Carb advice for OT car

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Aaron65

Aaron65

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I'd love a little advice. I've been having carb issues with my family heirloom '65 Mustang since I went through the engine three years ago. I've been driving this car for over 20 years, and have five carbed cars, and the other ones give me few problems, so I'm not a complete rube (I hope).

The engine is a 289, 9:1 compression (heads have been cc'd and I checked deck height), Comp 252H (206 @.050), Weiand Street Warrior intake, 16* initial, 37* total at 3000, 8* vacuum advance. I run a Pertronix Ignitor I with a full 12 volts and a Pertronix coil. I've run points in the past.

I have an Edelbrock 1406 on there right now that came on my Skylark and I've got tuned in well. It has two problems: so-so mileage (13 mixed, 17 full highway), and it picks up a slight surge if I am out on the road for over an hour or so (which is really weird).

I have tried a load of carbs on it, and they've all had problems worse than the Edelbrock (by far). The Edelbrock runs great except for what I've mentioned.

1. Summit 600...this was actually on the used 302 I bought initially that ended up smoking from the breathers and smoking the front pistons after 300 miles. Buyer beware! The Summit had an internal leak that fouled four plugs (one venturi obviously). I warrantied that one.

2. Pony Carbs Autolite 4100. Ran fine but I had to jet it up four sizes, and that carb was the one on the car when the used engine blew, so I sold it, which was stupid.

When I redid the 289, I put on my 1406, which was collecting dust in the garage.

3. New Holley 1850. I hit the gas and every time it would backfire through the carb. Holley's tech line seemed baffled because nothing I tried worked. I warrantied that one.

Back to the Edelbrock.

3. Quick Fuel Slayer 600. Lots of power, but idled rich and had a lean surge on the transitions. I probably could have tuned that out but I sold it because it was probably too much for a little 289 anyway. I was running as little as 1/4 turn out on the idle screws, so it needed smaller IFRs, but then I may have even leaner slow cruising.

Back to the Edelbrock.

4. I just bought a used Holley 390, installed a new baseplate (the old shafts were very loose), installed it. Idled great. Huge lean bog on acceleration (goes straight to 22.4 on the AF meter), won't get out of its own way, 15:1 AFR on full throttle. To be fair, this carb may be junk. It has what looks like a parting line horizontally across the middle of the primary side of the main body,like someone dropped it or something. I don't even know where I'd start to fix this.

Floats are adjusted, fuel pressure is about 4.5 psi (stock pump).

Back to the Edelbrock.

I'd like to drive this thing long distances without that annoying slight surge, but with the vast array of carb choices and my ADD/OCD tendencies, I would just like to talk out what to do next... Sorry to be so wordy. It's no hurry, because that old Edelbrock keeps plugging along most of the time, which is why I'm so frustrated now. Maybe I should just learn to love the surge. :)

I just realized I sound like an absolute carburetor idiot here. I swear I'm not; maybe this car is cursed or something! Maybe I'm just not persistent enough. :) Maybe I need to just buy Edelbrocks.
 
So like 23 different carburetors all have the same crappy-crap going on?

I am by no means an expert either, but it does seem an underlying issue is there as well?
 
Only similar case I can recall... Friend bought a 65 2+2 fb in 1975. Bone stock 289. Idled and cruised fine. Stretch it out and it seemed to starve for fuel. Reman'd carb, no change. Pulled fuel pump and found that arm severely worn, prompted further look. Pump eccentric had a hole worn through it. New timing set, etc.., cured.
 
Not to be a sour sounding fella, but I would have went with the 500 AVS styled Edelbrock. It is a driver right? 289 is a small displacement.

Is that 600 Edelbrock in really good shape?
What is the Stang's rear ratio and tire size?
Surge is lean. Surge on cruise is jetting. Adding more fuel may actually very well increase mileage since not enough fuel just does not power the car well enough.
Speaking of fuel, does it get better mileage with 89, 93?
 
8v-of-fury said:
So like 23 different carburetors all have the same crappy-crap going on?

I am by no means an expert either, but it does seem an underlying issue is there as well?
Click to expand...

Oh I get it...this car has driven me nuts for three years, and I've owned it for over 20. I have a Sun oscilloscope to check the ignition. It's fine. The timing curve is certainly not weird enough to be a problem.

Every time I try a Holley of any sort, it's a mess. I guess I'm Holley illiterate, but I've tried pump cams, squirters, and I've read up on them.
 
rumblefish360 said:
Not to be a sour sounding fella, but I would have went with the 500 AVS styled Edelbrock. It is a driver right? 289 is a small displacement.

Is that 600 Edelbrock in really good shape?
What is the Stang's rear ratio and tire size?
Surge is lean. Surge on cruise is jetting. Adding more fuel may actually very well increase mileage since not enough fuel just does not power the car well enough.
Speaking of fuel, does it get better mileage with 89, 93?
Click to expand...

That's my next move probably. The 600 runs perfectly fine most of the time, just not after a long trip (even then it's acceptable, just a touch surgy).

On my Innovate, it runs 15.2 AFR at freeway speed (but with 71x47 rods, it runs 14.1, and still has a bit of a surge after a long freeway trip). Full throttle is a little bit rich at 12.2 or so, but the next leaner power metering rod makes it hesitate.

The Mustang has a 2.79 gear and 25.3 inch tires, which is why the idle circuit is important; it's often running on the transition circuit.

I am baffled and sad by how much I can't make a Holley run on this car, but the Edelbrock runs well. Oh yeah, the fuel pump is newer and puts out about 4.5 psi. Full power is not a problem at all, ever.
 
Just a thought, but ever pop the gas cap after a longish drive? Pressure/vacuum? Have seen both cause issues when the vent(s) gets plugged by critters/crap.
 
I'm no expert on anything but here's my thought. "On my Innovate, it runs 15.2 AFR at freeway speed (but with 71x47 rods, it runs 14.1, and still has a bit of a surge after a long freeway trip). Full throttle is a little bit rich at 12.2 or so, but the next leaner power metering rod makes it hesitate." You didn't mention what type of gas you run, or what the ethanol blend is, the ethanol will change specific gravity with temp which may be ok around town but once you drive extended time and heat soak everything good, might become a factor. Sounds to me like you're right on the edge of being too lean maybe. The surge your referring to I'm assuming is a constant rpm surge which indicates lean. I understand your trying to be efficient but with the crap gas today you may need to go towards the rich side a little more. You say with the 71x47 rods it still has some surge but is it as severe as before changing the rods? If not it would seem your headed in the right direction. Also how do the spark plugs look?
 
I actually popped the gas cap on a 200 mile trip last month, and no big rush of air was noted.

We do have the standard 10% ethanol, and I run 89 octane because there's no evidence of ping at all. The plug insulators are light but the base rings are pretty well colored. I've found that this gas doesn't color up the insulator much unless things are pretty rich. I haven't run the 71x47s in a year or so; maybe I'll try them again.

Honestly, since Holleys are kicking my butt on this car, I've just wanted to try to get one to work to prove I've beaten the thing, but as Rob said above, a mild 289 isn't the best place for a 600 cfm carb. The Edelbrock has smaller primaries than a Holley, which may help. Any time I try a Holley 600 (except for the Quick Fuel), it bogs tremendously upon light to moderate acceleration. They may need just a huge pump shot to cover the lack of velocity.

If I were smart, I'd just buy an Eddy 500 and be done with it.

By the way, thanks for the replies. This car shouldn't be hard to tune perfectly and it's seemed to fight me more than any car ever has.
 
You may be a victim of the 2 step rods. If available try getting a 3 step rod setup, cap, pistons, jets, and rods. Almost any OEM Chrysler used them. The Best carb we ever had on my brothers 289 K motor was a 750 AVS from a 440 Plymouth.
 
I have a liking to the OE AVS carb myself. The best of the 3 squarebore Carters. The 3 step rod helps with driving fuel curves. Still a pain in the arse given so many rods combos and engine differences out there.
 
What kind of temps does the engine run? Are getting fuel boiling/vapor lock type issue on extended drives? Also remember you A/F meter is a tool not the be all end all as far as your fuel mixture, fuel type, like stated a few posts ago , and what the engine may need can be different. IE when I go to the drag strip I jet for MPH, sometimes the A/F meter is not necessarily where it should be on the scale.
 
Here's a thought ;
With only an 8* Vcan, cruise timing is likely not optimum. With your gears and tires, cruise rpm comes in about 2200@ 60 mph.And with your timing curve, centrifugal cruise timing may be about 24*. Add in the 8* equals 32* of cruise timing(I'm estimating). Ima thinking it could be a lot higher, say 45*.This would require a 21* Vcan.
Here's my thinking. With the lack of optimum cruise timing, you will be having to run deeper into the throttle than necessary. That would put the throttle blades up higher into the transfers, which, if they're lean, would send the engine into surge.

So here's an experiment that has worked for me. Put a vacuum gauge on the manifold. Take her out for a run at your normal cruise speed, on a straight, level road.After the speed and throttle position have stabilized, take a vacuum reading. Be very accurate.Take several readings, over a mile or so.
Next stop the car and crank 8 more degrees of timing into it. Repeat the test. Stay out of the secondaries. If the vacuum goes up, it's because you are further out of the throttle. If the vacuum goes up, stop the car and crank in another 4 degrees and retest. Keep this up til the vacuum goes down, or you run into problems accelerating up to the cruise speed.Go back to the last successful setting.
-This last setting is what the engine wants. So put the lite on it, and WITH the vcan operating normally, rev it up to cruise rpm, and take a reading. That is the magic number.Write it down. Return the timing to the original 37* of power timing. Now disconnect the Vcan, and take a timing reading at the cruise rpm. The difference between those two readings is what she wants in the can.
- Here's an example; suppose the magic number was 44* of total cruise timing gave the highest vacuum reading. And suppose the the no Vcan cruise rpm timing was 24*. Then 44- 24 = 20* required in the can.
-Sometimes it's hard to see the changes in the manifold vacuum readings. If this happens to you, try taking readings off the sparkport. Just Tee into the Vcan line. This circuit is much more sensitive. If you have a venturi port on the carb, that works too.I use the Sparkport, mostly.
-Once you give the engine the timing that she craves, you may find that you can fine tune the idle mixture screws.This is how I do that; With the engine fully warmed up, I block the throttle open at or about the cruise rpm. Then I simply set the mixture screws for the highest rpm. Release the throttle. Sometimes when it returns to idle, it wants a small correction, usually richer.
Hope you can find some help in this.
 
I've thrown a new wrench in the works! I got the Autolite 4100 I had sitting around the garage running. I just need to different spacer to make it all work, and then I can check out how it runs with that...it's a 480 cfm carb, which should play much nicer with a 289. I'll update when I get it out of the garage.

AJ, I can actually adjust my total vacuum advance up to 15* with washers (weird) on this distributor. I'll have to try the vacuum check on the highway.
 
yeah I've seen those cans. I used to wish I could find one for my MOPAR dizzy. But I'm all dialed in now.
I just want to add that, when you are tuning a cruising, or part throttle issue, the engine doesn't really care how big the carb is, cuz it's on the primaries. Most typically used carbs have primaries that fall between 1.2" and 1.6". These are not too big for a 289. Too rich/lean maybe. Tuneable? yes. Well 1.6 is getting up there,for a 289.
 
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