WHats the difference between cylinder psi and compression then? I have a
compression testor for an engine, but it does me no good on an engine thats
all apart. What I learned from bernd is that 150-160psi is actually
(9.1-9.5:1), then i would need to up my compression/cylinder psi to 165psi?
I'm gettin a good deal at the machine shop i go to because i'm good freinds
with the owner. I'm not worried about him cutting the heads, i just gotta
give him the #'s i need changed to acheive the right stuff. The help is much
appreciated.
-Aaron
""Will Coughlin"" <willcoughlin2@hotmail.com> wrote in message
news:F1633DjFbUcOV1EetVo000036c0@hotmail.com...
> Aaron, the nominal deck height of a standard 318 Magnum is 9.595". It is
the
> same for the Magnum 360's and the 3.9L V6 Magnum as well. It scares me
that
> you're using a machine shop that doesn't even know the deck height on the
> engine they're machining for, but oh well. As far as milling the heads,
I'm
> not sure what you'd need to take off the heads to acheive your desired
> compression ratio. Best I remember, Magnum heads are 60cc chambers. It's
not
> an exact formula, but as a general rule of thumb for every CC you remove
> from the combustion chamber, you can add one point to your compression
> ratio(EX: 60cc head with a CR of 9.4:1, take it down to 58cc's and the CR
> jumps to 9.6:1). Now, as for your compression ratio figures- the formula
you
> used is not right. The actual compression formula requires some specific
> measurements and a long equation. I'd tell you to ask the machine shop to
> help you figure it, but I doubt they'd know how after the deck height
thing.
> If you want to figure it out by yourself, let me know and I'll write up
the
> formula and you can try and find the measurements needed. The 165 psi
figure
> they gave you is cylinder pressure, not compression. HTH,
>
> Will Coughlin willcoughlin@hotmail.com
> '00 Reg. cab 2wd, 4.7L/NV3500HD/9.25" 3.92 sure-grip
>
> ----Original Message Follows----
> From: "Aaron Gasparich" <acg302@ptd.net>
> Subject: DML: engine compression.
> Date: Thu, 13 Dec 2001 21:41:20 -0500
>
> Well, i'm finally assembling my engine. But i'm trying to figure out what
> compession i need to up to to match my hughes 1418 cam. I know that hughes
> says it need to be at 165psi. if normal air is at about 14.5psi@sea level
> than 165 translates to about 11:1, is this true? I think I could figure it
> all out on my own if i knew the deck height of a 318, but since I
> dont(neither does the machine shop) I have to pose the question. Is the
> stock 9.2:1 compression ok on this cam, or will i have to mill the head a
> few thousandths to achieve a higher compression and the benifits of the
cam.
> Does anybody know the deck height of the 318? I feel a little bit lost
here
> when it come to the compression part of an engine. And if i need to shave
> the heads, does anybody have an idea as to how much i need to take off?
> Thanks to everybody for the help
> -Aaron
>
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