I have some aluminum rod questions

SVRE has some 6.690 GRP rods for sale in the for sale section. I am wanting to use these rods in a weekend driver and drag car. The pistons call for a 6.7 rod with my 4.5 crank and I am using a D9 block. The pistons say that they sit .005 in the hole on a 10.3 block. The D9 block is a 10.33 tall block. I know the aluminum rods grow and I already plan on decking the block. Can you guys tell me how much the aluminum rods grow and if these 6.690 rods will work?

Rule of thumb is .010. For a performace build, you should be very careful buying used rods, and know that the next pass may be the last. Make sure you can get documentation of the runs.

"Thermal expansion"


IMO I'd just get a set of H beams from Adney and be done with it.

Aluminum rods have their place. IMO when you said weekend driver they are not for you. Not only do you need to keep track of your passes but if you are street driving with them that's going to be hard to do. Like Jon said about "Thermal Expansion", I for one like to refer to aluminum rod life as how many heat cycles they have went through. A decent steel H or I beam rod would be more beneficial IMO ................ although you have not detailed your build either.

Travis

I always find this discussion interesting as Chris Alston used a set of Aluminum rods in a BBC shop truck without issue for well over 100,000 miles.

bigblok2000ranger wrote:I always find this discussion interesting as Chris Alston used a set of Aluminum rods in a BBC shop truck without issue for well over 100,000 miles.

To each his own. Roll the dice, and when the one pass is the one pass to many then you'll know the exact breaking point. Might be the 100,001 mile or the 440th 1/8 mile pass depending on the tune, and the RPM. Not saying you could not get 100,000 miles, but why chance it unless you got a bottomless wallet ..............and a point to prove. When it does break, what point have you proven and how many usable parts do you have left ??

Travis

bigblok2000ranger wrote:I always find this discussion interesting as Chris Alston used a set of Aluminum rods in a BBC shop truck without issue for well over 100,000 miles.

I would wonder if his shop truck ever saw over 3,000 rpm

I have seen a broken billet steel rod break the second pass also.

Like what was said earlier, each part has their place. For MOST people steel rods would be the choice. Aluminum is good but from what I have seen on the bigger motors is that it cost enough more to balance the engine in mallory metal that steel rods could have been paid for.

I will throw this out there for what it is worth....
Aluminum rods do have a heat cycle life. I also believe they are easier on the crankshaft due to their inherent material and their light weight.
Steel rods are much better suited for street and street/race motors unless you plan on changing the rods VERY VERY frequently.
Aluminum Rods are a much better fit for a "race only" motor and are cost prohibitive for a street driven vehicle.

My opinion is based on my experience with both rod types in a twin turbo SBF running over 200 mph.
Kaase could give a better explaination and the recommended rod change intervals for the specific cubic inch BBF.
I will say that a good friend has an over 900 cubic inch motor (not a BBF though) and has an aluminum rod change interval of 40 passes (1/4 mile).

Just my opinion though.

whatbumper wrote:I have seen a broken billet steel rod break the second pass also.

Like what was said earlier, each part has their place. For MOST people steel rods would be the choice. Aluminum is good but from what I have seen on the bigger motors is that it cost enough more to balance the engine in mallory metal that steel rods could have been paid for.

My experience has been just the opposite. Out of about 6 balance jobs I've had done with 6.7 rods and cast and forged cranks, I've never had to use mallory in any crank for an aluminum rod motor

The OP bought my old pistons, with a set of h beams and a Scat forged crank we had to grind a good bit on the counterweights to get the crank down to weight. Not sure what the crank he has weighs, I'm pretty sure the caliber of motor he is building a good H beam will more than suffice............I think its just a deal where the cost of the used alum rods is attractive, and honestly for the same money he could buy a set of new H beams with a bolt upgrade.

The Scat crank [4.5] with typical steel rods will not need wt. added.
The FMS units that Bryant sells have less counter wt. and will require heavy metal with a steel rod......not one answer.

Thanks for the knowledge guys, I will just buy some 4340 h-beams. I have heard aluminum rods would work on the street is why I ask, and I knew you guys would know the right answer.

I have an eagle 4.5 steel crank and if I remember right it is 87 pounds. Not trying to go real fast with it, trying for a low 10 or high 9 in 1/4.

The pistons are richter69 old pistons. I have a set of 6 eagle 6.7 long 4340 h-beams, and been trying to get two more rods and can't get them the same weight. Eagle can get me 20 g lighter.

how close should they be within each other? mine are 6.605 h beams...just curious

double post...

Check with Blake, he might have just what you need.

Just want to say I was not saying they were the right choice I want to hear both sides of the arguement to learn as much as possible as do others, I am sure.

bigblok2000ranger wrote:Just want to say I was not saying they were the right choice I want to hear both sides of the arguement to learn as much as possible as do others, I am sure.

Not taken that way on my behalf. Hate to see someone waste thier money for a cheap way out only to cost them more than double down the road. I've had both and would tend to lean torward a GOOD set of aftermarket steel rods (olivers or equivelent ) Just for the peace of mind. In Tigers case he said --Weekend Street Use-- Sound like the wrong application to me.

JMO
Travis

My machinist told me 20g was to much.

If anybody has 2 rods 6.7 long laying around with 234g on small end and 590g on big end with a total of 824g I would buy them


342g what is Blake username on here?

tiger wrote:My machinist told me 20g was to much.

If anybody has 2 rods laying around with 234g on small end and 590g on big end with a total of 824g I would buy them


342g what is Blake username on here?

IDT-572

First off I want to thank all you guys for the info. Eagle dug in their piles for a week and came up with 2 rods for me, that will make me a set of 8 eagle h-beam rods with L-19 bolts. So I will stay with the 4340 h-beam rods. Hopefully in the next 2 months it will be on the dyno.

I've sold probably 6 sets of Groden aluminum rods. Out of that many sets I had one rod in two of the sets self destruct this past summer and ruin two short blocks, our Street Stock motor and a customers BBC. I've sold a few... not many sets of Oliver rods. Out of those sets, I had one rod self destruct and ruin a short block which was about 4 years ago. There were NO oiling issues in any of these motors. I've come to the decision that the Grodens are junk IMO. and the Oliver deal was a fluke. Main point is... there are NO guarantees in racing stuff.

Bret

Bret Powell wrote:I've sold probably 6 sets of Groden aluminum rods. Out of that many sets I had one rod in two of the sets self destruct this past summer and ruin two short blocks, our Street Stock motor and a customers BBC. I've sold a few... not many sets of Oliver rods. Out of those sets, I had one rod self destruct and ruin a short block which was about 4 years ago. There were NO oiling issues in any of these motors. I've come to the decision that the Grodens are junk IMO. and the Oliver deal was a fluke. Main point is... there are NO guarantees in racing stuff.

Bret

Aluminum rods, (any brand), should not be used in any engine which has "engine braking" or a lot of "deceleration" within it's intended usage. The tensile strength of the aluminum rod as opposed to it's other properties is the weak link.

As Bret said, and SOoooo many people just can't grasp is ... "there are NO guarentees in racing stuff".

If you keep track of anything and follow the correct procedures when using a ALUMINUM ROD, it's a better choice IMHO. Light weight, if and when it breaks it will snap like a toothpick VS a steel rod will be a violent break. Alum rods have been proven to last over 100k street miles. Watch and know your Temps at all times. Let the car always warm before revving the motor. Just know your steps and ALUM is pretty cool to use. I have a set of BME alum rods in my street car. No problems here

Being short of a professional category, these may be things to consider.

If your competing in NHRA Competition Eliminator, you may need an aluminum rod engine.
If your using power adders that offer huge increases of power, you may need an aluminum rod engine.
If you like engine rod maintenance 4 to 5 times a season, you may need an aluminum rod engine.

If you like racing all summer without excessive short block maintenance, then an aluminum rod engine is NOT for you!

JMO concerning aluminum rod engines.
Dave.