The V8 Owners Forum -

Hi,

I am a new member, so sorry if my questions have already been discussed previously.

I have bought an engine that has a 3.9 Plenum, 14 crux ECU and what appear to be 3.9 heads (Info from previous post detailing casting numbers and fact that heads have 14 stud holes. The head gaskets that were fitted were composite and from reading previous posts, the compression ratio will be lower than the 9.35-1.

Q1. Am I ok fitting tin gaskets instead of composite in order to achieve correct compression ratio? I assume that the valves will clear the 4.6 pistons? Any down sides of fitting the tin gaskets?

Q2. Will there be any notable difference in performance refitting the 3.9 top end as opposed to the correct 4.6 top end?

Look forward to hearing your views.

Regards,

Michael

Generally, it's the pistons which set the CR. Heads designed for steel gaskets have a different deck height to those for composite.

Hi Dave,

Thanks for response.

Are these the head measurements for a 3.9 or a 4.6

My heads measure;-

Head 1.
A. 23.1 & 23.25mm
B. 63.0 & 63.5

Head 2.
A. 23.2 & 23.4
B. 63.0 & 63.0

So heads have not been refaced.

Regards,

Michael