302 cam change (engine/exhaust noise)

[Simon]

While I'm in the process of putting my GTD back together, I'd like to make it a little for user friendly.
At the GTD trackday, I noticed some of the '40's had a nice throaty burble, almost what could be described a quiet on tickover.
Now my engine (much though I love it) is bl**dy loud. (exhaust and mechanical noise) I was wondering if changing the cam to something milder would make much of a difference?
It currently has a solid lifter, big lift cam in it (can post specs if it'll help) and I was thinking of something like a performer plus with hydraulic lifters.
In my Cobra I built a 331 stroker lump with ali heads and the performer cam,. It was almost silent until given some wellie (throttle) and I miss that. I realise it's never going to be silent and I would'nt want it to be, but the noise is just too much.
Any advice gratefully recieved.
Thanks
Simon

 

[James]

Simon,

Why not spend the money on a decent silencer from Frank Catt.

Check out the article in the club mag.

There are 2 plus points.

1) You'll have a quiter exhaust note.

and..

2) You might end up with a few more BHP.

Regards,

J.P

 

[Lynn Larsen]

Much of the engine noise may be comming from your rocker system. There are rocker systems out there that are effective and quiet. The one name that has come up over and over again with these qualities is Yella Terra.

Not sure you have to go to hydraulic, especially, if you do and want to continue to, turn over 6500-6800 rpm. If you stay at or below these numbers, I would definitely look VERY hard at hydaulic. If, however, you do turn higher rpm, maybe you want to look at a more reasonable cam (not knowing what you have now). The Comp XR268 R-10 was chosen for my application. It has very reasonable durations (230/236 @ .050), lifts of ~.600 and lobe separation of 110º. If your durations are much more than these, you are likely getting some valve close noise as the ramp rates get pretty high in order to get the valve closed in time.

Where lift is concerned, you should look more at the area under the curve, the itegration, of lift vs duration over the period the valve is open, rather than just max lift. A cam with less max lift can actually have more total flow over the open duration than one with a very tall cam lobe. Bottom line, a less lumpy cam can actually produce more power.

Separation angles are still a bit of a mystery for me. In general, less separation equates to higher rpm and more separation equates to more torque. But, there is much more to it than that, which I have not fully comprehended yet. That said, it appears that 110º is a very good number for Ford engines. Extreme departure, in either direction, from that seems to be putting you into more narrowly defined areas of engine suitability.

HTH,
Lynn