Well, I don't know if anyone really follows these, but I've been trying to write "How To" stuff while I work on my car and build the slant. Well, the latest project was argueing with the old man about keeping the six since it's sluggish at the high end, however, the challenge keeps me coming back. So a while back I learned how to build 302's with an engine builder and he taught me a few tricks. The rest I've had to read and try on my own, and with all the talk of custom rods I thought I might run a set through for those who only need street rods and aren't trying to run 10 secs or less.
The Slant Six rod is forged and has proven to stand up to the abuse of hot rodders before me. So in prep for my next turbo beast I decided to start with rod polishing. This is relatively simple, but some basics need to be understood. The way I was taught you needed to shave the metal going with the grain which is working your way up the rod. Well, not quite sure how to do this learned to compromise. To start with use the roughest stone you have with a die grinder, I have a couple left over Port and Polish kits which works great for this. Work the rod in a diagonol sense keeping the stone moving to avoid digging. This is simply to take the flashing off the sides which are stress risers, you do not need to reshape the rod. Next move to a finer grit and so on. The next important reminder is to keep moving and rotate rods. Not only does this save time changing tool heads, but keeps the rods temp down. so I guess the pictures should explain the rest.



So the last image was kinda the stages I cut in. The top was the roughest and you see sploches were I didn't even touch the metal really. However, with steel you shouldn't spend days getting the polish down so make sure to use the grit for the job (does that make sense?). Next will be balancing the rods with a little gadget.

Nice looking work; I have couple questions though. First, hard to tell from the picture but the edges of the beam look a little sharp to me; did you do any radiusing there at all or does it even matter? Second, do you have plans to shot peen after you're finished grinding?

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

The edges are neither radius or sharp there kind of a taper into the "old" metal. The main focus is the edges where the oil would come down though I'm sure the beam area could benefit, it would be pretty infintisemal and kinda a waste of time. One major concern is you can do more harm than good...so take your time and work fluently. Don't spend days like I said, but don't rush it with the rough stone and have to polish out digs later.
I've read a couple things about finishing the rods, including: pingin, heat treatment, and cyro. Being an engineering student I'm kinda of having fun relating the stress and finding what would work best at least to my knowledge. Any opinion are welcomed, but for the most part I would like to do a heat treatment of heating to red hot followed by quench. This will harden the steel, but make it brittle. So there will be another session where I will "soften" just a little by heating it and letting it cool naturally, this of course won't have such high temps.
Another other rod prep ideas??? All opinions are welcomed.

not to mention that polishing them con rods is good for stress relief. I have polished a set of 198 rods that was going to be in a hot build but they went away. I polished everything including the caps. I used a tungsten carbide rotary file and hours of patience. Tungsten carbide has the downside of making extremely long and sharp shaves (like mini splinters of steel) that you may guess correctly, end up in your flesh. Plus those burrs don't produce as much heat as stone and then flappers. Gonna dig out pictures, hopefully I'll have some.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

The pictures and explanation are great! That is what my rods look like in my new engine. Pistons, rods and crank were balanced on the scale and then done dynamically.

Imagine this......., when I was going to college, for fun on the weekends we used to race winged sprint cars at two different dirt tracks. We would take the engine rods and grind/file and sand them flat (no I-beam, we left the web alone) and made knife edges then shot peen them with heavy shot then a lighter shot media, then an ultra sonic inspect. They looked very odd, you wouldn't think there was enough meat left to keep the piston from coming off or keep the rod from stretching. This was done to lighten them and reduce the friction from the oil spray. My Power Mechanics professor suggested we try it for a season in our race car.

We would take two weeks to break in the engines (another one of my professors ideas). We would run the motor 5 minutes the first time then let it cool for a day. The next day we would run it another minute longer, let it cool, etc... till we got to 15 minutes. Engine rpms during break-in never went below 2000 rpm. Then we were ready for the track. We ran 38" primaries and a 18" x 2.5" collectors which acted like a rev limiter. After a season of over revving night after night in the slick clay and then in the dry dusty conditions we would retire the engines out of respect. We did this three years straight winning race after race becoming track champions.

The polishing and balancing is a good thing to do, however you can go allot farther than you would think with the reduction of material as long as you shot peen them to put the strength back in. By building the engine loose (bore a few thou over) so when your running at 250 or 260 degrees the pistons won't seize, it reduces the strain on the rods. Allot of guys would seize and put a rod through the block when they got hot, especially on new motors. This is where I learned the importance of synthetic oils. We used synthetics after break-in instead of Lucas Oil treatment or STP which everyone else used, (another one of my professors ideas).

We never broke or seized an engine during our three years racing. I am not sure how our modified rods would have worked in a drag racing engine. Maybe Doc or others have tried this..........

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

For high HP / high RPM drag strip motors, I like to keep the con rods as strong as possible. I go so far as selecting rods that have a big, standing parting lines that add extra material to the beam of the rod.



I deburr and grind-off any rolled-over metal or nicks along the top of this extra rib but try to leave as much as possible so it can work as an extra gusset.



I do most of my grinding and smoothing along the edges of the beams, rounding and polishing them so oil mist can slip over the sides as the rod flings around. I do not spend a bunch of time getting everything "mirror smooth", just work the edges and knock-down any sharp corners around the cap / bolts and that's it.
DD

That's interesting Doug... kinda cool to get another idea in here. The major problem with keeping those ridges is they are stress risers for the rods. However, I suppose if you rounded them it would reduce it dramatically cause it doesn't have a point to send the force to.
What about polishing it to reduce windage? Have you ever heard / considered?

The ridges themselves are not stress risers. Nicks, sharp inside transitions, et cetera would raise the stress and invite cracks, and it sounds like Doug is removing those.
For any inside corners, we want large radii. Removing some metal to increase the effective radius helps. Outside corners are not as critical.
Deburring the ouside is nice for handling in the shop, and for the fluid dynamics inside the engine.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Some good points and ideas. I like A.T.'s comments about thinning the con rod beams and not breaking rods, I need to try that. I wonder how much weight could come off of the rods before they snap?

So for another "out of the box" idea, I want to try a cast crank long rod engine. Saving 15 lbs on the crank and another few lbs off thin con rod beams and light 2.2 pistons has got to help the engine spin-up. I just can't bring myself to milling down a set of 198 rods for that project. (cast cranks use a thinner con rod "big end" and bearings)
A fun project to think about...
DD

Weight vrs strenth is a funny thing. In the big blocks we had better luck with the ole LY rods instead of using the heavier duty six pack rods. In 30 years I have never broke a factory Mopar rod though. We always took them to the piont Doc is describing and I have never polished them like shown above. I think Mopar has some of the best factory rods out there in the old american iron stuff.


I have seen many guy do this though (polishes the beams), and even a few to the piont AT is talking about. They had good luck with durability also. I found over the years that the tune up (the main thing), and the piston weight had more influance on durability than anything else we did (out side of good machine and assy practices). But weight reduction was always a horsepower maker. Controlling windage is know to make HP also, some guys will only run H beam rods because of it. A polished surface should make oil shed much easier (but then again remeber the golf ball,dimbles make it go through the air better), the one thing I always questioned was its effect on cooling. Not saying its good or bad, but that I always wandered its effect on such things as rods and crank weights that where polished/unpolished.



BTW, nice looking rods Runvs_826.



Jess

Amen, and preach on brother!

The sixpack rods are a case of a solution to a problem that wasn't really a problem. The LY rods, as you say, never failed from being too weak. The sixpack rods are without a doubt *stronger* overall than the LYs, but the whole engine package suffers with them because they add enough weight to the whole assembly that they actually increase stress on other parts such as the rod bearings, the crank itself, and most importantly the conrod bolts.


If I ever built an RB-block engine that I intended to use with enormous cylinder pressures at low RPM, then the sixpack rods might make sense. Where that concept starts conflicting with the real world is that without a more advanced combustion chamber than any factory RB engine ever had, you're going to hit detonation before you hurt LY rods from cylinder pressure... except maybe in a heavily forced induction setup. I remember having a conversatioin along these lines with "Feets" from Fort Worth (of twin-turbo 440 notoriety) but he was pretty much using stock junkyard bottom-ends, and never had any trouble either. The bottom end of any B or RB engine is just about bulletproof, like the slant-6 (imagine that! )

So maybe if anyone ever builds a diesel 440, then we'll actually have a bona-fide need for sixpack rods...


By the way, there's another example I can think of where Ma Mopar added strength that ultimately doesn't help much: the fact that the main bearings in the RB engines are bigger than in the B engines. Yes, it lets the mains live a little longer for a given loading, but both B and RB engines wear the conrod bearings to the copper before the mains, so the point is moot. And when people started building 400 blocks stroked with 440 cranks, there was a debate over whether it was better to turn the crank down to 400 main bearing size, or line-bore the block out to 440 bearing size. The answer (last I read...) was that the overall package is stronger if you turn the crank down. The block webs benefit more from the extra meat allowed by the smaller bearings than the crank benefits from larger cross-section main bearing journals.

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about 20 years ago, in my tech school, I destroyed my share of slant six con rods (225) in material testing, stress, etc. Removing the ridge actually adds strenght. Fully polished and deburred rods would stand more pressure, traction and any mechanical force than a stocker unit. I don't have the figures in hand and I don't think I can find my highschool notebooks now, but I tested that. I polished a set of 198 rods and those are going inside a 90mm bore 225 stock stroke motor with 11,25:1 Static CR. I also selected a custom pin (for making a custom float pin setup without having to enlarge the small end of the rod too much). This project goes slow (friend's car) but I'll post results. I gotta find some pictures of my fully polished rods....

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Ummmm, guys.....if you're worried about lighteneing rods as to strength, you might want to consider something like this...... http://www.cryopro.com/

I hear it's some damn good magic.

Roger

didn't find the finished pictures but this of one in progress.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Not to be a downer to Argetina-Slantsixer, but the way I was taught it was a waste of time to polish anything but the sides like I had done. However, you had done some actual testing have you learned something to the conturary?
I was discussing this with a friend who drives a 350 '69 Camaro SS, who wants me to quit playing around and put the 340 in so we can end the great debate about which is better. That beside, we talk a lot about engines and he thought this was a waste of time and I should get some H-beams, I said, "From where?" (exclusion of K1's project).
We began to talk about the "old" hot rodder tricks and that is what I have to fall back on as a college student. However, if anyone has any others please shoot me a pm or we could make another thread cause I'm very interested. My next quest will be the crank and lightening it / knifing.