chevy rods?!?!

[rurouni20xx]

was digging thru the custom piston catalogs (wanting to go to flat top forged pistons and shaving her to 11:1 when i rebuild...) and found an odd piston in the srp pinto and wiseco books, when i looked it up on summit it says that the pistons are for 5.7" chevy rod custom applications, can somebody shed some light on this ive never see it b4, says itll work on the stock crank/stroke for a 2.3, this isnt a cheater 2.5 or just a longer stroke 2.3 by moving the piston pin upwards is it?

 

[4b316]

Yes,more or less just a cheater 2.5 or so.Nice thing about it is that you can use the lighter 2.3 crank.there are a couple running at the track and run well with a carb system,usaully a "D" port intake with a 350 holley.We are still in first place after 6 races with 4 wins,one second and a 4th with a mild 2.5 FI engine.

 

[rurouni20xx]

in other words the longer rod is used on the shorter crank and custom pistons are used to move the piston pin higher, does this actually increase the stroke any i mean the dimensions of the crank havent changed any. kawasaki 85cc 2 stroke racers were modding there cranks to use a longer rod and the same piston they just rewelded the pin further in the crank, it was called a stroker that still fit in the same cc class and they claim it helped, sounds similar to what the chevy 5.7 inch rod on a 2.3 crank is doing just dif way of doing so. my question is does it help that much and/or what is the benefit i mean does it stroke a hair making it breathe better on the same bore making more power?

 

[4b316]

You can tell the difference in just hearing the chevy rodded engines.They seem like they pull a lot more out of the corners with the additional torque.Don't see why you couldn't run it on the street ,as long as you didn't go too radical with a cam.I guess myself,I would just go the 2.5 route.

 

[rurouni20xx]

it sounds interesting to say the least, i may break down and save the money to spend and do it since its actually cheaper to buy that rotating assembly rather than a 2.5 assy from racer walsh, plus i like good pulling power. trying to build a good reliable street/strip motor for shits and giggles on the weekends, itll also be my dd for a time so im *not* going outlandish w/ boost or nos or anything just a lil more compression, pump gas special if you will. the motor revs great and everything w/ the open air filter and almost straight thru exhaust, i give the honda/chevy truck guys hell when carving corners (they like to jack their shit up and still say it races....lol) i just want to leave them a lil quicker.

 

[Byrd]

Thats odd, but very interesting to know. From what I have found (and I know I'm talking v8s here but still...) the crank journals on ford cranks need to be ground down in order to fit chevy rods on them (The 460 can fit chevy rods too). Its just strange that one of them would make the journal diameter the same as the other. Good for the budget racer though!

-Byrd

 

[fastpakr]

I may be misunderstanding your question here, but to state the obvious - if you aren't regrinding the crank, the stroke will not change no matter what changes you make to connecting rods or pistons.

 

[Byrd]

I may be misunderstanding your question here, but to state the obvious - if you aren't regrinding the crank, the stroke will not change no matter what changes you make to connecting rods or pistons.

+1, please enlighten us. I'd be interested in knowing how this is done because I too only know two ways to change the stroke (change the rod length or change the crank grind).

-Byrd

 

[fastpakr]

Changing the rod length doesn't affect the amount of stroke - only the crank grind does that.

 

[Byrd]

Changing the rod length doesn't affect the amount of stroke - only the crank grind does that.

Right you are... I was thinking about it like if you were to put a shorter rod in that it would change, but that would only change the size of the combustion chamber, not the stroke because the distance that the piston travels would remain the same.

Thanks for settin me straight, not sure where my head was...

-Byrd

 

[shadetree]

There are two schools of thought on the changing of the rod length. 1. It helps power. 2. It doesn't help power.

The thinking is the additional length of the rod changes the angle from the piston to the crank journal. Since the most torque is achieved when the crank is 14 degrees past TDC, making the angle of the rod straighter to the crank allows for more power from the piston to be transferred to the crank.

Also, the piston stays at TDC longer taking advantage of the burn time of the combustion process to build more pressure on the top of the piston.

Many say the difference isn't worth the cost/effort. In changing the rod length you also have to change to a different piston. If you want a 2.5, get a 2.5 block from salvage.shady

 

[rurouni20xx]

glad to see where shady sees my point, however i dont want to stroke it to a 2.5, when you stroke the engine your piston speed increases making your redline shorter, i want the benefit of the longer rod increasing the downward force on the crank making it rev off the bottom a little faster, but still be able to rev out as far as a 2300 motor. a 2500 motor has a shorter redline by a few hundred rpms. btw i would be purchasing the kit machined out already just drop in rotating assy the forged pistons .030 over 5.7 rods and machined crank matched assy is 1035 bux the 2.5 assy is 1450, for 400 bux less ill experiment to say the least. either way i get the benefit of new balanced crank fresh rods and higher compression forged pistons.