Are these con rods worth saving?

General engine tech -- Drag Racing to Circle Track

Moderator: Team

travis
Guru
Guru
Posts: 1611
Joined: Sun Mar 15, 2009 5:31 am
Location:

Are these con rods worth saving?

Post by travis »

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?
User avatar
modok
Guru
Guru
Posts: 3321
Joined: Sun Jun 06, 2010 1:50 am
Location:

Re: Are these con rods worth saving?

Post by modok »

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.
BCjohnny
Guru
Guru
Posts: 1772
Joined: Sun Feb 26, 2006 6:07 pm
Location: Black Country, England

Re: Are these con rods worth saving?

Post by BCjohnny »

travis wrote: Tue Nov 26, 2019 7:06 pmIt 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 ......
PackardV8
Guru
Guru
Posts: 7619
Joined: Sun Jul 30, 2006 2:03 pm
Location: Spokane, WA

Re: Are these con rods worth saving?

Post by PackardV8 »

BCjohnny wrote: Wed Nov 27, 2019 5:29 am
travis wrote: Tue Nov 26, 2019 7:06 pmIt 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.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Dan Timberlake
Guru
Guru
Posts: 1739
Joined: Tue Jan 15, 2013 8:10 pm
Location:

Re: Are these con rods worth saving?

Post by Dan Timberlake »

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.
BCjohnny
Guru
Guru
Posts: 1772
Joined: Sun Feb 26, 2006 6:07 pm
Location: Black Country, England

Re: Are these con rods worth saving?

Post by BCjohnny »

PackardV8 wrote: Wed Nov 27, 2019 11:02 amIf 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 .....
Tuner
Guru
Guru
Posts: 3184
Joined: Sun Apr 01, 2007 5:26 am
Location:

Re: Are these con rods worth saving?

Post by Tuner »

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.
BCjohnny
Guru
Guru
Posts: 1772
Joined: Sun Feb 26, 2006 6:07 pm
Location: Black Country, England

Re: Are these con rods worth saving?

Post by BCjohnny »

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 ......
Lizardracing
Pro
Pro
Posts: 394
Joined: Fri Sep 10, 2010 2:38 am
Location:

Re: Are these con rods worth saving?

Post by Lizardracing »

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.
User avatar
ptuomov
Guru
Guru
Posts: 3587
Joined: Fri Aug 07, 2009 3:52 am
Location:

Re: Are these con rods worth saving?

Post by ptuomov »

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?
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
User avatar
modok
Guru
Guru
Posts: 3321
Joined: Sun Jun 06, 2010 1:50 am
Location:

Re: Are these con rods worth saving?

Post by modok »

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.
Mark O'Neal
Guru
Guru
Posts: 1649
Joined: Tue Mar 06, 2007 7:23 pm
Location: San Tan Valley, AZ
Contact:

Re: Are these con rods worth saving?

Post by Mark O'Neal »

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.
User avatar
ptuomov
Guru
Guru
Posts: 3587
Joined: Fri Aug 07, 2009 3:52 am
Location:

Re: Are these con rods worth saving?

Post by ptuomov »

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.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Mark O'Neal
Guru
Guru
Posts: 1649
Joined: Tue Mar 06, 2007 7:23 pm
Location: San Tan Valley, AZ
Contact:

Re: Are these con rods worth saving?

Post by Mark O'Neal »

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.
travis
Guru
Guru
Posts: 1611
Joined: Sun Mar 15, 2009 5:31 am
Location:

Re: Are these con rods worth saving?

Post by travis »

It ended up being a $75 difference between properly rebuilding these vs a set of Scat rods set up for floating pins. The price difference included checking sizing on both ends. Plus it saved a few $$$ being able to assemble the rods/pistons myself
Post Reply