Matt Gruber

thanks to input from CF members i've made many changes to my web page
A/F tuning
click on link in sig
no pics; fast load
more input needed :yesnod:

Matt Gruber

if you have sig's turned off, click on my name :seeya

SmokedTires

That's great. I've yet to get the A/F gauge installed, but this will be very useful once I do ! Thanks :cheers:

74vetteman

To rival fuel injection, you better do more than just change jets. Most steady state street driving is done with only the idle and transition circuits.

I am using a O2 sensor to try to dial my speed demon dbl pumper in. My goal is to have stoich conditions at everything except wide open throttle. My plan was to jet to stoich, then open up my power valve channel restrictions (pvcr) a few thousands at a time until I reached 12.7:1 (which I believe is around 870mv). I found that in most driving conditions, cutting back on jet sizes made little difference to my O2 readings. This is because I didn't touch my idle or transition circuits. I am a little leery of drilling out the air bleeds.

So, I am still running rich. My idle and transition circuits are both rich (over 800 mv), and my spark plugs are sooty. At wide open throttle, everything is great. Where do I go now?

Fevre

Not sure if this would work on a speed demon but forum member Norval puts a thin wire, about .015 inch dia, in his idle circuit to reduce flow. He bends it at a 90 angle and places it between his basket and metering block. He says it help make the idle adjusters more sensative. I am going to give it a try on my Holley 750 dp and 383 combo next spring.

427V8

I've heard of the wire trick but could never understand how to keep it inplace :crazy:

Fevre

If you bend it a 90 angle part of is in the circuit and part of it gets wedged between the gasket and metering block. Like I said I have not tried it yet but from Norval's desc it makes sense.

Matt Gruber

74vetteman
idle works best at 13:1 (as per Vizard)
on my 650 DP #6298 idle transition is done by 1400 rpm! 1400 rpm is under 35 in my car, and at this point it is on the main jet. MyTC stalls wot at 2100, and 14-1500 under light acceleraton. i have not tuned the idle transition circuit because in my car it only passes thru it, but i did check it and it was 13:1.
Modern EFI makes a stock carb look like junk; after tuning i am impressed and mine rivals EFI. i am mainly interested in max. power. your goals and results may vary.
the 6210-6298 series is a spread bore q-jet replacement, i bet it has better, quicker to main jet transfer than your carb. You will have to "jet" your transition, or get a carb like mine.
Also, cruise can be 16-17:1

i was always told to stay away from square bore holley's; they are not street carbs. I don't konw about demons? call them and complain!

a test: plug a spare set of main jets with solder. go for a short ride and see what cruise speed is stoich. there is the begining of the transfer! tell us how fast. i guess 40-45 mph.(i have no idea)


[Modified by Matt Gruber, 11:42 AM 7/30/2002]

Matt Gruber

i just added this tip to my site:
To find the leanest cylinder, pull out all the spark plugs and pick the one with the lightest insulator. :cheers:
Simple, and it sure beats tying a friend on the fender with an IR gun as you floor it :yesnod:

Ingar, Norway

I have a sensor in each collector and the passenger side is always running richer than the driver side.
Is this carb (original Qjet) or engine (stock 350) related?

Matt Gruber

Ingar
it is engine related.
in 1997 the new LS1 changed the port layout and firing order to correct the problem.

Ingar, Norway

Thanks Matt!
Does TPI address this problem by operating left/right-hand injectors individually?
On which side of the engine is the O2 sensor located with TPI?

Matt Gruber

Ingar
to correct the problem i jetted the rear jets unequal. .088", .082" on my Holley #6298 650 DP
.

TPI? see the C4 section. i don't follow TPI