[GTO-relic]

you've may have seen these before.
ILF = internal loading factor= 1+S/2R
confusing, but it means this,
do the addition last:
(stroke / 2x rod length) + 1
so for a 455:
(4.21 / 2 x 6.625) + 1 =
(4.21 / 13.25) + 1 =
.317 + 1 = 1.317 initial loading factor.
lower is better.
longer rod, shorter stroke=higher rpm limit.
shorter rod, longer stroke=lower rpm limit.
M mass is weight, self explanatory, weight of piston/rod assembly
lower weight= higher rpm limit.
rod strength- the best material you can find/afford= higher rpm limit
but also best compromise between weight, length, and strength,
to work the top and bottom of formula, to get a bigger overall number
you want a biggest possible number above the line, smallest possible number below the line, after it's all summed out- to match the rest of the combination,
the cam, heads, carburetion/induction.,

[GTO-relic]

[QUOTE=Dragncar;6590576]What are we doing here ? This is not 1982.
You can not heat treat mild steel into good steel. And even IF you could those rubber rods are spindly in comparison to the cheapest offshore 5140 steel rods.
450 $, check over and be done with it.
Spend 300 $ more and get a Molnar rod which you will not have to put another dime into and will handle more horsepower than any OEM block can handle.

#1 Molnar forging cores are made in China. Since when is that high quality ?
#2 they're getting the living schit tariffed out of them.
#3 when we're at war with them, are you still going to buy that schit ?
#4 not everyone is building what you consider a high dollar engine. not everyone is putting Chinese bottom ends in motors, cores or otherwise, to save money. You have NO CLUE where those rods are made, or what they test on a Rockwell machine. You're slamming them in there and going. Like I said, we just had 2 of them bend/break in the past 2 years. one took out the whole block. since when it that good ? you build what you want, I'll build what I want, and this thread is about early forged rods. so what are we/you doing here ? I'm posting on topic and I wouldn't hesitate to run them, and I ran Pontiac forged rods for 30 year now including 2 sets SD455. Never lost a single one. I never even lost a GM cast rod.
#5 it's a free country I can post what I want within reason. what made you moderator of the thread and controller of the connecting rod market ? I could have sold my spare set of 58-62 rods 10 times already. there's a market for them. it's called patriotism. money will make you do things you don't want to do, like buy Chinese junk. that's the problem with the whole country today. we're building Dollar General Chinese engines with no heritage or pride in them. they're like throwaway toasters.
#6 I talked to Crower yesterday, they said the reason they got out of the rod business is, the Chinese cores are junk, and the billets are too expensive.
#7 If Chinese cores are so good, why all the bad lifters from them that wiped out 1000's of cams, to the point local shops won't even put a flat tappet in a new motor. it's hydraulic roller, solid roller, or NOTHING. and you're in line to buy this stuff ?

[locomotivebreath]

Where would you have a set re hardened ?

[AG]

[QUOTE=GTO-relic;6590601]

Originally Posted by Dragncar

What are we doing here ? This is not 1982.
You can not heat treat mild steel into good steel. And even IF you could those rubber rods are spindly in comparison to the cheapest offshore 5140 steel rods.
450 $, check over and be done with it.
Spend 300 $ more and get a Molnar rod which you will not have to put another dime into and will handle more horsepower than any OEM block can handle.

#1 Molnar forging cores are made in China. Since when is that high quality ?
#2 they're getting the living schit tariffed out of them.
#3 when we're at war with them, are you still going to buy that schit ?
#4 not everyone is building what you consider a high dollar engine. not everyone is putting Chinese bottom ends in motors, cores or otherwise, to save money. You have NO CLUE where those rods are made, or what they test on a Rockwell machine. You're slamming them in there and going. Like I said, we just had 2 of them bend/break in the past 2 years. one took out the whole block. since when it that good ? you build what you want, I'll build what I want, and this thread is about early forged rods. so what are we/you doing here ? I'm posting on topic and I wouldn't hesitate to run them, and I ran Pontiac forged rods for 30 year now including 2 sets SD455. Never lost a single one. I never even lost a GM cast rod.
#5 it's a free country I can post what I want within reason. what made you moderator of the thread and controller of the connecting rod market ? I could have sold my spare set of 58-62 rods 10 times already. there's a market for them. it's called patriotism. money will make you do things you don't want to do, like buy Chinese junk. that's the problem with the whole country today. we're building Dollar General Chinese engines with no heritage or pride in them. they're like throwaway toasters.
#6 I talked to Crower yesterday, they said the reason they got out of the rod business is, the Chinese cores are junk, and the billets are too expensive.
#7 If Chinese cores are so good, why all the bad lifters from them that wiped out 1000's of cams, to the point local shops won't even put a flat tappet in a new motor. it's hydraulic roller, solid roller, or NOTHING. and you're in line to buy this stuff ?

I thought this thread is about cars, but i was mistaken with the politics.

[carbking]

Some 30 years ago, I sent 3 sets to a well-known shop that shall remain anonymous in this thread.

I also sent a crankshaft, flywheel and clutch assembly for balance work.

According to the shop foreman, rods came back at C31 (I got one complete set from 3). They haven't failed yet. But 2 complete sets were destroyed getting one final set.

When I asked about redline, his answer (not going to mention here) elicited a "not with my feet in the car" response from me.

So far, quite happy.

And no, I won't name the shop, as they don't to my knowledge generally do work outside their own; but the shop owner owed me a favor.

Jon

[Dragncar]

[QUOTE=GTO-relic;6590601]

Originally Posted by Dragncar

What are we doing here ? This is not 1982.
You can not heat treat mild steel into good steel. And even IF you could those rubber rods are spindly in comparison to the cheapest offshore 5140 steel rods.
450 $, check over and be done with it.
Spend 300 $ more and get a Molnar rod which you will not have to put another dime into and will handle more horsepower than any OEM block can handle.

#1 Molnar forging cores are made in China. Since when is that high quality ?
#2 they're getting the living schit tariffed out of them.
#3 when we're at war with them, are you still going to buy that schit ?
#4 not everyone is building what you consider a high dollar engine. not everyone is putting Chinese bottom ends in motors, cores or otherwise, to save money. You have NO CLUE where those rods are made, or what they test on a Rockwell machine. You're slamming them in there and going. Like I said, we just had 2 of them bend/break in the past 2 years. one took out the whole block. since when it that good ? you build what you want, I'll build what I want, and this thread is about early forged rods. so what are we/you doing here ? I'm posting on topic and I wouldn't hesitate to run them, and I ran Pontiac forged rods for 30 year now including 2 sets SD455. Never lost a single one. I never even lost a GM cast rod.
#5 it's a free country I can post what I want within reason. what made you moderator of the thread and controller of the connecting rod market ? I could have sold my spare set of 58-62 rods 10 times already. there's a market for them. it's called patriotism. money will make you do things you don't want to do, like buy Chinese junk. that's the problem with the whole country today. we're building Dollar General Chinese engines with no heritage or pride in them. they're like throwaway toasters.
#6 I talked to Crower yesterday, they said the reason they got out of the rod business is, the Chinese cores are junk, and the billets are too expensive.
#7 If Chinese cores are so good, why all the bad lifters from them that wiped out 1000's of cams, to the point local shops won't even put a flat tappet in a new motor. it's hydraulic roller, solid roller, or NOTHING. and you're in line to buy this stuff ?

A few things, Molnar rods are made in China and finished here. Their steel cost more because it get quality checked more often than a Eagle/Scat and they are engineered better. Molars have been in 3000HP engines. If any Molnar rod/crank comes in out of spec Tom will send you a call tag on his dime and swap it out. Very, very rare thing. Myself, I do not know of any Molnar rod breaking where it just gave out. Oiling issues or the pin ripped out of the piston.
They are the best rod for the money on planet earth IMO. The power they can take compares with Carrillo/Callies and Crower. Probably a better rod than Olivers. A 850$ rod can swing with the 2500$ rod.
Crowers, now I have had Crowers and still have some 6.8 billets. I need 2 because 2 I have are heavier than the 6. Crower tech told me the reason is that Covid ruined that deal. The people with the expertise to make them retired or did not come back.
Also, I bet it is in fact hard to compete with a 900-1200$ rod handling as much power as a 2000$+ rod. I am USA all the way if I can afford it.
What are you going to do if you want a USA made Pontiac crank? They do not exist unless they are billet and you will spend 4K.
Its not like I have not tried and spent a lot of money on USA forged rods. I have had early SD rods, Crower Sportsman, Crower Billets, SD 455 rods. I sold my 455 SD rods because i did not want to risk my HO block. Some 299$ Cats were stronger as much as I hate to admit it so I ran them. I bought a 62 389 for the rods out of a 62 Cat, should have bought the whole car. It was all there, no dents or rust !
But the more I learned about the rubber rods, I traded them for a 71 400 block that might need a sleeve and I am glad I did. At least I have something worthwhile I can use someday if i choose.
But hey, maybe I am weird but if I had a numbers matching SD 455 I would have some press fit Molnars in there and sleep a lot better.
They really are a whole different deal than Eagle/Scat ect.
I am a millwright/welder /fabricator/electrician by trade and have heated and quenched a lot of steel in my time for different reasons. Experimented with different steels, heat ranges and quenching in water and oil. And the one thing I have learned is you can't take mild steel and make it any harder on the inside. You poor man heat treat some 4340, AR plate of even a grade 8 bolt and it gets very hard. But the hotter it is when you quench it the more brittle it is. I have learned when making a chisel or punch do not let it get real hot, little bit of dull red is fine. The steel is much tougher if you don't. But quench it bright orange and you might have a piece of chisel flying off when you use it.
Buy hey my fine Pontiac friend, if someone want to use those rods its a free country.
And no one is more sick about our industry moving to China than myself. Its a crime and I think people should be in prison for it. As in treason.
But I still want to race at a level I can afford too.

[mgarblik]

My 2 cents about Pontiac connecting rods. The rods in question, 58-62 "rubber rods"? I honestly had never heard this term before joining the forums. So I have run these rods in numerous engines, street cars to mild race cars, 389-462 Cu in. I never had a connecting rod failure or a spun bearing. But I did prepare the rods. I balanced the set +- 2 grams. I shot peened them. I replaced the hardware with ARP bolts. I held the big ends +-.0001 for size, taper and roundness. Small ends the same with .001-..0013" press. I also did not run them at excessive RPM's and they were run at stock stroke. Small journal engines 6200 RPM max. Large journal 5800 RPM. HP not exceeding 450 or so. I feel comfortable with that.
As the years have passed and I have learned more about connecting rods, I would be comfortable running stock cast Pontiac rods about the same way. Even though the forged rods look nicer visually and we generally consider forged parts better than cast. The cast "armasteel" rods are pretty strong.

Chinese aftermarket rods: The Molnar rods are by far, the best of the Chinese stuff IMO. I am not a metallurgist, but the machining of Molnar rods are as close to perfect as I have ever seen, period. Eagle and white box no name rods usually need some machining and correction to be safe to use in ANY engine. Not every rod, but it is still rare to find a set of 8 all within specs. Scat Brand is somewhat better than Eagle, not perfect.

[Jay S]

I think connecting rod metallurgy and design is a fun topic. The different connecting rod treatments and ideas on how mfg tried to make them beefier are at very least entertaining.

The old Pontiac rubber rods still hold my record for most rods thrown off a crank (3) at one time and the engine still ran and drove on a trailer. That engine went a season and a half in a 450 to 500 HP dirt track 455 often turning 6000. The weekend before it broke the track was fast and the car ran out of gear and was turning over 6500 at the end of the straight away in a 25 Lap A feature. So it isn’t like those old rods didn’t hold up to any abuse. I don’t know what went first, the rods or maybe it lost a bearing first. I have found if a rod bearing is lost at high RPMs a rod can get thrown out the side of an engine no matter what connecting rod is in the engine. I have yet to see a modern rod that was rebuildable after much of an issue with a rod bearing. I think it is quite amazing how fragile they appear to be when exposed to heat.

Molnar claims rods (I agree they are some of the best steel rods on the market) normally fail under deceleration, not load. He claims because of the way connecting rods fail, HP ratings companies put on connecting rods are at very least misleading. You can have a rod that is good for 2000HP and still throw the rod threw the side of your 600 HP engine. H beam rods are suppose to be stronger under deceleration than I beams and also create less windage. Those 2 things alone we can’t achieve with an old OEM rods.

On an old school 1971 454 LS7 Chevy build I did a while back, and thought I was being kind of nostalgic keeping the OEM rods. It had rare (dimple) rods with 7/16” bolts and a free floating pin that floats on the rods with no bushing. I had about a $1000 in those suckers after they were finished. The shop had to ream out the small end of the rod for bushings because the pins were to loose. Those rods were so hard he went through 4 reamers installing bushings. I doubt those rods are much stronger than any run of the mill BBC rod, but it was at least a little nostalgic, and at very least pretty entertaining talking to my friend trying to machine them, he had never ran across a connecting rod that was that difficult to machine.

[Jay S]

Originally Posted by carbking

Some 30 years ago, I sent 3 sets to a well-known shop that shall remain anonymous in this thread.

I also sent a crankshaft, flywheel and clutch assembly for balance work.

According to the shop foreman, rods came back at C31 (I got one complete set from 3). They haven't failed yet. But 2 complete sets were destroyed getting one final set.

When I asked about redline, his answer (not going to mention here) elicited a "not with my feet in the car" response from me.

So far, quite happy.

And no, I won't name the shop, as they don't to my knowledge generally do work outside their own; but the shop owner owed me a favor.

Jon

Hi Jon, was the issue that required 3 sets of connecting rods to find the correct procedures or treatment process, or was it from finding 2 extra sets of parts that were inferior and did not work?

[steve25]

Well we are always using the term RPM in this discussion so I have always thought we need to ask this.

Factory 58 to 62 production forged rods.

We rework them get them a tad stronger and let’s say run them in a 1/4 mile motor that runs 11 flat and see’s 6200 rpm at the shift points.
And we are not even looking at average numbers .

Now the motor has not spun around for 60 seconds, in terms of that 11 flat pass, so how many revolutions has it really turned ?

Hint, the number is pretty low!

[Skip Fix]

Barney Moravitz in San Antonio used to race Pontiacs in Stock and or SS. He had a company that did oil well tools that hardened them for his machine shop. I think he was even the source for Butler for those way back before we had decent Pontiac forged rods other than Carillo or Crowers. He was older than me so not sure he is still around. I got a set I sent to him. Had them treated(even billed me vs paying up front!) He also had the lighter piston pins that Butler had that fit stock rods/pistons-but they were about 0.001 larger.

[Shiny]

Originally Posted by Jay S

I think connecting rod metallurgy and design is a fun topic. The different connecting rod treatments and ideas on how mfg tried to make them beefier are at very least entertaining....

Me too. I am a metallurgist, at least I was 49 years ago.

I have zero experience with auto parts, let alone connecting rods, so I can't add anything specific to the topic. I do have a few decades of experience guiding materials, process, and design of parts for new products.

I expect a rod to fail in fatigue, not by one-shot overstress. Comparing the fatigue life of two designs is a lot more complicated than just comparing alloy and temper. The entire manufacturing history, metal quality, part geometry, finishing, etc. can influence fatigue life. When you add in variations in stress that happen in a product, it gets to be boggling.

That means fatigue failure of a part is difficult to predict and therefore, a PITA to manage during product development. Basically, to get any confidence requires making a lot of assumptions about use profiles, arguing about goals, testing a lot of parts to failure, building statistical models, then hoping what you tested is close to what you ship. And if you're lucky, they don't make big design or sourcing changes the week before they ship the product.

In general for fatigue, the variation in cycles to fail is huge... meaning one part that is as close to all others as you can make it might fail at 1 million cycles and the next one at 10 million.

So it's all statistics and margin... basically, you overdesign the part by a BIG margin so the weak ones exceed your goals.

I don't know how Pontiac did all this but it would be a lot of fun to know! I enjoy reading about the materials and processes they used so thanks for sharing some of that.

[tom s]

For a street only engine up too 4in stroke I would run a set of 69-70 cast rods before any of the 58-62 forged rods.JMHO,Tom

[Joe-Touring]

Originally Posted by tom s

For a street only engine up too 4in stroke I would run a set of 69-70 cast rods before any of the 58-62 forged rods.JMHO,Tom

Hmm interesting. Why those years and not say, 67 or 71-74?

[Sirrotica]

Originally Posted by tom s

For a street only engine up too 4in stroke I would run a set of 69-70 cast rods before any of the 58-62 forged rods.JMHO,Tom

I have to agree here, 3 seasons in a 428 dirt track engine with just resizing and good rod bolts, 5500-6000 RPM each and every lap.

I was going to build a new engine the next season, 455 with dished pistons and RA IV ported heads, I had a new set of SD rods purchased for that one. Life intervened, and the engine is still sitting not yet assembled 45 years later............
The 455 I have would have been the first engine of many I have assembled that didn't have cast rods in it.

In my experience the rod bearings spin first, then the rods break. Usually due to running factory clearances which are to tight for sustained high RPM. The reason RA IV engines had special rod bearings with an additional .001 clearance and still ran the same cast crank and rods the passenger car engines used. The additional clearance makes a big difference in longevity at higher RPM.

Back in the day most Pontiac build articles stressed blueprinting the bottom end of Pontiacs, for good reason too.

[Sirrotica]

LATE STYLE ROD



EARLY STYLE ROD



I always look for the extra stiffening rib at the bottom of the I beam big end when selecting cast rods. I feel that they added that rib when they came out with round port heads, and the red lines were raised. Not sure if 67 rods had it, or not.............

I believe it came in all standard deck engines until they quit building them 78/79.

[tom s]

I just did not want to remember from what year to what year those rods were used!I knew I was safe at 69-70.tom

[steve25]

I think it was 68 1/2 with the RA2 round port 400s.

If you look close at the two rods you will see that on the late rod the outer I beam section is thicker and it’ ends square and not rounded .

A smidge more weight, but worth it for strength.

Federal Mogul up into the early 90s use to sell reconditioned forged rods as seen here.

[sdbob]

Interesting about Federal Mogul didnt know that. I have 16 rubber rods I spent rainy Saturdays taking out of early 60s Pontiac engines in the late 60s. I had a 65 421 I rebuilt about 1970. Resized the rods, cast pistons,valve job. Ran that engine approximately 6 yrs. Took it to 5800 many times. When I pulled it apart to use the block. I noticed for the first time, the engine had 7 of the wide flange rods and 1 cast rod.The engine when I bought it out of a wrecked 2+2 seemed original, it had about 60 k when I bought
it. I still have those rods and pistons in a box

[GTO-relic]

Originally Posted by sdbob

Interesting about Federal Mogul didnt know that. I have 16 rubber rods I spent rainy Saturdays taking out of early 60s Pontiac engines in the late 60s. I had a 65 421 I rebuilt about 1970. Resized the rods, cast pistons,valve job. Ran that engine approximately 6 yrs. Took it to 5800 many times. When I pulled it apart to use the block. I noticed for the first time, the engine had 7 of the wide flange rods and 1 cast rod.The engine when I bought it out of a wrecked 2+2 seemed original, it had about 60 k when I bought
it. I still have those rods and pistons in a box

it's all in the heat treat. requires the skills or tutelage of an educated metallurgist. they cut the parts up, polish them, look at the grain structure under a microscope. then adjust/modify the heat treat process to get the grain structure needed for the strength required. so you take a little piece of the cut up rod, heat treat it in a small oven the size of a microwave, and then hardness test, polish/grain size cert it WITH PICTURES of the grain size. the camera is built into the microscope. until it's right. then you stick to that formula for the big run of parts, where the oven is loaded with a fork lift, with a big overhead garage door, and the quench tank is as big as a swimming pool. it's a whole different ball game. I did it for years in jet aircraft engine production of parts. the cutting, polishing, heat treat, loading/unloading the big oven, in the lab and out in the shop.
those rods you used were simply forged and not heat treated to save cost. on the early short stroke Pontiac engines 1955-58 they'd survive. they were marginal for a 389 w/3.75" stroke. they were too weak for a 421 with 4" stroke. that's why the SD421 went to it's own heat treated forged rod and won Daytona with it a few times. the 421 HO rod was a cheaper non-heat treated part to save money on street cars and blew up in their face. then they came out with cast rods across the board that were strong enough under 6000 rpm for the strokes used...but barely for the 428/455.
the reason Pontiac went to a cast rod, is they could made a stronger cast part in huge quantities, that was much cheaper to make than a non-heat treated forged part, and much cheaper than a heat treated forged part.
it was common approach back in the 1970's if you built an engine using factory GM, Ford, Mopar, AMC rods, to hardness test the rod top/bottom/center, and discard any rods that tested soft, and use the 8 best ones out of what you had or could get. we should all still be doing it NOW, no matter what forged rods are used.
the problem is, if you're buying CHINESE rods, you're trusting THEM on another continent, to do all the above competently, in your best interests. good luck there. that is a risky proposition. Chinese basically hate Americans and are an inch away from going to war with us in the South China Sea right now. are they checking every single rod for correct hardness on a Rockwell tester ? lol !!
#2, Pontiacs are all about the nostalgia now, let's face it technology has advanced, there's new engines out now make Pontiac V8 seem like a Model T. If we're always pushing the latest greatest, watch what you as for, cuz the then the electric car makes the gasoline V8 totally obsolete, and you have no Pontiacs at all.
if the HOBBY becomes drag meets and car shows with rows of cars with Speedmaster Chinese engines carb to oil pan, and Chinese sheetmetal, then it's all over but for the cryin'.... it becomes the silver dime, quarter, half dollar, dollar that no longer had any silver in it after 1964- totally irrelevant.
I'd put more confidence in what I can make and get done here myself, than what someone in China can make for me. The dollar store approach to engine building is not my cup of tea.