Jacko's Project

[Ausjacko]

2 October 2018
Single anyone?

AS I may have mentioned, I have been chasing a stumble/hesitation around 2300-2450rpm. The more I watched youtube and googled, the more I was thinking the Torker II single plane manifold that I picked up a while back was going to be the answer. The clincher was an episode of Engine Masters where they were discussing manifolds for torque v horsepower. In that testing, it was much of a muchness regarding dual versus single plane manifold. However, I think that is because they test at WOT and up to 6500rpm! For street, the convention when using a carby seems to be that dual plane works great and for higher rpm or drag racing you can’t beat the single plane. The thinking here is that the dual plane balances the plenum action across the runners and pulls more air through each side throats, thereby helping with atomisation of fuel out the discharge nozzle. The single plane on the other hand, due to the larger plenum volume does not create as much air speed down low rpm, hence not as good fuel atomisation on the street during ‘normal’ driving.

In their summing the Engine Masters spoke about the results and then the nugget, ‘and what about the new throttle body injection what is better there?
‘Everyone I know has used a single plane’ And dear readers, that was it- I must change!

Now the thinking behind the decision and observation is that fuel injection does not rely on air speed to suck fuel out; it uses fuel pressure and an injector nozzle or in Fitech’s case an injector ring. Mixture is preset and the O2 sensor works with the electronic brain to manage the amount of fuel you need to achieve the AFR target.

Changed the manifold over and did not find anything odd or worrying. Inlet and other gaskets were holding well. Unbolted everything and swapped in the new Torker II (new to me anyway). I had already cleaned it up and drilled and tapped a second water temp sender hole for the Holden sensor; the manifold only has one from factory. She came up really well and fitted on nicely. Hood height is not an issue as it is actually slightly lower than the Performer. First start was easy and after I advanced the timing from 15 ATDC to 18 BTDC she sounded and seems to be running well. I checked and reset the IAC steps after she reached operating temp. Will need to check the coolant level tomorrow. I am only getting 9 somethings of mercury as a vacuum reading at idle and may need to change the cam setting to No 3. The motor is fairly placid under 2400 but above that you can feel it getting onto the cam (and into the fuel tank).

[Ausjacko]

29 October 2018
Fitech and manifold update
Finally took the car for a good drive over the weekend and she feels much better. The stumble/miss is gone and she feels a lot smoother. AFR trim is fairly stable suggesting the ECU is much happier probably due to a more stable/consistant signal from the manifold/plenum.

Overall, I think the change is a good one and given my ‘druthers’ I would have opted for a single plane at the outset.