Aluminium vs Steel rods

[swampbuggy]

Chris S., i was told that A1 had got away from offering Hi End automotive fasteners ?? Thanks, Mark H. Central Fla.

[naukkis79]

Jager is shipping rods. They were outlawed in 2004 from NHRA Prostock. Available are 6.535, 6.700, 6.800, 7.100 and LS/SBC 6.125. A set of 6.700 we just sent out for a Drag Week build.

Is this rod meant to be used without bearing shells? One advantage of AL-rods is that they can be used without bearing shells.

[grant6395]

[naukkis79]

Shell bearings in connecting rods are always non-optimal solution, though it's much easier to assemble bearing clearances with replaceable shells. But for real high-performance engine you want to get rid of shells. Al-rods have been used for ages without shells - you can run round bearing(much tighter clearances), get rid of shell clamping force from rod bolts etc, to result lighter con-rod and less running friction. Nowadays they are sometimes plasma-coating bearings to steel rods also, benefits are there.

So second look I found that those Jager rods still has shell support tap so they aren't meant to used without shells though.

[Dave Koehler]

popcorn time

[Roundybout]

Won't a steel rod basically last forever where an AL rod will fatigue and fail? Add the heating of that rod and its accelerated also? An airplane doesn't have the heating like a rod does and there are graveyards full of planes. They're retired way before predicted failure.

Big inch engines almost have to use AL rods with the huge loads imparted. The side loads on the pistons with 1200g steel rods are big I'd imagine. Even those tiny R/C engines need AL rods at 28,000rpm. They have to their use in certain applications like everything.

[Little Mouse]

There is no such thing as lasts forever everything has a fatigue life steel or aluminum. Planes have millions of miles put on them if anything they are replaced for newer more efficent fuel cost engines. Think about the heat a piston takes and what it takes when it changes direction at the top of the exhaust stroke then it has iron rings in small goves that are jerking on it and of course down force on it. Yet today in modern engines not uncommon for them to run 350 thousand to over 400. And do it in a vette engine that can turn 7 grand anytime you want it to. All the heat a piston takes but yet 200 degrees oil temo will destroy an aluminum rod. Not happening.

[Little Mouse]

Mr struab i want a set of the 6.125 gen 1 rods are they at least close in price to bme or grp rods i have been looking at.

[randy331]

Planes have millions of miles put on them if anything they are replaced for newer more efficent fuel cost engines.

Aloha flight 243 may have needed pulled out of service sooner for reasons other than fuel efficiency.
https://www.youtube.com/watch?v=M8G0dviUr5U

Aluminum isn't used in aircraft because of it's fatigue properties. It's weight.
Aircraft go through constant inspections looking for the inevitable cracks will show up.

Randy

[MadBill]

... Al-rods have been used for ages without shells - you can run round bearing(much tighter clearances)...

Your would still need some eccentricity to compensate for the 'ovalizing' tensile forces at TDC.

[Little Mouse]

Planes also go through cycling of being pressurized then un pressurized and they fly millions of miles and a lot of years of service commercaily. Of course they are looked over peoples lives are at risk. Steel wheels on 18 wheelers are real bad about cracking aluminum do not. An aluminum frame on a truck has a 2 half times rvm rating compaired to steel and all the cross members even on steel rail trucks are made out of aluminum. I was in the trucking business for 29 years. Explain to me how all the heat a piston has put into it and all the streeses put on them and they will do it for 100s of thousands of miles and in a lot of cases just a cheap casting.

[Warp Speed]

Planes also go through cycling of being pressurized then un pressurized and they fly millions of miles and a lot of years of service commercaily. Of course they are looked over peoples lives are at risk. Steel wheels on 18 wheelers are real bad about cracking aluminum do not. An aluminum frame on a truck has a 2 half times rvm rating compaired to steel and all the cross members even on steel rail trucks are made out of aluminum. I was in the trucking business for 29 years. Explain to me how all the heat a piston has put into it and all the streeses put on them and they will do it for 100s of thousands of miles and in a lot of cases just a cheap casting.

And all of this has what to do with connecting rods?

[woody b]

Planes also go through cycling of being pressurized then un pressurized and they fly millions of miles and a lot of years of service commercaily. Of course they are looked over peoples lives are at risk. Steel wheels on 18 wheelers are real bad about cracking aluminum do not. An aluminum frame on a truck has a 2 half times rvm rating compaired to steel and all the cross members even on steel rail trucks are made out of aluminum. I was in the trucking business for 29 years. Explain to me how all the heat a piston has put into it and all the streeses put on them and they will do it for 100s of thousands of miles and in a lot of cases just a cheap casting.

And all of this has what to do with connecting rods?

Sometimes they use airplanes, or 18 wheelers to ship connecting rods?

Since this thread is pages and pages long I might as well chime in with my aluminum rod experience.
Decades ago before aftermarket rods and cranks were available (or at least affordable) I ran a few stock steel 350 cranks that have been offset ground. 3 9/16" stroke, 2" rod journal. I could run stock small journal rods with aftermarket bolts for 100 runs and the big ends would start to "pinch" the bearing. After 100 runs I could change the bolts, re size them, and run them another 100 rods. (perhaps others got alot more life with this set up though). By 125 runs, without maintenance the engine would pitch out a rod, doing a bunch of damage. So...I started running "SuperRod" aluminum rods. My car ran exactly the same ET with the SuperRods as the stock steel ones. I could run them 300 runs, then throw the rods away. At 350 runs on one engine I broke/pitched a rod. I had to replace one piston, and a couple valves. Besides that, no damage. Super rod aluminum rods was my solution both with 2" journal 3 9/16" stroke engines and "normal" 2.1" journal 3.48" stroke stuff until decent aftermarket parts became available at decent prices. My stuff wasn't fast by todays standards, but I was running 5's in the eighth with a single carb small block in the 80's. Most of the full bodied cars back then running similar ET's were running 468's and 482's with tunnel rams. A couple local tracks paid $25 for low ET. There was a guy with a really big ego and a 482 that was about a tenth faster than I was. I had nitrous. I had a timer. I could use 1 second of timed Nitrous and be .05 or so faster than he was for one run to get "low et and the $25. He put Nitrous on his 482 and blew head gaskets pretty much every time he used it. Good times.

[Morgo]

Perfectly well aeroplanes but the hours are done..
https://www.airplaneboneyards.com/mojav ... neyard.htm
You can take almost any of them and fly but....

[Caprimaniac]

So he is making a 6.125 for just the ls.

LS 6.125
SBC 6.00 and 6.125
SBF 5.400

A1 Bolts

Chris; the 5.4 SBF rods; can they be had with differen be sizes? I am after something like 2.00’ or Honda size.

RS