I run a 7.100 Molnar also with a similar power range. I do have an experience with Manley rods that I like to tell folks. About 5 years ago I broke a crank at the 1/8 mile mark at MIR. The block split in half, blew the bell housing to pieces but, never broke a rod. They were twisted all to hell but never broke. Good stuff

Just for information. I just broke a K1 rod in my 500 inch 8.71 engine. Big end of the rod was still attached to the crank, the section from about 2 inches up to the pin was lodged between the cam and the lifter galley, which broke two lifter bores out of the block.
Also took out 2 sleeves. One piston and pin were in the oil pan and I don't think there were any pieces bigger than a quarter left.
Car was on it's best pass to date and it let go about 550 ft into the run. The rods had been in the engine for 8 years so I think I found the limit. 1300 + HP.

My replacement engine until I get the block repaired will be my 572 with B1 heads, and 7.1 Oliver rods. Only complaint with the rods are the rod bolts are proprietary to Oliver. NOT Cheap. They are ARP and you can buy them through Summit and Jegs but they are Oliver design.
I'm thinking MGP when blower motor goes back.

Dave

Molnars ARP 2000 bolts are different also and you can NOT buy them directly from ARP
Does MGP make and steel steel rods or aluminum only?

Would be interesting to have the other rods checked for length and to have them x-rayed to see if any others were ready to exit stage left.

I didn't know that about the Molnar rod bolts.

MGP only makes aluminum rods that I'm aware of. I'm going aluminum because I may have reached the limit of a steel rod with a blower. I haven't had an issue with detonation is the reason I used the steel rod.
And, other than Oliver I don't know of any other manufacturer who's rods will handle up to 2000 HP. I'm sure there are some however.
I really haven't researched a steel rod under power adder conditions that much, at the time I got the Oliver's I was running NA.
I don't like the idea of changing out the rods often, but...... Not to mention it's hard to get a intelligent answer on how many runs I can reasonably expect. I'm told 50-1000 by different people


Dave
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[quote=Transman

Would be interesting to have the other rods checked for length and to have them x-rayed to see if any others were ready to exit stage left. [/quote]

Pay shipping and I'll send the leftovers to you cause the rest of them will never see the inside of one of my engines again.
I have no complaints about them really, other than the expense of getting the block repaired.
This is the first time I have ever had a rod break, other than one broke at the wrist pin that was caused by having a rod converted from press fit to floating. (machine shop had over heated them during previous swap)

Dave

Pay shipping and I'll send the leftovers to you cause the rest of them will never see the inside of one of my engines again.
I have no complaints about them really, other than the expense of getting the block repaired.
This is the first time I have ever had a rod break, other than one broke at the wrist pin that was caused by having a rod converted from press fit to floating. (machine shop had over heated them during previous swap)

Dave [/quote]

I wouldn’t use them either. Without exact measurements when they were new, checking them now would obviously be a waste.
As for x-ray, only as a learning tool at this point.

I can hear them hitting the garbage can from here.

What about "I" beam vs. "H" beam?
The tensile strength (pulled apart) is relative to the beam's cross-sectional area in inches. Either one may be heavier there. No, they don't publish that.
However, in nitrous, boosted applications where cylinder pressure greatly exceeds NA, the shape with the most effective use of material is the "H": the sides add bending resistance in compression to the rod's cross-plane axis (90 degrees to the crank, where it is free to pivot). The piston keeps it straight in the crank axis.

What else don't they do?
Run rods on big electric motors to destruction: spin it at high RPM with a piston. Add RPM, weight, then both to establish relationships: "rod X failed at 8,790 RPM with a 560 gram piston, but at 7,120 with a 770 gram piston" etc. I can't think of a way to incorporate the thrust vector (from the rod-to-stroke ratio angle) into this, but some polymath will.
Why not?
1. SEMA will boycott you
2. HRM etc. will link you to terrorism
2. your magazine/web site has 10 rod dealer ads, after the test you'll have 1

Did that rod bearing spin, or the wrist pin seize ?

Large cubes/high rpm, should have aluminum. If your going to run 7500+ . Just my

I’m really leaning to billet also, 7.1 Hussy rods for my 572.. on the street, and they clear everything with a 4.5 crank. I also have K1s but they look to skinny in the beam. Both are 2.20 bottoms and .990 top. Might never see 6500, yea right!
Still need 4.53 Hemi pistons though, hint hint

I have built 632 Chevys with aluminum rods, 4.75 stroke with standard cam height (same crank to cam centerline as a big block Mopar). You need 4/7 swap and sometimes need to add a little extra clearance on the rods depending on the brand. You put a medium zip tie on all the lobes of the cam and mock it up.

"Billet": advertising term, actual meaning "cheaper than a forging".
It's what to do if you only need a small volume.

Bearing still looked good. Pin was in a million pieces. Nothing left of the piston and pin to analyze.

Dave

I only need 8

Some good info for Aluminum Rods..Ignor the magazine but read the article
I would like to have some confidence on when the aluminum rod "must" be changed. I don't normally pull the engine down every season unless I must or I'm changing something.

For instance because I broke at the end of the season and It's going to be mid season before I can get the blower motor back in, I'm going to put my 572 in the car. To run mid 4.60's I hope,
I am replacing the rear gear (3.90-4.30), shorter(Big Bubba to Little Bubba)changing converter from the blower converter. Otherwise the car would have got a new set of tires.

I guess instead of aluminum rods I could just go with a set of killer steel one's.

It's a dilemma..

Dave

What it run with the blower ?

Is this in a lawn dart?

I run GRP rods.

around 300 runs depending on where its at at the end of a season on aluminum. Again just my opinion. Which used to be about 3-4 years/seasons when we used to race every weekend. I guess that could be every year for some.

How often should the steel rod be changed, in those conditions, would be the one I don't have a good answer for. They will need changed at some point also. Might be best to use Scat/Eagle and change those every 300.

Aluminum rods are permanently stretched every time they're run near their limit.
Steel rods recover to some extent, last much longer.

It's not design or quality control, it's metallurgy.

The important thing is the modern designs can be done to not run near their "limit"; so no permanent stretch occurs in applications like bracket racing.