Hi, I am going to check 4 corner idle mixture on my 650 dp, any tips? It may be set ok now so how do I check or do i have to just start over?

 

I need tips like what to do with the PVC valve, leave connected? plug it?

 

Anyone?

 

If your timing is where you want it, I would begin by setting the transition slots on the primaries where they should be (See the sticky at the top). Make any idle speed adjustments using the secondary adjuster after that. Make sure all four idle screws are adjusted the same. Then, depending on what you're tuning with, either adjust for your desired AFR or highest vacuum using the idle screws. Making sure to adjust them equally.

You don't need to disconnect the pcv or vac. advance or anything like that.


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What port should I plug the vac gauge into? Do I turn all screws in and then turn them out about 1 turn, start car then back one out say a 1/8th then the next intill all 4 are turned out a total of 1 and a 1/8th then start over and keep going intill I get highest vac and stop?

Transfer slots need to be adjusted even on a new carb? What is it for? I'll read the sticky also.

 

Adjust your main transfer slots to bearly be showing anything. I do mine about the thickness of a quarter. USe the secondarys to raise/lower your idle.

Now as far as the vacuum reading, hook up your gauge to a full vacuum source, usually the one on the front under the fuel bowl works best. Try adjusting the screws to get the highest reading and making sure all are within each others. Good starting point is 1 full turn and starting from there. I do mine while in drive, most i have seen just do it while idling. I also set the rpms around 600.

 

How do you adjust idle speed using the secondary's?

 

Plug the vacuum gauge into any port receiving full manifold vacuum. I typically tap into one of the lines that comes from the port on the rear of the carb.

If this is a new carb, all the idle screws should be adjusted the same but it wont hurt to check. 1 1/2 turns out is the usual recommended starting point. The transfer slots should be adjusted correctly as well but once again check. They meter fuel low in the rpm range before the mains come in.

There's a screw that comes through from the bottom of the carb base plate. Use it to open or close the secondaries accordingly.

 

What size is the cam in your car?
If it's stock or a smaller cam then just use the normal idle screw. If it's a decent sized cam then your going to need to open up the secondarys to bleed some air though at idle.

Where in New York are you?

 

Stock cam at the moment. I am about 1.5 Hrs north of you in Sullivan county.
I have a slight rumble/popping in the exhaust on decel that is driving me crazy, I am trying to tune it out.

I prob wont adjust sec yet, but where on carb is the screw? The main idle adjustment seems to work fine at the moment.

 

With the stock cam, I agree you probably won't need to mess with the secondaries. Here's the adjuster for reference. Circled in red.




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Yea don't bother touching the secondary stop screw.

Just watch this video on how to tune the screws.


Also make sure the timing is right otherwise it doesn't matter how much you adjust the carb.

 

Any tips on the timing?

How do you get to that adjuster? Isn't that the bottom on the carb?

 

What Distributor is in the engine?

Forget the secondary adjustment in the pic. With a stock cam you should never need to touch it.

 

I plan to swap cam's and heads in the future.

I have a Lager Cap HEI Dist, MSD Billet.

I Get a little bit of Popping though the exhaust on Decel, I am trying to tune it out.

 

It's not unusual to get a little popping from the exhaust on a manual trans car when you slow down and it's still in gear.

 

It's just that out of the three motors I have had in this car, this is the only one that does it, I had the stock 305, With the Qjet, I had a Summit built 350 cam heads hi Comp the works, that ran a Accel Dist and a Holley 750 DP, then I have this motor which ran the q jet ( also a Sean Murphy built q jet) and now this set up. The only thing that stopped it on this motor was when I unplugged the 4 pin connector that you had to unplug to set the timing on the comptuer controlled set up, it then never made a sound... I like the way a motor sounds on decel and the pop messes it up. It isn't as bad with the current set up but still there.

 

Set the timing like I said and see how it is

 

I'll give it a shot, I am waiting on the timing light to come, I also need to verify that the timing pointer is adjusted correctly, Have a adjustable pointer.

 

oh then in that case you need to get a piston stop and find tdc before you do anything

 

Id Like to find a fixed pointer that comes set already but can't seem to find one to match the summit SFI Balancer I have.

 

any one for a 6.75 or 7" balancer is fine.

like this

http://www.summitracing.com/parts/tr...make/chevrolet

 

I have this Balancer and they say since it is a touch smaller then the 6.75 that if I used one it'll be off.

http://www.summitracing.com/parts/sum-c4265

I don't know by How much though.

 

I hooked up the Vac gauge yesterday, I turned all four screws out to one turn, I then started to turn them in, I have them all at about 3/4 of a turn out now, and I have a Max reading of about 17. I then adjusted the idle when I was done. The screws should all be about the same amount turned out I tried to stay the same. If I turn a screw in or out now the Vac begins to drop.

DOes this sound about right?

 

Sounds right.

By the way, did you figure out if your Holley Ultra DP has a secondary idle speed adjustment screw on top? I thought they did, but can't find anything on that, either.

 

I didn't even look for it, I see on the box they offer a kit that says you could adjust sec idle with out having to take carb off with it.

The screws are close, to all being the same, I guess if they are off a touch it shouldn't be that big of a deal. But I did try to keep them all the same, Even started over a few times.