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Rex, the engine in my Grand Sport has a set of Eagle 4340 rods and there are lots of high RPM miles on them. They have stayed together so my opinion (not necessarily a qualified one) is favorable.
Rex, the engine in my Grand Sport has a set of Eagle 4340 rods and there are lots of high RPM miles on them. They have stayed together so my opinion (not necessarily a qualified one) is favorable.
Whacha thinkin' about doin'?
Jim
Thanks Jim. I was thinkin you had told me before that your GS engine had Eagle rods. Just thinkin about building another 427 ZL-1 engine for my 67, this time a little "peppier" than the one in it now. I like the look of the Scat "Pro Series" I beam rods with the polished side but Eagle rods seem to be more popular, at least around here.
Don't know if it matters to anyone else, but both Scat and Eagle are made from Chinese steel. Eagle is completely finished overseas, and just boxed up in the USA, whereas the final machining on Scat is done in the USA. I personally prefer to buy American made steel. Crower, Callies and Oliver are all made in the USA.
I would look at weight also, check out other rod companies, Manley H-beam, Crower, etc. too.
Doug
Someone please explain to me why H-Beam rods exist.
The H-Beam would make sense if the rod stress is longitudinal WRT the engine, i.e. parallel to the crank centerline.
It's not.
If there is any bending stress on the rods it is lateral (i.e. from side to side) and for that, an I-Beam is the configuration which makes the most sense.
Maybe it's a marketing breakthrough....
In the interest of full disclosure: The Eagle rods in my road race engine are H-Beam. I bought them before thinking through the stresses. Not sure I would buy H-Beam again until/unless someone shows me the error of my thinking.
Jim
Last edited by jim lockwood; 11-19-2018 at 05:28 PM.
Generally, mechanically engineering related, H beams are stronger for a given weight, IIRC. They are more expensive to produce most likely, and also have higher compression load capability, again, IIRC, its been decades since i took those classes. If anything causes the rods to bend laterally, you have other problems besides your rod selection choice.
Doug
Originally Posted by jim lockwood
Someone please explain to me why H-Beam rods exist.
The H-Beam would make sense if the rod stress is longitudinal WRT the engine, i.e. parallel to the crank centerline.
It's not.
If there is any bending stress on the rods it is lateral (i.e. from side to side) and for that, an I-Beam is the configuration which makes the most sense.
Maybe it's a marketing breakthrough....
In the interest of full disclosure: The Eagle rods in my road race engine are H-Beam. I bought them before thinking through the stresses. Not sure I would buy H-Beam again until/unless someone shows me the error of my thinking.
H-beam rods may be lighter for a given load bearing capacity, but the variation and volume of oil trapped windage mass is likely to negate any weight savings.
I personally have Oliver rods in my 357, and the former group buy small journal Crower Sportsman rods in my original 340hp/327 that sits rebuilt on a stand in the garage.
Eagle stuff should be finished over seas. They do some rework here but not every piece. As far as I know Scat cranks are finished here. I don't know about their rods. I have used both Scat has a better grip on quality control. I didn't take the time to look up the rods you are going to use but I would use 4340 H beam. Either of the brands of rods will work ou of the box, again I prefer Scat. Cranks are another story.
Eagle stuff should be finished over seas. They do some rework here but not every piece. As far as I know Scat cranks are finished here. I don't know about their rods. I have used both Scat has a better grip on quality control. I didn't take the time to look up the rods you are going to use but I would use 4340 H beam. Either of the brands of rods will work ou of the box, again I prefer Scat. Cranks are another story.
I was thinking of getting a scat crank. Care to elaborate? Thx
Just thinking out loud, but seems to me that conrod loads are the inertial forces of starting and stopping the assemby at both ends of the stroke and the compression load applied during the power stroke. Assuming the oiling system is working the rotational degree of freedom around the crank/wrist pin axes are released at each end of the rod and there is limited space for displacement so bending in that plane should not be a major issue. Power stroke column buckling might be why H beams exist. Or, maybe because Carrillo rods didn't fail as much as alternates back in the day.
I was thinking of getting a scat crank. Care to elaborate? Thx
There should be very good YouTube videos explaining why. I have had to have every Brand X crank I used ground because of taper in the journals. And when I say ground I mean to standard. They normally have taper worn in the grinding wheel that leaves the outer parts of the rod throw too big. The worst I've seen was .003" too big. I've never had to have a scat ground they have always been good on size. The crank grinder charges extra when you come in and want a crank ground to standard because it takes much longer to chase a crank that is on size in the center but not on the sides. There should be a video detailing this and it's not a rare instance, i just went and checked and yes it's there the first video on grinding the brand x crank. Now they may have cured this I can't say but this has always been my experience. And buy a forged crank not cast, that's just my opinion.
i just reread my previous post and I can see how it could be confusing and lead you to believe I was saying something bad about Scat cranks. That is incorrect I consider them the best in the cheaper line of cranks.
There should be very good YouTube videos explaining why. I have had to have every Brand X crank I used ground because of taper in the journals. And when I say ground I mean to standard. They normally have taper worn in the grinding wheel that leaves the outer parts of the rod throw too big. The worst I've seen was .003" too big. I've never had to have a scat ground they have always been good on size. The crank grinder charges extra when you come in and want a crank ground to standard because it takes much longer to chase a crank that is on size in the center but not on the sides. There should be a video detailing this and it's not a rare instance, i just went and checked and yes it's there the first video on grinding the brand x crank. Now they may have cured this I can't say but this has always been my experience. And buy a forged crank not cast, that's just my opinion.
i just reread my previous post and I can see how it could be confusing and lead you to believe I was saying something bad about Scat cranks. That is incorrect I consider them the best in the cheaper line of cranks.
11-19-2018, 09:40 AM
Scat or Eagle rods ?
than the one in it now. I like the look of the Scat "Pro Series" I beam rods with the polished side but Eagle rods seem to be more popular, at least around here.
That is what I was always told as well.
