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Are these con rods worth saving?

General engine tech -- Drag Racing to Circle Track

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travis
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Are these con rods worth saving?

Post by travis » Tue Nov 26, 2019 7:06 pm

I tore down another 351w...standard bore but with a ton of miles on it. It was WELL worn... .014”+ of ring to piston clearance, pretty nasty ridge, etc. The rods concerned me a bit...the rod bearings look surprisingly decent for some 287k miles, but the inserts just fell out of the caps when I pulled the caps off. Out of curiosity I stuck a new standard bearing in a few of them and they still fall out easily. It seems that the rods may have deformed a bit. Considering the miles, are these even worth trying to rebuild for even a mild build?

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Re: Are these con rods worth saving?

Post by modok » Wed Nov 27, 2019 12:01 am

if you want to know if the rods are deformed then measure them with a bore gauge.
It is virtually impossible for you to determine this based on how the bearing fits in one half,
The bearing being made in an arc larger then the bore is called "spread"
the amount of spread on a bearing is a fairly wide tolerance, and in most cases far larger than the rod could ever become.

the bearing shells losing their spread is sometimes a sign the bearing got hot, but.... assuming it had any to begin with.

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Re: Are these con rods worth saving?

Post by BCjohnny » Wed Nov 27, 2019 5:29 am

travis wrote:
Tue Nov 26, 2019 7:06 pm
It seems that the rods may have deformed a bit.
Not necessarily.

With that kind of mileage there would be extra clearance and the shells would have experienced some kind of mild 'hammering' in operation ...... not enough to spin 'em but enough to take the spring out, it's not exactly uncommon.

As said you need to measure, but with so many miles I'd doubt that they wouldn't benefit from being re-sized ..... as regards absolute mileage some would consider them 'well seasoned', others scrap.

As they haven't spun they've probably led an easy life, so maybe the former, but if you're going to push them now, without the cost of measuring, re-sizing, new bolts and magging it's a crap shoot .... if it's a lazy build measuring and eyeballing might get you by.

They're not exactly rare, so cost is probably an issue, and that will be the decider I guess ......
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Re: Are these con rods worth saving?

Post by PackardV8 » Wed Nov 27, 2019 11:02 am

BCjohnny wrote:
Wed Nov 27, 2019 5:29 am
travis wrote:
Tue Nov 26, 2019 7:06 pm
It seems that the rods may have deformed a bit.
Not necessarily.

With that kind of mileage there would be extra clearance and the shells would have experienced some kind of mild 'hammering' in operation ...... not enough to spin 'em but enough to take the spring out, it's not exactly uncommon.

As said you need to measure, but with so many miles I'd doubt that they wouldn't benefit from being re-sized ..... as regards absolute mileage some would consider them 'well seasoned', others scrap.

As they haven't spun they've probably led an easy life, so maybe the former, but if you're going to push them now, without the cost of measuring, re-sizing, new bolts and magging it's a crap shoot .... if it's a lazy build measuring and eyeballing might get you by.

They're not exactly rare, so cost is probably an issue, and that will be the decider I guess ......
At the large rebuilders, Jasper, et al, those rods get reconned every day by nipping a couple thou off the cap, torque, run by a powerstroke hone and good to go.

If we were doing it, we'd shotblast them, pound out the bolts, nip both cap and rod, torque with new nuts, hone them to the middle of the spec.
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Re: Are these con rods worth saving?

Post by Dan Timberlake » Wed Nov 27, 2019 12:45 pm

I think the rods should be checked for cracks early in the game. The wet fluorescent mag particle method is best. The bolt seats are hard to check properly with the bolts installed.

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Re: Are these con rods worth saving?

Post by BCjohnny » Wed Nov 27, 2019 1:14 pm

PackardV8 wrote:
Wed Nov 27, 2019 11:02 am
If we were doing it, we'd shotblast them, pound out the bolts, nip both cap and rod, torque with new nuts, hone them to the middle of the spec.
I do it pretty much the same way, although I'd remove the bolts before blasting (cast 230) and shoot a little towards the tighter end of spec, if they were going to see some action maybe even pull the parting line in a tad.

One of the things that always surprises people who haven't seen it before is, if you just spark out the wheel with the first cut, how much some rod/cap faces are out ..... not just cocked/splayed but, well, deformed .....
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Re: Are these con rods worth saving?

Post by Tuner » Thu Nov 28, 2019 4:07 am

After the fuel octane took a dive in the early '70s when you tore down '60s era high compression engines that you knew had been detonating it was not unusual to see bearing inserts fall out of rods like described in the OP. The inserts would usually be closed up some but sometimes the big end bores were spread wider across the parting line too.

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Re: Are these con rods worth saving?

Post by BCjohnny » Thu Nov 28, 2019 4:17 am

BCjohnny wrote:
Wed Nov 27, 2019 1:14 pm
...... they were going to see some action maybe even pull the parting line in a tad.
I've just read that back and can see how it might make inverse sense as posted ...... I should have qualified it with during honing of the big end ......
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Re: Are these con rods worth saving?

Post by Lizardracing » Sun Dec 01, 2019 3:36 pm

I'm not a professional but for the cost of aftermarket budget rods in the $250 range reusing stock stuff makes $0 sense to me.

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Re: Are these con rods worth saving?

Post by ptuomov » Sun Dec 01, 2019 5:22 pm

Lizardracing wrote:
Sun Dec 01, 2019 3:36 pm
I'm not a professional but for the cost of aftermarket budget rods in the $250 range reusing stock stuff makes $0 sense to me.
Do those $250 rods need to be reconditioned when new coming out of the box?

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Re: Are these con rods worth saving?

Post by modok » Sun Dec 01, 2019 6:07 pm

yeah, well, if youi want to talk what makes "economic sense" the whole thing doesn't.
The way you get 30$ con rods is usingt chinese steel and produce it in a country where labor is cheap. Now, if that's what you LIKe, that's fine. But, if you sent your old rods to a place where labor is cheap then of course you rebuild them even cheaper.
In fact send the whole car there while your at it, it would save so much money.

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Re: Are these con rods worth saving?

Post by Mark O'Neal » Sun Dec 01, 2019 7:11 pm

Why not? That's where most of it came from in the first place.

The same guys that gnash about Chinese part treat German parts like they're not a foreign nation.

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Re: Are these con rods worth saving?

Post by ptuomov » Sun Dec 01, 2019 7:48 pm

Mark O'Neal wrote:
Sun Dec 01, 2019 7:11 pm
Why not? That's where most of it came from in the first place.

The same guys that gnash about Chinese part treat German parts like they're not a foreign nation.
It’s not domestic vs foreign thing, it’s whether the parts come from a situation where an empty scotch bottle trades for 1/3 of the price of a full one and geese eggs sold on the market are fakes made out of plastic.

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Re: Are these con rods worth saving?

Post by Mark O'Neal » Mon Dec 02, 2019 2:35 pm

I've seen American rods break in a street car, and Chinese rods work fine at 2,000 HP......

There is so much redundancy in aftermarket parts that they are hard to break, absent an inept builder, inept tuner, or inept driver....no matter who makes them.

I've also sold 10s of thousands of Chinese rods, and I can count the ones that "just broke" on one hand. I built between 250 and 500 assemblies a year for 20+ year with the same experience.

Virtually everything breaks for a reason. Most from crappy tuneups.

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