Early Mac Third Port Blocks ?

[Ed DalPoggetto]

This is a subject that i have never really asked anyone, but have always wondered why it was changed. What was the reason behind McCulloch doing away with using the third port and changing the castings on the 91 and later blocks. Was it because they went to the big 91-101 carb, or was it something else. I have had a few early engines that had the third port filled with some type of plastic filler, and this was before the 91 engine were ever on the market.....Ed

[Rob Voska]

I have heard everything from it blew the sawdust out of the air cleaner on a saw to it obviously makes more power. The third port was open and not controlled by a reed but by the piston location instead.

[Ernie Fisher]

Ed-

The early Mac blocks had the third port that was controled by the piston position and was to become the most single important peformance increase, thanks to a man by the name of Vince Petruzzi. Vince discovered that by machining those three ports up to the height of the other six intakes, and removing the rib in the block under the intake manifold, we now had much more intake area. Thus--the "nine port" came to be. Vince's discovery completely blew away the competition! Soon, engine builders started coming with many variations, in an attempt to even out the playing field. McCulloch soon realized that this modification was significant, and the castings were changed. First with a large "window" type port, with a removable cover, and then the two "finger port" models were introduced, which remained with all the Mac kart engines up to the end of production. You hear very little about Vince Petruzzi, but I will never forget him and all he did for karting! I was priveliged to drive a set of stroked Mc20s on an A-bone, dirrect drive with Vince's nine ports. That was one very sweet ride!
Vince was gracious enough to share his modifications with other karters, Gary Emmick for one--and you know his history!

Just a litttle tidbit of precious kart racing memories that I had the opportunity to witness.

Best of vintage karting to you!

Ernie

[Ernie Fisher]

OOPS!

Now we know where the "eight ported" Benders came from!

Ernie

[Ed DalPoggetto]

Ernie,
Thanks for the info on this subject, very interesting....Ed

[louie figone]

And Vince is still alive and living in San Carlos, CA, he is about 94 now, I stopped by to visit him three years ago and tried to get him to come to one of the Davis events, he was being treated for cancer at the time and did not think it would be wise.
Vince Petruzzi was one of the leading innovators in the early years of karting but was never given the national recognition that he deserved.
Ask Butch Stewart about Vince Petruzzi next time you see him.

Louie

[ted johnson]

Ed; another reason you see a lot of blocks with the third port filled with epoxy is that we often used carburetion through the stuffer. This provided plenty of crankcase charging, thus deleting the need for the third port. If the third port was left open, the famous Mac "Rooster Tail" of raw fuel back out of the carb became evident. Several companies made engine mount/manifold combos in both single and dual carb versions. It was common to see early third port engines with a single carb in stock location and duals in through the stuffer and the third port blocked off. This was mostly before "9 porting" became popular, though there were some very fast non-9 port motors! Ted

[Ed DalPoggetto]

Ted,
I had a Mc-7 that was modified just like this, third port filled, with all Van-Tech speed equipment. This engine had the twin carb stuffer mount, and a Van-Tech slopper manifold on top. This was a pretty fast engine for a 12 yearold kid, on the school parking lot. My Father quickly replaced it with a stock Mc-6.....Ed

[Dan Flanders]

Hey Louie or Ernie-
Whatever happened to Bob Petruzzi?

Here is a shot of him with Tony Ramirez. I know Tony was looking for him. Here are some pictures Tony sent me of the early days of Northern California karting



Early Newman Club with GoKart Team drivers


Escalon

[Ernie Fisher]

Ted,

That MC7 would have been a good ride not just for a 12 year old kid! I can remember walking through the pits at San Carlos and looking in awe at a beautiful, polished up Mac with a Vantech Sloper manifold and a stack. what a nice machine! It went fast too! It was mounted on a very nice Caretta. The Petruzzi nine porters were famous for cover plates over the intake and dual carbs through the stuffer. I believe he started the nine port craze with the 7 and the 20. As a kid, and not being able to afford the newer engines, I had my Mc 10 nine ported and got pretty competitive.

Hope to see you at Adams!!

Ernie