I just wanted to verify that rounding down to a HG size will not cause any problems. My block measured out to 198.35, which is .15mm off stock after machining. The head was 115.25 or .75mm off stock. I need a 2.27mm HG. Cometic HG's do not come in that exact size, but after searching I saw IJ said it's ok to round down a size. If I round down from 2.27 to a 2.0mm Cometic MHG, will I be ok (I didnt see any other closer sizes on DM or HPF)? Will this significantly affect my compression (i'm running forged internals)? I know this is a frequent question, just want to verify on the rounding down before I place my order. Thanks in advance.
Head Gasket Thickness Rounding Down
- Thread starter 89gte
- Start date
SIP Racing 2.2 or 2.4 mls head gasket...Take your pick. I have never used them but ordered a gasket kit from them the other day and remembered they made different thicknesses.
http://www.sipracingmailorder.com/servlet/the-414/SIP-Racing-MLS-head/Detail
http://www.sipracingmailorder.com/servlet/the-415/SIP-Racing-MLS-head/Detail
http://www.sipracingmailorder.com/servlet/the-414/SIP-Racing-MLS-head/Detail
http://www.sipracingmailorder.com/servlet/the-415/SIP-Racing-MLS-head/Detail
My buddy just tried to order valve shims from SIP, and the order didn't get processed for over two weeks. Couldn't get him to answer the phone or respond. Not sure if I want to try after hearing that...his brother also said he thought that the guy who runs that site had been banned from SM at one point. I will try to get in touch with him before if I do try. Thanks for linking though, appreciate it. I'm not sure how far it is safe to round down the thickness or if .27mm matters.
worst case is you may need adjustable cam gears so you can set your cam timing is back to perfect stock spec
going to lower spec will advance the cams going taller would retard the cams
but were talking about .010 of an inc so I am pretty sure you will be just fine
even with out fancy pants cam gears
going to lower spec will advance the cams going taller would retard the cams
but were talking about .010 of an inc so I am pretty sure you will be just fine
even with out fancy pants cam gears
I chose a thinner than stock block height headgasket to bump compression up to ~9.0-1. Cams where 3.5* retarded, you might be ~1-1.5* off which isn't a big deal.
Nash, are you saying I'll be at an inc of .010 at 2.27mm from the 2.0mm HG or the 2.2mm HG? I'm not looking to add the adjustable cams. I'm already having to juggle the MAFT PRO into the build. I want to remain as stock as possible (after what's already been done until it's completely broken in). After I break in the engine, I will not be pushing the boost as I have a 57 trim that I will set to a max of 15psi. However, in the future I will upgrade. Thanks.
EDIT: Also, how much is an increase of .010? Will this have any negative impact on my engine?
EDIT: Also, how much is an increase of .010? Will this have any negative impact on my engine?
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89gte;1790210 said:
as I said I would not worry about it
the only issue I have ever encountered with head that was milled down to much was trying to time the motor since the cps was just no phased properly
but I am pretty sure you will be fine, Toyota does have a margin zone with the timing and your well with in it
Yes I know what your talking about on the processing...my order is still in that stage but they were the only ones I could find easily that sold the cometic gasket kit for our motors.
Stock compression = 8.4:1
Displacement = 2954cc
Bore = 83.4mm
Cylinders = 6
Each cylinder is 492.33cc, each combustion chamber is 66.53cc.
A change in the gasket thickness of 0.27mm will result in a reduction of the combustion chamber size of 1.475cc
This results in a static compression ratio of 8.57:1
I guess you can make your decision based on that.
Displacement = 2954cc
Bore = 83.4mm
Cylinders = 6
Each cylinder is 492.33cc, each combustion chamber is 66.53cc.
A change in the gasket thickness of 0.27mm will result in a reduction of the combustion chamber size of 1.475cc
This results in a static compression ratio of 8.57:1
I guess you can make your decision based on that.
Thanks Dan for doing that math for me. I was just failing to understand some of the concepts associated with the compression ratio. That is not as large of a difference than I thought. One more question, in general terms a lower compression ratio allows for more boost while a higher compression ratio will yield in less boost correct?
The 8.57:1 ratio should still be capable of sustaining a good amount of forced induction, especially with forged internals right? Later, if I upgrade my turbo from the 57 what is the max amount of boost you would use? I won't be looking to go above 18-20psi. Thanks.
The 8.57:1 ratio should still be capable of sustaining a good amount of forced induction, especially with forged internals right? Later, if I upgrade my turbo from the 57 what is the max amount of boost you would use? I won't be looking to go above 18-20psi. Thanks.
lower comp more boost, higher boost less
lower comp more timing higher timing less
ect ect
lower comp more timing higher timing less
ect ect
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Well, given that the 2JZ is 8.5:1, I'm pretty sure that shoudn't be a problem, but the numbers are what the numbers are.
If you are tuning to the absolute peak of what you can do, then the increase in compression ratio will reduce the amount of boost that you can run, but I'm pretty sure that most people would run into other limitations before you get there. Forged internals won't get you around all of them either, AFAIK. I guess it depends on what your ultimate goals are.
#include <stddisclaimer.h>
If you are tuning to the absolute peak of what you can do, then the increase in compression ratio will reduce the amount of boost that you can run, but I'm pretty sure that most people would run into other limitations before you get there. Forged internals won't get you around all of them either, AFAIK. I guess it depends on what your ultimate goals are.
#include <stddisclaimer.h>
LMAO some carbon on the pistons and combustion chambers could increase it by that amount, as I said in my PM unless you intend to run it on the ragged edge it's going to be fine... :nono: