All Small Six Marine Rochester Mercruiser 2 Barrel Carburetor on a 78 200 D7 head

[78_200_C4]

On the first drive it wound to 5,500 in low then pulled hard when in 2nd with a C4 + 3.25 gears.
Cam is a stock Enginetech 256. Head is milled .060
I haven't been able to test the C4 GV overdrive 6 forward gears yet.
I'll do that on my 2 favorite uphill I-80 on ramps.
The carb is a large base large venturi Rochester type Marine 2 barrel.
It only has one idle adjustment screw and no vacuum ports.

 

[78_200_C4]

It hauls @ss on I-80. In 3rd over at 85 mph + 3.000 rpm over it mows down any I-80 hill without shifting down or adding more throttle angle.
Today there was so much traffic on I-80 that I went in and around all the new cars until my 63 4 door 6 cylinder Falcon wagon was leading the pack at 85-90 mph.

 

[drag-200stang]

How much power would you say you gained with the change?

 

[bmbm40]

Excellent engineering on your carb. I have been very interested in the Rochester and Carter BBD. And awesome cold air setup, looks NASA related with that insulation.
I-80 is perfect for high speed testing. I get a kick out thinking what BMW owners and such reactions are to the Falcon wagon tearing along like that.
Hope you post more videos.

 

[powerband]

interested in the 2Bbl adapter - looks like you formed it with epoxy?. Howd' ya do it?
.
On similar 2bbl mod, trying to retain the 3-1/2 degree angle on the carb base to head/manifold to use Holley 2300 series 2 Bbl carb with float toward VC not over headers.
.
with non heat rated angle adaptor from 3D printer file:
.. .
. to replace current 2bbl adaper:
. .
any suggestions appreciated ...
.

thanks

 

[78_200_C4]

The adapter is 1/8" steel plate top and bottom. The sides are 3/4" angle steel.
The JB Weld epoxy was used to smooth my lack of tig welding skills with my old Harbor Freight tig welder.
I barely used any filler rod.
The D7 large log intake bore was enlarged with a carbide bit in a die grinder.
The intake was not milled, brazed or welded.
Adapting the air cleaner to the large base Rochester was as much work as the carb adapter but it turned out great.
The Rochester Mercruiser 2 Barrel Carburetor has the same size throttle bore and venturi size as the 500 Holley 2 barrel.
The 1 + 2 barrel 500 cfm rating is around 353 CFM at the 4 barrel rating.
This carb is not too large for my 78 stock cam 200 with an enlarged intake throttle bore.
With a new Lares 16-1 steering box I can do 80 mph on I-80 curves as I pass the new cars.
The new Lares steering box was around $230.00 when I bought it.

 

[Frank]

Rochester carbs have excellent engineering and can not be beat when set up right. The triple venturi provides excellent atomization= snappy power and good economy.