Hi Everyone, I have reviewed the forum and internet but I continue to not get it so hopefully I can get some useful input here.
Configuration: 1965 convertible NOM 1971 350 CID with GM Aluminum Intake, new professionally refurbished Holley 1850-5 600CFM, Mallory Unilight Tach Drive distributor

PROBLEM STATEMENT:
Engine fires up fine, you never even hear the starter as the ignition/start up is so instantaneous.
Sometimes it idles fine but randomly and more often the accelerator is stuck. If I goose the pedal the idle goes to normal.
Then when driving it suddenly appears to load up, backfire, lose power
It will randomly shut off at a traffic light but will immediately fire right back up
It will randomly shut off while cruising at 50MPH in 4th gear - it suddenly loses power and shuts off - it immediately will start right back up.

The restorer that I purchased it from told me right before delivery that it was "loading up" when it got hot and needed a new carburetor. He removed the alleged failing Holley 750 Dual Feed Double Pumper and replaced with this Holley 1850-5. Upon delivery last week I test drove it and it idled and ran fine for a short down the street and back. Then I took it for gas and experienced the accelerator sticking in terms of Idle went from 1000RPM to 1500-2000RPM. Smacking the pedal would knock it down. Next I went out for a cruise night and that's when all the issues were realized. Random loss of power, random backfire, Idle sticking and sometimes during all of this, it ran fine!

I suspect that the seller telling me it needed a carb could have been somewhat true however it appears that the symptoms have remained the same. I'm leaning towards the ignition system, Mallory distributor? But it's been 40 years since I touched this stuff and I don't know enough to begin.
I also see that the accelerator Rod is Mickey Moused, no bushings, in the wrong holes and sloppy. I've ordered reproduction Rod, bushings and swivel.....

I would appreciate expertise that may help me identify and resolve this. Thank you

 

does the accelerator stick with the air cleaner off? the screen door accelerator spring is not good for the carb. I would get that fuel hose off the intake. get your self the fuel line kit for the 64-65 327-350, 327-365

 

You don't come across as a do it yourselfer which is no insult, many similar lurk here and even I cannot do the stuff I used to do.
You have running symptoms that can be caused by innumerable problems and likely more than one. The person working on it has no idea what is the matter, so you want to give up on him. On top of that are aftermarket parts, a unilite distributor is well regarded but known to cause trouble too. However with all those replacement parts and little evidence anyone has been working on it knows what they are doing tells me you need help. We cannot help you much here but to give you advice.

There is likely nothing complicated wrong with your car but you will need a mechanic well versed at diagnosis of simple mid century carbureted engines. Find a shop as close as possible with a verifiable track record working on old American cars and bring it to them. If the engine is internally healthy which it appears to be than an experienced Chevy guy will straighten it out in a few hours, check it, time it, adjust the carb, tune it and you will be all set.

If it were mine I'd put the stock distributor and coil on it.

Dan

 

1. With the current accelerator rod in the wrong hole, your throttle must be very sensitive. The rod goes in the large hole at the top of the lever in the rubber bushing. I guess you know that as you ordered the right parts. The rod in the wrong hole may be contributing to the throttle sticking.
2. Your high rpm sticking may be the electric choke out of adjustment or the choke cam sticking. R66 has a vacuum operated dash pot to pull the butterfly open once the engine has started, but I don't know that one can be adapted to your Holley 1850. Look on the air horn for a LIST number. Here is where you can find direction on just about all the the adjustments you need to make to the Holley. https://www.holley.com/support/carburetor/ You may need to adjust the idle air after you figure out what you have.
3. The rubber hose from the fuel pump is a potential fire problem if it gets against the exhaust manifold or a rotating belt or pulley. You might consider replacing it with metal at least to the top of the engine if not all of the way to the carburetor inlet. NO MECHANIC that I know would plumb the engine like that with all of that rubber hose.
4. I don't see a vacuum advance can on the distributor. Yet there is a hose going from the ported vacuum (I think) on the carburetor, but I can't see where it goes. Maybe to the controls for the AC? If you are driving this on the street, I highly recommend you swap the distributor for one with vacuum advance if it does not have one.
5. Your problem sounds more like ignition as it is intermittent. You need to find the instructions for setting up the Mallory Unilite to see if you need to rewire it and if the ballast resistor is needed. Pull the model # off of the distributor and let us know what it is. You need to find the manual for the model of the Mallory Unilite you have and trouble shoot it. as well as check the cap, wires, and rotor for arcing or other damage.
6. Hand trace the wiring past the exhaust manifold to assure it is not burned and shorting out intermittently.
7. As the backfire is intermittent, it could be a bad coil if it does it only after the engine is hot. Or it could be as simple as low voltage to the UniLite pickup or dirt on the electronic eye of the pickup. The lack of a vacuum advance may be causing your backfire when you back out of the throttle quickly which will blow the power valve in the Holley and make everything go rich.
I hate to say it, but that engine is such a mess that I would recommend starting with a visual inspection of the wiring, and check every component for correct installation. It sounds like you just purchased it, I doubt the dealer has competent mechanics to straighten it out. So, return the car for a refund if you can or find a mechanic that deals with old cars or fix it yourself if you have basic knowledge and the the guidance from Mr. Good wrench in these two manuals. https://www.workshopservicemanual.co...-repair-manual. Start at the beginning with checking the timing, plug wire routing, etc.
For what it is worth - maybe $.02.
Ron

 

The 1850 carb is a 600cfm, cheapest 4 barrel carb Holley offers. I’m going to speculate here and say the seller wanted the 750dp, so he bought an 1850 and slapped it on without any tuning. While a 750cfm is typically too large for a 350, we don’t know the engine specs or how the carb was tuned for the application.

I think you have two issues: an untuned carb, perhaps over torqued causing the butterflies to hang up and a possibly heat related ignition issues (coil?) cause hot drive ability issues. I would start with the ignition problems and then address the carb.

 

As usual, a huge thank you Nowhere Man! You are always gracious and a fast responder. I will get the fuel line off of the intake.
I see at least 3 different return springs online. Would you please make a recommendation if you don't mind.

 

More 2 come but I made 3 changes.

1. Removed air cleaner
2. Removed Ignition shielding from on top of distributor
3. Moved rubber fuel line off of the intake

Results are only preliminary
- At first cold start I see that the choke is closed and Idle it at 1500 RPM. I goose the throttle and Choke opens and Idle drops to just under 1000RPM.
-Took the car around the neighborhood, Idle was no longer an issue, performance was fine

Next test - take it out on the highway in the same configuration. My concern is that if the backfire and sudden loss of power occurs without an air cleaner I run the risk of carb flame and hood burn!!!!

 

Then your air cleaner base is interfering

 

Thanks for your advice. I was once upon a time someone that could and has done it all. I've pulled engines, did 100% of the machining myself, yes I actually knew how to machine all aspects of an engine. Did a full body off restoration of a 67 Chevelle SS almost 30 years ago amongst all those things associated with being a "car guy"

However, I was never a Carb or Ignition GURU. Now in my retirement I find I can still turn the wrenches and detail things to a correct state (once I research and learn what is correct for the specific vehicle) but the workings of wiring, ignition and fuel systems remains a challenge for me :-(

 

2nd road test. Same configuration
NO Air Cleaner
NO Ignition shielding
Fuel line lifted off the intake

Now the idle issue is back. Keeps going to 1500 RPM while driving and in between gear shifts. A goose of the pedal brings it back down to 1000RPM
It too was a short drive but this time no backfire and no hesitation or sudden shut off.....

I've ordered the fuel lines and accelerator rod and bushings. I also have a correct air cleaner being shipped to me. I suppose there is nothing to do until I resolve the throttle linkage, install the new fuel lines and get the correct air cleaner.

As it fires up nicely immediately upon turning the key I remain unsure of what the issue is

 

I think it sounds like a choke suddenly engaging. Disconnect the power to the choke and wire the flapper open to see if that fixes the symptoms. It may be a little stubborn to start and idle until hot. Factory chokes used a thermo-spring on the intake which I think is simpler to manage.

If it's air cleaner interference... will you post a pic of the air cleaner with and without the lid? Also the underside of the base?

 

Hi Owen,

It's absolutely not the Air Cleaner as I've completely removed it for my last 2 road tests. The one I do have is an open element and does not fit correctly and I have ordered a correct one for a 65 350HP 327

It always fires up immediately so I don't anticipate that disconnecting choke will impact me. I am in Florida where cold doesn't seem to be an issue! I'll give the hard wire choke open a try and post here what the results are.

Thank you,
Rick

 

A sticky VAC can cause idle speed issues. I'm not familiar with the Mallory Unilite. Does it actually have a VAC, and if so does it use the family of Delco single point VACs?

Post a good photo or two of the distributor.

Duke

 

Hi Owen, I hard wired the choke open and disconnected the wires. At first start the idle was at 1500 and a quick goose of the pedal brought it down to 1000. I took a 10 minute road test and did not have the idle issue or any other issues at this time. Here are pics of the current air cleaner, which is off the car for these tests.

 

Hi Duke, The Mallory does not have a vacuum advance. Here are a few pics

 

I had similar issues with my 62----
It all began when I added a carb base insulator--it raised the air cleaner just enough so the hood wold ot close-so- I changed the air cleaner to a drop down base---this is when my problems started---with symptoms just like yours.
I would punch the gas and the engine would immediately shut down and restart---eve at 60 mph---
To make a long story short-----the drop down air cleaner lower unit redtricted the air flow so severely that if I tightened the top air cleaner screw 1/4 turn too tight, the engine would shut down.
Further---the dimple under the Top cover for the air cleaner was making contact with the choke rods so the shocke would not open and close correctly----

After MUCH trial and error--mostly error---I found a combination of lower unit---filter element thickness and adding a stop on the air cleaner screw to limit choke interference----
It all works fine now.

I recommend that you run the car without the air cleaner for a few tests drives and see if the problems go away. If you are that worried about backfire damaging the hood---remove the hood for a few days. I know its a bother but in the end if it solves your problem it will have been worth it.

Best
Eddie

 

Update for anyone who was interested in my problem. I finally solved it. I removed the choke completely (not needed here in Florida, I replaced the accelerator linkage with all correct components, installed the correct air cleaner and all was well except this constant shutoff while driving. It was becoming more frequent with each test drive. I finally thought maybe a coil issue so I started by tracing the coil wires. Keep in mind I bought this car sigh unseen and have zero history on it. BINGO, the wire from the coil to the ballast resister was falling off. The small screw and nut were on the verge of coming completely undone so the wire was flopping in the breeze. I removed the wire and the engine would not start. Then tightened it appropriately and Walla, this issue is resolved.

Thanks to everyone who weighed in to help me!

Rick

 

Congratulations on figuring out that annoying issue. Now, for your sake and your cars' sake, get rid of that rubber fuel line coming up from the fuel pump...quite the fire hazard. Looking at the carburetor on your car, I think the metal fuel line, fuel filter, and rubber fuel line for a '65 stock setup would work for your application. Keep up the work of unwinding bad issues.
https://www.zip-corvette.com/64-65-3...it-chrome.html

https://www.zip-corvette.com/63-65-g...ter-black.html

 

AHA ! good for you. Now post a pic of the whole car. I was going to suggest that the choke was sticking. I live in Pa and don't use chokes, but I'm a Hot rodder and quite often mill the choke horns off to pick up some air flow.

 

Thank you! I've been trying to figure out exactly what I need to correct the fuel line. I have a stud in the manifold where I believe the fuel filter gets mounted. So i think I also need that bracket.

You cannot see it but from the pump is the metal tube but it would appear someone cut the end off and clamped the rubber hose on just at manifold level.