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post #1 of 10 (permalink) Old 06-25-2005, 08:50 PM Thread Starter
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compression question

What would be the easiest (if possible) way to drop the compression without having to go into the short block? After owning a turbocoupe I have an undying love for turbos.
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post #2 of 10 (permalink) Old 06-27-2005, 01:16 PM
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Only way to drop the compression is changing you internals to lower compression ratios(pistons, rods, rings crank), no ther solution and certainly not cheap..

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post #3 of 10 (permalink) Old 06-27-2005, 01:21 PM
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Or bolt on a set of DOHC heads.... that will lower your CR by about one full point.

And… give you a HUGE nightmare trying to get everything to work!!

And.... 4.6L's have hypereutectic pistons.... which are not the "best" piston for boost.

And… if you're looking to turbo a 4.6L, plan on having deeeeeeeep pockets.

Have fun and good luck.

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post #4 of 10 (permalink) Old 06-29-2005, 04:01 PM
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Quote:
Originally Posted by Hobohuey
What would be the easiest (if possible) way to drop the compression without having to go into the short block? After owning a turbocoupe I have an undying love for turbos.
You may want to call Cometic and see if they offer thicker head gaskets that will fit your motor. I know they have them for the 5.0.

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post #5 of 10 (permalink) Old 06-30-2005, 03:27 AM
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They do make them for the 4.6, although I have been unable to find exact thicknesses (haven't called them though).

If they make a .090 compressed thinkness it'll drop you to ~8.5:1 compression. .039 is the stock compressed thinkness (technically it's 1mm).




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post #6 of 10 (permalink) Old 06-30-2005, 05:04 AM
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You could also try alcohol or water injection.
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post #7 of 10 (permalink) Old 06-30-2005, 11:16 AM
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Quote:
Originally Posted by GreenBird
They do make them for the 4.6, although I have been unable to find exact thicknesses (haven't called them though).

If they make a .090 compressed thinkness it'll drop you to ~8.5:1 compression. .039 is the stock compressed thinkness (technically it's 1mm).

I think it wouldnt be a good idea on just slaping in the gasket knowing that our internals are really weak when they go above 350HP. I mean, sure compression will go low, but I think more of a future effieciency. Did I make sense?


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post #8 of 10 (permalink) Old 07-01-2005, 12:08 AM
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CAMS

IF you install the correct cam with correct overlap/duration, it can lower EFFECTIVE compression ratio.

Dad always said,"Knowledge is limited but stupidity knows no bounds."
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post #9 of 10 (permalink) Old 07-10-2005, 05:08 PM
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Everything I've ever read says water injection is a really BAD solution to things... in the ultimate race application, people do anything and everything to gain an inch, but for street/strip use... no way. 2cc's can be gained by grinding out the swirl fins... but i dont know how the drivability would be when not under boost.
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post #10 of 10 (permalink) Old 07-15-2005, 04:19 PM
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Taking out the swirl dams is never a good solution. A thicker HG is the easiest way.

Tx_Cat, while your right the stock shortblock can't take a ton of abuse, lowering the compression ratio allows more boost, making more power for the same cylinder pressures.




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