[TransAm 474]

Originally Posted by Dragncar

Molnar rods are in fact a billet rod like Carrillo's. Not just a forged rod like Eagle, Scat ect.
You get a lot for your money.

Yep, Tom states that his rods are 4340 Billet material instead of the common 4340 Forged ... but there are a few high end steel rods that are 300M material, such as the Callies Ultra and Dyers Rods. 300M is a modified 4340, but here are the thoughts straight from Tom Molnar on the difference between the two .... pretty interesting read, so I thought I would share it here in this thread ...

"From Tom Molnar on 300m rods.

Ok, here is the 300M story. A lot of people think 300M is some sort of super alloy with magical properties. The truth is 300M is simply 4340 with vanadium added and a higher silicon content. This change allows the material to be hardened to a higher level. Several years ago I looked into making rods out of 300M and hired an independent testing lab to conduct some tests. The process they used was to make several samples of both 300M and 4340 and heat treat them to increasingly higher hardness levels starting at 34 Rockwell then test them in a fatigue until they failed. In every test, the 4340 had a much better fatigue life until the hardness reached a level near 50 Rockwell which is where the 300M performed better. The problem with this is, no one is heat treating connecting rods to this level because the rod becomes much more difficult to machine. The bottom line is, 300M sounds like a good deal and in some cases it can be but not at the range connecting rods are heat treated to. Something else I found to be interesting is, a couple of years after we did this test, I found out Carrillo did the same test using a different lab and they had the same results."

[TransAm 474]

.... and here is another great read from Mr. Molnar on the subject of H-Beam vs I-Beam designs ...

Tom Molnar

"The I-beam vs H-beam debate rages on and some people will not agree with this but here we go. First off, a little about my background, I have been designing connecting rods for over 35 years including I-beam, H-beam and Parabolic beam configurations. I not only was one of the two people who started Oliver Racing Parts, I designed all of their rods, tooling, fixtures, wrote every CNC program they ever used to make a rod or crankshaft as well as running the company until I left in 2005.

Almost all OEM rods are made as an I-beam not because they are stronger, but because it makes them easier to forge or cast. It is a cost issue not a strength issue for them. Keep in mind that most OEM engines are designed to go to the grocery store and take the kids to school so in these applications, they work fine. The way the OEM companies look at it, If $1 can be saved on a connecting rod and you make millions of them, it starts to add up to real money.

Personally I like the look of an I-beam rod and they are easier and less expensive to machine. When I started Molnar Technologies, I had a clean sheet of paper and designed our rods based on the best strength to weight ratio. To give you an idea of the forces on connecting rods, we have to understand how the loads are applied. When the fuel is burning, it pushes on the piston which in turn, pushes on the rods. Most everyone knows this part but what happens next is the piston is trying to drive the wrist pin though the center of the rod. With an I-beam configuration, you have the two large beams on the sides and the thin section directly below the wrist pin. The problem is the large beams are not directly below the wrist pin which means the thin section in the middle is trying to carry all of the load. As an I-beam becomes overloaded, the thin section will crush and the big beams on the side will split out like a banana peel. Yes, I have seen this and it is the reason Oliver changed to a Parabolic design which handles the load differently than a conventional I-beam in 1989. When this happens, you have catastrophic engine failure. The reason an H-beam is stronger is between the slots in the side of the rod, you have a column of steel that runs from the big end of the rod up to the wrist pin where it wraps around the underside of the wrist pin. An H-beam also has a front and back plate, all of which is directly under the wrist pin so you actually have more mass below the wrist pin which is where it needs to be and it handles the load better."

[Stan Weiss]

The next time someone talks with Tom maybe they can get a clarification on what is trying to pull the rod apart ATDC on the exhaust stroke. My understand is the 2 major factors are RPM and piston weight and power level is not a factor here.

Stan

[b-man]

I’ve removed some posts related to spell checking/grammar.

If anyone wants to try pointing out another member’s spelling/grammar errors here or anywhere else on the forums thereby effectively derailing a thread you won’t be happy after we see that I can guarantee you.

[Gach]

Not all 4340 alloy is the same whether it’s billet or steel. That makes it critical to know the steel mill, exact alloy of the material, and to deal only with the most reputable metal suppliers.

The entire steel manufacturing process determines the strength of these materials, as well. A simple designation of 4340 steel does not necessarily mean that two steel suppliers construct the final product to the same standards or with the same processes.


Billet connecting rods are built from a single piece of flat forged steel. They are designed using a CAD-type computer program, then individually cut from a billet material using a water jet or other CNC-controlled machine.

So Just because they are machines here doesn’t really mean a whole lot. So this is why it’s questionable about anything produced in China.

[Stan Weiss]

Don't assume because it is made in China that the steel is not any good and don't assume because it is made in the USA the steel is better.

Each item needs to be looked at and not just judged by where it is manufactured.

Stan

[Gach]

No I look at the history of the rods and cranks made in China over the past few years vs the ones made in US. Namely Scat and Eagle rods and their cranks. Compared to say Crower..and others USA made. China doesn’t have a very good reputation or history. That’s how I make my judgment it’s up to reader to decide.

You know it’s just like the Eagle rods, The same scenario a Pontiac guy spent a year or 2 building his motor, everything went great. Ran the numbers he was shooting for, probably put two dozen runs on it. A year or so latter builds a whole new combo better heads This time he puts motor on dyno and guess what one of those Eagle rods let’s go on the dyno. He’s so embarrassed he keeps it to himself, never talks about it, but his friend let’s the cat out of the bag.

[Stan Weiss]

I don't know if you are just lumping everything together or we travel in different circle or what. But I have no heard anything bad about Molnar rods.

Stan

[Gach]

Neither have I their new kid on block. Jury still out. There’s a lot of information in this thread the readers will decide for themselves.

[Tom Vaught]

Originally Posted by TransAm 474

.... and here is another great read from Mr. Molnar on the subject of H-Beam vs I-Beam designs ...

Tom Molnar

"The I-beam vs H-beam debate rages on and some people will not agree with this but here we go. First off, a little about my background, I have been designing connecting rods for over 35 years including I-beam, H-beam and Parabolic beam configurations. I not only was one of the two people who started Oliver Racing Parts, I designed all of their rods, tooling, fixtures, wrote every CNC program they ever used to make a rod or crankshaft as well as running the company until I left in 2005. "

I was aware of Tom Molnar's Connecting rod background for many years.
A friend from Kansas ordered and ran Oliver Rods many years ago for his Pontiac engine.

But I learned something new from this group of posts by Tom & others.
I knew he was the Chief Engineer for the rods but was not aware that he was
also a half owner in the business.

Thanks for the new info.

Tom V.

[slowbird]

Originally Posted by Gach

No I look at the history of the rods and cranks made in China over the past few years vs the ones made in US. Namely Scat and Eagle rods and their cranks. Compared to say Crower..and others USA made. China doesn’t have a very good reputation or history. That’s how I make my judgment it’s up to reader to decide.

You know it’s just like the Eagle rods, The same scenario a Pontiac guy spent a year or 2 building his motor, everything went great. Ran the numbers he was shooting for, probably put two dozen runs on it. A year or so latter builds a whole new combo better heads This time he puts motor on dyno and guess what one of those Eagle rods let’s go on the dyno. He’s so embarrassed he keeps it to himself, never talks about it, but his friend let’s the cat out of the bag.

Spun my Eagle rods to 8200rpm, most of the time 7600-7800. No issues

[R 70 Judge]

Originally Posted by Gach

Neither have I their new kid on block. Jury still out. There’s a lot of information in this thread the readers will decide for themselves.

I plan on using a Molnar 4” stroke crank and Molnar power adder rods when I rebuild for the turbo (1000hp-1200hp). I will have no second thoughts knowing I have their parts in the bottom end.

[Gach]

Originally Posted by R 70 Judge

I plan on using a Molnar 4” stroke crank and Molnar power adder rods when I rebuild for the turbo (1000hp-1200hp). I will have no second thoughts knowing I have their parts in the bottom end.

If you feel Secure that’s all that counts.

[Gach]

Originally Posted by slowbird

Spun my Eagle rods to 8200rpm, most of the time 7600-7800. No issues

Good for you

[Stan Weiss]

Remember when there is an engine problem it is not always the parts, but sometimes the person that put it together,

Stan

[mgarblik]

Originally Posted by Stan Weiss

Remember when there is an engine problem it is not always the parts, but sometimes the person that put it together,

Stan

Certainly, quality of assembly and careful attention to every detail play a major role in success. From low to moderate power levels, these details play a larger role than material quality IMO. However, many home builders do not have the luxury of precision measuring instruments and may have only a strip of plastigage and hand tools to assemble their short block. Given this common scenario, out of the box, accurate parts become awfully important. Having now installed 48 Molnar rods, I can say with confidence, on a Sunnen AG 300 gauge, all 48 rods measured +- .0001". That will keep you safe in any installation. Eagle connecting rods, we have seen hundreds of them come through the shop at school. It is very rare for a set of 8 Eagle rods to be safe for installation without some rework. The big or small ends generally need some attention. At best, the small ends may need a touch with the hone. At worst, the big ends need to be broken down, dowels removed, rods and caps cut, reassembled and honed. Essentially, rebuilding new connecting rods. In general, Eagle rods are +- .0002-.0003" through a set. Usable, but not perfect. I really like the fact that with Molnar rods, you have that one guy, the owner, Tom Molnar to talk to IF there was ever an issue. With Eagle, I don't have a clue who you would talk to. Their technical support essentially treated me like I was some kind of incompetent moron when I called to ask for a supply of dowels to fix their connecting rods. You just don't get that warm and fuzzy feeling talking to them at PRI or using their parts. All that being said, we have never failed an Eagle rod or crankshaft on our dyno.

[gtospieg]

R 70 Judge.....I looked for a 4" stroke crank on the Molnar site and did not see one....

[grivera]

Originally Posted by gtospieg

R 70 Judge.....I looked for a 4" stroke crank on the Molnar site and did not see one....

Have you seen this thread?

http://forums.maxperformanceinc.com/...ghlight=Molnar

[Gach]

Originally Posted by mgarblik

Certainly, quality of assembly and careful attention to every detail play a major role in success. From low to moderate power levels, these details play a larger role than material quality IMO. However, many home builders do not have the luxury of precision measuring instruments and may have only a strip of plastigage and hand tools to assemble their short block. Given this common scenario, out of the box, accurate parts become awfully important. Having now installed 48 Molnar rods, I can say with confidence, on a Sunnen AG 300 gauge, all 48 rods measured +- .0001". That will keep you safe in any installation. Eagle connecting rods, we have seen hundreds of them come through the shop at school. It is very rare for a set of 8 Eagle rods to be safe for installation without some rework. The big or small ends generally need some attention. At best, the small ends may need a touch with the hone. At worst, the big ends need to be broken down, dowels removed, rods and caps cut, reassembled and honed. Essentially, rebuilding new connecting rods. In general, Eagle rods are +- .0002-.0003" through a set. Usable, but not perfect. I really like the fact that with Molnar rods, you have that one guy, the owner, Tom Molnar to talk to IF there was ever an issue. With Eagle, I don't have a clue who you would talk to. Their technical support essentially treated me like I was some kind of incompetent moron when I called to ask for a supply of dowels to fix their connecting rods. You just don't get that warm and fuzzy feeling talking to them at PRI or using their parts. All that being said, we have never failed an Eagle rod or crankshaft on our dyno.

Quick question, I see he has his BBC power adder rods listed for $1118.00 but the Pontiac rods for only $750.00 so how much did you pay for you power adder rods. It’s a bit confusing, why are BBC listed for $1118.00 and Pontiac as only $750.00 are they same rod

[TransAm 474]

Originally Posted by Gach

Quick question, I see he has his BBC power adder rods listed for $1118.00 but the Pontiac rods for only $750.00 so how much did you pay for you power adder rods. It’s a bit confusing, why are BBC listed for $1118.00 and Pontiac as only $750.00 are they same rod

Not the same rod, the price difference is because the BBC rod you are looking at is the Power Adder "Plus" rod, they are indeed $1118 direct, that is Toms most extreme duty rod. The Pontiac rod is not the Power Adder Plus rod, so that is why there is a price difference.