My rolling road graph

[danny69]

Here it is,

You can see two graphs layed over one another.

The one that makes the most power is where the Holley carb vacuum secondaries have been allowed to come in. Unfortunately the moment thay come in causes a temporary leaning out causing a dip in torque and power.

You can see the Lamba line at the bottom showing a small spike indicating the leaner moment.

 

The dotted line is a run with the secondary chokes wired shut.

No dip in power but an overall loss in top end.

 

 

If anyone knows how to improve this situation I`d be very interested.

[Supercharged Nat]

impressive stuff. the lean moment on the holley can be fixed im sure. you need to get some info on the holley carb you have. i suspect it have an enrichment device on there some where to compensate for it or the carb can be modified in some way- maybe making the secondaries open slower or something (im not too hot on 4 barrels).

 

was this just power runs or was any tuning done? if no tuning was done, find someone whos knows these carbs and have them tweak the setup

[john_3.0s]

i take it thats on an essex? have you done anything else to it?

[danny69]

They just set the timing to a standard setting and the mixture by the exhaust probe and then did two power runs. Still cost £100 though

I thinking a stiffer spring to open them more slowly too

 

John, It has a kent V63 cam big valve heads and powermax pistons, lightened flywheel too.

[Supercharged Nat]

i would get onto the holley website or google the exact carb you have, i suspect lots of american sites/ forums etc would know all about them. theres also good books on tuning certain carbs, that may give you an insight.

[danny69]

Cheers! I have just got hold of some books and downloaded from the Holley website so hopefully I can fing out what I need to know.

[JP.]

What spring collor do you use on your secondairy. You might consider a slight heavier one.

Air fuel ratio looks good at that point so there's not much to worry about.

 

You might experiment with some differend cams or change position of the existing cam on the acceleratorpump.

 

Secondairies come in at about 3600rpm & co rises a bit at that point could be caused by the powervalve doing what it should do ( butterflies opening & leaning the mixture by the temporary lost of signal... powervalve reads low vacuum and enriches the fuel).

 

As I found Holley allways very helpfull you could trie and contact them by email.

[danny69]

I think the spring is the standard mid range one as it is a fairly new carb and hasn`t been altered. I am thinking about getting the quick change kit and a set of springs.

Thanks for your help, I might well try e-mailing Holley directly.