Connecting Rod Weight Reduction

[jayguy173]

@DrMMHMD oh thats 3000 you can buy a whole engine

what do you recommend for main bearing clearence on todays engines that run 5w-20 oil?

[monstermiataman]

i had this done it so much more revv happey

[c12letmefly]

Is that will feel the difference in engine revving?

[c12letmefly]

how weight you loose with this mod?

[fiatnutz]

@c12letmefly - Around 90 grams.

[scotts439]

John, ever done this mod to domestic V8 stuff? So i guess you would only weaken the rod wherein it would fail on decell, such as when rod bolts fail? Keep em comin. -scott

[fiatnutz]

@scotts439 - I haven't had any rods fail in this area. The LS-7's have similar weight reduction on the Ti rods, only more drastic. Diesels have been using this design for over 5 years, the automotive guys are finally getting it.

[undercoverLsX]

@scotts439

Wondering the same, even for extreme high rpm applications and deceleration, such as autocross, on gen 1 type rods, specifically your standard forged I beam.

[jawed6t4]

good

[jawed6t4]

good hobby

[jrgm3]

How do you replace the small end bushes on a trapezoidal shaped rod? Thx.

[fiatnutz]

@jrgm3 - I have special fixtures for doing some of the rods, others I replace with a cylinnderical bushing, fit the pis, and then shave the sides as needed. Getting them out is the fun part.

[jayguy173]

why not just buy some titanium ones

[madtownmadman]

@jayguy173 'cause they're expensive as hell.

[supershqipa]

Thats pretty interesting. Im surprised at how tiny they are. Though Ill say that they look pretty beefy for a stock rod.

[TeacherPHD]

I noticed your not too far from "Force Country"...ever get any of those engine part orders?

[guytjuh]

what angle did you used?

[fiatnutz]

12 degrees

[jacktheripped]

Then there the rod bearings where the clearance in the top and bottom of the bearing are real close, .001-.002 then the sides of the bearing are relieved to like .010-.015 With tight clearances there's is less room for the bearing to get pounded top and bottom but the relieved sides carry a film of oil.

[jacktheripped]

this is more for max low horse power motors like , let's say, a restricted 350 with a 350 cfm Holley 2bbl 9:1 motor. When you get to a non-claimer class then you end up with cranks weighing 32-34 lbs, Honda journels, flyweight pistons, titanium all over the place to make 425-450 hp

[928s]

I liked the video, some posters make some good points also. I have some Lentz rods, second most popular rod in Nascar, they have some of these features. The thing is that after the milling some smoothing and then shot peening etc. This is critical as you can develop stress risers. The pistons are also normally lighter as such loads are reduced. Use a stronger better material piston pin, that doesn't mean it will be heavier.

[rcjg24]

y would u want to weaken your rods, seems like u could throw them easier

[hybridracers]

I dunno JE, Im kind of sketch about this mod in any applications I can think of. I totally agree and understand that the majority of the pressure is from the downward stroke but to have something spinning massive RPMs Im gonna have to say physics dictated that the weight of a piston increases exponentially just like valve train forces and this mod (at least in my application) could create a massive failure as the small end let loose a piston. I could be wrong. Would love to see rod balancing....

[MostExcellentDude]

"I totally agree and understand that the majority of the pressure is from the downward stroke."

That's absolutely wrong.

The compression stresses on a con rod are nothing in comparison to the tensile loads created during the exhaust stroke.

[hybridracers]

So what part of my reply did you not understand? Small ends of rods dont let pistons fly on compression strokes. I said the same thing you did but I also understand his stance on what is going on. Reading with comprehension is fundamental

[marek0086]

max load is at around TDC on the exhaust/intake stroke.

You couldnt do this mod on a fully-floating pin configuration. It would wear out the small end and wrist-pin too quick. Because theres less bearing-surface-area to spread the load through. I dont like this mod at all.

[marek0086]

No sorry... its between TDC and the Centre stroke on the inlet stroke.

[69FordPickup]

Great Video! Love your work! Can you possibly enlighten me on the subject if this modification can be done to small engine connecting rods? Much like the briggs and stratton 10-12 Vertical Connecting rods?

I like doing alot of small things to make my lawn mower racer done and after seing some of your videos on wieght reduction I am intrested in trying some of this as well....!

Thanks,

69FordPickup

[citydriver]

dosent that reduce alot of strength in the rod?

[fiatnutz]

A lot of the manufacturers are seeing the light of day with this type of mod, Subaru, Nissan, and others are now producing this rod configuration for their street cars (STi and 350Z are ones that I have worked on). The majority of pressure is in the downward movement where the pin bore is the widest to support the wrist pin. What I'm looking for is rapid acceleration in a race engine and these mods help achieve that goal.

Thanx for your comment and question!

[citydriver]

makes sense  the pistons dont get pulled up

[marek0086]

actually they DO!!!

The highest load on a Rod is actually a "Tensile-load"......between the exhaust-stroke (just BTDC).....and the intake-stroke (just ATDC). Most people think that the highest load a Rod endures is the "Compressive-load" on the Power-stroke....buts its not.

Its the Inertial-load......and once u start going above 7000rpm....this load increases EXPONENTIALLY........and it is MASSIVE!!!

Thats why a *high-revving* engine strong rods, even if it makes low Torque/Power.

[34SkiLLz14Luck]

yes i agree with this, very right in many ways however wrong in 1 big way. think of the rod as two parts | <- 1 | <- 2 put them together you get || part 1 see's all of the pushing force and most of the pulling force aswell. part 2 "the part he was grinding away at" doesnt see much force at all. the only force it gets is for a split second and is also lighted from "part 2" the top part of a rod could so to say be aluminum and hold up. but the heat from ignition is an issue. thats why its steel

[marek0086]

maybe u should read what i wrote again!

that top half of the small end (which he's grind away) would see massive loads!

Also by doing this he is reducing the contact suface area the rod has with the top half of the wrist pin.......meaning....the same amount of pressure is being concentrated to a smaller area (more psi on wrist pin) which means there is more STRAIN on wrist pin....which means it will wear out quicker!

[albercarri]

Mate, you are right in what you said, but dont forget that factory engines are designed with a safety factor, and if you have decreased the piston weight, acceleration forces would be less,so you could kind of compensate that problem you mentioned. Off course the wear would increase radically, but when you care about HP and fast response you have to pay the price. It is all about how close you need to get to the limit of mother physic

[dattosam]

I totally agree, and he will gain nothing from removing such a small amount of material from such a critical area other than increase the chances of failure..

[RobDog8]

Agree....im not going to rush out tomorrow and mill off half my rods. lol

[marek0086]

sorry dude i really have no idea what u are trying to say.

[DarkLinkAD]

@fiatnutz Any realworld results? Or is it just to difficult to tell the difference?

[4x4Mudmaster]

yeah good vid but what was your starting weight?

[fiatnutz]

No, you didn't miss it, the rod weighed 430 grams to start. Should've put that in the video somewhere. JE...

[jawed6t4]

@4x4Mudmaster good question

[jawed6t4]

@4x4Mudmaster 

[phobiablack]

Did I just miss it......What was the beginning weight?

[fiatnutz]

No, you didn't miss it, the rod weighed 430 grams to start. Should've put that in the video somewhere. JE...

[phobiablack]

Im current in the process of doing a set for a 302, I dont think Ill go as far as lighten both ends like you do(dont have a lathe or a mill) but even just grinding casting flash off took the lightest to 544grams and the heaviest to 592(starting weigh was fairly high). Even my automotive instructor(at the college of eastern utah) was impressed with how much so little grinding did. Keep the videos coming John, I enjoy them and im sure a fair few others do too