Holley Accelerator Pump Tuning

deafwish · **Posted:** Mon Feb 17, 2014 2:45 am

Hi all,

I have a VP 5.7GL (pre-Vortec) with a Holley 2300 - 2BBL 500cfm carb'. Engine is stock, other than HiTek Headers.
I was setting up the timing and idle circuit yesterday (9 BTDC with 1 TO from seated with 18.5 In Hg vacuum) with a mate, who has a VP 5.0GL (Vortec, also with Holley 2300).
My throttle response is brilliant everywhere in the rev range, other than off idle.
When in gear, I can promptly go from 0% throttle to 100% throttle & occasionally get a stumble, sometimes a pop.
When in neutral & I grab a fist-full of throttle, it almost always stumbles & frequently pops.
My mate's 5.0GL Vortec revs extrordinarily fast in idle and his accelerator pump nozzle squirts copious amounts more fuel in than my nozzle.
I have a 28 sized nozzle & waiting on confirmation on what size my mate has.
Carb has a red coloured cam and lever clearance is to spec (0.4mm).
I have Googled that going up 2 nozzle sizes is ideal in automotive applications & curious as to whether marine is any different?
Was a 28 size with a red cam standard for this engine? Would my headers have made that much difference to flow?
Any other tips?

Cheers.

ric · **Posted:** Mon Feb 17, 2014 8:40 am

Running E10 I found I had to go 2 sizes up on the pump, it works the same as in a car. Might want to check the main jet too, they're usually too small.

What was "standard" for the engine doesn't matter as VP didn't tune them right to begin with. Read the plugs and go from there. There's o2 sensor flanges you can install also from Ebay (at least for mercruiser not sure VP )that will allow you to put a wideband O2 sensor in there to check it all out.

http://www.ebay.com/itm/OXYGEN-SENSOR-P ... 26&vxp=mtr

neutron · **Posted:** Mon Feb 17, 2014 2:27 pm

ric wrote:

Running E10 I found I had to go 2 sizes up on the pump, it works the same as in a car. Might want to check the main jet too, they're usually too small.

What was "standard" for the engine doesn't matter as VP didn't tune them right to begin with. Read the plugs and go from there. There's o2 sensor flanges you can install also from Ebay (at least for mercruiser not sure VP )that will allow you to put a wideband O2 sensor in there to check it all out.

http://www.ebay.com/itm/OXYGEN-SENSOR-P ... 26&vxp=mtr

I agree on the main jet probrably too small check the numbers on your buddys carb as well.
I went from a 69 jet to a 73 to get my Holley 2300 to run right on my last boat also get a powervalve that take less of a vaccume drop to open.

yup Ric, plugs tell the whole story

deafwish · **Posted:** Mon Feb 17, 2014 3:32 pm

I don't know about American fuels, but all the detergents in premium Aussie fuels make plug reading totally useless.
I will try a 31 sized squirter and then move to the main jets if this doesn't fix the hesitation.

Winter Sux · **Posted:** Mon Feb 17, 2014 5:12 pm

Deafwish, don't even consider the oxygen sensor thing. Your engine is carbureted thus you'll have no place to plug in to read the data stream.

The popping you're hearing is what concerns me. Are you able to take a video and post it with the flame arrestor off? I think I have an idea what's wrong but can't be certain without seeing and hearing it.

ric · **Posted:** Mon Feb 17, 2014 7:03 pm

http://www.innovatemotorsports.com/xcar ... t=0&page=1

deafwish · **Posted:** Mon Feb 17, 2014 7:15 pm

I'll try take a quick video.
My mate has a 55 sized nozzle on his 5.0GL (Vortec with 2BBL)!
I have borrowed a 31 and a 37 sized nozzles from a speed shop customer of mine.
I'll report back after a run, this evening.

Winter Sux · **Posted:** Mon Feb 17, 2014 8:34 pm

Ric, O2 sensors only send an either, rich, lean or neutral signal to the ECM. The ECM will then command the injectors to adjust their band pulse width to try to keep the O2 signal at neutral. That toy you posted is an over priced waste of time.

ric · **Posted:** Mon Feb 17, 2014 8:57 pm

Not a bit sir. It's a wideband o2 that directly and accurately reads the air fuel ratio down to the .1 percent. It's the gold standard how race teams and performance car modifiers tune their fuel.

deafwish · **Posted:** Mon Feb 17, 2014 9:09 pm

Winter Sux - You're referring to a Narrow Band O2 Sensor, not the Wide Band Ric linked to.
Regardless, I'm not welding in an O2 bung in to my stainless headers! :shock:

Anyone find any data on what components these 2300's should use?
A variance from 28 to 55 on the same carb' seems crazy!

fiznuka · **Posted:** Tue Feb 18, 2014 12:21 am

Use this link http://boatinfo.no/lib/library.html find your engine model and go to fuel system there should be a specification page that has the info your looking for. I don't think it has the squirter size.

deafwish · **Posted:** Tue Feb 18, 2014 4:15 pm

So it turns out that the 37 sized nozzle works perfectly & my throttle response is now great!
I now have to buy one (I borrowed these to trial) and see that there's two different types.

Is there a real world difference between these 2 types, in low power applications?

p.s. Thanks for everyones help! :wink:

ric · **Posted:** Tue Feb 18, 2014 4:36 pm

Well the dealer sets the carb based upon elevation when the vessel is sold, maybe it's possible in a previous life that boat was in some altitude?

deafwish · **Posted:** Tue Feb 18, 2014 4:47 pm

It was from Lake Mead...

ric · **Posted:** Tue Feb 18, 2014 5:37 pm

Could have been set a tad leaner than stock

www.iFourWinns.com

Holley Accelerator Pump Tuning

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