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Short Rod VS Long Rod FAQ

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Flash
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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by Flash » June 20th, 2009, 9:16 pm

1bolt wrote:Hmmm what is the LEAST decking needed to achieve zero deck clearance (gasket quench) with the "budget" stroker? Compared to custom/KB pistons/rods combo which need only a little shaved off?
With the stock piston in my spair block (piston set .022" in the hole) and a short rod stroker, you would need to deck the block .029" to get "0" deck. then the price of push rod..........Ya i thing it would be way cheaper.......even with needing the pistons dish enlarged.
Grate Quench, compression controlled with extra dish added to piston................but non of this help the piston skirt traveling below the bottom of bore, with the stroker crank.


Isn't it something very large? I'm not going on facts here, I'm going on what I seem to recall, but I recall that decking for "Gasket Quench" herein refered to by me as GQ with a short rod and off the shelf piston (because of the pin heights available) would end up with no deck left.
The short rod stroker lowers the piston .0075 more in the hole(according to my figures(different after market pistons will vary this slightly do to slight different pin heights.)

Again this isn't (or shouldn't be) about which rod gives "more benefits" on paper but which rods allows you to build the most well designed stroker, and in the end the most long term cost effective, and reliable as well as powerful stroker.

Getting your build to GQ and optimizing your compression ratio AFTER quench for the fuel you intend to use and the Cam you intend to use; is the proper way to build any performance engine... Otherwise as seen with all the so called "Budget" stroker recipes you end up having your fuel octane and your cam choice basically dictated to you by your choice of piston/rod/quench
when i did the figures, was kinda shocked that there was only 7-1/2 thousandths of a inch difference in piston height...........maybe i did something wrong with my Math :huh:

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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by 1bolt » June 26th, 2009, 7:11 am

Well that's interesting I recall it being bigger but you're right I think, just doing the math off the top of my head I should have realized the difference wasn't that huge. If the stock/Budget stroker quench is around .080 then we subtract .050 (give or take) for a gasket that leaves the piston .030 ish down in the hole. I've definitely seen some .090 quench builds around so obviously pin height is important here.

I think the budget build is also somewhat limited by piston dish for instance the classic Silvo's that can take something like 22 cc's of total dish, can't remember where they end up on the stock short rods.
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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by cavaliers1323 » March 6th, 2010, 8:47 am

With the availability of bull tears custom forged pistons, a lot of windows are now open. The use of eagle rods + custom pin height + custom dish = winning ticket IMO. Costly, but great quench, whatever CR you want, and the added benefits of longer rods w/o any decking....

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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by NavinRJohnson » March 8th, 2010, 11:16 pm

lafrad wrote:Well, Decking a block and new pushrods.


Everything gets made up *somewhere*... unfortunately. The REAL answer was suggested by someone in another thread: get the hypereutectic piston guys to leave the current 4.0L piston with an extra 0.025" on the quench pads, and just machine down. sell "extended quench" pistons, and "stock replacement" pistons. same effort for them, but it would fix a TON of stuff for us. better dish volumes, better quench with no decking, etc etc etc etc

ah well, everyone will figure out their way to do it.
i was just thinking this same thought... why - when using short rods - couldn't it be cheaper to simply raise the 'ring' around the dished center of the piston to make a 1.625" compression hgt? now you're at -0.0025" to -0.0075" deck height... with a 0.040" gasket you're going to have a quench hgt of < 0.050"

you'd think it would've been even easier for the forgings. i mean you're talking about leaving less than 1/32" on top of the piston. and i cant imagine that it would raise the SCR more than a couple of tenths - if that.
:huh:

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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by gonridnu » March 12th, 2010, 3:54 pm

1bolt wrote: If the stock/Budget stroker quench is around .080 then we subtract .050 (give or take) for a gasket that leaves the piston .030 ish down in the hole. I've definitely seen some .090 quench builds around so obviously pin height is important here.
I was just thinking this same thought... why - when using short rods - couldn't it be cheaper to simply raise the 'ring' around the dished center of the piston to make a 1.625" compression hgt? now you're at -0.0025" to -0.0075" deck height... with a 0.040" gasket you're going to have a quench hgt of < 0.050"

you'd think it would've been even easier for the forgings. i mean you're talking about leaving less than 1/32" on top of the piston. and i cant imagine that it would raise the SCR more than a couple of tenths - if that.
:huh:

Subtracting the gasket thickness from the equation is.....um.....wrong.

If you have a zero deck engine and a .041 gasket your quench is .041". If your piston is .050" in the hole and you have an .041 gasket your quench is .091". You have to add the gasket thickness to your piston to deck height to get your quench number.

Raisng the ring does not change the top of piston to combustion chamber quench surface number which is your quench height and even if it did (which it doesn't) there are minimum numbers required for a top ring land to keep it from blowing off the piston.

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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by NavinRJohnson » March 12th, 2010, 10:37 pm

gonridnu wrote:
1bolt wrote: If the stock/Budget stroker quench is around .080 then we subtract .050 (give or take) for a gasket that leaves the piston .030 ish down in the hole. I've definitely seen some .090 quench builds around so obviously pin height is important here.
I was just thinking this same thought... why - when using short rods - couldn't it be cheaper to simply raise the 'ring' around the dished center of the piston to make a 1.625" compression hgt? now you're at -0.0025" to -0.0075" deck height... with a 0.040" gasket you're going to have a quench hgt of < 0.050"

you'd think it would've been even easier for the forgings. i mean you're talking about leaving less than 1/32" on top of the piston. and i cant imagine that it would raise the SCR more than a couple of tenths - if that.
:huh:

Subtracting the gasket thickness from the equation is.....um.....wrong.

If you have a zero deck engine and a .041 gasket your quench is .041". If your piston is .050" in the hole and you have an .041 gasket your quench is .091". You have to add the gasket thickness to your piston to deck height to get your quench number.

Raisng the ring does not change the top of piston to combustion chamber quench surface number which is your quench height and even if it did (which it doesn't) there are minimum numbers required for a top ring land to keep it from blowing off the piston.

i was referring the "ring" shape of the quench pad. sorry for confusion

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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by SilverXJ » March 13th, 2010, 6:53 am

gonridnu wrote:
1bolt wrote: If the stock/Budget stroker quench is around .080 then we subtract .050 (give or take) for a gasket that leaves the piston .030 ish down in the hole. I've definitely seen some .090 quench builds around so obviously pin height is important here.
I was just thinking this same thought... why - when using short rods - couldn't it be cheaper to simply raise the 'ring' around the dished center of the piston to make a 1.625" compression hgt? now you're at -0.0025" to -0.0075" deck height... with a 0.040" gasket you're going to have a quench hgt of < 0.050"

you'd think it would've been even easier for the forgings. i mean you're talking about leaving less than 1/32" on top of the piston. and i cant imagine that it would raise the SCR more than a couple of tenths - if that.
:huh:

Subtracting the gasket thickness from the equation is.....um.....wrong.
No, for what he is doing he is 100% correct. He has the quench number and is looking for the deck clearance.

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Re: Short Rod VS Long Rod (Trying to wrap my head around it)

Post by amcinstaller » March 13th, 2010, 9:04 am

when i first skimmed i thought top ring as well, but i see what was meant now.
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Re: Short Rod VS Long Rod (FAQ)

Post by Muad'Dib » January 24th, 2013, 7:21 pm

Added to FAQ
If it feels right, then STROKE it!
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