SR20DET questions - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Male · 05-17-2016, 03:08 PM

Hello i have an s13 sr20det red top i believe, I'm getting it bored out to 87mm because i had some wise pistons laying around. I was wondering if i needed a certain sized head gasket because of this? and i was also wondering the benefit of having a thicker head gasket. I'm not planing to build something crazy I plan to keep it mostly stock

Mcflurry · 05-17-2016, 06:38 PM

You can talk to your machinist reg the headgasket, they will likely be able to modify a metal head gasket to suit your new bore. Thicker is bad for a number of reasons.. quench etc it can have the same negative impacts as reducing thickness and more. Are your wise pistons lower comp?

Male · 05-18-2016, 10:53 AM

they raise the completion 9:1 i believe

*anti tyler* · 05-18-2016, 11:44 AM

Well yeah, your head gasket is going to have to bore match the Pistons.

Male · 08-28-2016, 12:05 PM

Okay i have all the pistons in I'm wondering what would be a good thickness on the head gasket? they are 87mm wise pistons on stock rods.

cotbu · 08-28-2016, 12:52 PM

You don't get a head gasket base on that!
You get a head gasket based on bore and what is removed from the block and or head.
You might want raise, lower compression but it's still based on that.
And you are not mostly, slightly, or a lil bit stock anymore, after you bore the block!

hanzbrady · 08-28-2016, 01:14 PM

87mm-87.5mm head gasket will be fine, as for thickness it depends on deck height. 1.2 is generally fine in most applications 1.5 is good for if you need more.

As for boring head gaskets only certain designs are bore-able.

jedi03 · 08-28-2016, 04:49 PM

Yup...the fire ring is what needs to match...can't bore that out as it needs some overlap...I think Tomei had a good list of what sizes match what

cotbu · 08-30-2016, 12:43 AM

Direct bore fit or larger will work. Normally, .5-1mm makes sense, somewhere sombody says 2mm.

jedi03 · 08-30-2016, 07:32 AM

im using a stock on .5 over...no issues yet...

Male · 12-08-2016, 03:53 PM

Hey guys is there any links or formulas that will say how thick the head gasket would need to be to lower the compression back stock or close? I would like to use the stock ecu without having to tune it ... if possible.

rawgarage · 12-08-2016, 04:24 PM

Doubt it will affect ecu

jedi03 · 12-09-2016, 07:32 AM

I think tomei had one that I used to determine bore...the cr is what you want to calculate to determine gasket thickness that you want

Male · 12-13-2016, 09:43 AM

http://www.tomeiusa.com/_2003web-cat...asket_crc.html

Found it! thanks! Also the goal is to get it back to original compression ratio correct? Im wanting to use the original turbo, the higher compression will only be beneficial for a bigger turbo correct?

Trap Star · 12-13-2016, 11:56 AM

The goal is whatever you personally choose it to be as far as compression ratio is concerned but generally speaking a lower compression ratio would be better for higher boost levels. Was your motor previously damaged or something, causing you to do all this? If not this seems like a lot of trouble just to essentially stay stock. Also, why not replace the rods while you're at it?

Kamronman · 12-24-2016, 10:19 AM

Just know that the thinner the h/g, the higher compression. Typically a 1.2mm thickness is pretty thick, (runs the risk of blowing faster than a thinner one, BUT gets you closest to stock compression). Also, just because you bore out 1mm, doesnt mean your ecu wont run the car right. It will run perfect, no dofference will be noticed I promise! Maybe a few hp naturally but not lean running or problems I assure you. And as for bore on the headgasket. ONLY run a head gasket .5mm wider than your new bore. This is from Apexi. If you do 87.5mm bore on the cyls, do 88mm headgasket.

G/l homie. Its gonna sound great after rebuild.

05-17-2016, 03:08 PM	#1
Male Join Date: Feb 2013 Location: Kansas Posts: 8 Trader Rating: (0) Feedback Score: 0 reviews	SR20DET questions Hello i have an s13 sr20det red top i believe, I'm getting it bored out to 87mm because i had some wise pistons laying around. I was wondering if i needed a certain sized head gasket because of this? and i was also wondering the benefit of having a thicker head gasket. I'm not planing to build something crazy I plan to keep it mostly stock

08-28-2016, 12:52 PM	#6
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 49 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	You don't get a head gasket base on that! You get a head gasket based on bore and what is removed from the block and or head. You might want raise, lower compression but it's still based on that. And you are not mostly, slightly, or a lil bit stock anymore, after you bore the block! __________________ LoverTechnologies "Half Broken Things!"

08-28-2016, 01:14 PM	#7
hanzbrady Zilvia FREAK! Join Date: Apr 2015 Location: Floriduh Posts: 1,166 Trader Rating: (4) Feedback Score: 4 reviews	87mm-87.5mm head gasket will be fine, as for thickness it depends on deck height. 1.2 is generally fine in most applications 1.5 is good for if you need more. As for boring head gaskets only certain designs are bore-able. __________________ [email protected]

08-30-2016, 12:43 AM	#9
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 49 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	Direct bore fit or larger will work. Normally, .5-1mm makes sense, somewhere sombody says 2mm. __________________ LoverTechnologies "Half Broken Things!"

12-13-2016, 11:56 AM	#15
Trap Star Zilvia Junkie Join Date: Jan 2008 Location: ATL/Sylva, NC Age: 36 Posts: 409 Trader Rating: (0) Feedback Score: 0 reviews	The goal is whatever you personally choose it to be as far as compression ratio is concerned but generally speaking a lower compression ratio would be better for higher boost levels. Was your motor previously damaged or something, causing you to do all this? If not this seems like a lot of trouble just to essentially stay stock. Also, why not replace the rods while you're at it? __________________ 86 300zx/90 240sx/97 240sx/96 LS400/03 350z -Shake N' Break Racing-

05-17-2016, 06:38 PM	#2
Mcflurry Join Date: May 2016 Location: Australia Age: 35 Posts: 34 Trader Rating: (0) Feedback Score: 0 reviews	You can talk to your machinist reg the headgasket, they will likely be able to modify a metal head gasket to suit your new bore. Thicker is bad for a number of reasons.. quench etc it can have the same negative impacts as reducing thickness and more. Are your wise pistons lower comp?

05-18-2016, 10:53 AM	#3
Male Join Date: Feb 2013 Location: Kansas Posts: 8 Trader Rating: (0) Feedback Score: 0 reviews	they raise the completion 9:1 i believe

08-28-2016, 12:05 PM	#5
Male Join Date: Feb 2013 Location: Kansas Posts: 8 Trader Rating: (0) Feedback Score: 0 reviews	Okay i have all the pistons in I'm wondering what would be a good thickness on the head gasket? they are 87mm wise pistons on stock rods.

08-28-2016, 04:49 PM	#8
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,836 Trader Rating: (8) Feedback Score: 8 reviews	Yup...the fire ring is what needs to match...can't bore that out as it needs some overlap...I think Tomei had a good list of what sizes match what

08-30-2016, 07:32 AM	#10
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,836 Trader Rating: (8) Feedback Score: 8 reviews	im using a stock on .5 over...no issues yet...

12-08-2016, 03:53 PM	#11
Male Join Date: Feb 2013 Location: Kansas Posts: 8 Trader Rating: (0) Feedback Score: 0 reviews	Hey guys is there any links or formulas that will say how thick the head gasket would need to be to lower the compression back stock or close? I would like to use the stock ecu without having to tune it ... if possible.

12-08-2016, 04:24 PM	#12
rawgarage Banned from the Marketplace Join Date: Oct 2007 Location: h o u s t o n Age: 35 Posts: 5,986 Trader Rating: (75) Feedback Score: 75 reviews	Doubt it will affect ecu

12-09-2016, 07:32 AM	#13
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,836 Trader Rating: (8) Feedback Score: 8 reviews	I think tomei had one that I used to determine bore...the cr is what you want to calculate to determine gasket thickness that you want

12-13-2016, 09:43 AM	#14
Male Join Date: Feb 2013 Location: Kansas Posts: 8 Trader Rating: (0) Feedback Score: 0 reviews	http://www.tomeiusa.com/_2003web-cat...asket_crc.html Found it! thanks! Also the goal is to get it back to original compression ratio correct? Im wanting to use the original turbo, the higher compression will only be beneficial for a bigger turbo correct?

12-24-2016, 10:19 AM	#16
Kamronman Join Date: Jul 2012 Location: NorthWest Posts: 32 Trader Rating: (1) Feedback Score: 1 reviews	Just know that the thinner the h/g, the higher compression. Typically a 1.2mm thickness is pretty thick, (runs the risk of blowing faster than a thinner one, BUT gets you closest to stock compression). Also, just because you bore out 1mm, doesnt mean your ecu wont run the car right. It will run perfect, no dofference will be noticed I promise! Maybe a few hp naturally but not lean running or problems I assure you. And as for bore on the headgasket. ONLY run a head gasket .5mm wider than your new bore. This is from Apexi. If you do 87.5mm bore on the cyls, do 88mm headgasket. G/l homie. Its gonna sound great after rebuild.