Updated October 2008
Holley MPFI

We’ve been a little disappointed with the power output of the ZZ502, on the Dyno it only produced 325rwhp and  the fastest time at the strip was 12.88

Talking to several people on the net they felt that the Holley Commander 950 was the problem. When I installed  the Holley manifold I noticed that the ports were way smaller then the head ports. I called Holley and they said it was no problem and go ahead and install them. I wish I hadn’t!

You will notice how small the ports are from the pictures. I started to port them in the bottom picture to give you an idea of the difference! We’re hoping to pick up another 75rwhp when all is said and done, we’ll see.

 

The original manifold port size was 1.580x1.596 avg. after porting they were 2.090x1.820 for a whopping 51% increase in size! No wonder we gained so much on both et and MPH
Look how small the ports are!
another view
after first step in porting them
Looking down the into the ports you can see how far I opened them up. I would’ve like to open up the runners  more but I just didn’t have the time.

** Sept. 5, 2001 **

The result of the port matching was a gain of almost 3MPH and .25 reduction in et at the strip. With tuning, I think we can get it down even more now! Before the porting the engine didn’t respond to fuel and spark modifications but now when we increased the fuel 5% it dropped the et by .15

** Sept. 7, 2001 **

Again, with altering the fuel, this time I reduced the fuel between 2500 and 3500 RPM and richened it a little above that I  was able to get the et down to 12.43 @ 111MPH! This sure beats the low 13’s before porting the manifold.

With all said and done, the porting and the additional tuning gained me an average of about 1 second reduction in et’s. We havent been back to the dyno yet so we have no new dyno HP numbers.

** January 2002 **

I got a Pro Yank 3400RPM stall for Christmas! I’m going to run the car with the stock converter for the first few weeks of the 2002 season then I’ll install the new converter so I can get a real difference. I expect to get deep into the 11’s with  this converter, as long as I don’t have traction problems.