I beam vs H beam rods....discuss
06-23-2011, 04:42 PM
#1
I beam vs H beam rods....discuss So I'll admit it; I don't know **** about building a bottom end for a LT1 and need somebody to school me some on what parts are best for the money for a mild street/strip 400 RWHP (450HP) LT1. I know forged parts are better than cast but; What's the difference in strength/HP rating for I beam vs H beam connecting rods? H is bigger/better right? Is it the connecting rod themselves or the bolts that usually let go first? I'm definitely going with forged pistons and ether the stock crank or a forged 383 crank regardless of what rods. Any thoughts on this?
06-23-2011, 04:50 PM
#2
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For the power levels you want it doesn't matter what style rod you go with. I have heard through a couple of different machinists that because of today's technorogy regarding rod design, I-beam rods can be just as strong as h-beam.
06-23-2011, 05:12 PM
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For that power level the stock rods and crank should be fine. I would rebuild with the stock parts and add SRP forged pistons and ARP hardware, thats what I would do if mine lets go. Its a good strong bottom end for people on a budget in the 400rwhp range. Id like to know what let go on your motor, the usuall suspect seems to be the rod bolts, they're said to be the weakest point in the stock bottom end.
06-24-2011, 12:05 AM
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For that power level the stock rods and crank should be fine. I would rebuild with the stock parts and add SRP forged pistons and ARP hardware, thats what I would do if mine lets go. Its a good strong bottom end for people on a budget in the 400rwhp range. Id like to know what let go on your motor, the usuall suspect seems to be the rod bolts, they're said to be the weakest point in the stock bottom end.
06-24-2011, 12:13 AM
#8
I really dont know where in the hell you guys get your information. But let me spell this out.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
06-24-2011, 12:43 AM
#9
I really dont know where in the hell you guys get your information. But let me spell this out.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
06-24-2011, 12:55 AM
#10
What do you mean "just as strong"? LOL
That's like saying tool steel is "just as strong as plastic"....
I beams have always been designed to be stronger than H beam.
I guess somewhere in internet land someone got things confused and the concensus was H beams were stronger but heavier???
Every entry level rod I've seen is going to be an H beam, and the max effort type of rods are I beam.
A lot of people think I beams are lighter too, but usually not the case, at least when comparing apples to apples. If you compare a cheap Scat H beam rod to an Oliver I beam. Well of course the oliver may be lighter as a function of its design. But that's not really apples to apples.
That's like saying tool steel is "just as strong as plastic"....
I beams have always been designed to be stronger than H beam.
I guess somewhere in internet land someone got things confused and the concensus was H beams were stronger but heavier???
Every entry level rod I've seen is going to be an H beam, and the max effort type of rods are I beam.
A lot of people think I beams are lighter too, but usually not the case, at least when comparing apples to apples. If you compare a cheap Scat H beam rod to an Oliver I beam. Well of course the oliver may be lighter as a function of its design. But that's not really apples to apples.
06-24-2011, 06:10 AM
#11
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Yes, it is a bigger job than it sounds. You really should have the rods resized when changing rod bolts. Some say they add them without resizing but it is not recommended, you run the risk of spinning a bearing if you don't.
06-24-2011, 07:53 AM
#12
I really dont know where in the hell you guys get your information. But let me spell this out.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
an H beam design however does require more material to build vs. an I beam design there fore H beam weights of comparable rods are usually heavier than I beam designs.........the I beam is also a stronger design by way of compression and deflection......the h beam is a cheaper easier rod to manufactuer and is quite strong for the design/price factor that it has.......
most every high rpm high horsepower motor you will see will be running some type of parabolic I beam rod such as the Oliver, Crower, Lentz Billets........when i built my shortblock this was one of the main reasons I went with an Oliver Parabolic I beam design........the strength vs. weight ratio.......another issue with H Beams is the small end of the rod.....i remember a while back seeing a FEA analysis from Oliver on H-Beams vs. I beams......it showed where the small end design on the H-beam has a very high compression stress point localized to a small area..........the I beam has a much more spread out load point down at the end of the rod......
again this is what i've seen and learned more from an engineering stand point versus a discussion and opinion stand point........there is much more to connecting rods that i wont get into to confuse this thread however..........from an engineering stand point an H Beam design will always requrie more material than an I beam design........
06-24-2011, 11:25 AM
#13
One would think so by simply looking at them. However go look at callies site. H beams are the lightest and the weights go up from there. Its not speculation, its fact.
I agree that there's a LOT to it and what's best depends on the application. One type can deal with tensile load (RPMS) better, while the other can deal with compressive loads better (cylinder pressure ) .
I agree that there's a LOT to it and what's best depends on the application. One type can deal with tensile load (RPMS) better, while the other can deal with compressive loads better (cylinder pressure ) .
06-24-2011, 11:29 AM
#14
I really dont know where in the hell you guys get your information. But let me spell this out.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
H beams - Strong - Lightest
H/I beams - Stronger - Heavier
I beams - Strongest - Heaviest
This is in regard to Compstar products but thats the way it should be. All this "I beams can be as strong as H beams" and "I beams are the lightest"...... a little misinformed.
Eagle I=595g
Eagle H=650g
Lunati I=635g
Lunati H=675g
06-24-2011, 11:31 AM
#15
Every BME Aluminum rod I have seen has been a variation of an I-beam. They are not only strong but light as well. So strong in fact, that it took a Crowler crank and beat stress fractures into the fillets of the crank. The crank was something similar to this Crower UL95133.
06-24-2011, 11:35 AM
#16
One would think so by simply looking at them. However go look at callies site. H beams are the lightest and the weights go up from there. Its not speculation, its fact.
I agree that there's a LOT to it and what's best depends on the application. One type can deal with tensile load (RPMS) better, while the other can deal with compressive loads better (cylinder pressure ) .
I agree that there's a LOT to it and what's best depends on the application. One type can deal with tensile load (RPMS) better, while the other can deal with compressive loads better (cylinder pressure ) .
07-02-2011, 08:46 AM
#18
I too could get confused in here.
I'm rebuilding a very low mileage stock 4-bolt main motor. Plans of AI H/C 400rwhp area, so nothing extravegant. Plans of staying below 6800rpm also. I have no cylinder wear at the tops of my cylinders so I'm not planning on replacing pistons(measurements may change plans). However, I do want to address the weaklink rod bolt issue. Which is what the OP was asking about. I have read some negative issues about stock rods getting larger arp bolts. This was my plan for a while.
How about some intelligence discussed about forged 5.7in., SCAT, EAGLE, COMPSTAR H-beam, I-beam rods with 7/16 rod bolt.
Like,
) the negative issues of the stock rods with the replacment bolts.
)Is the Scat/Eagle rods a sufficient replacement?
)Is the compstar the right one?
Thank you
I'm rebuilding a very low mileage stock 4-bolt main motor. Plans of AI H/C 400rwhp area, so nothing extravegant. Plans of staying below 6800rpm also. I have no cylinder wear at the tops of my cylinders so I'm not planning on replacing pistons(measurements may change plans). However, I do want to address the weaklink rod bolt issue. Which is what the OP was asking about. I have read some negative issues about stock rods getting larger arp bolts. This was my plan for a while.
How about some intelligence discussed about forged 5.7in., SCAT, EAGLE, COMPSTAR H-beam, I-beam rods with 7/16 rod bolt.
Like,
) the negative issues of the stock rods with the replacment bolts.
)Is the Scat/Eagle rods a sufficient replacement?
)Is the compstar the right one?
Thank you
