General Information
Note: The information contained in all
of the "Engine Detail" sections should be read before proceeding with
modifications, etc., because some information that applies to all engines, or
all small blocks or all big blocks, might not be duplicated in every section.
Buildup
4 BBL Modification
If you want to use a 4 BBL on this engine, you must change the heads
to 5A castings as found on 307 Olds motors. If you mill them .030-.040,
then you'll gain back compression.
Then you can bolt on the Edelbrock Olds performer intake. A set of
Mondello heat riser plugs installed in these heads will make more
power. Just drill a 1/4" hole in each plug to get back just enough carb
heat. The Mondello 15-100 cam works great in those little 260's.
The heads on the 260 are designed for the 260's small displacement.
So, in order to increase torque (I'm assuming) the intake runners are 1/2
the size of conventional runners. Unfortunately the way the accomplished
this was to fill the bottom half of the runner with material - BIG flow
stopper! Not to mention a good spot for fuel to puddle.
Being undaunted by this (plus I had already purchased the intake and
carb) I went forward with the installation. What I found was that the 260
required me to do a LOT of tuning to the carb to keep it from bogging out of
the hole.
I had the motor tied to a TH-350 and 3.42's. After getting the carb
staightened out, had to rejet and fiddle with secondary opening rate, the
combo ran noticibly different. Part throttle was very similar (slightly
stronger) but where the big difference was, was in the top end. I had put
an "RV" type cam in it, PAW special, and it definitly liked the 4 barrel
over the 2 barrel. Unfortunately never had the car to the strip either
before conversion or after, but it did make a very marked improvement. Gas
milage was about the same for both combos as long as I kept my foot out of
it (aprox. 17mpg).
[ Thanks to Scott Woodworth, Todd Daenzer for this information ]
Buildup Examples
Rebuilding
Tuning / Power Boost