I'm wanting to use the motor out of my 60's drag boat in the gl*** 28 chev 3 window build. Its a blower motor and was all good stuff at the time it was built, includeing the C&A aluminum rods. It has very low time on it. The rumors I keep hearing are that you cant use aluminum rods with a manual trans because although they are very strong in compression,they are weak in tension and will stretch quickly from the rapid deacceleration between shifts. Does anyone have any real-time experience that will back this up? edit) its a .060 over 427 chev,4 bolt,steel crank ,proper blower pistons (do not remember brand,it was a while ago), o-ringed heads,stud girdle,moroso lube system.Mooneyham 671,mag nose,teflon rotors and end seals,cog 2" drive.It currently has a schiefer forged alum fw,which I would like to use.
That's theory/claim is total BS. Unless we are talking about top fuel or something super radical, highest stress on a rod is at TDC, at "overlap", when the exhaust stroke finishes and the intake stroke begins. The level of that force/stress is totally a function of RPM, and is the same regardless of how much the engine is loaded, or what the engine is driving. People do get away with running GOOD aluminum rods on the street. How long they will last is pretty much a function of what the rods are subjected to and how lucky you feel. For a hobby car that isn't driven much it's not a big worry. If we are talking about lots of miles, or being in a situation where a failure would leave you stranded alone on a desolate desert road, don't do it.
I ran Howards aluminum rods in a street engine for years.... Everybody said they wouldn't live, but did fine. It was a 4-speed car too, so myth debunked. Just Sayin'....
We ran a set of M/T aluminum rods in a SBC for years after it was retired as a race motor. It is sitting in the corner of the garage waiting for the next project. It was a 4;88 geared four speed car.
If I'm not mistaken..."Old Gold", this '39 Chevy has Alum rods BBC and is a street driver/drag racer that has been around for years in the NW
When Bill Miller(BME) rods were introduced they were a lot better than what everyone else was doing. Since then they have upgraded at least twice that I know of. At this point they have most of the aluminum rod business. With so many having CNC machining equipment these days there are quite a few billet aluminum rods available. I can't tell you which of those are good and which aren't. I can tell you that a properly done forging(BME rods are forged) is better than a comparable billet piece. So, if I was shopping for aluminum rods I would be talking to the people at Bill Miller. Before you could buy the crankshafts and rods to do it there was a guy in my area who built a LOT of Ford 514 big blocks with offset ground cranks and aluminum rods. Although none of those engines was being used for coast to coast deliveries, last I knew none of those engines ever lost a rod. That included the shop's crew cab truck that was used for general transportation, pick-ups and deliveries by every knucklehead in the shop, , and for towing his race car. Having tested rods for a living that didn't make me feel too warm and fuzzy, but real world results are what they are.
If the piston is in the hole, probably no worries. IF its setup for high compression with zero deck clearance might be different animal.
Just let it get up to operating temp before you snap the throttle, aluminum rods don't like to be stressed when they're still cold.
My buddy runs GRP in his alky engine with 48lbs of boost, 2850HP, (1.100 lift cam!)and in this situation they change them every 30 p***es or so but the builder said these rods would sustain 5-700 HP virtually forever. The kicker is a bunch of math with load x rpm x the size of your foot or such!
I've run the OLD Forgetrue rods on the street MANY years ago without problem. The C&A rods are a good rod. As long as they haven't been beat on too hard, I'd say they should be fine. I used to know a guy that ran C&A rods in a blown big block Chevy in his weekend/ski boat for years with no problems. Just make SURE of your rod side clearance. Alum. rods need more clearance than steel rods. With thinner oil, you may have a low rpm (idle) pressure problem if the clearance is on the loose side. Mike
i ran aluminum rods in a hot vw motor for years with no prob and i beat the snot out of it, went thru a bunch of pushrods and a set of heads never a prob with rods or crank
I had a set of Childs and Albert aluminum rods in a drag motor that probably made around 600hp and was only turning it 6800 and lost one. Completely ruined the block and crank, a chunk got jammed under the cam and stopped it turning and bent 14 of the 16 valves and put a huge divot in my aluminum head when the piston dome hit it. This turned into a really big bill and I will never run aluminum rods again. Plenty of excellent rods, I run ****, available for $250 to $400 dollars really cheap insurance rather than destroying a bunch of other parts.
That's not quite right. The engine guy was exaggerating to make a point. Even premium steel rods get tired. Because of that, pro race teams replace seemingly good Carrillo rods just for insurance. Aluminum has much lower fatigue resistance than steel, and metal fatigue in aluminum is harder to predict than steel. Because of that, in any situation where an aluminum rod is being seriously used(like a 700 HP engine) it's not going to last forever. It's not a question of whether it will fail, the elusive answer is; when.
My only experience with a problem with alum. rods was a friend who put the 388" sbc from his g***er into his boss's dirt oval car one weekend, just for the Hell of it. Don't remember brand of rods, but they were alum., and this was about '67. Ran like a bat outta hell till it blew, and as an earlier poster related on his, it virtually destroyed that engine. My thoughts are, considering the risk a failure and the likely damage upon failure against the cost of a set of rods and a rebalance, ***uming you're gonna teardown and freshen engine anyhow before installation , aren't you? Dave
Other than resealing the blower nose,I had not planned on any engine work. It only has a few hrs on it and ran fine when I pickeled it.It will probably bite me in the *** though! Biggest thing is that I wont run an automatic and if looseing the motor was going to be a sure thing, I'd just build a steel rod 454 and set this one in the corner.
The Bill Miller rods are hard to beat for sure. If you can find a good set of Brooks 88's they where great rods also. The reason most don't run aluminum on the street is because they will get millions of cycles on them ( up and down ) compared to a drag motor. Steel has a property called elasticity. If a steel part is designed properly for a certain application it can theoretically cycle for ever. But aluminum does not posses elasticity. No mater how it is designed it will break in time. JC
Both steel and aluminum are elastic. Both can act as a spring, deflecting and then returning to the starting point. Although a 1" diameter aluminum rod isn't as strong as a 1" diameter steel rod, the aluminum rod will actually flex more without yielding than the steel rod will. The difference you are referring to is fatigue resistance. Aluminum gets tired of being stressed over and over quite a bit faster than steel does.
Well here it goes.... I would not run alluminum rods.... I just wouldnt... I run H-Beam, Alluminum stretches, and cracks.... There you have it 1 nay sayer..... I cant believe he ran alluminum rods under a blower??? WoW... Whatever... All my years drag racing, and hot rods on the street, I build the bottom end for durability, and play with the top end.... I have seen to may failures with alluminum rods..Alott of gernaded engines as a result of this.... Maybe I am runnin extreme. My Camaro ran 8:10s at 168mph.... My mustang ran at the HotRod Mag fastest street car, and took that trophy in 82 at PV...
To put an end to all of the myth's regarding this topic simply go to this linc, www.bmeltd.com. The web site for Bill Miller Engineering. I have used thier aluminum rods for over 20 years and zero failures. Besides addressing all of the " myth's " , Bill goes right into details regarding the proper clearances and preperation for the correct install of his rods even for street use. Even if you consider yourself a engine builder, it would be wise for you to check out the site, and enjoy reading the truth behind aluminum rods from the best in the business. A safe Memorial Weekend to all, TR
Good advise here. Rum BMEs in our 1600hp nitrous motor for years. They stretch.060, so ya need the right deck,valve, and chamber clearance. Also need more side clearance on the rods. That will drop oil pressure, so ya might have to raise the pump pressure. OK for limited street use, but steel rods will last forever.
Exactly. It's important to see this from the right perspective. There are good reasons why manufacturers don't used aluminum rods in production cars, why they aren't used in airplane engines, and why Caterpillar engines have steel rods instead of aluminum.
If I'm not mistaken..."Old Gold", this '39 Chevy has Alum rods BBC and is a street driver/drag racer that has been around for years in the NW <fieldset cl***="fieldset"> <legend>Attached Thumbnails</legend> After watching a few near bumper dragging launches, that is one impressive 39 too! </fieldset>
Just to be sure, you don't have a set of those 'windage' rods do you? I don't think C&A made any of them, Manley had some for sure, but they were supposedly the hot ticket for a while (back then) and the beams were narrow and relieved for crank windage so they'd slice thru the oil that is roping around the crank. Treacherous pieces they were.
The specific property is fatigue as stated by Al. But the real reason fatigue is an issue is that aluminum does not have a fatigue limit. It will develop a crack eventually, no matter how small the cyclic tensile loading. Steel does has a fatigue limit that if you are below that limit it will last forever without any fatigue cracking. The elasticity that is referred to is a property called elastic modulus. For steel it is approx 30 x 10E6 (30 million) psi. Alum is about 10 x 10E6 psi. In real terms this means alum is one-third as stiff compared to steel. This is the reason alum rods need to account for some stretch. They stretch about 3 times more than steel for the same applied load. Steel does stretch as well, just not as much. The actual stress that the material yields at is dependent on heat treat, so stating one is stronger than the other is not a valid statement. Thus concludes today's metallurgy lesson.......
I remember the Manley versions well, the cross-section of the beam was kind of diamond-shaped with the corners rounded off.
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