Holley street avenger tuning

[69stang_250]

Got the car running and front end aligned and it's super fun to drive, but it does need some tuning.
So I've got a 670 Holley street avenger, 66 primary and 64 secondary jets, and the lightest spring I have for the vacuum secondary.

I need to double check my timing, but it's set at 34* at 3000rpm+-100 and have the vacuum advance hooked to manifold vacuum. It seems to run great with that but I can't get it to idle under 1000rpm +-100.

For those that haven't followed the build:

250 .030 over
Forged Pistons 10.25 CR
CS cam 280/280 110 1* advanced
RAU 1.6 adj rockers
CI head and intake port and polished with double valve springs
CI dual out headers
Custom curved DSII distributor
MSD ignition mod
Blaster III coil

So as of now my AF gauge jumps between 13.5-16.2 at idle. Average is like 14.7.
Cruise the gauge calms down a lot and reads between 15.6-16.7. That's cruising at 2400-2600 rpm.
I have a stumbling issue right now that I am trying to work out and get that smooth transition off idle.
The AF gauge jumps to 10.0 and leans down to 13.5 when I give her a little gas.

Anyone have an order of operation to tuning a Holley? Anyone have an idea of where I need to get my AF ratio at idle since it jumps around so much?

Now yesterday when I drove it, though it was idling at 1000rpm before hand, it idled down to 900 when I got to a stop light and the acted like it was starving and kept going down till it died. The only way I could get it to crank was to hold the gas down all the way and keep cranking it over for about 5 seconds. If I kept the Rams over 1500 I could keep it running, but once I got her to the house and parked it would run and idle with no issue. Any ideas what that issue is?

Thanks guys

 

[B RON CO]

Hi, I would check for a vacuum leak, and try the ported vacuum port. Good luck

 

[pmuller9]

With that cam the initial timing needs to be greater than 10* BTDC.
Check it with the vacuum advanced disconnected and plugged.

 

[wsa111]

I believe your carb is too big, but??
All the A/F ratios are way to lean. Do you have a vacuum leak between the intake & head??
With that cam your idle should be closer to 13-1, cruise 14.3-14.7, WOT 12.5-13.1.
What is your fuel pressure?? Should be close the 5#-5.5# area.
A 1000-1100 idle speed is perfect for your combination.
The 34 total should be check with the vacuum disconnected to the can. Then hook up the vacuum advance to manifold after you set the initial or the total.
If you get the A/F ratios correct & still can't get the idle speed to the settings i mentioned, what PCV valve are you running? Is it for a 250 engine. A 460 pcv will flow more because of the size of the engine.
Double check the float level.
Its possible the secondary throttle blades are cracked open too much at idle & supplying too much air.
To adjust that you have to remove the carb & the secondary blade stop is controlled by a hex set screw at the under side of the base.
The stumble on initial acceleration could be that you need to richen the accelerator nozzles. You can enlarge them or purchase one that is in the .029-.031" area.
You may have to install the 50cc accelerator pump housing on the primary bowl & install the brown pump cam that comes with the 4412-500 two barrel carb.
Make sure you adjust the pump to specs as needed. Open the primary throttle all the way & with a pair of pliers open the pump lever till it bottoms, there should be .015" clearance between the lever & adjustment screw.
Questions just call me, Bill

 

[69stang_250]

I will double check my timing. I set it at 34* BTDC at 3000 rpm. Once set to that It started running better than it had, but I did not check to see what the initial timing was once set. I know I should have and I will asap.

Bill- I was told that by the machinest, but after looking at my air fuel ratios and him turning in the idle air mix screws and it killing the engine he told me that it doesn't seem too big for the engine. So, I'm just running it and tuning it till I go fuel injection down the road.

I have checked for vacuum leak between the two, but have not found anything. I did not put any sealer between the intake and head, just the gaskets that will set me with the head. I may take off the intake and put some sealer on there. I know there is sealer between the carb adaptor and the intake.

I am shooting for those AF ratios, but should I worry about those quick readings of 15-16? I'll take a vid of the idle tuning so y'all can see how it's reading and let me know what y'all think.

I have not checked the fuel pressure, but I am probably gonna go get a fuel regulator and install it so I can monitor it.

I set the timing with the vacuum advanced disconnected and once I connected the vacuum to the manifold port it started running better and drove better than it did while connected to the port on side of the metering block.

The PCV is for a ford 250. Would one just a little bigger help with how it idles?

The fuel levels are running just at the bottom of the sight glass on both primary and secondary's.

I will have to check the secondary blades when I pull the carb and see if that is the issue.

 

[drag-200stang]

The stop light hard start sounds like carburetor icing...Was it cool and damp out, holleys are good for that. Does not have to be that cold out either..Does the carb have any heat plumbed to it?

 

[69stang_250]

Yes its been in the 30s-40s here. No heat is plumbed to it, but with the heat the headers put off it gets plenty lol
That one issue was weird. The engine was running great before that and after I parked it and drove it again. The other thing was that when I got it to crank back up it sounded like my belt was slipping if the engine got over 1100 rpm. Drove it for 1/4 mile and it stopped.

 

[drag-200stang]

Yes its been in the 30s-40s here. No heat is plumbed to it, but with the heat the headers put off it gets plenty lol
That one issue was weird. The engine was running great before that and after I parked it and drove it again. The other thing was that when I got it to crank back up it sounded like my belt was slipping if the engine got over 1100 rpm. Drove it for 1/4 mile and it stopped.

I will not say that the one problem is for sure carb icing but I can assure you that headers will not cure carb icing....My 200 with headers would ice, and had a 340, 830 holley in a early van dog house with headers that would too ..Thought that much heat in a box it would be impossible, took off air cleaner and there it was.The ice melted away fast with the engine not on with no air flowing Thur the venturi.

 

[chad]

2 me it's the speed of the air goin thru the venturi
so the water in the gas is the most crucial.
Hot water choke might B the only thing 2 stopit due
to whole carb being a 'heat sink' from that approach...

 

[RichCreations]

Yes its been in the 30s-40s here. No heat is plumbed to it, but with the heat the headers put off it gets plenty lol
That one issue was weird. The engine was running great before that and after I parked it and drove it again. The other thing was that when I got it to crank back up it sounded like my belt was slipping if the engine got over 1100 rpm. Drove it for 1/4 mile and it stopped.

I will not say that the one problem is for sure carb icing but I can assure you that headers will not cure carb icing....My 200 with headers would ice, and had a 340, 830 holley in a early van dog house with headers that would too ..Thought that much heat in a box it would be impossible, took off air cleaner and there it was.The ice melted away fast with the engine not on with no air flowing Thur the venturi.

Funny, I had carb icing the other day in my 200 powered early econoline, stalled out, and would not restart for a few moments. It can happen...

 

[69stang_250]

How would you go about plumbing heat to the carb? Is that why the oil breather running the the breather?

 

[RichCreations]

How would you go about plumbing heat to the carb? Is that why the oil breather running the the breather?

you would use a factory v8 air cleaner with the snout/flapper, and a piece of duct to a shroud over the exhaust...

 

[chad]

I think the oe 'choke stove' wrks -
that lill pipe, comes up from the exhaust
to drift the warm air up there (opens the flapper)...

 

[RichCreations]

I think the oe 'choke stove' wrks -
that lill pipe, comes up from the exhaust
to drift the warm air up there (opens the flapper)...

, nope, thats for cold starting, I am talking about the large "heat riser" that many cars have

 

[drag-200stang]

How would you go about plumbing heat to the carb? Is that why the oil breather running the the breather?

you would use a factory v8 air cleaner with the snout/flapper, and a piece of duct to a shroud over the exhaust...

If done carefully it can look ok, or only use when needed. I have just lived with it also.
Not sure of the second question but I do not think that it applies to this issue.
Does your manifold have provisions for coolant to flow thru the manifold, that may be enough. It will help moderate carb temp and help fuel mileage.

 

[chad]

"..."heat riser" that many cars have…"
yes, inch & 1/2 silver or black ribbed flexable paper like conduit.
Some heat permiates the carb frm small channels w/in w/the "choke stove'.
On the 'riser' above - the flipper in the snout can B closed 4 more heat
in the riser to drift toward the carb

 

[69stang_250]

I think that is something I will just have to live with. The intake does have those provisions, but I'm not sure how I would run the coolest to it. Since I'm running a screen air cleaner would this condition happen more often? I am thinking about switching to a carb hat and trimming the hood brace for clearance. The current one had to be hacked up to fit and it still rubs the hood a small bit.

 

[drag-200stang]

I think that is something I will just have to live with. The intake does have those provisions, but I'm not sure how I would run the coolest to it. Since I'm running a screen air cleaner would this condition happen more often? I am thinking about switching to a carb hat and trimming the hood brace for clearance. The current one had to be hacked up to fit and it still rubs the hood a small bit.

It simply goes inline with the heater, cannot remember if to or after flow wise ...Maybe someone can check theirs, early engines ran it.
It is the venturi effect that does it in conjunction with the fuel evaporation , screen will have no meaningful effect.

 

[chad]

"...screen will have no meaningful effect…."
X2
still not sure that's the correct diagnosis (icing), tho.
(I'd get mine on some of the hottest daze of da yr).

 

[69stang_250]

Well honestly I think it's something I will have to just deal with.
When tunning the carb should I go in this order? Idle, wot, off idle?