.0030

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Post  rmcomprandy on December 17th 2019, 11:06 am

bbfguy1 wrote:This is a very mild, cast piston, stock truck rod (resized with ARP bolts) 460 I'm assembling for a driver Torino. My main clearance seems livable, ranging from .0027-.0003. The rod clearances give me some concern. I have measured multiple times, just to confirm what I'm getting. Are the figures below too large for a 100% street driven engine? The crank is .010 on the rod journals and .020 on the mains. Rod bearing is Speed Pro 7185CH. Measurements taken using Mitutoyo dial bore and Mitutoyo outside mic. I'm measuring crank journal and then setting (0) dial bore to crank specs. I even took #1 rod and tried a set of new .010 Clevite bearings and got the the same .0033. Any thoughts?


#1-.0033
#2-.0028
#3-.0027
#4-.0031
#5-.0030
#6-.0034
#7-.0029
#8-.0030

Better to loose than to tight ... use a thicker oil on that engine.

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460 Rod Bearing Clearance Empty Re: 460 Rod Bearing Clearance

Post  Paul Kane on December 17th 2019, 4:43 pm

bbfguy1 wrote:This is a very mild, cast piston, stock truck rod (resized with ARP bolts) 460 I'm assembling for a driver Torino. My main clearance seems livable, ranging from .0027-.0003. The rod clearances give me some concern. I have measured multiple times, just to confirm what I'm getting. Are the figures below too large for a 100% street driven engine? The crank is .010 on the rod journals and .020 on the mains. Rod bearing is Speed Pro 7185CH. Measurements taken using Mitutoyo dial bore and Mitutoyo outside mic. I'm measuring crank journal and then setting (0) dial bore to crank specs. I even took #1 rod and tried a set of new .010 Clevite bearings and got the the same .0033. Any thoughts?


#1-.0033
#2-.0028
#3-.0027
#4-.0031
#5-.0030
#6-.0034
#7-.0029
#8-.0030

This is splitting hairs but if you want to be prudent and assuming those are engine block cylinder numbers, you might want to rearrange the rods to the cylinders like this:

1. 0.034”
2. 0.033”
3. 0.030”
4. 0.029”
5. 0.031”
6. 0.029”
7. 0.028”
8. 0.027”

Also, idle oil pressure is a function of oil pumping speed vs engine clearances bleed off rate and you have large clearances.  So if “low” idle oil pressure alarms you, then you might want to consider an HV oil pump.  But frankly with your modest power engine combo a low idle pressure is nothing to worry about.

Lastly given your description of the engine combo and if I could get a bit academic, you really could get away with 0.001” less bearing clearance on both mains and rods and run the std pump and be happy for tens of thousands of miles.  That said, your clearances are not worth chasing down, hurt nothing, and oil pressure can be tuned with pump type, oil viscosity, etc.
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Post  dfree383 on December 17th 2019, 5:06 pm

Bad grind job? Lots of taper?
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Post  bbfguy1 on December 18th 2019, 9:41 pm

Thank you for the replies and advice. Very much appreciated; 429-460.com is a special place for Lima freaks like no other!

I decided to go ahead and leave as is with clearances. I finished assembling the short-block today. This is .060 460, stock front sump (5qt) pan engine, with a Mellling M84, modified for more pressure. It's a temporary engine for the car, that was put together with many parts that were laying around, where money had been previously spent (the rods were resized and had been sitting since Sept. of 2000, heads done back in 2014, crank done in 2004, new pistons bought from a closing machine shop, for $20 in 2009, block was sold to friend back in 2003, he moved and told me I could have it back, bored with cam bearing installed, circa 2010 and a free Edelbrock performer intake, that I forget where it even came from).

The pistons are heavy, .060 Silv-O-Lite 1143. Measured deck today and they are .012 in the hole, in a C9VE block, that the deck was cut .010 on. Heads are a set of C8VE's (milled 70cc chambers), with good stainless, stock sized valves 2.08/1.65, machined for studs & guide plates and mild exhaust port cleanup. After paying for the balance job on those heavy ass pistons, I will not ever do another cast piston .060 460 deal; just isn't worth cost for such an OEM type engine. Balance job (2 slugs mallory) was more than parts in the whole engine. lol





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