Thread: bearing life

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Thanks Pat, it has been several years since I built a motor and had rods re-sized, so chances are there is more new machinery and methods in use that I don't know about. I've used the same old guy for about the last hunnerd years

so the cross hatch on the rods surve no reel purpose. There just machining marks. Iam guessing you look at the cross hatches in the rods to if the bearing starts to get a liitle loose then it would start to where them out. Right.

Yeah, everything is gonna squirm a little under the pressures that a motor is subjected to, so like Erik said, if the marks are worn away or gone because the shells are grating against the rod and cap, you know the shells have made the "pinch" looser in the rod/cap and it's time to do some R & R.

I've seen an experienced machinist mic a rod bore with the rod laying on the bench and then pick it up and hold it in his hand for a minute, then mic it again and there will be a couple of ten-thousandths difference in the measurements due to expansion just from the heat in his hand. A rod/cap assembly is actually a pretty flimsy piece of equipment. It's amazing that it can take all the punishment it takes and keep on tickin' through millions of cycles.

While we're on the subject of rods, I'll add this....

If you're going to use stock rods, at least buy the best rod bolts that money can buy and tighten them using the "stretch" method with a stretch gauge rather than depending on a pre-determined torque figure........
http://chevyhiperformance.com/techarticles/49258/

Originally posted by techinspector1
Thanks Pat, it has been several years since I built a motor and had rods re-sized, so chances are there is more new machinery and methods in use that I don't know about. I've used the same old guy for about the last hunnerd years

my rod machine was made in 1957 floor model mbb1290 sunnen the rod boring machines have been around for a very long time the rod boring machines were used to cut babbit pored rods to sizes and are still used to day and still made i have see this type of machinery ran by old flat belt s. the rod boring this done on very big rods to like somthing like diesel s rod s and are use on the small end pin end for bushing the pin end

I am not going to run stock rods in the next rebuild. I am looking at a rotateing assemly from speed omotive, ether the 383 or the 395. dont know yet. But an aftermarket rod will stretch and where also right it just takes longer.

the scat I beam are good and if you are driving this every day i wound keep way from bushed pins and go to a press in pin so you do not beat them out. the press pin make the rod stronger. I beam rods are ligther than H beams. i would look at i beam rods and buy a set of srp pistons and keep a way from hypereutectic if you are buzzing this up you want the mass as ligth as you can watch out some of them cheap I beam rods out there are no better then what you had. look for rods made from 4340 steel and ohio crank and competition products is were i would buy from but thats my opinion

Originally posted by techinspector1
Aw, come on Joe, we've got a 3-pager goin' here. With any luck, we could stretch it to 6. Keep postin'.

i think we can get 6 out of this hop on techinspector

Currently, Summit's brand of I-beam rod is actually a Scat rod. It is a decent piece, but is a little heavier than stock at 630 grams. I am using a set of them in my engine. No mallory had to be added to the crank for balance, even with KB hypereutectic pistons which are considered by some to be heavy. I am using bushed rods in a daily driver because they only cost $10 more than the press fit and saved me a lot of money not having to have the machine shop press them. I don't know where the idea of not using bushed rods in low hp street motors came from. Full floating wrist pins are used in most diesels which go many times longer between overhaul than gas, because of their increased durability and reliability. Floating wrist pin arrangements also have more bearing surface area to support the load, so the pressure on the wrist pin is more evenly distributed. I also disagree with a pressed pin making the rod stronger. When a pressed pin is driven in, it expands the small end of the rod a little which creates a tensile force in the steel which adds to the tensile force on the rod during a piston direction change.

Originally posted by pat mccarthy
the scat I beam are good and if you are driving this every i wound keep way from bushed pins and go to a press in pin so you do not beat them out. the press pin make the rod stronger. I beam rods are ligther than H beams. i would look at i beam rods and buy a set of srp pistons and keep a way from hypereutectic if you are buzzing this up you want the mass as ligth as you can watch out some of them cheap I beam rods out there are no better then what you had. look for rods made from 4340 steel and ohio crank and competition products is were i would buy from but thats my opinion

WHAT PAT SAY'S HOLD TRUE FOR ME 100 %.IN OUR SHORT TRACK ENGINE WE TURN TO 7,200 WE HAVE THE I- BEAM RODS WITH THE BETTER CAP SCREWS INSTALLED.WE HAVE RUN BOTH THE SRP PISTONS AND THE WIESCO PRO TRU PISTONS,THEY SEEM VERY SIMILAR.

Originally posted by 76GMC1500
Currently, Summit's brand of I-beam rod is actually a Scat rod. It is a decent piece, but is a little heavier than stock at 630 grams. I am using a set of them in my engine. No mallory had to be added to the crank for balance, even with KB hypereutectic pistons which are considered by some to be heavy. I am using bushed rods in a daily driver because they only cost $10 more than the press fit and saved me a lot of money not having to have the machine shop press them. I don't know where the idea of not using bushed rods in low hp street motors came from. Full floating wrist pins are used in most diesels which go many times longer between overhaul than gas, because of their increased durability and reliability. Floating wrist pin arrangements also have more bearing surface area to support the load, so the pressure on the wrist pin is more evenly distributed. I also disagree with a pressed pin making the rod stronger. When a pressed pin is driven in, it expands the small end of the rod a little which creates a tensile force in the steel which adds to the tensile force on the rod during a piston direction change.

why would you buy a rod from summit if made by scat ?? i can get them cheaper from scat?? press pin are stronger and did you get the pin fitted ? a diesel have bigger pin in them and the rod are made to be stronger. with the press makes aT out of the rod and will and dose make it stronger and a rod that is a floating the rod this weaker on the small end WHY less steel you bored it for a bushing and get back to me at 30.000 miles

yes some shop press the pins in but the right way is with a rod oven and there may be a place for bushed rod but for evey day use i can not see it. a lot of bushed rods need to be fitted to the pin this is done with a sunnen rod hone or somthing like it and hone so it clearanced for the pin to work i have work on race engine where the the pin stop working on the bushing and now you are back to a press pin rod. you are only as good as the bushing how good are they ?? what is the make up will it last is it good bronze ? if it hammer out you need them rebushed and now you have to buy bushing and have them expande in the rods and hone to size this is takes some time to do and $$ i have done it and do not forget you need oil. a low rpm engine you have to make shure it get in them bushing

Is a I beam rod stronger than an H beam. And if they are then why do they make a H beam rod. I was planing on SRP or Wiesco.
I also noticed you can get bearings with groovs on both halfs or one half, and with a whole in them or with out. What do theses do the help.

I beam or H alot people have many veiws on this i have used many of both .steel what the rods is made of has alot to do with how good they are . i beam would take side loading better the hole in the rod bearing is to keep it from moving in alumm rod and i never see a full groovs on rods ? mains yes old hot rod trick more oil helps the rods but hurt the load handing of the bearings i use the 3/4 groovs on mains. rod bearings are cut down or chamfered for larger fillets on the crank

Originally posted by joe bogger
Is a I beam rod stronger than an H beam. And if they are then why do they make a H beam rod. I was planing on SRP or Wiesco.
I also noticed you can get bearings with groovs on both halfs or one half, and with a whole in them or with out. What do theses do the help.

VERY FEW PEOPLE NEED H- BEAM RODS IN A STREET CAR.I.M.O. THE H-BEAM ROD IS A NOT REALLY NEEDED IN A STREET CAR THAT WON'T SPEND MUCH OF IT'S LIFE AT HIGH R.P.M.S.