[gtofreek]

The first experience we had with Molnar rods was not good. We build late model Hemi's and we had a couple customers[over the course of a couple years] bring us their blown up engine that had Molnar rods in them. Both engine suffered from rod failure. Gave us a bad taste on his rods. Looking at his Hemi rods, they were very small, and the beam was not very beefy compared to the Callies rods we use in them. Since then, we have looked into Molnar, and found out he is a very Knowledgeable guy, and knows a lot about rod bolts. He has some good ideas, and makes a great bolt from what I understand. His Pontiac stuff may be great. We just think he made the Hemi rod too small for any kind of boosted application. I'm finding out his stuff is better than we first gave credit for.

[hurryinhoosier62]

Gentlemen, I spent more than few years in the warbird world. ALL the connecting rods used in the high horsepower engines(really, in all the engines) are "I" beam in design, whether it's a master rod or a link rod. I agree with both Tom and Paul. There are applications where "H" beam rods work better than "I" beam rods. I want to thank Mr. Vaught for posting the info about Molner Technologies. That gives us another source for rods and cranks. As I said earlier, I just wish they had a 4" stroke crank...

[Will]

Is there any reason to *NOT* run an H-beam rod? I have a set of 6.8" Eagle H-beams which were the go-to rod 16 years ago. I can't imagine why these wouldn't be perfectly fine to use...?

[b-man]

All connecting rod theory and experience aside, can anybody here recommend an affordable stock replacement forged rod for the thread starter who's building a mild street 400 engine that will likely end up making 400 HP or less?

He's not building a race engine and doesn't need a high-end rod.

[Tom Vaught]

Originally Posted by gtofreek

Not sure where some of you guys get your info from. I forget which way it goes, but I-beam resists either twisting or bending better than H-beam, and H-beam resists the other better than I-beams. I balance a lot of connecting rods, and size for size, H-beam are always lighter than I-beam, unless you're talking one of those skimpy little SCAT I-beam rods for a SB Chevy.

Thanks for mentioning that each design has its better points. Just need to figure out the application you are working with. Also glad you found out Molnar is a smart guy after all.

Tom V.

[Tom Vaught]

Originally Posted by Will

Is there any reason to *NOT* run an H-beam rod? I have a set of 6.8" Eagle H-beams which were the go-to rod 16 years ago. I can't imagine why these wouldn't be perfectly fine to use...?

The old Eagle Rods, 1996 time frame when Marty Palbykin ran them were good for 1600 hp for 3 years. I have two sets of 6.8" long Eagle rods bought about 10 years ago and except for a bolt change to the ARP 2000 bolt, plan on running them with boost. Marty as you know, ran some pretty decent numbers on boost. Not this 10-15 PSI stuff.

I have not investigated the latest Eagle Rod stuff but maybe someone else can comment on the higher boost applications with a Pontiac.

Tom V.

[Tom Vaught]

Originally Posted by b-man

All connecting rod theory and experience aside, can anybody here recommend an affordable stock replacement forged rod for the thread starter who's building a mild street 400 engine that will likely end up making 400 HP or less?

He's not building a race engine and doesn't need a high-end rod.

I thought I did that early on with the recommendation to use the $600 per set Molnar Pontiac rods.

Tom V.

[ponyakr]

Originally Posted by b-man

All connecting rod theory and experience aside, can anybody here recommend an affordable stock replacement forged rod for the thread starter who's building a mild street 400 engine that will likely end up making 400 HP or less?

He's not building a race engine and doesn't need a high-end rod.

The RPM 5140's are the cheapest, initially, at $300. But, Paul Carter has posted that most all those rods that he's used have needed big end resizing. Therefore, depending on the total cost of rods + machine shop cost to make 'em usable, at $400, the RPM H-beams MAY be his best $ value, and is definitely a stronger & lighter rod.

If the RPM H-beams also need big end resizing, but the Eagle rods don't, the Eagles may be his best choice.

Are those $600 rods a better buy for his engine ?

I'd guess no. But, that's just an opinion from a non-pro.

[Will]

Originally Posted by Tom Vaught

The old Eagle Rods, 1996 time frame when Marty Palbykin ran them were good for 1600 hp for 3 years. I have two sets of 6.8" long Eagle rods bought about 10 years ago and except for a bolt change to the ARP 2000 bolt, plan on running them with boost. Marty as you know, ran some pretty decent numbers on boost. Not this 10-15 PSI stuff.

I have not investigated the latest Eagle Rod stuff but maybe someone else can comment on the higher boost applications with a Pontiac.

Tom V.

I bought these rods in early '99 so guess it's been closer to 18 years. At the time they were the best Compromise of strength weight and cost. The bolts have been through a few torque cycles so need to be replaced but otherwise they should be fine. The big ends checked out fine but of course the small ends needed honing for proper pin fit.

[b-man]

I've seen the stock dimension bushed Eagle H-beams going for right around $480, that's probably about the cheapest 'ready to run' rod out there.

Getting harder to make the case against the use of reconditioned cast rods for the milder builds that could be properly prepped with good bolts for about half the cost of a new forged rod.

Personally have had no problems running the cast rods in two 455s and a 400. One of the 455s was a 400 HP bracket engine (12-flat at 110 MPH) and the other was a 335 HP daily driver, the 400 was a very mild build making 300 HP at best. None of those rods had ever been rebuilt nor had the rod bolts replaced.

[Cliff R]

We have a 455 here topped with 260cfm #62 heads from Dave at SD and his Road Paver cam that has cast rods in it and heavy TRW forged pistons on them. Been fine for many years now and sees a good bit of track time shifting past 5500rpm's.

Now that I've put that in print it will probably break one and window the block on the next outing!....LOL....Cliff

[Schurkey]

Originally Posted by b-man

All connecting rod theory and experience aside, can anybody here recommend an affordable stock replacement forged rod for the thread starter who's building a mild street 400 engine that will likely end up making 400 HP or less?

He's not building a race engine and doesn't need a high-end rod.

He doesn't need an aftermarket rod at all. Mild 400, no excessive RPM or HP goals? WHY look at aftermarket rods?

Originally Posted by b-man

Personally have had no problems running the cast rods on two 455s and a 400. One of the 455s was a 400 HP bracket engine (12-flat at 110 MPH)

^^^ Yeah, that.

[Cliff R]

At this point in our learning curve we've used just about every offering out there for connecting rods.

Crower, Oliver, Eagle, 5140 "I" beams, 4340 "H" beams, and PPR lightweight "I" beams.

Never had any issues with any of them, but I prefer the Eagle "H" beams these days over the generic "H" beams due to fit and finish. Even with that said we've done a number of these engines using the "no-name" H beams right off the boat in the weird cardboard packaging. The biggest problem we see with those is that more times than not you're going to have to open up the small ends to get the pins to fit (full floating). With few exceptions all have been fine for weight, length and big end sizing......FWIW.....Cliff

[ponyakr]

You gotta love this thread. It's just like the cam threads. Just depends on who you ask.

We have original stock cast rods, with stock bolts, up to $600 forged rods, and everything in between.

I too, raced several 455 bracket engines, with original cast rods--no resizing, and no failures. But, I had a rev limiter set at 5500rpm. It saved all my 455's, several times, such as when trans & rear ends let go.

[Tom Vaught]

My point was the Molnar rods, in most cases could be installed right in the engine after a basic check of the dimensions. No rework required by another shop. The word is Molnar's stuff is with-in .0002" on average across the rods. So do you pay Peter or do you pay Paul.

That being said, good "checked out" cast rods from a low mileage engine on a PURE street driver would not bother me a bit to use.
Also expensive rods are not $600.00 rods, they are $3800 rods or higher. When the bolts alone cost over $300.00 you are talking some expensive rods.

Tom V.

[Will]

I would agree that as long as you're not paying over $300 or thereabouts to have your stock rods weight matched and resized with ARP bolts then there's no reason to go aftermarket in a mild driver type build. If it's going to cost near $400 or more (and why would it?) then the aftermarket rods make more sense.

[hurryinhoosier62]

Originally Posted by Tom Vaught

My point was the Molnar rods, in most cases could be installed right in the engine after a basic check of the dimensions. No rework required by another shop. The word is Molnar's stuff is with-in .0002" on average across the rods. So do you pay Peter or do you pay Paul.

That being said, good "checked out" cast rods from a low mileage engine on a PURE street driver would not bother me a bit to use.
Also expensive rods are not $600.00 rods, they are $3800 rods or higher. When the bolts alone cost over $300.00 you are talking some expensive rods.

Tom V.

Well said, Mr. Vaught

[hurryinhoosier62]

Originally Posted by Tom Vaught

My point was the Molnar rods, in most cases could be installed right in the engine after a basic check of the dimensions. No rework required by another shop. The word is Molnar's stuff is with-in .0002" on average across the rods. So do you pay Peter or do you pay Paul.

That being said, good "checked out" cast rods from a low mileage engine on a PURE street driver would not bother me a bit to use.
Also expensive rods are not $600.00 rods, they are $3800 rods or higher. When the bolts alone cost over $300.00 you are talking some expensive rods.

Tom V.

Originally Posted by b-man

I've seen the stock dimension bushed Eagle H-beams going for right around $480, that's probably about the cheapest 'ready to run' rod out there.

Getting harder to make the case against the use of reconditioned cast rods for the milder builds that could be properly prepped with good bolts for about half the cost of a new forged rod.

Personally have had no problems running the cast rods in two 455s and a 400. One of the 455s was a 400 HP bracket engine (12-flat at 110 MPH) and the other was a 335 HP daily driver, the 400 was a very mild build making 300 HP at best. None of those rods had ever been rebuilt nor had the rod bolts replaced.

Bart, you've been lucky. When we magnafluxed the bolts in the connecting rods from the 160,000+ miles YX 400 I built in the late 80s, all the rod bolts showed fatigue. This engine was out of a Catalina that had very well taken care of.

[Will]

It was always my understanding that the bolts were the failure prone components in the stock rods, not the rods themselves. I think it just makes sense to replace the bolts with ARPs then resize the big ends.

[hurryinhoosier62]

Originally Posted by Will

It was always my understanding that the bolts were the failure prone components in the stock rods, not the rods themselves. I think it just makes sense to replace the bolts with ARPs then resize the big ends.

IF the rods are out of a low mileage engine and pass magnaflux, yes; however, the cost of properly reconditioning a set of OE cast rods is not much lower than the cost of off-shore forged rods. If you plan on not exceeding 5500rpm on 455s or 5700 on 400s, the OE rods CAN last a long time. The problem is fatigue. ALL castings are subject to it. You can't see it because it occurs on the molecular level. Are you will to gamble with a casting that you really don't know how many cycles are on it? I'm not...