Holley hesitation

bigblock665 · 04-27-2011, 12:05:40 AM

My holley has a hesitation around 1700rpm.
Happens when Im going 35mph through town, than when I slowly push into the accelerator when I hit the 55mph zone the car hesitates briefly and the straightens out and goes fine.

My idle screws are (1-1/4) turns out, If I turn the idle screw in 1/8 turn I have a hesitation of idle. If I turn it out any more My idle mix will be to rich and load up my plugs.

It hesitates When slowly accelerating from a low cruise speed and stomping on the gas from a standstill.

Could it be my powervalve opening to early? Its a 10.5 and my vac at idle is 17 hg at idle.

Or could to light of a spring in my vacuum advance cause this possible?

Bikefixr · 04-27-2011, 12:15:28 AM

No, it's opening too late. The flat spot you are feeling is when the idle circuit runs out of capacity, but the main main jets haven't kicked in yet. The Power Valve opens and fills in that transition. You might consider a 2-stage PV, one that opens part way at 12.5 and then opens all the way about 6.5. To see for yourself, pop in a 12.5 and I'll bet it;s silky smooth.

muscl car · 04-27-2011, 12:27:00 AM

i had the same issue and went up from a 6.5 to a 8.5pv and my lean surge issue went away !! . a couple months ago i thought i needed a smaller power valve and the smaller i went the lean surge got worse

gingerbreadman · 04-28-2011, 04:34:50 AM

if you have 17 at idle i would be using a 8 pv

dubs74camaro · 04-28-2011, 07:41:53 PM

For one thing.....what are you running for jets? How are your throttle blades set? My BBC truck runs around 15-16 hg at idle and the 6.5 valve works perfect. Problem with Holleys is if you have one area not correctly setup, it will affect other circuits and cause you to chase your tail with no luck of catching it. Best thing to ALWAYS do with a Holley is to set it back to bone stock, out of the box setting and they sure didn't come with anything over a 6.5 from Holley. I had to bump up to 8.5s on my tunnel ram but there is a little plenum issue there! ;o)

COPO · 04-28-2011, 07:46:13 PM

Quote:

Originally Posted by gingerbreadman

if you have 17 at idle i would be using a 8 pv

PV is never 1/2 of your idle vacuum? Where do you get this from?

Per Holley: To decide what size, use a vacuum gauge and measure the vacuum at idle and subtract that reading by 2.

dubs74camaro · 04-28-2011, 08:56:37 PM

Well you guys are both right and you are both wrong. It's a bigger picture than just manifold vac at idle and assuming you even have the carb properly tuned in the first place for max hg at idle. Everyone look at Holley's latest tuning DVD and then I guess let the debate continue!!!

http://www.youtube.com/watch?v=6vKlAnKdcB4

Bikefixr · 04-28-2011, 10:40:15 PM

Holley's are frustrating. But I have found over the years that if you buy the correct carb, the factory setting is always in the ballpark. They spend a pile of $ tuning these. I'm not talking about swap-meet carbs, new in box only. If the carb is waaay out of whack, I look at the rest of the engine first because Holleys should be damn close. As a previous poster said...using the old vac at idle divided by 2 doesn't work unless you have your package really optimized. Trying to tune a carb when the timing is a mystery, the 'tune' was done by ear..that just won't work. You must get the rst of the combo dialed in, then tune the carb. If you don't, you're going to blame the carb for issues caused by bad timing settings or poor ignition. The Holley power valve is a great tool allowing you to really move the fuel curve around. But each engine has unique requirements. I personally like the 2 stage valves. Single stage are an all-or-nothing, while the 2 stage gives you some early enrichment, then another step as the mains start to kick in. I find I can run a smaller main primary jet thihs way and that makes the carb crisp. Bottom line, get a big-dial vac gauge, hook up to full vacuum, drive car. Look at the vac reading where you get a flat spot. Your PV should be at 1 inch HIGHER. If the bog is at 9" vacuum, put in a a #10 P-valve. the engine wants what it wants. Dial in your package, don't guess, baseline the carb, do the simple things 1st. If you feel you need serious carb intervention, you probabally have another problem. Don't blame the carb.

bigblock665 · 04-28-2011, 10:55:12 PM

If I drop my pv any lower then 10.5 I have an even worse hesitation.

And I also have a hard starting problem if the temp outside is any higher than 70*F after driving the car.

Man im about to pile this car into a tree a tree and walk away, or buy a new carb (witch is hard to dig any deeper in my pockets for more money. My camaro is my daily driver and I need it to run top notch!
Im about to say hell with it and spend the cash on a new carb if I cant figure out this carb soon.

Right now my carb is set accordingly.
63 jet primary and 66 sec., 10.5 pv. Idle mixture screws are out 1-1/4 turns, secondary stop screw has 1/4 turn (any further open I have high idle bs).

Any further info needed just let me know!

Im so close to parting with this carb and buying a new one.

bigblock665 · 04-28-2011, 10:58:50 PM

Quote:

Originally Posted by Bikefixr

Holley's are frustrating. But I have found over the years that if you buy the correct carb, the factory setting is always in the ballpark. They spend a pile of $ tuning these. I'm not talking about swap-meet carbs, new in box only. If the carb is waaay out of whack, I look at the rest of the engine first because Holleys should be damn close. As a previous poster said...using the old vac at idle divided by 2 doesn't work unless you have your package really optimized. Trying to tune a carb when the timing is a mystery, the 'tune' was done by ear..that just won't work. You must get the rst of the combo dialed in, then tune the carb. If you don't, you're going to blame the carb for issues caused by bad timing settings or poor ignition. The Holley power valve is a great tool allowing you to really move the fuel curve around. But each engine has unique requirements. I personally like the 2 stage valves. Single stage are an all-or-nothing, while the 2 stage gives you some early enrichment, then another step as the mains start to kick in. I find I can run a smaller main primary jet thihs way and that makes the carb crisp. Bottom line, get a big-dial vac gauge, hook up to full vacuum, drive car. Look at the vac reading where you get a flat spot. Your PV should be at 1 inch HIGHER. If the bog is at 9" vacuum, put in a a #10 P-valve. the engine wants what it wants. Dial in your package, don't guess, baseline the carb, do the simple things 1st. If you feel you need serious carb intervention, you probabally have another problem. Don't blame the carb.

Thanx, thats a good idea with the vac gauge.. Im gonna try this tomorrow.

I got my timing in perfect now. Engine seems to like anything between 6-8* bftdc

dubs74camaro · 04-28-2011, 11:47:49 PM

Man what is your motor? That's 1975 gas crunch timing numbers. I just did a swap in my truck, changing the 454 for a 396. I hit the timing light button accidently and set my timing at about 10*........didn't run too good. I bumped it up to 18*, where my other 2 BBCs are and it was like a new carb.....but I didn't touch the carb. Get the point?

dubs74camaro · 04-28-2011, 11:58:35 PM

Quote:

Originally Posted by bigblock665

Right now my carb is set accordingly.
63 jet primary and 66 sec., 10.5 pv. Idle mixture screws are out 1-1/4 turns, secondary stop screw has 1/4 turn (any further open I have high idle bs).

Man....what carb are you running that you have a 63 in the front and a 66 in the back? can't be an 1850 because they have a #9 plate. If you have a block in the back it might be a double pumper or an avenger. Maybe that's why it likes that high PV......it's running way too lean. An 1850 runs a 66 main and a 80457, which is the E choke version runs a 69 primary.

BTW.....I have 2 brand new and not reman Holley 600s in the box that I was getting ready to list. Maybe you need one of these. About $50 off Jeg's and Summit. Just a thought.

lol.....I just realized that I started each post with the word "man".

gingerbreadman · 04-29-2011, 03:47:46 AM

Quote:

Originally Posted by COPO

PV is never 1/2 of your idle vacuum? Where do you get this from?

Per Holley: To decide what size, use a vacuum gauge and measure the vacuum at idle and subtract that reading by 2.

maybe check out this link direct from holleys site copo.... its divide not subtract

http://www.holley.com/TechService/FA...ory=Carburetor

gingerbreadman · 04-29-2011, 04:03:21 AM

bigblock665 the absolute first thing you have to do with a holley is turn it upside down and set your transition slots. they need to be set at .020 or simply as small squares like you can see in my picture. this is very important and once they are set they must be left alone.

next if your big block is stock i would be looking at setting your initial timing around the 8-10 mark but if you have a slightly roudy cam or more aggressive then dial that initial up to at least the 14 and more like 16-18....then limit your total timing with your distributor to the 36 or 38 total timing depending on what works best for you.

it sounds like i have created some debate on choosing a powervalve but its in black and white on both holleys site and barry grants but you make up your own mind on which way you would like to choose a powervalve.

http://www.holley.com/TechService/FA...ory=Carburetor

next its just a simple matter of starting with 1/2 turn out on all corners of your mixture screws and adjust them in even and 1/4 increments till you find your best vacum . float height is also very important and having the fuel only just pour out of your float holes is critical.

Dukes72 · 04-29-2011, 09:21:16 AM

I have in the past, and still, think Holley's words are confusing:

"QUESTION How do I tell what size power valve I need?
ANSWER To properly size a power valve, take a vaccum reading at idle and if it is above 12" for a standard transmission a 6.5" will be safe to use. For automatic transmissions take a vaccume reading in gear at idle and if the vaccum is below 12" divide that in half for proper size. Example 9" of vaccume in gear at idle will require a 4.5" power valve."

What if my auto trans reads over 12" at idle in gear? (And why is vacuum spelled wrong two different ways?)

"a 6.5" will be safe to use" "safe" to use? What does that mean? I think the suggestion of the dual power valve and using a vacuum gauge while driving will improve the tune from "safe" to "best."