Short Rod VS Long Rod FAQ

All FAQ's Go here... Most basic questions can be answered if you look here!
User avatar
Flash
I love JeepStrokers.com!!
I love JeepStrokers.com!!
Posts: 693
Joined: February 17th, 2008, 10:45 pm

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

Post by Flash »

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:

Flash
89 XJ with 300,000 on the original eng

"I've also never completed a motor, yet. My mouth (fingers) is also writing checks my ass can't cash."
User avatar
1bolt
Donator
Donator
Posts: 545
Joined: January 18th, 2008, 4:06 pm
Location: Culpeper Virginia

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

Post by 1bolt »

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.
--
Simon
Looking for a 232 crankshaft see my want ad: http://www.jeepstrokers.com/forum/viewt ... =17&t=1292
http://www.jeepstrokers.com 94 XJ Stroked lifted locked. 89 MJ restored Work truck, 88 YJ going on third build up and second Stroker.
cavaliers1323
Making Progress
Making Progress
Posts: 57
Joined: February 26th, 2009, 3:06 pm

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

Post by cavaliers1323 »

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....
NavinRJohnson
Posts: 3
Joined: September 3rd, 2009, 11:21 am
Vehicle Year: 1997
Vehicle Make: Jeep
Vehicle Model: TJ

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

Post by NavinRJohnson »

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:
User avatar
gonridnu
Movin on up ^
Movin on up ^
Posts: 332
Joined: December 22nd, 2008, 9:36 am
Stroker Displacement: 4.6L
Vehicle Year: 1989
Vehicle Make: Jeep
Vehicle Model: XJ 2 door

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

Post by gonridnu »

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.
NavinRJohnson
Posts: 3
Joined: September 3rd, 2009, 11:21 am
Vehicle Year: 1997
Vehicle Make: Jeep
Vehicle Model: TJ

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

Post by NavinRJohnson »

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
User avatar
SilverXJ
Global Moderator
Global Moderator
Posts: 5789
Joined: February 14th, 2008, 7:14 am
Stroker Displacement: 4.6L
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Radford, Va

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

Post by SilverXJ »

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.
User avatar
amcinstaller
I love JeepStrokers.com!!
I love JeepStrokers.com!!
Posts: 604
Joined: May 22nd, 2008, 11:57 pm
Stroker Displacement: 4.6L
Vehicle Year: 1980
Vehicle Make: AMC
Vehicle Model: Spirit
Location: Red Deer, AB, Can

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

Post by amcinstaller »

when i first skimmed i thought top ring as well, but i see what was meant now.
1980 AMC Spirit Restomod in Progress
SilverXJ wrote:Roller rockers won't help that mess you have created. Nor will God for that matter.
User avatar
Muad'Dib
Site Admin / Owner
Site Admin / Owner
Posts: 1497
Joined: January 8th, 2008, 10:55 am
Stroker Displacement: 4.7L
Vehicle Year: 1990
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Bend, Oregon
Contact:

Re: Short Rod VS Long Rod (FAQ)

Post by Muad'Dib »

Added to FAQ
If it feels right, then STROKE it!
You're lucky that hundred shot of CAPS LOCK didn't blow the welds on the forum!!
Post Reply

Who is online

Users browsing this forum: No registered users and 9 guests