performer rpm camshaft question

I am about to start putting together the engine for my Southern GTand am thinking about using Edelbrock Performer Rpm cam together with Performer RPM inlet manifold. I already have TFS Track Heat heads. The engine is a 302 with .30 overbore
Does anybody have any experience of this combination as regarding drivability and overall performance
I have been told that because the heads have 2.02" inlet valves that there will be little in the way of low speed torque and that throttle response will suffer.
The car will be used mostly on the road and maybe the odd track day.

Incidentally ,I also have a Torker cam and inlet manifold and wonder if these are as unsuitable as I have been told
Any information gratfully received

 

[Mike Dozier]

John

The TFS heads may be a little large for your application...but considering
the weight of our cars, and the manual transmissions used, I don't think
they would be a huge problem. I'd try them before buying another set.

I used the Edelbrock RPM cam/intake on my Cobra....worked fine on the street. Stay away from the Torker intake...it's really a high rpm unit only...
really poor for street use, despite what the name Torker implies.

MikeD

 

[Jason Lycett]

performer rpm cam

Biggest mistake i made was fitting this cam. Lost all bottom end torque. I was told by Pete Knight racing it only works with at least 10:1 compression. Mines going in the bin. I was advised to go for short duration, high lift for street use with 9:1 compression.

I would give them a call for advise, they are very knowledgeable

 

[aji]

John

I have no idea who related valve size and lowend power/torque. The larger valve makes the head flow better at smaller delta Pressure.

If you can post the specs of the cam as in "lift and duration" this would be helpful to comment on.

best

 

[Doug S.]

Might the issue not be valve size?

I have no idea who related valve size and lowend power/torque. The larger valve makes the head flow better at smaller delta Pressure.

Having had considerable experience with the Ford Cleveland V-8, I wonder if the issue with the TFS heads might be port volume/intake charge velocity rather than strictly the size of the intake valve. U.S. Clevelands with factory fitted 4-V carbs had heads with larger ports and valves and intake manifolds with larger port sizes than did the 2-V equipped cars. My 2-V (smaller port size) Cleveland equipped full size car would easily outrun a 4-V Cleveland equipped Torino (a somewhat smaller size car) up to about 80 or 90 MPH, at which point the 4-V motor's ability to flow volume through the intake system took over and the Torino would charge past me, leave me eating his dust. Low end torque seems to be very dependent on intake charge velocity and most of us Cleveland lovers use the 2-V sized heads (such as the Edelbrock RPM alloy heads) for anything other than NASCAR type racing--particularly anything that will be run on the street. I realize he's not running Cleveland style heads; I just mentioned this b/c of your comment regarding the issue of valve size relating to low RPM torque.

Just a thought, since I don't know the port volume, etc. figures on this particular Trick Flow head.

Doug

 

[Lynn Larsen]

Yerdougliness is exactly right! The other part effecting this is runner shape and volume; this, of course, includes the head ports and valve openings. In a gross oversimplification, the longer the runner length, the greater the low end torque and the shorter the runner length the greater the high end torque.

It is the inertia of the incoming air, which is proportional to the velocity (in reality it is acceleration F=MA), that makes the difference. As the piston is reaching the bottom on the intake stroke, it slows down. If the incoming air charge has enough inertia, preferably using a constantly tapering, lg-sm, profile to keep the air charge accelerating, the molecules will collide with the piston face and start to stack up (compress) and fill the cylinder with more air. If you don't keep the air charge confined (shorter runners) and give it more volume to fill (larger port sizes) it won't compress as much. This as a lot to do with the same theories of wave harmonics from which the term TUNED exhaust comes from. Intake manifolds and head designs present various compromises to provide torque in the rpm range that suites the use of the engine. Variable valve timing and variable runner lengths are technologies which attempt to provide maximum torque over a wider range of RPMs. (I think BMW's circular, variable runner length manifold is one of the coolest designs in this vein.)

Regards,
Lynn

 

[Jac Mac]

Well Done.

Jac Mac