Hi, I have recently joined your site - very informative

My first thread comes really out of a thought of using what is available(wasted though the thought may seem)

where one could use for 6 inch rod pistons and just hang them on available 5.7 inch rods - in a just get up and running effort

are there any mechanical plain would not work reasons for not doing this??

It seems to me that the pin would be higher in the piston, so on 5.7 rods the piston would be down in the hole too far at TDC.

The pistons compression height HAS to equal the rod length and 1/2 the stroke so that they ALL add up to 9.00" plus, say about .025" down-in-the-hole piston position for a stock block's usual deck height of 9.025"!!!

Compression height is the distance between the center of the piston pin AND the pistons flat top generally around it's edge..

DO the math and see how far your pistons will be down-in-the-hole?? Or for that matter, sometimes sticking too far outta the hole!

Don't think it will work..

pdq67

are there any mechanical plain would not work reasons for not doing this??

Seriously?? :confused:
Other than the pistons being at least .300" down in the hole and having a compression ratio of slightly greater than atmospheric pressure, there's not any reason I could think of for doing this. ;) :(

EDIT...thought of another reason...piston skirts probably won't clear the crank throws on the down stroke.

5.9 to 1 compression, hey this would make for a great blower motor..........lol

PDQ67 - thanks for that calculator

I think that I have latched onto something here now

If I use super dome pistons - 1.568 comp height - for 6.00" rods and hang on 5.7 rods - with a 3.48 stroke crank - your calculator is as follows

1.568 + 5.7 + 1.74 (1/2 of 3.48) = 9.008

when I stack that up against 6 inch rods , I get

1.568 + 1.74 + 6.00 = 9.308

and when I use std. comp height domes of 1.268 (instead of super domes) for 6.00 inch rods

1.268 + 1.74 + 6.00 = 9.008

So, my theory of using a superdome piston with a shorter rod brings me to 9.008 - which is the similar to the standard piston in the hole measurement as if I use less radical (more popular dome comp height of 1.268) with 6.00 rods

any more thoughts - now I have fleshed out this idea some more??

Yeah, but you'll have a quench distance of over .300"...not very efficient flame travel.

the correct compression height of a Chevy 350 piston is 1.560. Don't know what that 1.568 is. the compression height is the distance from the center of the wrist pin hole to the flat deck surface of the piston. it does not include the height of any dome on the piston deck.

Things will go a lot better for you if you get the right pistons for the crank/rods you have or the right rods for crank/piston you have.

>>>If I use super dome pistons - 1.568 comp height - for 6.00" rods and hang on 5.7 rods" huh? I don't know what you're thinking here. if you have 1.568 pistons ( probably actually 1.560) they're for 5.7 rods, not 6".

don't know what "super dome piston" means either. the height of the dome (if any) is unrelated to the compression height of the piston.

Tom, actually it was a piston set I saw advertised in Jegs - very low clearance price -

I figured something was up if they are knocking off near $250 off the price and when I checked specs - it was ROSS pistons for 6.00 rods with yes - 1.568 - comp height - notes said : special hand fitting for straight plug heads required

I was just wondering out loud if I could avoid these issues by using shorter rods


I hear all of you anyways - there is a right way to approach this - and that is to buy the right pistons

Thanks

Are they used in the 9.3" tall decked SB block with the 6" rod??

I haven't ran the numbers is why I am asking??

pdq67

PDQ67,

Funny I could not find number on ROSS site among its "in stock offerings" - so you are probably right on that one

Thanks for indulging me anyways