Troubleshooting my FE

[CompFi]

An update to this thread is overdue. But after weddings and graduations, finally able to get back to tuning the carb per Holley’s instructions. Along with the assistance of a knowledgeable buddy, since I was making little progress on my own,

My carb is the Holley Ultra XP 80805, equipped with an Idle Bypass Valve. Lots of trial & error, we tried Fully Open, Fully Closed, and many settings in between on the Idle Bypass Valve. But we could not detect any noticeable difference. So, we left the Idle Bypass Valve on a neutral setting and moved on to the Idle Speed Screws. The car proved to be extremely sensitive to any adjustments to these screws, particularly the Primary. But Holley instructs that “this adjustment should be made to both the primary and secondary screws in equal amounts, so that the throttle plates are opened the same amount.” We didn’t notice much sensitivity to the adjustments on the Secondary Idle Screw, but I stuck to the instructions to make equal adjustments to primary and secondary screws together. Once warmed up, we were able to get the car to idle at around 950 RPMs. And then, we returned to tweaking the Idle Bypass Valve. This did NOT seem to do much to the idle speed itself, but as we adjusted this valve, we could hear changes to the air flow and therefore the fuel / air mixture. And then something encouraging happened – the engine began to cool itself down. From about 85 degrees C to 75 degrees. Yes, the fans were already on by the time the temps hit 85. But last summer, the fans alone were not enough to cool the engine back down to 75 degrees.

Was the engine running too lean and therefore that was the root cause for running hot? Unclear, but promising.

So, I finally had a break in the weather yesterday to take the beast for a short test drive before the rains rolled in for the weekend.

The engine got hot, but maybe not too hot. Short drive, maybe 5 miles. Seemed like lots of back pressure/ popping and cracking when I got off the gas above 3000 RPM. More popping than I recall. Responsiveness seemed good, though I didn’t really push it very hard. But, I did NOT notice any hesitation or sluggishness. When I got home, I noticed some coolant had spit from the overflow tank but no coolant in the driveway which is progress.

I declared this initial test a success. Certainly more tuning and testing to do before declaring victory, but progress.

Does anyone here have experience with Holley’s Idle Bypass Valve? Holley claims it is a new feature, but I don’t have a sense for what “new” means at Holley. Wondering if I might now be close using the Idle Speed Screws, and so I should be attempting to fine tune the carb via the Idle Bypass Valve.

The Holley instructions describe additional steps to set the mixture using the four mixture screws. I have NOT done this. Not yet anyway, since Holley recommends installing a vacuum gauge to a vacuum port in the manifold. I have zero experience with vacuum gauges etc, but if that is what must happen next then ok.

As always, insights and guidance are welcomed and appreciated.

[twobjshelbys]

Lean engines run hot.

Rich engines backfire.

[patrickt]

Originally Posted by CompFi

Does anyone here have experience with Holley’s Idle Bypass Valve? Holley claims it is a new feature, but I don’t have a sense for what “new” means at Holley. Wondering if I might now be close...

Once upon a time guys used to drill holes in the primary butterflies to help them idle and transition better with big performance engines. Why would they do that? Because they had a mill that put off a good bit of heat, the air under the hood would thin out, the idle would drop, maybe even stall, and when they "upped" the idle by turning in the idle adjustment screw it opened the primaries up past the transition slot which causes 98% of the carb problems in performance autos.

There are two solutions to the hot idle blues. One is the idle bypass valve and the second is to install a cap screw that lets you open the secondaries a bit for more air. Both do the same thing. Read this thread and you will understand:

Best Way to set the idle mix on a 4160

There's a pic in there of my installation of the cap screw, which you don't need because you have the idle bypass. There's also a lengthy explanation of why setting the primary butterfly properly to the transition slot is so important. Super important. As important as tightening your spinners before you tackle the twisty mountain road.

[Grubby]

There is likely a plug in your intake that can be replaced with a vacuum fitting. It won’t be in the ideal location, but will work to give you the vacuum signal needed to adjust the idle mixture screws.

On Edlebrock Performer intake it is on a runner in front of the carb and to the Left.

John

[Grubby]

There is likely a plug in your intake that can be replaced with a vacuum fitting. It won’t be in the ideal location, but will work to give you the vacuum signal needed to adjust the idle mixture screws.

On Edlebrock Performer intake it is on a runner in front of the carb and to the Left.

John

[Gaz64]

The purpose of Holley's bypass valve is the same as a Barry Grant Idle-Eze, or any other adjustable "vacuum leak".
You should set both Primary and Secondary idle speed screws so the transfer slots resemble a small square as viewed from the bottom of the carb.
At that point, the bypass valve has enough range to have almost any engine idling at respectable speed.
Back off your idle speed screws, open the primary side 1/2 turn, secondary side 3/8 turn, and the mixture screws at 3/4 turn out. Bypass valve in the middle of it's range.
Warm the engine up, adjust the mixture screws 1/16 turn either way, monitor engine vacuum and rpm, monitor ignition timing, adjust bypass to bring idle speed to near target, adjust mixture either way, depending on what the engine wants. Highest vacuum, then check AFR at idle.

[CompFi]

Apologies for the delay here updating this thread.

I have been tending to a series of repairs to my own chassis. Swapping some worn out parts etc. In another thread inquiring about the age of the members here on the forum, MrMustang responded that he is older than his teeth [which is a great line]. So, I am borrowing it and modifying it. As I am now older than my knees…..

As for the important business of updating this thread:

Lots of great feedback above. To include Ed’s insight that try as I might to chase down this problem and its ultimate solution, I will likely require the expertise of a pro to resolve this issue for me. And right you were, Ed. [That pro is Restoration & Performance Motorcars of Vermont Restoration and Performance Motorcars by the way. More on RPM in another thread that I posted in the New England forum]

Turns out I was confusing multiple issues, and chasing my tail in circles as a result.

1. First, there was a vacuum leak from the passenger side of the turkey pan. That much I knew. I tried to address the leak with different gaskets and spacers etc. No joy. At least not completely anyway. Which means that no amount of tuning the carb itself was going to get it right. Turns out, once the turkey pan was secured with the proper studs, then it made a nice tight seal. And the carb tuned per the detailed instructions from Holley. Important lesson: identify and resolve the vacuum leak first. Do not attempt to tune a carb with a vacuum leak. Do not pass GO. Likely an obvious point to most here, but not me
2. Rising heat temps. An old thread on radiator caps and overflow tanks was recently revived here on the forum. I need to revisit that thread so that I get my terminology correct. And so I don’t repeat this mistake. But the cap on my overflow tank was losing pressure. So I was seeing lots of coolant escaping from the overflow hose spilling onto the ground [I don’t currently have a bottle like Patrick’s to capture the expelled coolant]. Important lesson: troubleshoot for the simple problem first. Replacing the cap with one that holds an actual seal is a good place to start. Now, is it the proper single stage / dual stage cap etc? I don’t know that yet. Like I said, I will need to review that other thread to ensure that I am properly identifying the cap and that it is the correct cap for our application.

So, I hear back from the shop that they have dialed in the carb and that the car is once again idling well, running strong etc. SO, I race down there before they close and retrieve the car. And of course, I take it for a long drive thru the country. Absolutely spectacular. Easily, the most smiles per mile of any drive in the past year.

I pull into a buddy’s driveway to take him for an overdue ride. I kill the engine while we chat etc. I get him buckled in, without any snake bites. We are ready to launch.

1. I turn the ignition. Nothing but a single click at the cutoff switch in the passenger wheel well. [or is it the MSD box up behind the dash in the passenger wheel well? From the driver’s seat, I could not discern which….]. But the starter did NOT crank. Nothing.
2. The fans are running, so I keep the key turned and wait until it the fans shut off. I turn the ignition again. Now, the starter cranks but doesn’t turn over. Which could have been my fault. At this point, I might have flooded it.
3. I had a freshly charged marine battery in my garage, so I retrieved that. I added the extra battery via jumper cables. Engine cranked strong and turned right over. But I kept the extra battery connected for the short drive home just in case I was drawing down the installed batteries from a faulty alternator.
4. Uneventful drive home. I confirmed the charge on the installed batteries. So, should I focus my attention on the Street Fire box? And whether it misbehaves at higher temps? Based on feedback from sunman, 767Jockey, Kevin and others, then the Street Fire box is the primary suspect. [I will open a new thread on this issue.]

So, closing out the issues in my original post of this thread:
• Car now idles strong, once again with a slow rolling growl.
• Car runs strong. No lag across the power band.
• No longer running hot. No longer expelling coolant.

Again, thanks to all for your very helpful feedback. This forum is just so valuable.

[My427stang]

I would start the car with an alternator tester or voltmeter connected. After start, and maybe a blip of the throttle, you should see about 13.8-14.5 volts.

If you see 12V, or less, then it is not charging.

With either output, I would probably then start with battery cable connections (clean and tight) as well as all grounds to engine and battery/frame, then if all good load test the battery

The jump box working tells me either bad/dirty battery connections or not chargimg