Quoting bom tie <bomtie@xxxxxxxxxx>:
>
> I did this swap and put in a very mild cam (one step from stock) and the to
> items lowered the compression to the point that a have less off the line than
> I started with. So the old heads are rebuilt and going back on the car. If I
> am wrong about this, someone please correct me as I would like to run the
> bigger valves.
> Charles
>
Your loss off the line is most likely due to the larger cam. Larger cam means
more duration and overlap, which typically favors high rpm torque at the
expense of lower rpm. If I am correct, you must have gained upper end, but you
may not fully notice that unless you have a decent exhaust system and your 4
barrel carburetor opens completely at wide open throttle. But I think Mikey is
correct that the compression ratio may have also dropped some with the later
heads. I think that the late 60's 440's had domes on the piston to compensate
for the higher volume in the heads in order to retain their 10.1:1 compression
ratio. So, there is a chance that the reduced compression ratio plays a part
in your lost low end, but the biggest part is probebly the bigger cam.
Personally, I would be willing to sacrifice a bit of low end for a stronger
upper end (both my Imperials are set that way), but in order to really be able
to take advantage of the upper end potential, you need the better exhaust and
fully opening carburetor (and may be an extra hole in your air cleaner, that
will reduce air cleaner restriction at high rpm's). Also, the bigger and/or
lower compression ratio cam may alow you to advanve the timing some more. That
may give you back much of the lost low end. But a free exhaust will allow you
to advance even more before your engine starts knocking (I assume you are using
premioum here, that's what these engines need).
D^2
> _______________________________________________
> Join Excite! - http://www.excite.com
> The most personalized portal on the Web!
>
>
Back to the Home of the Forward Look Network