carb tuning???

[ocbaud]

okay, i bought a vacuum gauge today and am gonna borrow a tach that works from a friend of mine. my dad is getting a timing light today and tommorow we are gonna get the thing running right.

so, after the timing is set correct this is what i need to do?:

1. turn the idle mixture screws 1.5 - 2 turns out from completely in
2. set the idle speed(which screw do i set it with? the one by the choke, or the one by the throttle bracket?)
3. continue turning the IM screws out about a 1/4 turn each time, while bringing the idle back down after they are turned.
4. continue doing that until the vacuum will not rise anymore on the gauge. so that it has the highest vacuum at the desired idle rpm

does that sound right?

[Captkaos]

#2, it is the one by the throttle.

[ocbaud]

whats the difference between the 2 different screws?

[Russell]

One is for the cold idle speed, and the other for the hot idle speed.

When the truck is cold, it is suppost to run faster than when it is hot to keep it from dying.

The one by the throttle bracket is the one that you will be wanting to adjust

[ocbaud]

do i need to have it warmed up before i adjust it?

[Captkaos]

If you are having alot of problems with it, by the time you get started on adjusting it it will be warmed up by then.

[ocbaud]

so pretty much it does

[79BIG10]

Should have gotten a Edelbrock Much easier to tune.

[NeCrOmAnCeR]

To each their own. Yes, warm it up and continue. Be sure you get your ignition problems straightened out before you start tweaking the carb. Jet produces an excellent product. If you got the recommended carb for your engine it should not require much else other than setting the idle speed and mix.

[ocbaud]

my cam is a little above what they recommend for there stage2 carb, which is what i have.

but i believe all i need to do is set the idle and mixture

[67_SS396]

You have the right idea and yes, the engine needs to be up to operating temp before you start making adjustments to the air/fuel mixture.

[ocbaud]

i got the timing set to 12 degrees, but now i need to tune the carb to run well. it keeps wanting to die on me in idle

also, i cant get my friends autometer sportscomp tach to work

[NeCrOmAnCeR]

Where did you end up hooking the vac advance?

And what kind of vacumme is the engine making?

[ocbaud]

Originally posted by NeCrOmAnCeR
Where did you end up hooking the vac advance?

right now its on ported, but i've tried both and it doesnst seem to matter which one its on. it does idle a lot higher with it disconnected though.

[NeCrOmAnCeR]

It idles higher with it disconnected from the ported source?

[ocbaud]

yes

[NeCrOmAnCeR]

If you put your finger on the ported source can you feel it pulling on you? In that elplanation I gave on you're post asking where to put the vac advance line, you can hook it to the EGR port for a ported source. the one labeled for dizzy is a full port.

[ocbaud]

i've hooked it up to both ports. and it seems to idle higher with it disconnected.

[NeCrOmAnCeR]

Try hooking the vac advance up to the EGR port. It is the one in the above pic just below and to the right of the "PCV label box" The one to the left of the PCV port. This is also a ported source. At idle on a ported source, the vac advance should see no vac at all. So disconnecting the line should not have any effect on the idle speed. Also, just a reminder, when you set the timing to remove the vac advance line and plug the carb port. Connect it all back up when finished.

[toytruck]

Why don't you lock out the advance and not hook it up. You don't need it with that converter anyway.

[milner]

Sounds like your idle circut needs to be opened up. I had a Comp cam w/230 dur. at .050" and it would not idle. I can't remember the size to drill the circut with but with the cam you have it sounds like it needs to be.

[ocbaud]

well the carb should run because its already been worked on. its a stage2 qjet by jet performance. although, the recommended specs on the box it came in were a little smaller cam then what i had.


it says this:

" This carburator is intended for Chevy Truck engines with mild performance upgrades such as:

DUAL PLANE ALUM. INTAKE MANIFOLD
HEADERS
COMPRESSION RATIO OF 8.5:1 - 9.5:1
MILD PORTING ON CYLINDER HEADS OR pERFORMANCE HEADS
CAMSHAFT SPECS:
duration @ .050 MIN. 210 DEGREES
MAX 222 DEGREES
LOBE SEPARATION ANGLE 110-114 DEGREES

[bpmcgee]

Did you set your initial timing with the vacuum advance connected? That's a no-no.

Brian

[ocbaud]

no, it read 12degrees with it disconnected. and read about 22 or so with it connected.

we got it running and idleing good. i'm leaving in a bout an hour to go to the exhaust shop to put pipes on it. its just really slow. the 305 was faster

i dont know if thats from it only having 4 miles on it, or from the cam, or from the 2500 stall, of from my 2.70 gears, or all of them

[NeCrOmAnCeR]

The stall converter will help your acceleration with that cam. It lets the engine rev more to put it into its power band. Those gears though, they have got to go. Is it finally ideling like it should? When in park does ir respond nice and quick?