burning rich

[McGraw]

okay, I'm sitting here gapping my spark plugs (which is right up there with indexing plugs in my book.) And despite I've already bought the plugs. I was wondering what you guys think.

 

the monte has a 350 in it from a 87 GTA. with a Holley 600 carb with vacuum sec. I've turned down my idle and adjusted my idle mixtures down to just above 'running' (1 1/8 turns right now) for the car. and the float levels are perfect. But the car still burns rich. Though no more hideous black smoke now you just smell it, could this because :

 

A) The days I spent trying to make it stop burning rich while the carb was dumping fuel through the base plate could of caused the plugs to foul.

 

B) The gap in the plugs was only .035 and I have a HEI system.

 

C) It's a carb engine and I'm going to smell gas regardless.

 

And do you guys think I might get lucky with simply getting a hotter plug and gapping it right (I'm doing now.) This is what I've heard from my some people, while there are others that say it wouldn't make a difference. I know the gap will, but will the plug temp matter that much on a NA engine?

 

Thanks in advance.

[Total Sign]

When is it rich? Around idle? Enough for it to load up a bit?

 

What power valves?

[McGraw]

I notice it more when I'm at idle (I want to blame it on an exhaust leak.)

 

The power valve was 'fixed' (removed) and a bolt was put in place of it. I was tired of replacing them and was told it was an okay alternative.

[Tinman]

I notice it more when I'm at idle (I want to blame it on an exhaust leak.)

 

The power valve was 'fixed' (removed) and a bolt was put in place of it. I was tired of replacing them and was told it was an okay alternative.

 

Put a power valve back in it! The power valves allows extra fuel at WOT, without it you will have to jet it up around 8 steps and that will cause a very rich mixture at cruising speed.

[Total Sign]

Its about 6-10 steps.

 

Put the powervalve back in. Start with a 6.5. If the engine loads up at idle, step it down to a 4.5/3.5/2.5. You must step it down slowly and notice if there is any flat spots or hesitaton.

[desperado]

Power valve has NO effect at idle. None. The power valve feeds throught the boosters just like the main jets do. So at idle, they are dormant.

 

OK, things to check

 

1. Fire up the car and pull the air cleaner, look down the thoroat of the carb and make sure that you are NOT getting any fuel off the boosters at idle. It you are then you have high floats/to much fuel pressure. (I just went through this myself).

 

2. If you are not getting fuel, then there are a couple other things that need to be checked. You will need to pull the carb, and check the adjustment on the butterflys. There is a slot in the side of the venturi that you need to locate. Ther should be only

.07MM showing, if you have more showing, thenyou are into the intermediate circuit of the carb. This gives the motor extra fuel during the tip in of the motor, where you lightly apply throttle to put in fuel ahead of the acclerator pump shot. This is a FIXED amount of fuel flow, by that I mean that there is no interchangeable jet feeding it. If you are showing alot of the slot, you need to readjust it to what I said then drill a 1/16 or 5/64 hole in both p[rimary butterflys and thenreinstall the carb and see if it will idle. As Malibu Stacy about this, his car went from not idling below 1200 RPM to idling at 600 RM once this was done and it gave the carb back the ability for the idle mixture screws to work correctly. Another quick way to see if you are needing to do this is to run both idle mixture screws in, the motor should die. If not you have the carb improperly set. THe cause of this is a lot of duratiion in the cam, or too big a cam for the rest of the motor.

 

3. When was the carb rebuilt last, and did the perosn that did it know what the hell they were doing? Ham fisted shade trees will most always over torque the screws holding the float bowels on and they will warp and leak internally. THe other thing I see occasionally is the gasket between the main body and the throttle plate leaking into the venturi. That will cause a rich condition. Also, rare but not unheard of is a cracked main body, causing fuel to leak into the intake tract. I've personally never seen this, but the rest of this shit is all first hand stuff I have delt with.

[desperado]

Oh yeah, power valve,,,, although going to a 6.5 will possibly work, the correct way to get a power valve is geta vacuum gauge and find out what vacuum the motor idles at, then go 2 FULL numbers below that. Meaning if you idle at 10 you want an 8. You want to verify that your crusing vacuum is higher than that as well though. If it's lower then go 2 numbers under that. You don't what it opening except under high loads and under accleration.

 

If none of this woks chances are that your carb's emultion tubes or idle air and main air restrictions have been fucked with. In that case, you will need to either send the carb off to have the air restrictions drilled out and replaced with jets, or replace the main body. I have two bodies here that are fucked up. One I screwed with, before I knew better the other was one that I replaced with one of mine when someone brought me a carb that someone else had "modified".

 

Good luck and let me know if you would like some hel sorting out your carb problems.

[Total Sign]

Power valve has NO effect at idle. None. The power valve feeds throught the boosters just like the main jets do. So at idle, they are dormant.

 

 

When the correct power valve is used your right. But if too high a number, it will flutter at idle, and dump fuel, causing a rich condition.

[McGraw]

so bad?

 

http://memimage.cardomain.net/member_images/8/web/764000-764999/764451_27.jpg

 

:-)

[desperado]

When the correct power valve is used your right. But if too high a number, it will flutter at idle, and dump fuel, causing a rich condition.

 

Uhhh, gonna have to question this. An open power valve feeds fuel to the primary metering circuit (boosters) so if the carb is set properly, the power velve will not richen the mixture untill the carb begins to draw fuel from the boosters.

 

Now if the diaphram in the powervalve is ruptured then because the vacuum that makes it work is a manifold source, then fuel will go through a ruptured power valve and richen the mixture at idle. But running the idle mixture screws in will indicate if this is a problem becasue the motor will continue to idle wiht the adjusters closed.

 

And as far as going way down in the power valve numbers to a 4.5 or lower is a good way to lean out an otherwise properly tuned carb and cause real problems. Not knowing his combination, making a suggestion like that is a bit irresponsible. If he gets that carb jetted correctly, and runs a 4.5 or lower power valve, with a vacuum secondary carb, there is a possibility with a mild profile cam that his manifold vacuum will climb above 4.5 and going down to a 2.5 it becomes a real possibility at WOT, amd for sure at around 3/4 open throttle. This is going to lean the car out 6 to 10 jet sizes, and could put the motor in a serious lean condition, at a high RPM under load. If his secondary spring is a bit too heavy (typically the case) it's only going to increase the problem, both causing the manifold vacuum to increase at WOT as the motor moves up in the RPM range, but it spting not letting the secondaries open will not add the additional fuel causing the lean condition to get worse.

 

This is why folks HATE Holleys. If they are setup right they work great, but getting them setup right, typically sucks ass.

[McGraw]

amen

[Total Sign]

You know more that I do.

[desperado]

You know more that I do.

 

 

Dude, be assured that I am not trying to make this into some Iknow more contest. I just been a study of Holley's for a long time, and read EVERYTHING I can find on the subject. And to be perfectly frank, there is alot of shit that I have ran into that the 6 or 8 books that I have on Holley's have been the difference between throwing up my hands and sending a guy down the road happy. Even as late as when I started setting Marc's car up, I came close to over drilling the butterflies inhis carb. I went back to the book to verify the starting size of the holes. I was thinking 1/8 and the book said 1/16 or 5/64 to start. Had I drilled it at 1/8 I would have been replacing the butterflies because the motor would have had so much air at idle it wouldl have idled at around 2500 or so.

 

I have started looking at EFI and turbos now. Specifically blow through carbed setup's. So sometime down the road, in a few years I will have some knowledge on that topic. I figure it will be several blown motors, spend turbos and hopefully a few blown trannies and twisted driveshaft's as well. But I am finding out that some of the stuff I knew, was right, and some of it was bullshit.

[Buckeye1647545503]

I have been told buy more than one person to get the power valve number you take the vac in half +2, I know this worked well in my ranger

[nurkvinny]

I have been told buy more than one person to get the power valve number you take the vac in half +2, I know this worked well in my ranger

 

This works.

 

I HAVE NOT READ ALL the thread; I am in a hurry

You can remove the power valve if you compensate by adjusting the jetting.

 

Carry on.

[McGraw]

thanks guys, so who would be willing to give me a Carb lesson some time? could use hands on from a pro.

[desperado]

Yeah, I can do that.