what rods would be better for my build

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70Swinger

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hello, what rods should I go with for my 318, balanced rods that came out of a 73 340, or go with stock 73 rods no idea wut they came out of, I can email you pictures if you need them.

thnx adam
 
The 340 rods may be a little stronger, but they wilol be a little heavier too. This may mean balancing may be a little more. If it were my build, I'd use the factory 318 rod, with good bolts. What pistons are you using? the 340 rods will be bushed for full floating piston pins, while the 318s will be for pressed pin. It costs extra to bush the 318 rod for full floaters, but full floaters are not required in a lot of builds.
 
im going with the 318 build up, that was in the mopar muscle magazine, cuz they use later 318/360 heavy-duty rods, but these rods are pressed pin. i was going to go with keith blacks (PN 167) piston. so which are better floating pins, or pressed pins? will these pistons work with floating pins?

thnx Adam
 
The KB167s are designed for floating pins. That means if the rods you are using dont have the small ends bushed, you will need to have this done to run them. In the case of the rods you asked about, the 340 rods are bushed for full floating pins. The 318 rods are not. So perhaps with that piston choice, the 340 rod IS the better choice. You'll save a little on the price of re-doing the rods. A 3rd choice is the cheaper lines of aftermarket rods, that come bushed. But, these rods need to be carefully checked and corrected before you install them. For me, that adds $100 to the cost of cheap rods. Going with your 340 rods, resized with new bolts and the bushings replced/checked, you'd be looking at $250 or so.
 
Keith Black pistons can be used in either pressed or floating applications. In pressed pin applications you don't use the spirol locks that are provided.

The Eagle SIR rod is a screaming deal for a 500HP or less application. I got them from Mancini for $219 for the set. They are stronger than a 340/360 rod, weight less, come with top shelf ARP cap screws and are bushed for floating pins.

The machine shop that did my machine work checked them out and the machining was dead nuts and they were all within a gram of each other weight wise. The owner said that he uses those rods in a lot engines he builds and is always amazed at the quality of the rod for the money.

My observation is strickly visual but the forging is much more consistant and has a much finer finish than a stock rod and the quality of the machining makes the stock rods look pretty bad.

FWIW, The machine shop also comment on Keith Black pistons. The consistency of the weight and dimensions of their pistons are far superior to a lot of the high end forged pistons they use in their race engines.
 
My experience with small block Eagle rods is limited to H beams, but I know I've heard/read a lot about casting flaw issues with the SIR rods.
 
Don't know how you could get a casting flaw in a forged rod and the only negative thing I have heard about the rod is they are forged in China but so is everything but the very high end billet parts.
 
It was posted a time or two on another site. With pictures of broken rods..the grain structure is different on a forged rod, but it's still a cast piece. Just cast under pressure. In thesecases, the rods fractured, so the builder had them Xrayed, and could see flaws in the beam, just under the pin bore. That is where the others had broke (different engines). I never really persued it further, I just decided not to trust them...lol. It may just be me...I know there are tons of guys running them, so they cant all be bad. But stories/details like that make me avoid them.
 
Unless something has changed since I was a process engineer and was responsible for the forged parts used in pressure vessels, casting and forging are two unrelated processes.

Casting melts the base material and it's poured or injected into a die (bye gravity or under pressure it's still casting). Forging takes a piece of solid material and beats it into a shape in dies (either cold ot heated). Because of the hammering process the grain structure is very small and is aligned along the surface and this is what makes a forged part so much stronger than a cast part. Forged parts also have a rougher appearing surface than cast parts.

There is a third process used for making connecting rods that the OEM's are using more and more an it's called sintering. This process takes very fine particles (almost powder like) of metal forces them into a die at very very high pressures.

I am quite sure some people have broken SIR rods and I guy here at work has a wallpaper on his PC of a broken Eagle H beam rod from his Mustang. Eagle is a reputable company that has an excellent reputation and I can't imagine them allowing it to be ruined by an inferior part. The SIR rod is a better piece than a stock rod and if you are looking for a cost effective way of up grading and aren't building a 500+ HP motor they are a good choice as is the equivlent I beam rod from Scat or a multitude of other manufacturers.
 
Dave, you better clarified that for me. My understanding was with a forged part, the molten metal was cast, and pressurized as it cooled. Not starting as a base shape, ingot, billet, whatever, then hammered hot or cold into the final shape. I'm attaching a chart of possible defects..They are talking about valves, but same concept. The issues was poor dies/quality control (from teh Chinese industrial environment) resulting in grain flaws in the beams of the rods. I call them casting flaws..That's wrong as you pointed out. And like I said, not all rods, not every part..Only some. I agree anything can be broken, and they will work a little better than a stock rod, I just dont want to risk a problem due to something I cant see or resonably inspect for.

Table.jpg
 
A forging process starts with a piece of solid material (typically steel or aluminum), it may just be a piece of bar stock or could be a roughly shaped to match the final shape. With steel the piece of stock is normally heated up until it's red hot (actual temperature will be dependent on alloy) aluminum is forged at room temperature most often.

Back in the day when I was visiting our forging suppliers they had three stage dies built into one forging press. The piece of material would be hit by the press in each die 3-5 times. You can actually hear when the part is not being formed any longer when the noise goes from a dull thud to a sharp bang then would move to the next stage. The last step before the part was quenched was another die set that trimmed off the flash. This is why you can id a forged crank from a cast crank, the area where the excess metal is trimmed is very wide compared to a small parting line in a casting die.

FWIW, a forged crank is forged with all the rod throws in the same plane. It is then twisted to get them offset by 90 degrees.

The defects in the table above are real issues that any outfit that forges or casts material has to deal with.
 
I know from the 318 I built very similar to the mag head 400hp build it will be a wash if the new rods can be had for $219 ready to go. I would have purchased the new ones insted of using the floating HD stockers if the new ones did not need any work.
 
That is the reason I did not have the stock rods resized and good bolts installed.
 
Thanks Dave..Learn somethin new every day..lol. I knew about the twist a while ago, when I was first seeing ads for "non-twist forgings". I just never looked into the casting vs forging processes themselves.
 
so these SIR rods are a good choice, for the 400hp build up used in the issue of mopar muscle? dont sound to expenssive.

thnx, Adam
 
I would not buy them from Indy Cylinder Head if you decide to go with Eagle SIR's. The set I bought from them were junk. I bought another set of SIR rods from Mazzolini and they were capscrew rods and were okay. I would not hesitate to use a set of stock rods but I needed floating pins so i went with the eagles. It was more economical to buy them then have the stock rods set up for bushings.
 
ok, wut ones should i go with the ones that came out of a blanced 340, or the ones that arnt balanced?
 
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