[mgarblik]

I am using Molnar connecting rods for the first time in a personal build. We have used a few sets in student's engines, (non Pontiacs), and have had no issues. In my own application, I wanted to explore the fastener technology specifically, and the true dimensional accuracy they claim. All measurements were taken with Sunnen dial bore gauges, Sunnen connecting rod specific gauge, AG 300, and Starret micrometers with .0001 resolution. As delivered, the big ends measure better than +- .0001 for size and .0001 max taper and zero out of round. Small ends, I have not checked yet. The interesting thing about Molnar rods is they do not have a torque spec. for the fasteners. They use only bolt stretch or torque + angle. I used both methods and then measured the housings with bearings to see what effect either method might have. Also, my electronic torque wrench will read maximum torque at a given angle. It is important to use the recommended lubricant, which they include and lube the underhead especially because they don't use washers as well as the threads. Results were as follows: These are ARP 2000 fasteners, 7/16" and 1.6" underhead length. Stretch specs are .006"-,.0064" Using the pre-load of 30 Ft. lbs. plus 60 degrees. The bolts all stretched .006-.0065" Very consistent and within specs. This might scare some, and one of the reasons for the post. The torque value varied quite a bit, from 78.3 ft. lbs to 86.1 ft. lbs. Yet the bolt stretch, the real indicator of clamp load, was very consistent. This points to the friction factor and why a torque wrench alone on critical fasteners isn't a great idea. Also the actual torque value may scare some for a rod bolt. Also, after installing the King bearings and measuring the big ends for oil clearance, they were all within +- .0001. Overall, very impressed with the process and accuracy of these rods. IMO, they are a huge step ahead of the typical Chinese made aftermarket connecting rods. Cost a bit more and machining is done here in the states. They will be put to the test in this engine with a 4.25" stroke and an anticipated 7200 RPM red line. Has anyone else had similar or different results with Molnar connecting rods?

[cgeise]

I have some ordered for a hot street build ----If I could ever get them Ill let you know.

[PAUL K]

Mike you are seeing what we typically see. Great products from Tom Molnar.

[PAUL K]

Originally Posted by cgeise

I have some ordered for a hot street build ----If I could ever get them Ill let you know.

We have 6.80 power adder and non-power adder in stock. If that helps. Been out of the 6.625 Pontiac rods for a while.

[Dragncar]

I have 2 sets, both 6.8, one Power Adder. My buddy has a set in a Ford 351W build with AFR heads, he used the stretch only method. He ended up with almost 100ft lbs of tq to get the required stretch.
So he advised me to do the tq+ angle method.
I do not have the 500$ Snap On wrench that gives the angle. So I bought one of the cheap plastic ones from the parts house. Do not use those. In examining it I found the little plastic disc can "slip" and give a false reading and you can end up turning more than actual angle. You do not want that.
Lisle makes a simple all steel one that can not slip so that is the one I used. You just can not index the pointer wherever you want when you start out.
Note, its a bit of a process doing all of it. Mark every bolt that you complete right after you remove the socket with a paint pen- marker. If you get distracted, phone rings or whatever you need to make sure to start back up on the right bolt. Having a second person with you helps. Can not be too careful.

Talking to Tom about his products is a good experience, very knowledgeable. He sells a rod over the Power Adder for big time builds. He priced them at around 1000$ simply because people associated less expensive with inferior. He could have sold them for less as they did not cost much more to make. But sells more because the price is a little more.
I asked him about making some fully counter weighted Pontiac cranks like he does for BBCs. But for the money he would have to put out and the 10 years it would take to sell them it did not work.

[Bill Eveland]

I have a set in my 455, the only issue I had was finding replacement packets of their rod bolt grease. Its not as readily available as ARP lube is

[Bill Eveland]

If anyone else needs some, here is whats used

https://www.speedwaymotors.com/Dart-...xoC1sAQAvD_BwE

[455Grandville]

+/-.0001 is pretty impressive

[mgarblik]

Originally Posted by Bill Eveland

I have a set in my 455, the only issue I had was finding replacement packets of their rod bolt grease. Its not as readily available as ARP lube is

Extreme pressure grease #3 is available at Summit racing and Jegs. Also some industrial supply houses like McMaster Carr and MSC. This will be in larger yellow and green tubes. One of those tubes would last a lifetime. Jesel uses that grease almost exclusively. Good stuff. Great for rocker arms and push rod ends.

[69Goat1]

What kind of HP can these rods take?

[Dragncar]

Their basic rod has been to over 1000 HP. Their Power Adder Plus is intended for 2000+ HP engines.
I have a cross section pic vs a Eagle, night and day. Ed from Molnar sent it to me.
I will see if I can dig it up.

[mgarblik]

Checked the small ends of the same connecting rods this evening. All 8 small ends .001" clearance. Possibly a couple had .0001" variation in a spot or two. That could have just as easily been my gauging error. Zero taper, zero out of round. They are really nice. As far as Eagle is concerned, we use quite a few in my classes as well as Scat and some no-name E-bay rods the students find. The students are responsible for their own parts purchases. The instructors help them make informed decisions. It is pretty much the quality projection you would expect, you get what you pay for. The no-name E-bay stuff, you have to count on breaking them down, cutting the caps and rods and re-honing them before use. Sometimes you have to buy a set of +.005 pins to fix the small ends. Eagle and Scat, all seem to be within factory tolerance now, which is roughly +-.0005. That is not nearly close enough for any build I want my name on or our school's reputation. So we repair as necessary to get +-.0001. Molnar is a cut above those IMO now after really checking these out. Crower, Manley, Carillo, Oliver may be better yet, at a more premium price. But from static measurements, the Molnar rods are almost perfect.

[Jack Gifford]

Once again, thanks to Mike for sharing.

[Dragncar]

Molnar on left, I beam in middle, Eagle on right.

Notice how the Molnar rods beams are more narrow and thicker. Right under the load. Tom described steel rod failures like this. I beams split downward from the pin, like firewood.
Eagles/Scat rods have thin H beams. They go wavy right under the pin and are done.
Last time I talked to Ed they still had not gotten back any blown up engines to inspect with the rod ripped in half with piston still attached.
The pin was ripped out of the piston in all cases. Rod still intact. Might be bent but the piston failed first bending the rod.
They had a 3000HP dragster with their rods and crank and doing well.

[Elarson]

Originally Posted by Jack Gifford

Once again, thanks to Mike for sharing.

I feel pretty confidant in saying that we couldn't have broken the Pontiac 250 mph barrier without Mike's attention to detail.

And back to the topic....I have a set of Molnar power adder rods on hand for the buildup of my aluminum road race engine. They were very reasonably priced (from Butler) and I wanted zero worries about durability.

Eric

[mgarblik]

Originally Posted by Dragncar

Molnar on left, I beam in middle, Eagle on right.

Notice how the Molnar rods beams are more narrow and thicker. Right under the load. Tom described steel rod failures like this. I beams split downward from the pin, like firewood.
Eagles/Scat rods have thin H beams. They go wavy right under the pin and are done.
Last time I talked to Ed they still had not gotten back any blown up engines to inspect with the rod ripped in half with piston still attached.
The pin was ripped out of the piston in all cases. Rod still intact. Might be bent but the piston failed first bending the rod.
They had a 3000HP dragster with their rods and crank and doing well.

Thanks for that picture, Interesting to study. I like the smooth transition of the Molnar small end from the beam to the pin end and pin bore. No 90 degree junctions like the Eagle stuff. The Molnar rod looks a little heavier if that is a concern. It wouldn't be for me at the RPM's we run. Until we raced a nitro engine, I never realized the real force applied to the small end and pin. I knew it was high, but no graphic examples. When we bent all 8 BME wrist pins, tool steel, H11, 1.094, thick taper wall, you know there is some serious compressive force being applied.