Compression Test

[Mark 8 U]

Who here has done compression tests on their VIII? What mileage and result did you get?

Mine '98 is between 175-180psi on all cylinders with 159K on the clock. IIRC our CR is something like 9.9:1 so that would be somewhere in line, but they seem a little tired to me.

 

[unity]

The 4.6L Quad Cam has a 9.8:1 ratio with 150 to 175 being a normal reading.

 

[segxr7]

The important thing is that the numbers are all uniform.

Here are the issues with this engine:

-Broken valve springs in earlier models. It's pretty rare, and your '98 isn't affected.

-Cam tensioner rattle on startup. This affects most (if not all) Marks. On cold starts you'll hear a nasty-sounding clattering/knocking noise for 1-5 seconds. Despite how it sounds, it's entirely harmless and nothing more than an annoyance.

..and that's pretty much it. I wouldn't be worried in the least about the engine at 160k miles; it's very durable. In fact the Mustang guys like to use our engine blocks because they can withstand up to around 1200 hp!

 

[Mark 8 U]

Good deal - then my compression is pretty much spot-on. Depending on which turbo(s) we have lying around at the time of installation we might just have to test that 1200HP block theory.

 

[Dern Humpus]

Im curious as to how you will mount a turbo in the mark.

 

[unity]

Im curious how the aluminum block will take 1200HP.

 

[Dern Humpus]

with a smile on it's face

 

[Mark 8 U]

There are a couple of options upon initial inspection ... twins in place of the factory CATs, or a single with some intricate piping sitting in front of the engine. Either one of those is going to require some flat-box piping under the subframe. Where there's a will, there's a way ... we've tackled much harder projects than this.

 

[segxr7]

Im curious how the aluminum block will take 1200HP.

You'd be surprised.. I was. Apparently back when our cars were being designed, Ford didn't have much experience with making aluminum engine blocks. They didn't want to risk screwing up, so they overengineered it and then had them manufactured by Teksid. It's an Italian company that usually makes engines for Ferraris and the like.

All Marks and some Mustangs have Teksid blocks. They're considered to be pretty much indestructable. Ford started making their own aluminum blocks around 1999, and those are only considered good to 700-900hp.

From http://www.svtperformance.com/forums/showthread.php?t=192162 :

"John Mihovetz has successfully used a teksid @ .020" over to 2000HP @ 40psi."

 

[unity]

Ya, I heard that but still - 1200HP! That is going to require better parts from the engine output back!

Gonna be a blast!!!!! <grabs some popcorn>