Dual fuel PFI rails....

[SPECTRO COATING CORP.]

 Anyhow, what I envision isn't 2 injectors per cylinder, but two rails
feeding a single injector (already in place) w/ two different fuels.  Would
have to fab a complete manifold for my Sy to mount two injectors per
cylinder, *definitely* something I don't want to get into!

(snip)

Shannen aluded to the single rail 2 valve but perhaps it wasn't clear,
perhaps i can offer a better explanation.

First  - drilling the parallel holes rails is indeed possible as you  -
however - 5/16'' id will be marginal for size with the flows i suspect
you'll need. Second your going to get some drill drift at that length. If
you have some one that gundrills nearby then they could easily do it, but i
think that you don't want to proceed in this manner.

Here's why -

when you are running regular fuel - say tank 1 you've filled your dual fuel
setup with the regular fuel - as you shift to race fuel (tank 2) you'll have
to purge the entire system - including the tank 1 fuel rail before you get a
true shot of the good stuff.

However (as Shannen said) if you were to run a single rail (fed from the
normal tank and from the race tank but isolated by valves at inlet and
outlet you could operate it this way -

poor art

Tank 1 ----check valve 1 -----rail------ valve 2 ----- return to tank 1
                                              /         \
tank 2 ---- check valve 3 ---/           \--- valve 4 return to tank 2


say your running on tank 1 as normal driving (valves 1 & 2 are open and 3 &
4 are shut) and want to switch to the good stuff

then start the pump on tank 2  and shut tank 1 pump off (make before break
switch or timed relay)

this allows the race fuel to purge that pump gas into tank one.

after so many seconds (purge complete) then open valve 4 and shut valve 2 -
this prevents "wasting" your expensive race gas by dumping it into the pump
gas tank

to shift back open valve 2 shut 4 and then start pump 1 and stop pump 2

i think this is pretty much how the dual fuel tank pickup trucks shift
there fuel supply - someone here can probably confirm that

just my $.02 worth - Jason