First Carb mustang - Need help running!

507 Views 3 Replies 2 Participants Last post by mikeymac, Jun 3, 2019

90lxhatch93

Discussion Starter · Jun 3, 2019

Hello,

I’ve picked up a 4 eye mustang that’s been sitting for a while. This is my first carb mustang, so I don’t have a lot of experience with the setup on a carb car. I’m wingin it >

Here’s the issue I’m facing: it will start and run and idle for as long as you want. However, when you try to add throttle it will choke up and if you add too much, it will stall. If you hit the throttle way too hard, it’ll shoot a ball of flames out of the carb...not cool, very scary lol.

What I’ve done: i’ve changed all fluids since I got the car, cleaned the carbs with fresh everything, dropped the tank and emptied as much old gas as I could. I put a fresh 5 gallons of fuel in the tank. When I cleaned the carbs, I did not mess with the tuning screws, I was scared to. They claimed the car was running when it was parked which isn’t necessarily true. But I thought if it was running when parked, I shouldn’t need to touch the screws.

The setup: Holley street warrior 600, Edelbrock performer RPM, mechanical fuel pump, vacuum lines: 1 to dist, large one in bottom goes to vacuum block, the rest are capped (only one more from what I can tell)

Thanks in advance!

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mikeymac

· #2 · Jun 3, 2019

I would first verify timing. Disconnect the vacuum line on the distributor and cap it, the hose not the distributor. If you want to run the vacuum advance, its optional, the vacuum hose should be from distributor to the timed spark port on the side of the metering block on the carb. If timing looks good check to make sure fuel is coming out of the squirter when you whack the throttle. A pop through the carb can be a lean pop sometimes. Could be bad accelerator pump or out of adjustment.

What size primary jet and squinter? What size power valve? Heads, cam, exhaust? Power valve will be determined by how much vacuum it is pulling.

To tune it you will need a vacuum gauge and hook it up to the large port on the bottom of the carb. Try to adjust the mixing screws at idle for the most vacuum. Turn them in and count how far it went it. It should stall all the way in. Back them out a turn and watch the gauge.

Holley has a ton of good videos on youtube that make it pretty simple.

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90lxhatch93

Discussion Starter · #3 · Jun 3, 2019

mikeymac said:
I would first verify timing. Disconnect the vacuum line on the distributor and cap it, the hose not the distributor. If you want to run the vacuum advance, its optional, the vacuum hose should be from distributor to the timed spark port on the side of the metering block on the carb. If timing looks good check to make sure fuel is coming out of the squirter when you whack the throttle. A pop through the carb can be a lean pop sometimes. Could be bad accelerator pump or out of adjustment.

What size primary jet and squinter? What size power valve? Heads, cam, exhaust? Power valve will be determined by how much vacuum it is pulling.

To tune it you will need a vacuum gauge and hook it up to the large port on the bottom of the carb. Try to adjust the mixing screws at idle for the most vacuum. Turn them in and count how far it went it. It should stall all the way in. Back them out a turn and watch the gauge.

Holley has a ton of good videos on youtube that make it pretty simple.

To answer your questions:

The jets are 64’s which I believe came in the carb stock. Heads are factory, it does have a cam as far as I can tell from idle.

My questions to you:

It was connected to the metering block, you say it’s optional altogether or take it off while I adjust the timing? What do I set the timing to? Is it different for a carb engine?

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mikeymac

· #4 · Jun 3, 2019

You don't need the vacuum advance. You can just cap it at the carb. A lot of people have the vacuum advance hooked up to the intake so its pulling vacuum while idling and then when they set timing off that its way too much all in. That's why I suggested capping it while setting the timing so its not in play. Since it is on the metering block you can leave it as is to set timing. That port doesn't pull vacuum at idle.

What distributor do you have? Timing is the same for carb/efi to get started. 10 degrees to start at idle. While watching it with a light rev it up to see where it goes all in. If you are using a stock duraspark, they have a plate inside them that limits the amount of advance. Some are too big and you end up like 40+ degrees. I welded up my slot in the distributor to measure at a "10L". So it gives 20 degrees of advance + the base timing. I have my base set at 16 so all in is 36 total. Any more and I lose MPH. Tons of web pages out there on this if you have a duraspark.

You can put light weight springs in it too so the timing comes in earlier. Mr Gasket sells them. I have them so its all in at 2800 rpms. If yours is stock you will have to rev it past 4000 to see it all in. Then when you left off the throttle the vacuum advance will put it way past 40 degrees as it revs down, thats normal.

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