We are in the process of rebuilding the Buick straight 8. New flat top blower pistons, reground cam from Donnie Johansen, "O" ringed block. Are changing to a 6-71 blower with 6 EFI injectors above the blower.

Pictures?

Pleeeeeease.

I'm curious why you would put the injectors above the blower. Do you get more charge cooling that way? Seems like distribution and throttle response would be better with them closer to the valves....where is the throttle?

Trying to learn something here.......

Leif

If he's running enough boost to require O-ringing the block, I suspect he needs the cooling effect for the supercharger itself (to keep it from heating up too much).

Of course around here you never know, it might be an 'updraft' blower.

"Updraft Blower" that's a GREAT idea for a vintage look! This forum is the BEST!

Leif

Leif, we have been hashing and hashing on the location of the injectors. In the intake ports (4 of them), in the plenom (4 injectors), or above the blower, or a combination of all three. We have decided, because we will be running out of time, to put all the injectors above the blower. This will give some cooling to the blower and charge air. We know the intake temps will be high, but this is what we are going for this year.

A problem found when contiplating the building of port injection with siamised port engines, as most of our older inlines were, is firing order. For a port injection to work properly, the cylinders sharing the port would need to fire 360 degrees apart.

On the Buick straight 8, the firing order is 16258374. The number 1 cylinder fires at 0, and #2 follows 180 degrees later. #1 then fires again 540 degrees after #2. An injector that is a constant flow variety, would flow 1/4th the fuel to #2 cylinder and 3/4 to #1. Every pair of cylinders in a straigt 8 have the same timing between cylinders in their pairs as number 1 & 2 have.

Tom Lowe has been working to over come this same phenominum in his 292. Cylinders 3&4 fire 360 degrees apart, but pairs 1&2, and 5&6 do not. This created a lean and rich cylinder with-in the first and last pair. I understand that a "timed" injection pattern helped but didn't cure the problem. He'd be the one to talk to about that, and the trials he's had.

With that in mind, bringing the fuel in above the blower means the engine should get a more homogenous mixture to each cylinder, and benefit from some charge cooling.

Thanks! That's a good explanation. Old Chryslers have the same problem. Why can't you use an injector for each cylinder (2 per port)? They would just have to be sized smaller.

I've noticed that a number of aftermarket injection systems say they work with anything as long as it doesn't have siamesed ports (nuts!)

Leif

Soon megasquirt is coming out with a sequential injection system that will allow for per cylinder fuel trims that will help fix this problem. To tune you would need a wideband O2 sensor in the problem header pipe and in the collector. So in the case of the 292 number 1&2 could be leaned out and 5&6 richened up. It does require a cam sensor to tell the system which half of the firing sequence the engine is on.

There are other systems that have this built in - just cost more.

And you don't learn as much from using those either.

Glad to hear they have it coming along that well.


GH Good luck.

FWIW I had an instructor in A&P school by the last name of Weiand (related? dunno) that talked of adding enrichment to an engine under boost with the 'cold start injector' (off a VW, Bosch CIS injection system) Could you maybe add something like that to the head (aimed at the back of the valve)?

I know you probably won't have time this year for that, but I just thought of it, hope it helps.

'cold start injector'
Ohhh that sends shivers down my spine! In 1973 I had a '71 911 that had a thing like that built into the air cleaner. Unfortunately, it malfunctioned and built a fire that melted the booster ventures on the carburetors. It cost almost $1,000 between the carb and the expensive German plastic air cleaner. When I handed him the bill, the State Farm guy in Elizabethtown KY just about swallowed his cigar!

Leif

great to here about this fun project.

here is what i have and have done so far.292 port injected, 2 injectors per port( side by side) 42 lbs each. i use a holley commander 950 to control the injection. the system is a batch fire setup. meaning when used on a v8 , it fires right bank then left bank 180 crank degrees later. i will name the injectors for 1, 2 port a and b. 3, 4 c and d and so on.the engine was first ran with injectors abcd firing as right bank and ef firing 180 degrees later. it worked but had a bad idle, almost stuttery, but at road speed seemed ok.
i also can set the injectors to fire every revolution or everyother revolution. every rev worked better.
i then rewired my injector harness to make injectors a, c, e be right bank and b, d , f be left bank. that made the siamesed injectors fire at different times. this helped alot and the idle is much better! so each injector fires every rotation and fires 180 degrees off from the other siamesed injector.
another thing i did was to make intake port dividers that split between the injectors and go into the head dividing the valves. that was the biggest ticket to engine smoothness. with the turbo i still have good airflow.
this winter i am going to really open up the sides and roof of my intake ports to maximize airflow

I bet.


'Specially in '73 dollars.

Guys,
When thinking about siamised ports don't just look at the firing order. You have to plot the valve opening and closing to each other in each port.

Harry

Tom
I guess on yours the Holley Commander doesn't have fuel and just controls air... with the injectors down near the ports...is that correct?

Leif