Aluminum rods pro's and con's

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Aluminum rods pro's and con's

Post  57ford custom on October 15th 2017, 9:40 pm

I am going to update my engine this winter and need to know the pro's and con's of aluminum rods in a 98% drag and 2% street use engine. I have a 466 early block engine which now has iron cobra jet heads and it is coming out this winter. I am going to do a stroker either 4.3 or 4.5 stroke haven't decided on that yet. I have Kasse P51 heads and a roller cam that will replace the flat tappet came that is already in it. This engine made 596hp in its present condition. It has a well modified Weiand tunnel ram with 2 elelbrock 750 carbs and it runs good for a 3600 pound 63 fairlane. So back to the rods, need the good and bad info. Also should I worry about the shorter block cylinders versus the later blocks. This block has been converted to 4 bolt mains on the center 3 mains. I have done a 545 a few years ago but can't remember what block I used on that one but think it was out of a 76 merc but not sure. Its still running good with the 4.5 crank I put in it then. With flat top pistons I think it will still be around 12 to 1 compression. I run it now with 110 octane. Very Happy
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Re: Aluminum rods pro's and con's

Post  rmcomprandy on October 16th 2017, 12:24 am

57ford custom wrote:I am going to update my engine this winter and need to know the pro's and con's of aluminum rods in a 98% drag and 2% street use engine. I have a 466 early block engine which now has iron cobra jet heads and it is coming out this winter. I am going to do a stroker either 4.3 or 4.5 stroke haven't decided on that yet. I have Kasse P51 heads and a roller cam that will replace the flat tappet came that is already in it. This engine made 596hp in its present condition. It has a well modified Weiand tunnel ram with 2 elelbrock 750 carbs and it runs good for a 3600 pound 63 fairlane. So back to the rods, need the good and bad info. Also should I worry about the shorter block cylinders versus the later blocks. This block has been converted to 4 bolt mains on the center 3 mains. I have done a 545 a few years ago but can't remember what block I used on that one but think it was out of a 76 merc but not sure. Its still running good with the 4.5 crank I put in it then. With flat top pistons I think it will still be around 12 to 1 compression. I run it now with 110 octane. Very Happy

Other than a limited life expectancy the biggest con for aluminum rods in a stroker engine is just plain physical SIZE.

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Re: Aluminum rods pro's and con's

Post  Mark O'Neal on October 16th 2017, 2:12 am

and the biggest pro is............




gimme a minute, I'm thinkin'........

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Re: Aluminum rods pro's and con's

Post  cool40 on October 16th 2017, 1:42 pm

Mark O'Neal wrote:and the biggest pro is............




gimme a minute, I'm thinkin'........
they're not as hard on the block when they exit? Razz
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Re: Aluminum rods pro's and con's

Post  Lem Evans on October 16th 2017, 7:14 pm

cool40 wrote:
Mark O'Neal wrote:and the biggest pro is............




gimme a minute, I'm thinkin'........
they're not as hard on the block when they exit? Razz

You'd think that until you saw the block that hunk of a aluminum rod got between the #1 rod throw and the pan rail. Shoved the side off the block....oil filter mount pad and all.

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Re: Aluminum rods pro's and con's

Post  cletus66 on October 17th 2017, 2:08 am

Lem Evans wrote:
cool40 wrote:
Mark O'Neal wrote:and the biggest pro is............




gimme a minute, I'm thinkin'........
they're not as hard on the block when they exit? Razz

You'd think that until you saw the block that hunk of a aluminum rod got between the #1 rod throw and the pan rail. Shoved the side off the block....oil filter mount pad and all.

Well, I appreciate the fact that you didn't send me any of those aluminum devils... Laughing
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Re: Aluminum rods pro's and con's

Post  Mark O'Neal on October 17th 2017, 3:54 am

cletus66 wrote:
Lem Evans wrote:
cool40 wrote:
Mark O'Neal wrote:and the biggest pro is............

gimme a minute, I'm thinkin'........
they're not as hard on the block when they exit? Razz

You'd think that until you saw the block that hunk of a aluminum rod got between the #1 rod throw and the pan rail. Shoved the side off the block....oil filter mount pad and all.

Well, I appreciate the fact that you didn't send me any of those aluminum devils... Laughing

I used to make them,and I don't miss them.....either.

I am working on having the Probe line manufactured for me.

Thought about you the other day, It's been a while.

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Re: Aluminum rods pro's and con's

Post  57ford custom on October 17th 2017, 2:07 pm

enough of the frivolity guys and I do have a sense of humor:D  but am really looking for good sharp info. This most likely be the last expensive engine I build and I want it to last like the 545 that I built a few years ago. For all you OLD guys I am 77 years old and still racing and to me a .050 or so is a good light. I will quit racing when I can't get over the roll bar anymore. Shocked So please let me hear the good and bad info. And at the possible 750 na hp it shoud make and maybe at the end of the day I might like to run a 9 as my car is only good for a 10 flat now and a 9 is only a 100 shot away. Laughing Lem I have bought parts from you so you know I am not a troll or poser or whatever one calls them. I also take this car to a show once in a while and I have a little sign on the windshield that says."this car may not be as pretty as yours but it is way way faster" and in that vein I may send the intake out to (Induction Solutions) and have them put a fogger on it for shock and aww to go with the 2 cheater plates on it now that hasn't been needed so far. There is an 1/8 mile track in our area that has a couple of street races that I think they relax the rules a bit and it looked fun when I went to the second one as a spectator this year. Very Happy
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Re: Aluminum rods pro's and con's

Post  Lem Evans on October 17th 2017, 2:32 pm

If it were my money I'd use a steel rod. You'll get more passes out of them.

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Re: Aluminum rods pro's and con's

Post  wayney on October 17th 2017, 7:53 pm

Not as experienced as Lem or Randy but for your application steel would be my choice . If you were talking 350+ of nitrous on top of 750 motor i would say aluminum .

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Re: Aluminum rods pro's and con's

Post  cool40 on October 17th 2017, 7:56 pm

I'm making something north of 1000 NA hp with a steel rod shifting @7800. I wouldn't consider aluminum for anything NA unless maybe something over 10,000 rpm but probably not then. JMO... Smile
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Re: Aluminum rods pro's and con's

Post  maverick on October 17th 2017, 8:25 pm

57, I think all the guys WERE giving you good info...just had a bit of humor sprinkled in. A little sifting will separate the jokes from the pearls. It all sounded like "Use steel rods." to me. Wink
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Re: Aluminum rods pro's and con's

Post  BOSS 429 on October 17th 2017, 10:17 pm

57ford custom wrote:I am going to update my engine this winter and need to know the pro's and con's of aluminum rods in a 98% drag and 2% street use engine. I have a 466 early block engine which now has iron cobra jet heads and it is coming out this winter. I am going to do a stroker either 4.3 or 4.5 stroke haven't decided on that yet. I have Kasse P51 heads and a roller cam that will replace the flat tappet came that is already in it. This engine made 596hp in its present condition. It has a well modified Weiand tunnel ram with 2 elelbrock 750 carbs and it runs good for a 3600 pound 63 fairlane. So back to the rods, need the good and bad info. Also should I worry about the shorter block cylinders versus the later blocks. This block has been converted to 4 bolt mains on the center 3 mains. I have done a 545 a few years ago but can't remember what block I used on that one but think it was out of a 76 merc but not sure. Its still running good with the 4.5 crank I put in it then. With flat top pistons I think it will still be around 12 to 1 compression. I run it now with 110 octane. Very Happy


on an eng that runs higher rpm 8000 and up we change the alum rods 120 passes avg

steel rods last longer,but have dated life also in higher hp builds.

2 engs built the same except for 1 with alum rods The later WILL BE quicker because of the acceleration rate will be faster .
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Re: Aluminum rods pro's and con's

Post  Mark O'Neal on October 18th 2017, 3:47 am

The toughest requirement you have with aluminum rods is the requirement to change them out one run before they break. Oil temperature is critical, which makes them iffy for any street use in an engine that makes higher oil temps, whereas they're fine in boat where making heat is a bigger issue than losing it.

The 73,000 lb Tensile Yield Strength (7075-t6) at ambient temperature drops to 27,000 at 300* (7076-T6 is actually better, in that it has more elasticity) but the only ones I ever knew to use it was Superod, but they vanished soon after we divested ourselves of it.

Here's some hard data.....enjoy!... Very Happy Very Happy

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091014.pdf

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Re: Aluminum rods pro's and con's

Post  57ford custom on October 19th 2017, 11:29 am

Thank you guys for the help with this decision as I am staying with the steel rod for this build. This build is an early block that I converted to 4 bolt mains so it is the shorter cylinder length. So next question the 4.3 or the 4.5 crank and a 6.7 or 6.8 rod with the proper piston to address the piston sticking out the bottom of the bore. I hadn't heard of this glitch or is it not to be worried about? My 545 that my brother is using that I built quite a few years ago is still running fine and hasn't had any problems other than a rod bearing for some reason or other that I fixed by having the one journal ground and slapped it back together and that was several years ago. My good friend Kurt who builds FE's and others too turned me on to the little addition of adding an oil line front to the back and I did that after the rod bearing failure. Most say that it is unecessary but it is cheap and easy to do. Yesterday when I was at a dyno session with Kurt he brought along an article that was about  Jon Kasse's boss nine build that made 834 hp. Guess what he was using the oil line to the rear on that one. Now we know he thinks "out of the box" as they say but its hard to second guess a guy that built that MEL that won the antique engine class this year at engine masters. I would add that the MEL was in my opinion a POS for making power as I put one (stock 383 312 hp rated) in a 57 tudor htp in 62 or 63 and it was a dog it signed off at around 4500 rpm but it did have more torque than the 292 it replaced but the acceleration just wasn't there.  Very Happy
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