New Holley Street Avenger 670 - Part 2

I decided to do a bit more work on the new carburetor today after work.  I put a vacuum gauge on the engine and planned to set the curb idle and the idle mixture screws.  Unfortunately, the car would not start and in checking under the hood, I found the accelerator pump nozzle wasn't squirting.  It's strange that I have that same problem with a new carb but the front float is full.

I didn't have any gas sitting around to put down the carburetor so I just keep working the gas and it ultimately started.  After it idled a while, I adjusted the curb idle down to 800 RPM.  At that RPM, the AFR was 15:1 and the vacuum was at about 11.5 inches.  I made sure the choke was off and the engine temp was 180 and backed out the idle screws an 1/8 turn.  This raised the vacuum to 12, the RPM increased to 900, and the AFR to 14:1.

I turned the idle screws out another 1/8 turn.  The vacuum went up to 13 and the AFR was 13.5 to 1.  I didn't adjust the RPM before and it was now at 1,000 RPM.  I adjusted the idle screw down to get the idle back to about 850 to continue working on the setup.  With this changed, the vacuum was still 13 inches and the AFR was around 13.7:1.

I backed the idle mixture screws out another 1/8 turn (3/8ths in all).  This dropped the AFR down to about 13:1, raised the vacuum to near 14, and the idle stayed in the 900 RPM range.

I decided to go further and went another 1/8 (1/2 turn in all).  This dropped the AFR down to the 12:1 range.  The vacuum went up to 13 and the RPM was about 950.  I decided to go back to 3/8 turns out from the original setting and go for a drive.

Strangely, when I went for a drive, the engine was really lean.  When cruising, I was at 15-16:1 AFR.  I don't really know what changed since the last time.  The idle mixture is much more rich so if anything that would have helped.  The temperature was about 60 so perhaps that was much different than last time but I can't imagine it having that level of impact.  I was however a little low on gas but I can't imagine that doing it either as the float bowl shows as full.

I decided to stop for the moment and came home.  Since the engine was now off, I checked the idle mixture screws and found that they were not the same at the start.  I adjusted them out 3/8 of a turn.  When I checked them, the passenger side (with the 02 sensor) was a total of a 1/2 turn out (1/8 out as a starting point) and the driver side was 5/8 turn out (1/4 turn out as a starting point).  

I might need to turn them in an 1/8 turn but I'm going to leave them at this point for now.    

Baseline with New Holley Street Avenger 670

I installed a new Holley Street Avenger 670 carburetor and was surprisingly able to start up the car immediately.  The idle was decent and the air fuel mixture wasn't bad.  Without any tuning, I decided to drive it around the block just to see what it was like out of the box.  I didn't have any trouble but watching the AFR gauge, I could tell a little tuning was needed to get it to run good.  

I decided to go ahead and start tuning straight away and went with the float level first.  As a starting point, the front bowl level was about the middle of the view window.  I drained a little out of the bowl using one of the four bolts which hold the bowl in place.  I loosened the set screw and turned the nut for the needle and seat a half turn clockwise.  When I turned on the key, the electric fuel pump filled it right to the bottom of the sight window.  Done.

The rear fuel bowl was about 3/4 of the way up the sight window before any adjustment.  This one took two adjustments to get set to match the front bowl level.  The first adjustment was a 3/4 turn clockwise followed by another 1/2 turn clockwise.  It was then in good shape.

At idle, the car was at 13.5:1 so I thought I'd check the idle mixture screws.  I turned them in to see how far they were unscrewed and found they were only screwed out 1/8 to 1/4 turn each.  I just set them back as they were originally and left them alone.  

When driving, the AFR was about 14:1 which isn't bad.  When I really get on it, it seems to need a little more accelerator pump but I'll wait to change that.  However, I'll wait on that as there are other things more important and I'd like to work through this in a good order.

Stock Configuration of 670:

 Front Jet: 65 

 Rear Jet: 68
 Pump Nozzle: .031

Bad Timing for Carburetor Troubles

This past weekend, we moved to a new house.  I'd driven the Mustang a few weeks prior so driving it over to the new house seemed like the easiest part of the process.  The Mustang was a little tough to start but I got it going and out of the driveway.  However, once I started to drive down the road, it seemed to stumble and required quite a bit of gas to keep running.  It then almost died at the end of the street when I went to turn.  When I stopped at the next stop sign, the car died and would not restart.

I lifted the hood and started thinking of what might be wrong.  I looked down the carb and moved the throttle linkage.  I noticed the accelerator pump nozzle wasn't squirting out any gas.  I walked back to the house, got a gas can, and put a little down the carb and tried to start it.  It started immediately but then seemed to hesitate when I attempted to take off.  If I didn't press the gas, it would idle no problem so it just seemed to be the accelerator pump.

I decided to drive it over and just give it quite a bit of gas when accelerating and planned to just go a route that would not require many stops.  I made it to the new house with this approach.  Once at the new house, I checked again and the accelerator pump nozzle still wasn't working.  Content that I knew what was wrong, I started working on moving everything else.

Post HRPT Clean-Up & Action Items

This morning, I finally pulled the Mustang out of the garage to give it a good wash.  With the rain we encountered and all the miles on the road it was covered in dirt.  The worst was the front wheels which were covered in a dark layer of brake dust.  The job was quick and easy and included using my wash mitt on the inside of the engine bay some to get it clean.  

Before cleaning up the interior, I decided I'd drive it to get it dry and then change the oil.  As with my previous oil changes, I used a Wix 51515 and 5 quarts of Pennzoil ZR1 10w30.  The oil level was still perfect so if I burned any oil over the 3,000 miles it was minimal.  There was a little debris on the drain plug magnet but nothing concerning.  This bit trip likely has the motor now fully broken in as it reached 8,401 miles today.

I then vacuumed the carpet which was still a little damp from the A/C leaking into the passenger floorboard.  After vacuuming the carpet, I pulled the sill plates, kick panel, and shifter bezel so that I could pull up the carpet allowing it to dry better.  I put a little Febreeze on it and then left a fan blowing into the window so that it will dry in all the 100+ degree heat we have been enjoying lately.  

As with every trip, I come home with a few things I'd like to work on.  This list is really minor considering the size trip and what could have gone wrong so I'll probably work through these slowly.   

• Install driver headlight wiring
• Reinstall lowering blocks
• Replace transmission fluid
• Front disc brakes squeak
• Rattle behind rear seat back
• Buzz noise from behind dash
• A/C vent tube 
• Hot start issue
• Clutch reservoir
• Throttle return spring

HRPT Day 10 - Home!

Today is Father's Day and the last day of the Power Tour trip.  We did nothing but drive all day from Lousiana back home.  We made good time but it was still such a long drive.  We pulled into the drive with 2,884 miles on the trip odometer and had reached the goal of 10 states in 10 days.