Contructive Info On Aluminum Rods?

[BoredDSM]

I would like to make a thread of all the gathered information possible on all aluminum rod users and abusers. This is still a strange mystery to the DSM world and I would like for anyone who has any info to post and let it be discussed on the rods. I will tell what I know and see if any disagree or agree. Please use constructive responses and NO FLAMING!

From what I know aluminum rods are said to be lighter but weaker than steel rods. Mostly used in those high revving anorexic rotating assemblies. The main issue with aluminum rods is that they will stretch. Possibly a misconception or a fact? What makes sense to me is that aluminum does expand because they are a material with lower melting temperatures compared to steel. This expansion with heat applies an extra amount of force on the rod bolts. After a while the bolts stretch and cause a cap failure. That is the theory I believe in and I would like to hear yours.

As most have noticed the guys running 8s and faster are most likely using aluminum rods. But none have really seen them being daily driven a whole lot like they would a steel rod. Most of those guys freshen up there motor every season if not more and will most likely check the rods every oil change. Thus that is why they do not really run into issues with them. After reading countless threads I have yet to see one person blow there motor due to rod failure.

I would like to gather weight measurements on a all the aluminum rods out there to compare who are the light weights and heavy weights. If any vendor would please jump in and provide what they can it would be greatly appreciated.

MGP:
Groden:
R&R:
GRP:

If I have forgotten any please post them. Also remember these are only for 4g63 connecting rods. Without bearings. Only the Rod with cap and bolts.

 

[1992awdlaser]

You are wrong about most of this. Aluminum rods USED to stretch back in the day when they didn't have today's technology.

Aluminum rods are just as strong as the best steel rods. They accomplish this with a weaker material by using more material. This is why the main cap that the oil pump pickup bolts to needs to be grinded for clearance.

The rod bolts do stretch and need to be checked about every oil change. Replace as needed. That is the only difference with aluminum verse steel when it comes to driving the car and maintenance.

Aluminum rods will save your connecting rod bearings from abuse compared to steel. This is because the aluminum absorbs a good amount of the abuse instead of translating all of it into the rod bearing.

It is even more important to make sure the engine is at operating temperature with aluminum rods than it is with steel rods before driving the car. Obviously this is because of expansion. And this should be done with steel rods anyway so it isn't something to consider when choosing between steel or aluminum rods.

Basically, the only reason not to get aluminum rods is because you have to check the rod bolts every few thousand miles. Everything else says go for aluminum rods.

There are people on the dsmlink forums with aluminum rods with over 10,000 street miles on them with no problems.

 

[talon20g]

FFWD Connection - Race Injuns That Will Freeze Your Brain

Good info. The 1st response about sums everything up. Above is a link with a little more info, check it out.

 

[Slippi84]

I talked with darren he said that the checking the rods is overrated and doesn't even reccomend it really like you said there are plent of people on the link forums that use alumnium rods. I am running them in my new build and don't plan on checking them except once after the first 3k mainly for regular break in check though.

 

[BoredDSM]

Yes, thanks for the info 1992awdlaser. Here are some pics that Dan from Fast Track Auto gave me to show some of the grinding you have to do on the block so that you have clearance.

http://i65.photobucket.com/albums/h209/91TSiGuy/dsm parts for sale/100_2574.jpg
These are the bearings as you can see and the oiling oils are larger after modified to work with the aluminum rods. They are larger because the holes do not line up so they drill them out more?

http://i65.photobucket.com/albums/h209/91TSiGuy/Talon/100_2576.jpg
If you look closely at the bottom of the cylinders you can see it was ground down for clearance of the rod.

http://i65.photobucket.com/albums/h209/91TSiGuy/Talon/100_2581.jpg
In this one you can see the main caps had to be ground down to give more clearance for the larger rod caps.

It was also brought to my attention that the aluminum rods stated above all need 22mm wrist pin pistons which means you would have to use 2g pistons if you wanted to run them on your 1g. Is this true? I know it is true for the MGP's but not the other ones.

 

[1992awdlaser]

In this picture you can see on the rod cap why the holes in the bearings are bigger. It's like that to keep the bearing from spinning.

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I'm not sure about the wrist pins.

 

[Slippi84]

In this picture you can see on the rod cap why the holes in the bearings are bigger. It's like that to keep the bearing from spinning.

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I'm not sure about the wrist pins.

NOt to mention that there's a pin in them to keep them from spinning

 

[DoyoFCT]

Im very interested in reading more about aluminum rods. I have heard that most of the aluminum rod hearsay out there is based off of experiences in V8 motors which supposedly are harsher on the rods than an inline 4 cylinder.

 

[1992awdlaser]

Im very interested in reading more about aluminum rods. I have heard that most of the aluminum rod hearsay out there is based off of experiences in V8 motors which supposedly are harsher on the rods than an inline 4 cylinder.

Post number 2 "Aluminum rods USED to stretch back in the day when they didn't have today's technology."

 

[DoyoFCT]

Right, I would definitely agree with that. I would also think that the experiences that V8's have had with them may skew the opinion of people when it comes to 4 cylinder applications. Like I said generally before I'm sure v8's would require much more attention to bolt stretch and other wear effects when compared to a 4cyl.

 

[1992awdlaser]

Like I said generally before I'm sure v8's would require much more attention to bolt stretch and other wear effects when compared to a 4cyl.

Not at all. It's the expansion of he rods that cause the bolts to stretch. It has nothing to do with number of cylinders. It would only be different if the V8 rods expand more than the 4 cylinder rods.

 

[DoyoFCT]

I c, I did not mean just by the number of cylinders I assumed since the rods operate at different/more agressive angles/rod ratios in most popular V8's this would cause issues. But ya im only making assumptions, thanks for the info.

 

[BoredDSM]

After more research this is what I came up with. All aluminum rods for the 4g63 utilize a 22mm wrist pin unless stated. Some go as far and make custom pistons to utilize a 23mm wrist pin and machine the rods to accept them. There is a member on another forums that I met who is currently running the groden rods and states that he has no trouble with them. He has put a few thousand miles on the car already on the streets and has checked for rod bolt stretch every oil change during break in and every thousand miles after. No stretch in rod bolts yet but he will keep us updated as he continues using them.

 

[Blindsey]

After more research this is what I came up with. All aluminum rods for the 4g63 utilize a 22mm wrist pin unless stated. Some go as far and make custom pistons to utilize a 23mm wrist pin and machine the rods to accept them. There is a member on another forums that I met who is currently running the groden rods and states that he has no trouble with them. He has put a few thousand miles on the car already on the streets and has checked for rod bolt stretch every oil change during break in and every thousand miles after. No stretch in rod bolts yet but he will keep us updated as he continues using them.

I just purchased MGP rods for my stroker. I will let everyone know how they turn out.

 

[dsm-onster]

Question. More meat is used to keep stretching down. Now, are aluminum rods as heavy as steel rods? Since more meat is used.

I'm asking because aluminum rods f they are lighter would be a great addition to a stroker build. The stroker would have lighter pistons becasue of the higher wristpin height. Add a lighter rod and you're looking at probably the same tensil force on the rod bolts that would be seen in an 88mm stroke.

 

[Slippi84]

Question. More meat is used to keep stretching down. Now, are aluminum rods as heavy as steel rods? Since more meat is used.

I'm asking because aluminum rods f they are lighter would be a great addition to a stroker build. The stroker would have lighter pistons becasue of the higher wristpin height. Add a lighter rod and you're looking at probably the same tensil force on the rod bolts that would be seen in an 88mm stroke.

Yup they're lighter.

 

[1992awdlaser]

Question. More meat is used to keep stretching down. Now, are aluminum rods as heavy as steel rods? Since more meat is used.

I'm asking because aluminum rods f they are lighter would be a great addition to a stroker build. The stroker would have lighter pistons becasue of the higher wristpin height. Add a lighter rod and you're looking at probably the same tensil force on the rod bolts that would be seen in an 88mm stroke.

The aluminum rods are still lighter than steel rods.

Groden rods weigh about 122 grams less than crowers.

I'm trying to decide between a destroked 2.4L(2.1L) or a 2.0L for the future. Either way I will be using Groden aluminum rods and Mahle pistons. The piston will be $200 a piece if I do the destroked 2.4L since they will be custom pieces. Not sure about the rod price yet for the 2.4L though since they will need to be 162mm.

 

[Freerevving]

how about titanium connecting rods?

Crower Cams & Equipment - Mitsubishi - Connecting Rods (read fine print, $477/rod for titanium)

Introducing Pauter Titanium Rods

I agree that with today's available grades of aluminum and forging techniques, that aluminum can be used effectively for connecting rods.

... Either way I will be using Groden aluminum rods and Mahle pistons.

Good choice on the Mahles, LMK if you get confused on clearance (like everyone, including myself did). It's pretty simple but they don't clearly provide the information. In fact, they provide some misinformation... So did one of the Mahle techs.

but I cut through all of the confusion and I have the bare truth on the clearance, confirmed by everyone I've cross-referenced and the techs at Mahle.

 

[90laserRSfwd]

Gordens are very light rods, and plenty strong for a daily driver. I think the warm up time would kill people more then the stretching rod bolts. Most of the "myth's" floating around about aluminum rods comes from back in the 70's and 80's when forging processes were not as "matured" as they are today. I would be more worried about over revving the engine and spinning a bearing before I'd worry about stretching a rod bolt. But to each his own...

 

[dsm-onster]

The aluminum rods are still lighter than steel rods.

Groden rods weigh about 122 grams less than crowers.

I'm trying to decide between a destroked 2.4L(2.1L) or a 2.0L for the future. Either way I will be using Groden aluminum rods and Mahle pistons. The piston will be $200 a piece if I do the destroked 2.4L since they will be custom pieces. Not sure about the rod price yet for the 2.4L though since they will need to be 162mm.

Holy he!! The tensile force on a 2.0l motor is the same at 8K as a 2.4 at 7.3K; same weight pistons (same wristpin height) and same rods. A stroker can get away with 400rpms more than a 2.4 motor because of only 45grams less weight at the piston because of the taller wristpin height. . . 122grams less weight vs. decent steel rods? Wow! You can rev higher with a stroker than a built 2.0L.

 

[BoredDSM]

Holy he!! The tensile force on a 2.0l motor is the same at 8K as a 2.4 at 7.3K; same weight pistons (same wristpin height) and same rods. A stroker can get away with 400rpms more than a 2.4 motor because of only 45grams less weight at the piston because of the taller wristpin height. . . 122grams less weight vs. decent steel rods? Wow! You can rev higher with a stroker than a built 2.0L.

You lost me . Please explain all the math and science behind it?

I just got an email back from a rod company and they gave me some info on some titanium rods. Costing around 1180 per rod they are stronger than steel rods and generally 65% lighter. So in general aluminum rods are the best bang for the buck.

 

[dsm-onster]

No need to go over the math if the above lost you . Just know that weight and accelertation is what kills rod bolts. You can have more piston acceletation, or higher rpm, with lighter rods. Force = Mass X Acceleration (Newton's second law). Less acceleration saves rod bolts, low rpm; less mass saves rod bolts, less weight.

 

[Blindsey]

No need to go over the math if the above lost you . Just know that weight and accelertation is what kills rod bolts. You can have more piston acceletation, or higher rpm, with lighter rods. Force = Mass X Acceleration (Newton's second law). Less acceleration saves rod bolts, low rpm; less mass saves rod bolts, less weight.

Exactly the reason i decided to go with aluminum rods on my stroker. I really wanted an all around good motor.

 

[Freerevving]

No need to go over the math if the above lost you . Just know that weight and accelertation is what kills rod bolts. You can have more piston acceletation, or higher rpm, with lighter rods. Force = Mass X Acceleration (Newton's second law). Less acceleration saves rod bolts, low rpm; less mass saves rod bolts, less weight.

well said.

A lot of people forget about rod ratio... another ingredient in damaging your engine at high rpm. The force from the power stroke cares very little about the weight underneath the piston and the angle of the rod can scuff cylinder walls, bend rods and break rod caps/bolts. Of course, major weight reduction reduces those risks.

 

[dsm-onster]

Right. I'm not negating the benefit of a longer rod. But just that if you really want more stroke, make the most of it .