adjusting my vac

[Johnny Dart]

Im trying to adjust my vac...i cant get higher than 5 but the needle is moving like crazy....when i put a higher pv in like a 6.5 it steadys out a bit and then likes to be put leaner...but with the 4.5 in it wont steady out...its a 750dp with 74 jets up front and 82 in the rear...do you think its a leak?

Looking back at your original question,the power valve has nothing to do with your vacuum at idle. The power valve comes into play when the engine is under load.

Put the 4.5 or the 6.5 back in and get your vacuum reading.It doesnt matter what power valve you put back in.Get your reading,then decide what power valve you want to go with.
The needle will fluctuate a little when testing vacuum.

Or you can put a Ede 750 on it and be done with it.....8)

 

[SRT_DSTRHOLC]

im going to get the 3.5 and put that in...also you say it has nothing to do with idle, what if my vac is lower than the pv? it would open the pv...then causing a rich condition no?

 

[crackedback]

Or put a PV plug in it until he gets the idle figured out, get a clean reading in gear and see if the supplied PV is correct.

NO... I'm saying dial in initial timing until it kicks back on the starter, dial it back 2*, take a reading. Figure out what you need to get your total number, bigger bushing.

More initial will allow you to close up the throttle plates, which is my guess as part of your issue.

 

[SRT_DSTRHOLC]

ill see what i can do...can i put in a rear metering block that has no hole for a pv instead of a plug, its just i dont have a spare plug...then i can figure out what i need...I also have a little bit of white smoke coming out when i turn the car off...is that too much fuel pooring into the intake? i hope its not water

 

[crackedback]

leave the PV alone would be my suggestion, 3.5 or 4.5 isn't going to make a big difference.

Get the initial timing dialed in FIRST before worrying about any of this other crap.

 

[Longgone]

Moper and cracked are on the right track, get the idle/vacuum up and figured out first before you pick a power valve. The power valve should not be part of the circuit in idle. The cam you have may not yield more than about 10 in. of vacuum and if that`s the case a 4.5 pv would be just right.

 

[SRT_DSTRHOLC]

ok, so im not use to timing my car and I usually have a friend help, when will the starter kick back? when I turn the car off and try to start it? or while its running it will kick back?

 

[Longgone]

When you`re rolling the engine over. It may seem like it`s straining to turn the engine over at first and then will want to kick back.

 

[Johnny Dart]

Instead of getting a 3.5 PV,get a Holley book and :read2:

 

[SRT_DSTRHOLC]

hmm i guess that means set it at 20-24...turn it off...and try to start it...if it kicks back lower it 2 degrees and turn it off and try it again....and im running 11.0 compression with 95 octane just to inform

 

[crackedback]

And if it doesn't kick back at 24* what are you going to do?

 

[SRT_DSTRHOLC]

haha on two 26 really? do i need to change the bushing in the dizzy to put this much initial?

 

[moper]

If it drops that far into gear (rpm wise and vacuum wise) and the timing is what you stated originally (18° initial, 36° total) the carb is off. It sounds like the idle air bleeds are too large and it'slean at idle. As a stop-gap measure, take a couple small pcs of copper wire about 4" long... I use a single strand out of a 16 gage copper wire... and stick it down into the idle air bleeds until it bottoms, thenbend it to conform to the carb's air horn. Then try to adjust the idle mixture again using the vacuum gage. If it settles out call Bigs and get order smaller air bleeds. You can also make sure if it's 4-corner idle that you have it balanced propoerly and the secondary throttle plate is positioned right. I think it's a carb issue in any event. I would expect about 100 rpm drop in idle speed and about 2/3 of the "park" vacuum reading when it's in gear and running right.

 

[SRT_DSTRHOLC]

so a high stall wouldn't cause the drop in gear? the carb running lean would? ok ill tune it and see what happens thanks

 

[SRT_DSTRHOLC]

ok to update everyone just to double check everything I said...it idles at 1000 in gear at 180 degrees of temp...with 18 initial 36 total In park it has 8-9psi of vac which is why its steady...ok IN GEAR...the idle drops to 5-650 with less than 5psi of vac.The needle moves from 1-5 MAX...The jets are 74 up front 82 in the rear...The floats are set because I double checked them...All that needs to be done is like you said up the initial too 20-24 and make it rich correct? Also this might be a rookie mistake =( haha but I forgot 2 say it has a spacer underneath the carb =/ its a HVH spacer would this cause it to run lean if i just threw it on without adjusting the jets? And the thing is I called HVH and they said using the spacer would actually make it run richer...so is it too rich or too lean? or take the spacer off and check?

 

[moper]

I would not give it more timing. It doesnt need it. By changing the PV to one that opens at idle as you were doing, you are simply adding fuel to the engine. Nothing else. Just extra fuel. It likes it to the point of cleaning up the idle. Which is why I say try richening the idle circuits byeond what they can be as shipped. I dont have a lot of faith in spacers other than adding plenum volume, but if you did not tell Bigs about that it could have affected the setup.

 

[SRT_DSTRHOLC]

so what do you recommend doing moper? Take the spacer off and tune it? and what do you have to say about the RPM drop? do you think the converter that I bought isnt really the correct stall or is it? It wont get more than 1-5 psi of vac in gear and likes it when i turn the mixture screws in..so im guessing its running to rich now?

 

[crackedback]

I would not give it more timing.

Sorry Dave, I disagree.

16* is stock cammed/268H territory for a 340/360, he's got a 260 at .050 camshaft.

The primary throttle plates are open too far is my guess. What happens when you run the idle mixture screws all the way in? Does the engine die? I bet it smells really rich out the pipes right now.

My other guess is that burping out the carb at shut down is the engine attempting to run on from too much throttle plate opening.

Burnt...
Want to play with your vacuum gauge, keep the engine idling at 950-1000 or so, start dialing in more advance. Does the RPM pick up? If so, the ENGINE WANTS MORE INITIAL ADVANCE! PERIOD, END OF STORY! As it picks up rpm, close down the idle speed adjustment screw to remain at the 950 rpm. Keep doing that until it stops picking up RPM. Watch how the vacuum reacts to the increase in timing.

Mad_Dart has 24* of initial... take that for what it's worth. 24* is definitely in the realm of possibility for your engine.

There are plenty of intelligent people on this board that can pull a number out of mid air for what the initial timing should be. HOWEVER, only your engine can tell you what it wants for timing. You have to find that point through trial and error. Don't worry about total timing at this point, it's irrelevant now, and needs to be adjusted later (you'll need a bigger bushing on the MSD dist). There are plenty of ways to make one, you can make one yourself.

 

[SRT_DSTRHOLC]

ok thanks and i have a light blue and light silver spring in the DIZZY would this cause my timing to come in too early with this setup? or should I call msd?
And with the BIG rpm drop in Gear im afraid i have less stall then what was sold to me...is this possible or just focus on the timing first?

 

[crackedback]

If it was me, you need to eliminate every outside influence on the initial and carb adjustments.

If your timing remains constant at 16* after being dropped in gear, then the mechanical is not having a negative effect. If the timing drops below 16*, then it may be bleeding mechanical, you would then need to install heavier springs to keep that from occurring. You don't want any mechanical advance involved at idle... NONE. I'd put a heavier set of springs on it anyways just to eliminate that as a possibility. They are easy to change over when done.

 

[SRT_DSTRHOLC]

i have 18 not 16...and i will check everything tomorrow and put heavier springs in

 

[SRT_DSTRHOLC]

so im putting in 2 light blue springs so timing is in at 3k putting more initial timing in...and calling jess bout the carb...

 

[moper]

I dont think 2° will change anything. It's just my opinion tho. Try the wire trick in the idle air bleeds... I've doen it a bunch of times when needing to get a direction to go in and costs nothing.

 

[SRT_DSTRHOLC]

Ok ill try it after i set my max initial, but i have to buy some which ones are the idles? The inside or out side ones? Because i just lowered the inside 4 front and back before brake in because it ran lean before with the old setup. And i know you say the pv does nothing at idle but with a 6.5 pv in there and the vac being less than that in gear wouldent that cause it to run rich?? And i need to buy some wire.. What size wire??

 

[moper]

Idle air bleeds are the outer ones on each venturi. Usually much larger in oriface size than the main air bleeds. You dont need to buy wire... All you need is a 4" section of 16 or 18 gage. Take the insulation off and take four strands (4 corner idle, yes?) and stick one in each bleed.

I said the PV should do nothing at idle is things are done right. Because as others said, the PV should be held closed by vacuum at idle. When you put in one that has too stiff a spring for your idle vacuum, it begins to open. That is un-metered fuel being added to the idle mixture. So what I'm asking you to do is to stick a PV plug or the 3.5 PV in it and using the wire, richen the entired idle circuit. When you block the air bleed off partially you really enrichen the mixture and sensitivity of the idle mix screws.