Quote from the EBay guy..
> Now with this combo lets recalculate cause long rod will help your
> high rpm horsepower by slowing piston speed down over tdc and helps
> your motor breathe,its all in the angle of the dangle and gives you
> light piston to do those revs and is easier on cylinder wall loads
The rod is way too long. The whole dwell at the top of the cylinder is
pure fantasy. It is all about intake air speeds both peak and mean and
that is what you are playing with when you change rod length along
with the angularity to the cylinder wall which has a substantial
effect on the mechanical efficiency of the engine i.e.. torque.
There is no difference in block deck heights between a 302 and a 350
so no gain in looking for a 302 block. A like new 302 crank that can
be destroked is rare. You never mentioned what you are going to use
for heads and intake. Most are sized for a 350 or larger engines and
work poorly with a 305, they need to be specifically built for the
smaller engine. Why the D class engine is the first question? The
cheapest engine to build and have come out well for standard parts is
a 355 to 368 chevy. If I was going to build one of those I would use a
6 inch rod to 6.125 with the 368 and no more than that. The reason
being commonly available heads and intakes. If you want to go for a
custom ported set of heads for a longer rod engine then fine use the
longer rod but you will need a longer wallet to go with them.
If you have to build a D engine with a Chevy the first part i would
look for is the low deck block that was made by GM. It is as rare as
the perfect 302 crank but well worth the effort as it offers a
approximate 8.5 deck height and was built for racing. This will allow
you to use a 5.85 rod and some pretty standard pistons. as well as
pretty much readily available heads. The intake will be custom but it
would have been anyway unless you are building a 350.
A combination NOT to build.. 2.85 stroke X 4.125 bore with 6.2 rods...with
18 degree heads..
If you are really set on a Chevy then a 3 X 4.020 X 5.85 or 6 with 23
degree heads.. EX Brodix -8 high port and a custom intake as usual
unless there is one for it now. I don't fool much with single 4 barrel
intakes so really have no idea what is available. a good Kinsler 3
piece IR setup is a bolt on though.
If you really want a D engine then the Ford is the real answer.. has a
low deck block standard.. Yates heads are about the best you can
buy.. 3 X 4.020 X 6 rod.. ought to be an off the shelf combo.
Another combo that works well is the Buick V-6 but that is another
discussion. Especially in turbo trim their performance is legendary.
Oh one other thing a turbo engine is the same as a NA engine don't get
sucked in to the 'but with a turbo' sort of bull. A turbo engine is a
NA engine running at a different altitude period. Yes the cam may be
slightly different but emphasize the word slightly.
And the long rods allowing more RPM.. How high you going to rev it??
ever price the valve gear to run a SBC at 9800 for 5 miles ??
rememeber that is 20 passes at you local drag strip and you can't
check the springs every 5 passes as you won't be at the first measured
mile yet..
Above all don't build an egine because you have 1 or 2 parts laying
around and have to buy the rest. It all becomes a compromise for the 1
used part and the results will bear this out. If you want to build an
engine with used or low buck parts only buy the ones used that are
specifically a match for what you are trying to accomplish in the
first place. Yes the rest may have to be new. For a Chevy the only
parts I would ever buy up front for no particular purpose is a good 4
bolt 4.000 in bore block and a set of 6 inch large journal Carrillo
rods.
As always your mileage may vary....
Dave Dahlgren
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