I have a standard size set of bushed connecting rods with 2.125 small end diameter. I'm considering a forged 4.125 stroke crank with 2.00 small end. Can the bushing be removed & "resized" down to 2.00? Or should I just buy chevy rods?
Connecting Rod Question
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68 Formua-S fastback clone 367/A833/GVod/3.55s
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IDK the answer, but if memory serves me, Chevy rods have side-clearance issues on Mopar cranks, introducing new problems.
NC Engine Builder
Grumpy Old Man
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The big end is the crankshaft end, and no you cant use the rods you have. Buy the correct "chevy" rods. Then remember your pistons need pins that match the chevy size, as that is smaller also
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Grumpy Old Man
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There is no issues created by using the chevy rods.
I've seen Jim Laroy say .100" or more side clearance won't hurt a thing. lol
NC Engine Builder
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It wont. I mean, think about it, if you got say .0025 oil clearance in the bearing, that controls how much oil is passing through the bearing, the side clearance has zero effect.
dusterbing the peace
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Chevy rods are 015 wider on the big end, each. I had my rod journals taken out a little wider (1.9 I think with some radius to mate up to the rod) to compensate when turning the diameter down to run the Chevy rods. Maybe the radius on the outside of the rod’s big end rod bore gives room on the standard Mopar rod journal width, but I didn’t want to take the chance. I trust that you’ve built quite a few more engines than me though.
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I was speaking generally about using narrower rods. If you dont have ENOUGH side clearance, then that is definitely a problem! The oil has to be able to get out of the rods
mygasser
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if the stroker crank is ground for chevy size journals aren't they also ground to suit the width of the chevy rods? or is that too sensible? 
neil.
neil.
That's what I was thinking too.
Professor Fate
Push the button, Max...
Use the rods that the crank is ground for.
If it's ground for Chevy rods, use Chevy rods.
If it's ground for Mopar rods, use Mopar rods.
Then get the proper pistons for whatever rod you use.
Seriously, get a kit. Everything is matched and balanced, no guesswork, no one-off machining. Crank, pistons, rods; all new, all there and hopefully all ready. And they can be had for a price that's no worse than having all your stuff reworked.
Just check/have checked all the clearances and the balance just to be safe.
If it's ground for Chevy rods, use Chevy rods.
If it's ground for Mopar rods, use Mopar rods.
Then get the proper pistons for whatever rod you use.
Seriously, get a kit. Everything is matched and balanced, no guesswork, no one-off machining. Crank, pistons, rods; all new, all there and hopefully all ready. And they can be had for a price that's no worse than having all your stuff reworked.
Just check/have checked all the clearances and the balance just to be safe.
dusterbing the peace
FABO pyrite member
You’d sure hope so! But I certainly made it a point to ask (and probably annoy) the crank grinder since he probably turns 100 Chevy cranks to every 1 Mopar crank…and even less of those Mopar cranks with Chevy rod journals.if the stroker crank is ground for chevy size journals aren't they also ground to suit the width of the chevy rods? or is that too sensible?
neil.
dusterbing the peace
FABO pyrite member
As the Russians say: “trust, but verify”
Yeah, I think somebody needs to study up.
What's the purpose of using chevy rods in the first place?
price, availability-- both in type & construction, design.
before stroker kits were prevalent it was common to grind 360 rod journals to chevy size and go that route.
The bushing is in the small end. I am not sure where you got the bushing is on the big end, but that's what you wrote.
I'll save you a lot of headaches, don't use a 4.125" stroke crank. 4.00" stroke is more than enough for 99.9% builds, and you can buy and use off the shelf parts.
I get 4-5 guys a year that want to build a 426" small block because they saw one in a magazine article.
Remember, Magazines and Hot Rod shows are designed to sell parts, not longevity.
But hey it's your party.
Tom
dusterbing the peace
FABO pyrite member
Options. I opted for a lighter weight set from eagle to reduce overall mass of the reciprocating assembly, which helps to reduce distortion and stress on the crank and the block.
Other options include different lengths, even smaller rod journals, heavier duty, etc
All of the above are good answers, but additionally the virtually unlimited amount of choices in connecting rod bearings and wrist pins with a SBC.
All engines regardless of brand or nothing more than a collection of mechanical parts. They don't know what brand they are, so using parts that have a better selection at usually a lower
cost just makes it easier all the way around.
Tom
I guess I had a brain fart. The more I rack my brain around it, a 4.00" stroke is easier. The Molnar cranks I've looked at though, the price is the same so I figured why not go bigger.
33IMP
Well-Known Member
Smaller rod pins on the crank to use chevy rods give more lower end clearance for stroker cranks.
Pistons designed for chrvy rods also use chevy diameter pins which are much lighter than mopar pins.
Result: lighter pistons, and pins, revs quicker, rods in effect become stronger because it's easier to change direction with a light piston than a heavy one. Stroker cranks with light pistons and chevy rods are a win/win.
Edit: this response applies to big block mopars also!
33IMP
Well-Known Member
And I agree with ProstockTom.
Four inch crank small blocks are hard enough to feed with run-of-the-mill cylinder heads. 4 1/8 just makes it harder.
Four inch crank small blocks are hard enough to feed with run-of-the-mill cylinder heads. 4 1/8 just makes it harder.
You can get a large amount of off the shelf pistons for a 4" stroke now, and down the road should you have an issue and need a single piston.
As mentioned above very few guys have enough cylinder head to feed a really good 408" (360) or 416" (340) properly.
Probably okay for most street engines, but you get to a point that one should really step up to heads with offset rockers.
I try to advocate for the best combination of cost and certainly longevity, as most of use can't afford to do it twice.
Tom
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