8BA rod bushings
 

Any one know of source for undersize r8BA od bushings. By undersize, I mean the ID of the bushing itself. I understand that the OD comes in 3 or so oversizes, but the ID is usually real close to .750 so it can just be honed.
I would like the option of being able to have them bored so I get an exact 7.000, OAL, or whatever I need for the engine assembly to get the pistons the same distance in relationship to the deck surface. Also, does the Tobin Arp or Sunnedn rod machines have the capability to adjust the OAL of the rod during machining. Thank you Fordbarners.

Re: 8BA rod bushings
 

Hi can not help with a wrist pin bush but I have pressed in a solid piece of bronze and than bored and reamed them on a lathe with a jig mounted on the tool post
this way you can adjust OAL
this is how I normally ream new bushes anyway

Re: 8BA rod bushings
 

Of the two machines you mention only the Tobin-Arp will allow you to "dial-in" any "center-to-center" numbers, cannot be done by honing.

You would have to be very careful about any substantial length changes using the bushings as a correction factor, these are considered "thin-wall" bushings. When resizing a Flathead rod, "shrinking" the holes by removing material only from the caps, you don't really alter the C/C that much. Normally speaking you only need .003" from the caps, assuming the rods (big ends) haven't been totally destroyed, like "spun" and "burnt blue"??

Thanks, Gary in N.Y.

P.S. Out of all the OEM (Flathead) rods we've worked around over the years I have never seen any "dramatic" differences in the lengths. At least not enough to cause any issues overall!!

Re: 8BA rod bushings
 

russcc, check out the bottom left of this page. I can't believe you could custom size a set cheaper.

http://www.socalsac.com/category-s/1966.htm


Lonnie

Re: 8BA rod bushings
 

Well - I'm going to go back to your original problem/question and see if I can help. If you're trying to tune the overall deck/compression height to be the same (as it is typically off), you don't do it with rod length, you need to square deck the block and remove the necessary amount of material from each bank to correct any differences.

On a recent 1942 Merc hotrod engine that I'm building, I put the new stroker crank, new bearings and new rods and measured the compression height EXACTLY on each side. There was a difference of .008 side to side. I then had the block decked .010 on the one side (to clean-up the deck surface) and .018 on the other to clean and set a consistent deck height.

I also accurately measured the stroke of the crankshaft and determined the true compression height I needed for the pistons to put them exactly where I wanted them. If I'd ordered 'stocking' pistons off the shelf, I would not have had the piston to head clearances at .040 for my desired quench - they'd have been off. I then had Ross make me a set of custom forged pistons with my exact compression height.

Fast Forward: After all of this, I just measured everything in the new engine last week, the compression height was accurate to just over .001 side to side - perfect! The machine shop and everybody making parts did their jobs.

These are a lot of minute details to mess with, but if you want exact clearances, exact combustion chamber volumes and quench, it is what one has to do. The engine is a full-race engine -- so it is worth it to me. (And I have the time and interest to do so . . . plus investing a few extras $$$).

B&S

Re: 8BA rod bushings
 

The Tobin Arp has the capability but I wouldn't want to take out much meat out of one side of a flathead bushing. I used a TA for 18 years, mostly big rods Mack, Commin, industrial engines. Walt