2000GT4.6

What supercharger application are you talking about??

I am 99.9999999 percent sure that there is absoluty no change in the compression between 99 and any other PI year. I have seen this misprint a few times, and i think it just got passed around. A compression change would require a different piston setup or something being differn't in the heads, and I have not found any evidence to show there is a difference here.

I have never seen anything offical from any website that I trusted that made since claiming there was a difference or even mentioning it. Also, any significant change in compression ratio would be showing up by the 99 cars generally dynoing more RWHP stock/with the same mods as the 00-04 cars. This also has not been the trend.

I think its just someones mistake. I think I saw it over on modulardepot? And that was where the compression ratio was higher but hte compression chamber was larger (on their spec sheet) and this is virtually impossible lol, would require both a piston change and head design change, and there isn't one.

sweet99

A friend has a 2003 GT and in the owners manual it has the NA motor having 9.4:1 compression and the S/C motor at 10:1. Seems backwards. My '99 came after 3 previous owners and the manual is gone. Anyone with a '99 owners manual that can check to see what the compression is stated as? Thanks, Mark

VARifleman

The Cobra was not mentioned in the GT manual that year. The Mach I motor that was mentioned is N/A.

As for the Compression ratio, how do you "Know for sure" that it's 10:1? Have you tested it? Taken out your pistons to see what kind of dish they have and then divided the volume at the bottom of the stroke by the volume at the top (taking account for the thickness of the head gasket)? Also, what kind of fuel did your 99 GT manual tell you to run?

sweet99

If you are referring to me I don't know much for sure about these cars. I even thought that Cobra's were factory S/C motors, yes/no? My car did not come with a manual that is why I am trying to find out what compression the motor came with.
I am just curious as to what the '99 2v has for compression, 9:4 or 10:1. Thanks, Mark

96cobra10101

SC it ftw.

VARifleman

The first part of my post, was about you. Your friend has an 03 GT and you stated that his manual says 10:1 for a supercharged car, which is incorrect. The Manual didn't mention the supercharged cobra that was put out in that year, only the v6, gt, and mach I, cobras had a different manual. The second part of my post was directed to the thread starter.

sweet99

Ok so an '03 Cobra did come S/C'ed from the factory? 10:1 compression? More importantly my '99 Gt has 9.4:1 correct? Many names used by Ford for the many models used and being new I am not familiar as to what is what.
What year did the plastic intake manifolds start as my car has one but I read that they did not come into use until the '01 model year however it sure looks like the manifold on my motor is original.
Yeah a S/C would be the way to go as getting much from 281 NA cubic inch motors is expensive! Mark