bluesman2a : Is there a Holley-Doctor in the house?

Is there a Holley-Doctor in the house?
Post by bluesman2a on Sept 24, 2006, 11:47pm

I've been doing a lot of reading on general Holley tuning here lately and have learned a lot. I now have some specific questions for the Holley guys here. Looks like SpicerGear and Elwenil had some good input over on Pirate... I'm close, but I could really use a hand here folks... Any assistance appreciated.


Specs:
Vehicle: Heavy ASS M-715
Engine: 383 stroker with vortec heads and air-gap intake 9.5 to 1 compression
Cam:LIFT 486intake, 508 exhaust, DURATION @ .050 234 intake 244 exhaust
Carb base specs: Holley Truck Avenger 670CFM (Gen#2, so that's taken care of)
Ignition: MSD HEI distributor, with AC Delco plugs 41-932 gapped at
.045

Where we started (stock):
Stock Jetting: primary 68 secondary 89
pump: nozzle .028 30cc diaphragm orange cam
Power valve 2.5
Secondary spring: black

INITIAL PERFORMANCE:
The carb ran super rich right outta the box. Also had the flat spot everybody talks about at around 2500 RPM's. Per Spicergear's post, I checked the linkage on the accelerator pump and it was WAY off. Essentially it was running partially depressed all the time and probably responsible for fouling at least one set of plugs.

Adjusted linkage and flat spot cleared up, but coming off-idle, it'd still fall on its face, then pick up. If I blip the throttle sitting still it would sputter and die.

CHANGES:
Moved up to .035 squirter
Performance improved, again, but coming off-idle is still not great. Almost acceptable except pulling off from a dead stop.

CHANGES:
Moved up to 50cc diaphragm and .040 squirter.
Haven't had a chance to test this yet, ran outta time.

QUESTIONS:

1) I am seeing noticable improvements here, does it sound like I'm on the right track?

2) The orange cam seems to have the best engagement aside from the yellowish or brown ones. Should I have to step up to something that radical?

3) Any advice on cam/pump diaphragm/nozzle selection to at least get me started would be greatly appreciated.

4) Should I change over to the hollow screws for the .040 nozzles?

5) I haven't gotten into re-jetting yet, but at this point I'm thinking I'm about to the point where I need to run it and get some time on it to read the plugs before I jump into that, am I correct in this assumption?

Any other general thoughts or input? Am I missing something here?

Tomorrow I'll give Holley a call as well to see if they can give me any recommendations, if I get anything useful, I'll post back.

Re: Is there a Holley-Doctor in the house?
Post by elwenil on Sept 25, 2006, 9:15am

I'd tinker with the jets and power valves first. I had some info on getting started in the right direction with the power valves and whatnot but someone borrowed my book and I haven't seen it since. The net should have some of the same info out there but as I am at work I can't search crap since we block Google for some reason.

Re: Is there a Holley-Doctor in the house?
Post by wetcj on Sept 25, 2006, 9:20pm

Just from reading your post it sounds (to me anyway) like your pump may be adjusted improperly. "It was running partially depressed all the time" a properly adjusted pump will be partially depressed, a minute amount but that way there should be no delay from when the throttle linkage moves till the pump works. "Probably responsible for fouling at least one set of plugs" not sure how this was possible, pump should only be providing fuel when throttle plate opens, this is when you need it. Make sure floats are adjusted properly, fuel should be level with the bottom of the treads, not running out. Another thing worth checking is the power valve, bad valves can leak extra fuel into the system causing other ailments.
Here's Holley's recomendation for pump adjustment-
QUESTION My vehicle has a stumble from a dead stop. What can I do to cure this?
ANSWER The most common cause of a stumble is not having an adequate accelerator pump shot. The first thing to do is to look at the discharge nozzle and make sure you are getting a good strong pump shot. If not then you need to inspect the pump diaphram for a hole or tear. You will also need to make sure that the pump passage is clear from any trash or debris. First you will need to check the adjustment on the pump. To do this you will open the throttle all the way (WOT). Push the pump arm lever down and then adjust the pump override spring to obtain .015" clearance between the pump arm and lever. If you are having a stumble and no black smoke out the tailpipe then you will need to increase the shooter size. If it stumbles and you are getting black smoke from the tailpipe then it will be nessasary to decrease the shooter size.