8BA Rod Measurements

[Binx]

I'm measuring my rod big ends to determine if I need them re-sized. Since I don't have the proper rod vise, I tightened them wrench tight in hand and found all but one measure minimum spec (2.2905") lengthwise and maximum spec (2.2910") crosswise. All the big ends have crisp hone marks all the way around. I thought the wear would show lengthwise but this seems to be the opposite. Though tagged as a rebuild in 1972, the motor was obviously taken off the road shortly after since even the bores are in spec for the oversize. So was this maybe a machine shop method to tighten them up lengthwise in anticipation of future stretch or will fully torqued caps reveal different measurements?

Thanks for your help

Lonnie

[Walt Dupont--Me.]

Lonnie, I'd say there allright, thay have probably been reconditioned, you have to gring alot off the caps to close up the parting line. Walt

[GOSFAST]

Originally Posted by Binx

I'm measuring my rod big ends to determine if I need them re-sized. Since I don't have the proper rod vise, I tightened them wrench tight in hand and found all but one measure minimum spec (2.2905") lengthwise and maximum spec (2.2910") crosswise. All the big ends have crisp hone marks all the way around. I thought the wear would show lengthwise but this seems to be the opposite. Though tagged as a rebuild in 1972, the motor was obviously taken off the road shortly after since even the bores are in spec for the oversize. So was this maybe a machine shop method to tighten them up lengthwise in anticipation of future stretch or will fully torqued caps reveal different measurements?

Thanks for your help

Lonnie

Hi Lonnie, best to torque them a up then measure!

Torque is 45#/50# with oil!

Many of the Ford rods, especially the "FE" series, were "wide" at the parting lines, you simply couldn't "shrink" the holes diametrically no matter how much you took off both the rods or the caps (without destroying the rods)! In the end it wasn't all that critical as long as the vertical dimensions were held. Same scenario on the Flathead rods!

Years ago when we worked with these rods we would make certain to finish hone them to the "small" dimension. It created some add'l "holding power" (crush) on the brgs due to the "sides" being slightly "relaxed"!


Thanks, Gary in N.Y.

P.S. The bearings today are NOT round (on the I.D.) when installed, they are more "football" shaped by design!

[JWL]

Whoa, whoa, WHOA!! DO NOT follow the torque advice as written by Go Fast!! Instead, adhere to the Ford shop manual information for the type nut being used.

It is a little unusual to find rods which are wider at the parting line. The general tendency is for the parting line to squeeze inward, especially when the revs have been above normal. The bearings are slightly thinner at either end and what you have will be fine. Remember, the Ford spec calls for 2.291 as the MAXIMUM, not the minimum diameter.

[Karl Wolf]

You HAVE to torque the rods to the torque you're going to use before they can be measured... A LOT of the flathead rods I've seen seem have been relieved at the parting line (I don't want to say alll)... This has doesn't make any functional difference, What matters is the shape of the rest rod that holds the bearing...
When I first worked in a shop, one of my jobs was to grind flathead rod caps... There is a way to grind them so as to get the sides of the rods to suck in a bit when they're torqued... But I don't like it much, any one wants to know can ask...
Karl

[Binx]

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Great info! Thanks! A question about the bearings though -- Gary mentioned newer bearings being elliptical on the I.D. and Karl added they're thinner on the ends. Wouldn't that make for a pretty sloppy fit on the sides. I'd think an elliptical shell with a perfect I.D. would be the way to go.

Lonnie

[GOSFAST]

Originally Posted by Karl Wolf

You HAVE to torque the rods to the torque you're going to use before they can be measured... A LOT of the flathead rods I've seen seem have been relieved at the parting line (I don't want to say alll)... This has doesn't make any functional difference, What matters is the shape of the rest rod that holds the bearing...
When I first worked in a shop, one of my jobs was to grind flathead rod caps... There is a way to grind them so as to get the sides of the rods to suck in a bit when they're torqued... But I don't like it much, any one wants to know can ask...
Karl

Hi Karl, good info!

In years of doing these builds I have also literally seen hundreds (this is not an exaggerated number) of rods "wide" at the parting lines. It is a "non-issue". Most were Fords by the way!

"Back in the day" when TRW sold "reconditioned" rods under their brand name they would systematically "angle-grind" the caps which in turn "forced" the rod together at the parting line. Just plain old bad practice. I believe this is what Karl is hinting?

Never sold 1 single TRW connecting rod in my all my years in business!

(Binx) This is an inherent brg design to keep them from "grabbing" the crank during normal running at higher loads. Those parting lines tend to pull inward slightly (on the sides) when running fairly hard!

Thanks, Gary in N.Y.

P.S. With respect to the rod torque above, those are the numbers in Federal-Mogul's catalog AND I would add, where we have torqued every (later) Flathead rod I've ever done! If they won't take at least the lower number (45#) you need new rods! You are working with a bolt that needs to be stretched to perform properly. I would say that 45# would place that near the 75% (nominal) yield point! Would also never reuse any original Flathead 3/8" rod nuts! All builds get 16 new pieces!

[Karl Wolf]

I take a fair amount for granted, just cause...
After the cap grind, the rods are machined/honed to be perfectly round, they hold the bearings just that way... At the parting line, there can be an unfinished area, as much as 1/8-3/16", the to ME does not make a bit of difference... When the engine runs, most of the load is compression, and a bit of pressure the other way, as the crank pulls the piston down for the intake... A lot less side loading, (at the parting line)
TRW rods were just about the same price as shops charged to rebuild a customers own cores, and as I remember, their cores could be pretty wide ranging in terms of relative weight and quality...
(I'm grateful not to be in THAT buss anymore)
Karl

[Walt Dupont--Me.]

Originally Posted by Karl Wolf

You HAVE to torque the rods to the torque you're going to use before they can be measured... A LOT of the flathead rods I've seen seem have been relieved at the parting line (I don't want to say alll)... This has doesn't make any functional difference, What matters is the shape of the rest rod that holds the bearing...
When I first worked in a shop, one of my jobs was to grind flathead rod caps... There is a way to grind them so as to get the sides of the rods to suck in a bit when they're torqued... But I don't like it much, any one wants to know can ask...
Karl

Yes Karl, it's called angle grinding, you put the cap in the cap grinder and put a feeler guage on one side, grind one side then flip it over do the same on the other side, It does pull the sides toghter, but I wouldn't worry about on a flathead. Walt

[Ol' Ron]

Considering the fact thay we used to rebuild our engines on a chain fall in the back yard and nobody owned a torque wrench. I surprised they even ran, not only raced.
You could buy a rebuilt Flathead from Sears for 125 dollars with a trade in. I was in Industral engine rebuilders in Patterson NJ back in the early 60 and they had hunddresa of Flatheads on skids they had rebuilt for aftermarket sales. They were an otherised Ford rebuilder but also did every engine you could think of. I saw a rack with 4" merc cranks, hundreds of them. They never used them because they didn't buy stroker pistons. SSOOO they scrapped them. I suda brought some home, but nobody was working on Flatheads anymore, Chevys, Oldsmobile and Chrysler were in vogue then. And now get pickie over a few thousands of an inch.
I'd like to know what one of these hi tech Flatheads cost these days?

[Binx]

Thanks to all for this info. It's great to hear from folks who know about the physics of hot metal in a violent environment --especially in a flathead that is off-center and inconsistent in many aspects. Ol' Ron, I get what you're saying, but these engines are getting so rare these days that you have to treat them like raising a child -- pray you don't make any permanent mistakes.

[GOSFAST]

Originally Posted by Ol' Ron

I'd like to know what one of these hi tech Flatheads cost these days?

Hi Ron, I had the privelege of building one of these reasonably "hi-tech" units last year for a '49/'50 Merc. It took some awards at the "James Dean Run" recently.

Had all the goodies, Eagle stroker crank, Scat rods, Ross pistons (metric "Moly" ring pack), Isky cam/springs, Johnson tappets, Edel 1116 heads (flycut valve reliefs & fire slotted spark plugs), Offy intake, and a Holley (390) 4 brl carb (for dynoing). Later rec'd a tri power setup by the owner. We didn't get to dyno the "trips"!

This was the first build for us with the "pinned" heads I've mentioned here.

The "full-flow" oil filter setup, ARP main and head studs, Fel-Pro copper head gaskets, etc.

Had some "bowl porting", stock (stainless) valve sizes, bronze-lined guides, viton stem seals, and some other little goodies.

We actually got the job over H&H out in Ca. due to the fact they didn't want to do the oiling system mod and were unable to pin the heads and gaskets! I can probably safely say today we have built the ONLY Flathead in the country with these "dowel-pinned" heads.

We did not supply either the manifold, carb, distributor, or water pumps, these were purchased separately by the customer! A build of this calibre alone is in the area of $11,000.00, including the dyno!

There's a tremendous amount of labor in this build.

The only other real options left would have been large valves, full-porting, and center main "girdle" (bridging the center main cap and tying the pan rails together)! Didn't feel it was necessary on this unit!

(Add) Back in the mid '90's I was involved in fabricating an intake to build a "Tuned-Port Flathead" for a friend, but fate intervened and ended the program. It would have been very unique for sure!!

Thanks, Gary in N.Y.

P.S. I still have a faxed estimate here from another area builder in the Northeast from the time I was pricing this one out and it reads:$14,000.00 delivered (400.00 was shipping fees)!

[Junknshit]

Ol Ron, Goesfast, or any of you other serious flathead builders, years back there were a couple of different guys around the country playing around with and I believe one even ran one in a dragster, a reversed flowing ??? flat motor where the exhaust came out between the top of the heads where intake would normally set. Any of you know anything about it other than it was probably pretty spendy? I remember seeing articles about it, but not much sunk in because I was playing with early Olds and Cad then.

[Ol' Ron]

Gary, awhile back, I ran into a fellow that had one of the westerns biggest rebuilders engines. 10K very few goodies.. My friend Will (UVMS) in Whitriver, was a rebuilder for the past 50 or so years. Had the weardest farm engines in there all the time. Told me once that the Flathead was the best engine ever designed im the world, and he hated them. Because any Assh**e could put one together and make it run. He's gone now and can't be replaced, like the Flathead we're a dieing breed.
I guess the Flathead is expensive because they're becoming ext-ink. I wonce sold a Cadalac V12 for 800 bucks, a 37 HD 74 nuckel jead for 50 and it ran. So 14K for a dressed Flatty ain't too bad considering the price of bread.

[Canguro]

Hi, I´m in Peru trying to rebuild my friends 8BA and need the Bore diamter of the large end of the rod.
I see here where you guys are mentioning 2.2905", I'm assuming as the standard diamter. I set my dial gauage at 2.290" and have one rod that's 2.2905" but the rest are anywhere from 2.865" to 2.288". Different sizes but all are round.

Any and all advise welcomed.
Thanks Greg

[Canguro]

Hi, can anybody please tell me the Bore Diameter of the "big end" of the 8BA Connecting Rods.

From the chats I've seen looks like it could be 2.290". My rods are ranging from 2.2865" 2.288" with one at 2.2905".

I think I've just confirmed - to myself anyway - that 2.290" is the correct measurement cause the 2.2865 to 2.288" rods all sieze up when tightened.

Looks like I'll have to correct the other seven rods.

Amy and all comments welcomed.

Thanks
Greg

[Will D]

Originally Posted by Canguro

Hi, can anybody please tell me the Bore Diameter of the "big end" of the 8BA Connecting Rods.

From the chats I've seen looks like it could be 2.290". My rods are ranging from 2.2865" 2.288" with one at 2.2905".

I think I've just confirmed - to myself anyway - that 2.290" is the correct measurement cause the 2.2865 to 2.288" rods all sieze up when tightened.

Looks like I'll have to correct the other seven rods.

Amy and all comments welcomed.

Thanks
Greg

You got it, 2.2905"/2.2910" 8ba big end. Welcome to the barn Greg. Its best to start a new thread when posting your question, you'll get more responses.