I-Beam or H-Beam

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xring

xring

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FABO'ers,

What would you recommend for my build? 340/416, Eagle forged crank, Ross dish pistons, now looking at ported J-heads and small roller mechanical cam, like Comps XR280R, 242/248*@.050;.57/.576. May switch to Eddy heads down the road; planning on 9.8:1 with the J-head; 10.5:1 with the aluminum heads.

I ordered the Eagle SIR full floating rods, which are supposed to be good for 500 hp/7000 rpm. I figured I'd be safe since I don't plan on revving this engine that high. Now I'm wondering if I shouldn't get the H-Beams. They are more expensive and I think may require some block clearancing.

The pistons are back-ordered so I can change the order if I decide to.

Don't have the car yet, planning on an early 70's A-body with 3000 stall/3.91's.

Opinions, please.
 
I haven't seen it personally, but the 500 HP rating on the SIR is close. I have heard that any more than that and they break. I used H-Beam Scat for my 408.
 
I don't use SIR rods. I'll run re-done factory rods first or step up to an H beam as an upgrade.
 
I thought the breakages were isolated and due to material problems more than design. The ones I read about were under the supposed 500hp/7000 rpm limit.

I figured when I started this project that stock rods would be OK; the Eagle rods are (supposed to be) stronger and they are lighter than stock. And I would have to buy stock rods and have them reconditioned if I went that route.

The H-beams are quite a bit more expensive. I don't have any problem paying for them if I need to; just don't see any sense in buying the more expensive part if the I-beams will do just as well.

Thanks
 
scat makes a nice 4340 I beam rod that is only a few dollars more then the 5140 eagle rods.
 
My problem was at the time, it wasnt "just high rpm engines". They simply pulled apart at whatever rpm they were at, and in some cases that was only 3500 cruising down the road. It was a metalurgy issue, and one can't economically test for that. So I just avoid them. There are thousands of sets that work fine. But I still get nervous about it so I don't. I can get a set of seasoned factory rods that I know can take 500hp ready to install with ARPs for about $25 less. A little heavier, yes. But after correcting the SIRs (which I also have heard about) stockers are closer to $150 cheaper for me. If the engine needs rods, I'll go Hbeams or K1 I beams.
 
FWIW, here is my experience with the Eagle SIR rods;

When I had my block/crank at the machine shop I was discussing the plan of attack with the owner (this shop is a highly respected performance engine shop and builds the motors for a local IHRA Top Alcohol Funny Car driver). My original plan was to just have the stock rods reworked and new ARP bolts installed. The owner recommended that I go with the Eagle SIR rods for the following reasons;

1. They are stronger than the sb mopar rod. And are very under rated at 500HP.
2. They are bushed for floating pins.
3. The rods are very well machined and generally do not require any work before installing.
4. They are very accurately matched and balanced which makes balancing the rotating assembly less costly.
5. The cost of him reworking stock rods and installing a good bolt like an ARP is more than the cost of the SIR rods.

He told me that he built a lot of engines a year with the SIR rod and has never had an issue. I have almost 30k miles on my 360 now and it regualrly sees 6000 rpm shifts and is holding up fine.
 
not sure if its still going on but manley had a good sale going on for thier rods.
 
Heres my personal experience with Eagle sir rods,i ran them in my 520 h.p. 416 stroker for 2 1/2 seasons,until i over-revved the engine snapping one of the rod bolts,up until that time they performed just fine,the engine was apart and checked 2 times before the failure,and everything looked fine if your putting them in a basically street motor they should work just fine,but have them checked over by your machinist first...
 
I've got about 5 years on my Eagle SIR rods. The engine is a 415 SB with 450 hp been down the track 100 plus times runs 11.50 no problems. Jayson
 
I went with the SIR rods. They aren't very pretty but I hope will get the job done. I actually was going to change to the H-beams but the shop had already balanced my assembly and shipped it out.

Thanks for the replies.
 
Why do you say they aren't pretty?

The big end looks just like the big end of the Eagle H beam rod and uses the same ARP 12 point cap screws. Compared to a rod they are a work of art.

I don't have a picture the entire SIR rod but here is a picture of the bottom end of my short blcok.

BottomShortBlock.jpg
 
dgc333 said:
Why do you say they aren't pretty?

The big end looks just like the big end of the Eagle H beam rod and uses the same ARP 12 point cap screws. Compared to a rod they are a work of art.

I don't have a picture the entire SIR rod but here is a picture of the bottom end of my short blcok.

BottomShortBlock.jpg
Click to expand...

Don't know if this is in the car yet but beware of using old pick up tubes, make sure there are no hardened seals stuck in it and the screen is good.jmo

They are pretty cheap brand new from mancini.

btw the rods look pretty to me, there in a mopar!:cheers:
 
Who cares if there not pretty!
You aint gonna see them!
As long as they work!
 
dgc333 said:
Why do you say they aren't pretty?

The big end looks just like the big end of the Eagle H beam rod and uses the same ARP 12 point cap screws. Compared to a rod they are a work of art.

...
Click to expand...

I mean compared to the H-beam rods. I know it doesn't make any difference on the practical side, I just like smooth, shiny things. \\:D/

Anyway, I didn't think the bottom end was the same between the two...it was my understanding the h-beams would require some clearancing on the block...I could be wrong about that.
 
The only thing shared between the I & H beam is the 2 lines across the cap, otherwise the parting line/around the bolts and cap it's is different and is way beefier on the H-beam let alone the rest of the of it.
 
1wild&crazyguy said:
Don't know if this is in the car yet but beware of using old pick up tubes, make sure there are no hardened seals stuck in it and the screen is good.jmo

They are pretty cheap brand new from mancini.

btw the rods look pretty to me, there in a mopar!:cheers:
Click to expand...

Yep it's in the car! I have very close to 30,000 miles on that engine now. And yes I did check it out before re-using it.
 
Its all a matter of what you like,i have an engine builder buddy who builds some high dollar motors,and he prefers i-beams over h-beams..to say the h-beams are better is just an oppinion...
 
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