How to bring compression down?

pb_paulie_b

Founding Member

May 19, 2001

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Chaptico, Maryland

Apr 7, 2006

#1

• Apr 7, 2006

• #1

According to Rick91gt, my compression ratio is going to be 9.03 to 1. This is not very boost friendly. Is there anything I can do to bring it down some? Thanks...PB

 

B

blue302stang

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Jan 23, 2006

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Apr 7, 2006

#2

• Apr 7, 2006

• #2

How much boost are you planning to run? 9.03 to 1 isn't to bad for boost if your running like 12-15 pounds of boost. There is not much to do but run a thicker head gasket or get some material milled out of your pistons

 

pb_paulie_b

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Apr 7, 2006

#3

• Apr 7, 2006

• #3

Eventually 15 psi, no intercooler and I have to keep it running on 93 octane. How much difference will a thicker head gasket make?

 

crazypete

All my crevices are greased.

Oct 22, 2004

930

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Arlington, MA

Apr 7, 2006

#4

• Apr 7, 2006

• #4

If you're really crazy, you can stack head gaskets though this, of course, is not recommended.

If you are less crazy, you can cut valve reliefs and polish the chambers with a heavy hand and grind off some material from the plug boss rim and take a bunch of material out of the combustion chamber. This will probably improve flow a bit and lower compression a tad and reduce carbon buildup while you are at it.

Then add a thick headgasket and you should be all set.

 

vristang

15 Year Member

Mar 31, 2005

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Apr 7, 2006

#5

• Apr 7, 2006

• #5

I have a file on my website that will let you look at the difference changing the headgasket thickness will make. I would post a link, but I can't get to the website from work. Look into the Math/Calculations section.

It will also allow you to make piston dish dome changes, and it provides some indication of how blowby/leakdown results will affect your CR.

Let me know what you think as far as user friendlyness, I am always looking to make improvements.

jason

 

pb_paulie_b

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Apr 7, 2006

#6

• Apr 7, 2006

• #6

vristang said:

I have a file on my website that will let you look at the difference changing the headgasket thickness will make. I would post a link, but I can't get to the website from work. Look into the Math/Calculations section.

It will also allow you to make piston dish dome changes, and it provides some indication of how blowby/leakdown results will affect your CR.

Let me know what you think as far as user friendlyness, I am always looking to make improvements.

jason

Click to expand...

I checked it out but for some reason windows wont let me open the file

 

Blk91stang

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Apr 7, 2006

#7

• Apr 7, 2006

• #7

The only was to do it is order new pistons. If you do it any other way, chances are your going to increase your chances of pinging even more with reduced quench inside the chamber. I don't understand how you think 9:1 compression is too high for 15psi? If you have any doubts, pull a little extra timing.

 

pb_paulie_b

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Apr 7, 2006

#8

• Apr 7, 2006

• #8

I like to be on the safe side of things. 9:1 compression will be ok for me than?

 

stang8urimport

Autozone Junkie

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Apr 7, 2006

#9

• Apr 7, 2006

• #9

Port your water pump???

 

D

Daggar

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#10

• Apr 7, 2006

• #10

Blk91stang said:

The only was to do it is order new pistons. If you do it any other way, chances are your going to increase your chances of pinging even more with reduced quench inside the chamber. I don't understand how you think 9:1 compression is too high for 15psi? If you have any doubts, pull a little extra timing.

Click to expand...

...and richen your fuel.

 

T

tooth

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Feb 1, 2006

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Apr 7, 2006

#11

• Apr 7, 2006

• #11

thicker gaskets

Call cometic gaskets1-800-752-9850. I just bought a set from them about 200.00, not cheap but reasuable. Do a search for a comperssion caculator online and puug in the numbers, head gasket thickness makes a tremendous difference. They sell several thicknesses of gaskets. A normal felpro is about .043 torqued, mine will be .074 torqued.

 

vristang

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#12

• Apr 7, 2006

• #12

pb_paulie_b said:

I checked it out but for some reason windows wont let me open the file

Click to expand...

Thanks for letting me know, I'll look into it. Let you know if I figure it out.

jason

 

ALMOST STOCK

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#13

• Apr 7, 2006

• #13

PoopDawg said:

Port your water pump???

Click to expand...

Or.... pull all the rings out of all the pistons .

 

pb_paulie_b

Founding Member

May 19, 2001

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Apr 7, 2006

#14

• Apr 7, 2006

• #14

vristang said:

Thanks for letting me know, I'll look into it. Let you know if I figure it out.

jason

Click to expand...

No problem J, let me know when you get it workin. I'd like to check it out...
tooth, Cometic does make the best gaskets, too good. I'd like to blow a gasket rather than toost my motor with a bad tune...
Thanks guys...PB