Idle screws non responsive

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,762
Ok it's a holley 4160 4bbl on a 5.8 ford 1990 OMC.
I rebuilt the carb and since have had it off apart like 3 or 4 times trying different things to get the idle in sync. It idles ok but hunts a little and I can screw the idle screws all way in it still runs. Here's what i've already tried.

secondary throttle plates closed stop set to just touch
float adjustment triple checked just level with body when inverted
idle needles are sharp and true
definately have a new gasket at base
all I have read about idle screws unresponsive says big cams and idle slots exposed high idle, but i can get the idle down to 400, it will idle fine at 500 with the idle screws all the way in or out not much difference.
I think I mighnt have a tiny vacuum leak somewhere but where would the likely place for a vacuum leak be? there seems to be no external vacuum lines or fittings anywhere on the manifold with the exception of the pcv valve that feeds from a spacer plate below carb base, the spacer was stuck pretty good to the manifold I didn't pry it loose to relace the gasket so i suspected it may leak so I sprayed ether around it and no change in rpm. also sprayed the ether around the intake runners and nothing, any advise would be greatly appreciated, Oh yea I ran the carb on another engine and it does the same thing idle screws just do anything so the problem seems to lie in the carb itself.
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Idle screws non responsive

I could be mistaken, but I read on here in another post, the idle screws on a Holley work inverse to other carbs, all the way out is lean, and it gets richer as you screw them in. It makes no sense to me?, but maybe give that a try.
 

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,321
Re: Idle screws non responsive

mikdee said:
the idle screws on a Holley work inverse to other carbs, all the way out is lean, and it gets richer as you screw them in. It makes no sense to me?, but maybe give that a try.
.

yep this can be true but it depends on the exact model of the carb. there's 2 ways carbs adjust idle. 1rst way and the more common is with an idle fuel jet(more so in 2 strokes) or and idle fuel adjuster (in 4 strokes).
the 2nd way is an idle AIR jet, or and idle AIR adjuster.

start by disconnenting the throttle linkage from the boat, that will ensure that the linkage is not pulling on the throttle plates at all. next, back out the idle SPEED screw all the way. (the one closest to where the throttle linkage hooks up). put the boat in the water. now, you should be able to get the mixture screws to respond. If they do not, and you are compensating by working the throttle plates, then you have an air leak. get a spray bottle full of water and mist around the carb base, the throttle shafts, and finally a little down throat of the secondary.
make sure your not getting confused by idle mixture and idle speed screws. they are 2 different adjustments. you should be able to get the engine to idle very low by having the mixture screws set correctly. (i do the lean drop method, always works for me) then, once the mixture is set correctly, you can bring up the idle speed with the idle speed screw.
always start first though by removing the boat from the engine. you don't want to spend 5 hours on this thing because you have a sloppy cable.
 

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,762
Re: Idle screws non responsive

yes thats exactly the way I did it, I did remove the cable linkage, this is not a reverse idle carb, thing is when i put the carb on my car it acyed the same way. Anyhow tell me, what will mist water do to seek out vacuun leak?
 

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,321
Re: Idle screws non responsive

if there is a vacuum leak, the motor should injest the water and dog a little.
 

wire2

Lieutenant Commander
Joined
Jun 25, 2007
Messages
1,584
Re: Idle screws non responsive

if there is a vacuum leak, the motor should injest the water and dog a little.
? Not likely.

The tiny bit of water it would ingest would be similar to driving in the rain and sucking in high humidity.

In fact, a bit of water is beneficial to combustion by reducing combustion chamber temperatures. In doing so it expands to steam and generates a bit of energy in there.

That's why you can buy water injection kits for engines.

To find a vacuum leak, use a small propane torch, unlit.
 

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,321
Re: Idle screws non responsive

at idle it will definitely dog the motor
 

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,321
Re: Idle screws non responsive

i don't use propane because if there is a lean pop... your askin for trouble.
 

Benny1963

Lieutenant
Joined
Sep 17, 2006
Messages
1,476
Re: Idle screws non responsive

blown power valve will stop your holley from taking adjust
check vac at intake replace poer valve with one that matches intake vac
adjust your holley by turning needles in till you feel it sart to die then back off slowly till you reach max rpm on tach then do same to other
b1963
 

wire2

Lieutenant Commander
Joined
Jun 25, 2007
Messages
1,584
Re: Idle screws non responsive

at idle it will definitely dog the motor

Tell you what, Jason; ask your daddy for permission to undo the air cleaner box on his car, ask him to start it. Then, with a spray bottle of water, shoot a full spray directly into the intake. That's probably 200 times as much water mist as you'd suck in through a small leak, and it will still have NO effect on the idle speed.

I'm going to guess you're 21-24 years old, you mentioned you've taken some courses, and now you feel you'd like to offer advice to help people on these forums. That's a fine gesture, but not if the advice is wrong. You've obviously had no/very little actual experience and your physics knowledge is visibly lacking.

i.e., The erroneous water vapor advice,
A tilted motor reading high on a dipstick,
Last week you recommended a boater with salt water in his engine cylinders wait until after the weekend and then take it to a shop.
And others before that.

i don't use propane because if there is a lean pop... your askin for trouble.

A "lean pop"? You mean a backfire?

IF there was one, at idle, it would go out of the carb, not through a tiny manifold leak.

And IF it happened to provide a flame near the propane torch, the worst it would do is light it. There's not enough propane coming out on a low setting to let it accumulate enough to do anything. Professional mechanics use it.

Jason, I can guess you're not going to like my comments. I suppose you may even threaten to have me "soon learn to not contradict you!" :eek:

Well, I'll just have to risk it.:cool:
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: Idle screws non responsive

And if the plug is out and the bloer is running, there will be no accumulation.
 

Benny1963

Lieutenant
Joined
Sep 17, 2006
Messages
1,476
Re: Idle screws non responsive

yes i agree propane works fine also carb ceaner at base and throttle shafts for vac leaks, fine mist of water is a fair upper cyl carb cleaner
the old hot rods of older day used spray for small hp gains and reduced cyl temps
benny 1963
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Idle screws non responsive

The advice about the power valve is not correct. Use the specified 2.5 powervalve. Boat engines are always under load, the vacuum "curve" is not the same as a car.
 

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,321
Re: Idle screws non responsive

wire said:
ask your daddy for permission to undo the air cleaner box on his car, ask him to start it. Then, with a spray bottle of water, shoot a full spray directly into the intake

hmmm... daddy's toyota has a maf, not a map.... i won't even spray so called "mass airflow cleaner" at maf.
and by the way, i do it all the time. always works for me. i'm not giving the motor a misting, i'm fairly liberal with the spray bottle.

wire said:
I'm going to guess you're 21-24 years old, you mentioned you've taken some courses, and now you feel you'd like to offer advice to help people on these forums

nahhh... i'm 30... self employed, have been for the last 4 years. got a degree in marine technology when i was 24 though. as well as certificates from other schools/classes. i love my life... i work on boats from march to october/nov... take the rest of the season off and ski about 100 days a year. I get paid for that too!! :) Telluride this year baby!!
The best part about it, is that I don't have to turn the wrench 40 hours a week. I work well over 40 when you take into account the endless emails, phone calls, and parts hunting. But i only spin it around 20... doesn't suck. It affords me a 3 bedroom home with a barn on an acre. a car, a truck, (the womans car that i somehow mostly pay for now) 4 boats (well... 2 real ones, 1 is a canoe and the other is an 8ft alumimonster with an old johnson 10 horse) My subieroo... (that i put new cams in today!!! can't wait till i get it all together tomorrow to test run it) got a yammahammer yz250, got a triumph TT, got a widescreed with surround sound. got one of those select comfort mattresses (which is why i never loose any sleep!!!) I have a building that I lease... it's not huge, but it's pretty. 1/2 my business is with clients... repeat business... so that automatically cuts any headache factor in half. and i got my good looks, and my endless charm to boot~~ honestly... who could complain about that??

on the otherhand. I bet your old, fat, and not so easy on the eyes. I bet your probably overworked, feel like your underpaid, and probably hate your job, and life in general. You probably wanted something better for yourself, like most people do, but never had the drive, the balls, or the brains to go out and do it yourself.

wire said:
You've obviously had no/very little actual experience and your physics knowledge is visibly lacking.

huh... physics???? listen, i never claimed to be the best mechanic in the world.. and i know i'm certainly not the worst.. however what makes my morgage is the fact that i'm resourcefull.

wire said:
i.e., The erroneous water vapor advice,
A tilted motor reading high on a dipstick,
Last week you recommended a boater with salt water in his engine cylinders wait until after the weekend and then take it to a shop.
And others before that.

1. yep... and not vapor bucko... full on streams of water from the spritzer is what i'm talking about.
2. a tilted motor will absolutely effect dipstick readings. Some more than others... however... I do it a few times a year at least... pumping out overfilled crankcases.
3. I actually recomended that he wire brush out the cylinder walls and heads, and roloc the head and block mating surfaces. (i don't use wire brushes on gaskted mating surfaces) and then i specifically recomended he coat the entire thing in wd40 or a similar water dispacing oil.... i recomended all those things then i said talk to a shop on monday, because honestly, the dude that wrote the original post didn't sound like he had a clue or an ounce of aptitude.... so whatchu talking bout willis??????

wire said:
A "lean pop"? You mean a backfire?

No dang it... i meant a lean pop..... as in up through the dang carb. last time i checked my powerwheels a backfire happens out the BACK!!!!!!!!!! as in through the dang exhaust!!

wire said:
IF there was one, at idle, it would go out of the carb, not through a tiny manifold leak.

no sh!t... how do you check for air leaks???? personally... and i don't know your way, so i can't say it's right or wrong, i start at the carb, specifically the throttle shaft seals, down to the base and mounting gaskets and out towards the perimeter of the manifold... i suppose you could start the other way around... doesn't hurt, but most of the air leaks i've found have been at the carb base and throttle seals.... so.. and i quote "it would go out the carb".... uhmmm yeah.

wire said:
And IF it happened to provide a flame near the propane torch, the worst it would do is light it. There's not enough propane coming out on a low setting to let it accumulate enough to do anything. Professional mechanics use it.

hmmmm maybe... but are you firemarshall bill all of a sudden? but you maybe also have the potental to lose your eyebrows... (or unibrows, to you canadians) also... to the unfamiliar... a lean pop will scare the crap outa ya. Hell i'm use to it and I had a 454 pop on me about a month ago during diagnoses... made me jump a bit.
Now lets say jon doe customer takes your advice and uses the torch. (which, i'm not argueing with you on wether or not it works, it absolutely will make the idle pick up... i don't use one because i find water to work just fine, and on top of that i'm on the ocean half the time, and with the breeze propane is useless) If johnny on the spot customer toasts his eyebrows, burns his face, gets the crap scared outa him and hits his head as he falls off the boat and gets run over by the QE2.... so what, right? I mean, your just like me... some dude on the internet. Theres hardly a possibility of legal recourse because you, some dude on the internet, said it was ok to do it like this.
I however, get real time customers that call me, and ask me for advice before they decide to bring the boat in, or call me out. And I understand why they do it... they want to learn, and they want to save a few bucks. The big difference between me and you wire, is that when somebody asks me how to test something, i'm going to tell them the SAFEST way i know how. When i get called out to a job that's a running issue... the first thing i do is put my KV meter on it... almost every time. I'll never recomend it to anyone, and the reason being is that I get bit every once in a while, it hurts, and it sucks, and i deal, and i move on. But there is no way i'd ever recomend to anyone using a kv meter. I don't know if johnny customer has a pacemaker, or poor balance. So you know... I just don't take the chance with anything i don't feel is safe for the less educated.


wire said:
Jason, I can guess you're not going to like my comments. I suppose you may even threaten to have me "soon learn to not contradict you!"

dude whatever... its your eyebrows. And if your customer hurts themselves on account of your advice, nomatter how uneducated the customer may be in interpreting your instructions, it's still on you, and not me.
 

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,762
Re: Idle screws non responsive

The advice about the power valve is not correct. Use the specified 2.5 powervalve. Boat engines are always under load, the vacuum "curve" is not the same as a car.

Cobra service manual calls for a 6.5 power valve for the 5.8 which I have tested and it's good, I'm going to take the carb apsrt once again and look for a hairline crack somewhere or anything else unusual along those lines, and by the way I wouldn't be a bit afraid to use the propane method, in fact when in the dead of winter I stick a lit torch into the carb of my old tractor while cranking the engine, it's the only way She'l start when it's 10 degrees out and the drive need plowed, I haven't lost any eyebrows yet.
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Idle screws non responsive

A70, I should have worded it like this..."use the specified power valve", sorry!

My post was for those looking for info for issues like this, main point is don't vary from the carb specs for the boat application.
 

erikgreen

Captain
Joined
Jan 8, 2007
Messages
3,105
Re: Idle screws non responsive

What is it lately that this board seems to be attracting more people willing to engage in personal attacks, one-upmanship, and this sort of "I am better than you so you should believe me" crap?

I could point out how much of a fallacy it is that you're trying to win arguments with each other by listing your possessions, but I'd be wasting everyone's time here as much as you are.

The bottom line is, by engaging in arguments like this on the board, it doesn't matter which of you (or both, or neither) is right or wrong. You both look like retards (with apologies to developmentally disabled folks).

Take it to personal email, or even better just drop it.

Erik
 

Buttanic

Senior Chief Petty Officer
Joined
Sep 25, 2003
Messages
711
Re: Idle screws non responsive

Make sure the secondary throttle plates are completely closed. Sometimes the L shaped link that controls how much the secondary will open in relation to the primary is not ajusted to hold the plates completely closed. Also there is an ajustment screw stop for the secondary plates. Make sure it is not holding the secondary open. It should be just enough to keep the plates from sticking shut in the bore.
 

Benny1963

Lieutenant
Joined
Sep 17, 2006
Messages
1,476
Re: Idle screws non responsive

i simply stated that matching the power valve to the vacume level
of a givin engine at idle is the way ive done it for years
due to different level of vac on any givin motor
but again im not a inboard pro but i am learning form these post
have been running holley carbs for 25 yrs as well as rochchester
carter and others
thanks b1963
 

wire2

Lieutenant Commander
Joined
Jun 25, 2007
Messages
1,584
Re: Idle screws non responsive

What is it lately that this board seems to be attracting more people willing to engage in personal attacks, one-upmanship, and this sort of "I am better than you so you should believe me" crap?

I could point out how much of a fallacy it is that you're trying to win arguments with each other by listing your possessions, but I'd be wasting everyone's time here as much as you are.

The bottom line is, by engaging in arguments like this on the board, it doesn't matter which of you (or both, or neither) is right or wrong. You both look like retards (with apologies to developmentally disabled folks).

Take it to personal email, or even better just drop it.

Erik

You're absolutely right, Erik.

It should never have gone that far and I apologize to the forum members. It will not happen again.

I've offered advice, and I've received advice on various threads.
In fact, just this afternoon, I poured 5? gal of Seacast into my transom, a product I learned about here.

wire2
 
Top