74 Slant 6 Bogs & Stalls Under Load / 30 mph
New to working on a Slant 6, with limited mechanical ability.
As soon as you can, get the three books listed in
this thread and start readin'!
Tune-up parts and technique suggestions in
this post. Pay careful attention to the spark plugs: were good ones put in? Did the installer know to remove the metal ring washer from each spark plug before installing it? Pay similarly close attention to the quality of the other replaceables in the ignition system—distributor cap, rotor, plug wires, ignition box, etc.
Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted
here for free download.
Last year, replaced 1920 for a Holley 1945, which I read was original on a 74
It was, but the first few years of the 1945 carb, which started in '74, were godawful. There were
numerous revisions and tweaks to them, attempts to address a bunch of design and calibration flaws, while at the same time emissions standards were growing tighter, so Chrysler and Holley were in a tight spot and these carbs were jetted very lean. A thoughtfully-chosen new 1945 carb, skillfully rejetted, can run well. There is virtually zero such hope with a "remanufactured" carburetor (1945 or any other model), no matter what name is on the box. But new old stock Slant-6 carburetors have grown really scarce and costly any more, so now
you're the one stuck in a tight spot.
So... I replaced the coil, ballast resistor, ignition module, voltage regulator.
I understand the urge to
do something about the problem, but…stop doing this. Throwing parts at the car like this is an efficient way to drain your wallet, but will almost never fix the problem—in fact, you can easily worsen it, because a lot of the parts on your list are now no longer available through usual parts sources in quality worth having, and you can replace a good/old part with a crap/new part. More than that, if you take this shotgun approach and you do happen to accidentally fix the problem (or seem to fix it), you won't know what the problem really was and you'll learn nothing about how the car works.
Instead of just buying parts at random, you will need to do some diagnosis to home in on the problem and figure out what needs to be fixed, adjusted, or replaced. That's why my first advice was to get and read those books. Yes, this will take some time and effort…that goes with the territory when you own an old car.
bog on acceleration once warm at about 30-40 mph. Restarts after about 5 mins, and I can limp home at slow speed.
If I were faced with a car that would stall like this and refuse to restart until some number of minutes had passed, one of my first suspicions would be that there's still trash in the fuel system. You mention the tank was dropped and cleaned—perhaps not all the crud was cleaned out, and/or perhaps the mechanic reinstalled the old strainer (or no strainer at all). Or maybe that's not it, but there's trash in the upstream side of the fuel filter. Either way, what can happen is that the trash gradually gets sucked up against the filter sock in the tank and/or the dirty side of the fuel filter, then when you punch the gas there's not enough fuel flow to meet the engine's needs and it dies. Your five minutes are spent waiting for the trash to float back off and away from the strainer and/or filter, then the engine will start again.
But that's just one thing that could cause this problem, it's not the only thing. Could easily be a fault in what I'm guessing is a "remanufactured" 1945 carburetor, among other possible faults.
Researched this, and replaced EGR valve
This, as you found out, was not the solution. The symptoms you describe are not those of a faulty EGR valve. Be careful not to confuse
research with
reading stuff on the internet. They aren't the same. There's a ton of bad advice available for the asking (or clicking). Some of it right here in this thread; for example, no, you do not need/will not benefit from an electric fuel pump. No, you should not fling open the hood and pretend to be a caveman ("Hurr, derp! Emission crap bad! Hulk smash! Hulk rip! Grr! Snarl!").
I did hear a bit of a quiet backfire as it died on the road.
Spitback is a symptom of a very lean mixture, and since your engine appears to be starving for fuel, a cough like this as the engine dies is in line with expectations.
I re calibrated carb settings (mix and idle) by setting screws and backing out 2 1/4 turns each on the Holley 1945.
Sorry, no. You did not recalibrate anything. There is no magic number of turns (2-1/4 or any other) where any screws are supposed to be placed. That's just not how any carburetor adjustment is actually done. Info on how it's actually done is in that carb-manuals thread I linked.
Figured it's drowning on fuel?
No, opposite.
So... I'm thinking vacuum advance on distributor
No.
No.
Maybe so, but that would be on top of whatever's causing your symptoms.
As determined how?
No.
Btw, tranny seems to shift fine prior to under load death, hoping it isn't the tranny.
It's not.
No.
Pain in the butt emissions crap?
Probably not.
heard the carter bbs is a better simple hassle free carb than the holley
Yes, but they are hard to find in condition worth having. The optimal one for your '74 would be the '73-'74 Dodge truck BBS, and those have never been particularly easy to find. The further back you go from there, the more adaptation will be required. None of it's terribly difficult, but beware of "feature creep"—none of these BBS carbs has a provision for venturi vacuum, which you need if you're keeping your EGR system operational, and there is no workaround for this. If you disable the EGR, you will likely have to recurve the distributor to avoid damaging ping/knock.
should i upgrade to a super six set up
The Super Six 2-barrel setup gives much better driveability, performance, and economy than the wheezy 1-barrel setup, but it requires a pretty long list of parts, some of which have grown very difficult and/or costly to buy, and you'd still need to find and buy a good carburetor.
clifford or aussie 2bbl intake
No, neither. Those are race/hotrod pieces, not appropriate for your engine configuration or the kind of use your car gets. You would be paying expensive money to doom yourself to endless hassles trying to get the car to run right. If you want to take on a 2bbl swap—which I do not recommend until you have a stronger working knowledge of how cars like yours are put together and what makes them run—you would want to stick to mostly factory-type Super Six components.
Eventually ( I know this is slant 6 blasphemy) drop a 360 crate in it, update the 904 tranny to a 727 and update the rear end 7.25 to an 8.25 sure grip posi
This is not the way to fix the problem. If that's the kind of car you want, go find and buy it—if you set out to turn your existing car into this what you describe, you will spend a staggering amount of money and the overwhelming odds are that if the project actually gets completed—which it probably won't—you will wind up disappointed and unhappy.
If this was your child, what would you do?
Read, learn, diagnose, repair.
