A Little Help From Holley Users

D.Hearne · Jul 10, 2005

ddonaca351 said:
Ok, so youre saying the car is running rich just sitting there???

If its rich at idle you need to check:
-float level ... ( thats good you said )
-the idle mixture screws
-the condition and rating of the PV
thats it,
-the jets DO NOT CHANGE IDLE MIXTURE
if they do, then youre idle stop screw is set too high allowing the throtle blades to be held open and causing the carb to run on the transfer circuit / primaries instead of limiting it to the idle circuit.

8 is very low vacuum for idle. (i think thats about what my dads dragster made...) Most good street motors I have seen still pull 10-12 at idle and mild street motors can be 14 or higher...
Are you sure you have the cam and ignition timing set correctly?

Dave-

This guy's got your number. I second his emotion. YOU CANNOT JET A CARB JUST BASED ON WHAT THE ENGINE'S DOING AT IDLE. You HAVE to take it out and run it hard to do that.

67bluestang · Jul 11, 2005

oops, wrong topic.

shotsy · Jul 11, 2005

pulled the carb off and the secondary idle adjustment screw is totally galled in the base of the carb, wont go in or out? Should I drill it and re tap it? Secondarys are totaly closed off, which sounds like could be a big portion of my prob running rich, also a good time to change the power valve. Still can't get the Vac up over 8" dunno, guess that I should pull the intake, but I'll be damned if thats it, I used the fel pro printo seals and a big fat bead of blue sillycone on the front and rear of the valley? I'll check the Xfer ports in the primaries when I get home, and as far as vaccum at the at the top pot of the carb at idle, if it's there It's not enough to advance the timing, I didnt put a gauge on it though? **** I'm sure you guys are getting tired of this by now, I'll post more news later or maybe just scrap the 100 dollar hand me down and buy new one

D.Hearne · Jul 11, 2005

You REALLY need someone who understands carbs to help you. You haven't a clue. DO NOT pull the intake. That's not your problem.

shotsy · Jul 11, 2005

Good deal!! I'm not to proud to admit when I'm beat!!!

D.Hearne · Jul 11, 2005

I don't mean to come off sounding harsh, but you really sound like someone who's lost as a goose. The secondary idle adjustment screw also wouldn't cause it to run rich at idle. It's main purpose is to provide extra airflow to increase the idle speed when the primary won't do it alone. I agree with Dave, in the culprit most likely being the power valve. It's either the wrong one, or it's leaking or busted. And I'd also put the 72's back in there till you get the rich condition fixed. As I said before, you've got to run it wide open on the road under a load to be able to know if it needs rejetting.

pabear89 · Jul 12, 2005

DH, they will never learn.

just from wandering thru this, I see that the setscrew is bunged up.
Well that would make me recondition the carb with a kit and repair and preset the thing before i tryed to tune it.

but the 750 holley on mine works like a charm.

The off idle stumble is an easy fix once you have a good starting point and start tuning your carb to the engine.

PB

shotsy · Jul 12, 2005

8 inches of vac is normal for the cam I have as quoted from the Comp cams tech support e-mail I just got

This is normal for a 280 Magnum. I would recommend using a Vacume
Canister. This should help. Or you can go to a smaller cam to get more
vacume.

One prob solved, so I do need the 4.5 power valve for starters as It's just dumping gas correct?

Crs · Jul 12, 2005

I'm also getting about 7-8 inches of vacuum at idle (in drive). My cam is a Isky 280 Mega (280 adv duration .232@ .050), and .517 lift. I have a 2.5 power valve, but I still need to de-jet the primary (it has 72's up front).

D.Hearne · Jul 13, 2005

shotsy said:
8 inches of vac is normal for the cam I have as quoted from the Comp cams tech support e-mail I just got

This is normal for a 280 Magnum. I would recommend using a Vacume
Canister. This should help. Or you can go to a smaller cam to get more
vacume.

One prob solved, so I do need the 4.5 power valve for starters as It's just dumping gas correct?

Check the power valve you have now to see if it's busted and what size it is before assuming that it's the problem. Sometimes, if it's installed incorrectly, the gasket behind it gets "****-eyed" and cause it to leak.

pabear89 · Jul 13, 2005

Or the wrong one gets used,
they have both in most kits.
the one with the 3 sided internal is for a differant power valve,
and if it is used instead of the round thin wahser seal it will leak also.

I bought a year old 600 holley from a guy that couldn't get it to run right,
when I pulled it apart he had used the incorrect seal on the power valve.
I replaced it with the right one and it has been working flawless for 3 years now.

PB

shotsy · Jul 13, 2005

Pulled the old power valve out and it was a 125-65 which I figured from all of your info/advice that that may be cutting it a bit close to my 7-8 inches of vac, so I dropped in a 4.5 and got the secondary butterflies adjusted as per the holley manual where the screw just touches the arm and then another 1/2 turn, this puts the secondary butterfly thingie just between the little pin hole and the little vertical slot just above the pin hole. I then backed the Idle speed screw all of the way out and then back in until it would barely run. and set both mixture screws to 3/4 turns out from the bottom. I've got tomorrow off of work so I'm going to put the vac gauge back on and adjust both mixture screws for max vac at idle in gear with the vac advance on the distributor disconnected and capped off at the carb. correct? then adjust idle down or up from there. Oh and also check for vac at the top port on the carb at idle (where the advance connects to)? Thats my plan I'll report back here. thanks to all of you for your help. I'm a bit of a noob in the carb dept but damn I'm determined!!

Sorry edit (set screw worked fine after I let the base of the carb cool down

pabear89 · Jul 13, 2005

Turn your idle speed screw 1-1 1/2 turns in from the screw just touching the
throttle plate stop.
then turn your idle mixture screws at 1 turn open from bottom out.

Warm engine and make your setting from there.

PB

D.Hearne · Jul 13, 2005

shotsy said:
Pulled the old power valve out and it was a 125-65 which I figured from all of your info/advice that that may be cutting it a bit close to my 7-8 inches of vac, so I dropped in a 4.5 and got the secondary butterflies adjusted as per the holley manual where the screw just touches the arm and then another 1/2 turn, this puts the secondary butterfly thingie just between the little pin hole and the little vertical slot just above the pin hole. I then backed the Idle speed screw all of the way out and then back in until it would barely run. and set both mixture screws to 3/4 turns out from the bottom. I've got tomorrow off of work so I'm going to put the vac gauge back on and adjust both mixture screws for max vac at idle in gear with the vac advance on the distributor disconnected and capped off at the carb. correct? then adjust idle down or up from there. Oh and also check for vac at the top port on the carb at idle (where the advance connects to)? Thats my plan I'll report back here. thanks to all of you for your help. I'm a bit of a noob in the carb dept but damn I'm determined!!

Sorry edit (set screw worked fine after I let the base of the carb cool down

You sound like someone who's come a LONG way forward from the guy who started this thread. "By Jove, I think he's got it" I usually start with the mixture screws out 1 & 1/2 full turns to start tuning. If it'll idle with them out half that, it sounds like you're back on track.

pabear89 · Jul 14, 2005

D.Hearne said:
You sound like someone who's come a LONG way forward from the guy who started this thread. "By Jove, I think he's got it" I usually start with the mixture screws out 1 & 1/2 full turns to start tuning. If it'll idle with them out half that, it sounds like you're back on track.

You know Ollie........I think your Right!

We might have another Holley Fan yet!

PoliceInterceptor · Jul 14, 2005

Sounds like a real good start.

ddonaca351 · Jul 16, 2005

And the best part is the next time one of those "experts" starts talking about what a POS this or that holley is, he can explain to them what an idiot they are....

Oh, on the idle vacuum thing, I usually do it in neutral just for safety sake, but its just a personal preference...

Otherwise sounds like he's a gu-ru in the making.

Wait till he starts playing with pump cam profiles and sec springs, etc... like a kid in a candy store.

Dave-

shotsy · Jul 16, 2005

I'ts much better now I think that it's still a bit out of wack but hella better than it was. Guess that it will be close enough for the time being all it's doing at the moment is driving in and out of the garage as I'm prepping for paint , I'm hoping to get her painted sometime in Sept. Thanks for all of your help guys, YOU ROCK!!!

Boo Boo Foo · Jul 19, 2005

PoliceInterceptor said:
You are never going to get this thing to run right until you get it off the mains, the way you do that without having it idling at 250 RPM is to open the secondary air gap with the little hidden stop screw in the base plate. (you can only get to it with the carb off) Open it about a 1/2 turn at a time until you can get your desired idle speed without the carb being on the main circuit.

This is a great post. And indeed, I think I've learnt more from this thread regarding Holley carburettors than any single other place since I've owned my 66 Fastback.

I'm quoting the above paragraph because I too have a low vacuum 289 which is running very, very rich. I intend to research, research, research and tune my Holley myself because, hell, that's part of the hobby, isn't it? And yes, I'll be buying a vacuum guage, a compression tester, a jetting kit, and a timing light.

My current carburettor is a 600CFM Vac Secondary 80457-2 model. Can I confirm the following please? (I haven't taken it off yet) Would my particular carby ALSO have the "little hidden stop screw in the base plate" as per the carby originally mentioned in this thread? If so, does anyone have a link to a source of photos or an online manual regarding my model? Since I first read this thread, I've done probably a hundred man hours of online research - including the official Holley site. But the secondary idle circuit reference seems to be thin on the ground.

Thanking everybody in advance for the wonderful learning curve in this thread.

shotsy · Jul 19, 2005

As far as I can find that screw should be in until it just touches the adjustment and the 1/2 turn more, I'm still running rich but not near as bad as I was.

A Little Help From Holley Users

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