Slant 6 troubleshoot help!

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ReegDawg707

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I’ve been trying to track down the problem with this slant since January.. my schedule is busy as heck but u try and work on it as I can.
Starts but won’t idle or run right. I can make another video if need be. Replaced carb(3 times...), distributor, wires, plugs, points, vacuum advance, most relays on the firewall, fuel pump & filter, fuel lines and a few other things I may be forgetting. Anybody have any ideas on what else I could check? I understand it’s hard to make a guess with a video opposed to being here in person of course. I appreciate any and all of your time!
 
adjust your valves, .012/.022 a little on the loose side of .010/.020. Also check your intake gasket. Where is that large vacuum line going? Plug it for testing purposes. Its PCV, not needed for idle testing. I bet you got low vacuum on a guage at idle, massive vacuum leak.
 
A compression check is in order. What year model is the engine and how many miles? If it is pre '73, has it had lead substitute to keep the valves from sinking? Have you checked valve lash yet? Could be anything from timing chain having jumped, a few exhaust valves not seating, or maybe a crack in the bottom of the intake manifold sucking exhaust gas into the engine (My last \6 came afflicted in said manner). Or vacuum leak, as mentioned by others.
 
When I was having problems with my slant I wish I would have just started by verifying everything was at the correct 'settings' instead of trying to diagnose why it wouldn't keep running. It would have saved me days of frustration. I see you have replaced a bunch of things but have you verified that they are all correctly working? points gap? Old Fuel? Vacuum leak(s)? Valve lash? Distributor advance degrees? Whats your vacuum reading? Float height?
 
adjust your valves, .012/.022 a little on the loose side of .010/.020. Also check your intake gasket. Where is that large vacuum line going? Plug it for testing purposes. Its PCV, not needed for idle testing. I bet you got low vacuum on a guage at idle, massive vacuum leak.

Is that engine running or still warm and turned off lash gap?
 
Do 12/22 cold: if it starts and runs, run it till warm and readjust to 10/20. Ditch all vacuum lines except the carb dash pot and distrubutor feed. I bet that PCV line is the culprit. If it runs better with the PCV plugged, you probably have a bad PCV valve (if you have one at all) As they are supposed to be 99% airtight at idle and WOT.
 
adjust your valves, .012/.022 a little on the loose side of .010/.020. Also check your intake gasket. Where is that large vacuum line going? Plug it for testing purposes. Its PCV, not needed for idle testing. I bet you got low vacuum on a guage at idle, massive vacuum leak.
Awesome! Thank you. I’ll check for vacuum leak and re-adjust valves. I’ll replace intake gasket as it was sitting for about 20 years before I got it. I’ll update back on my next free day Thursday!
 
I went .010 and .020 on mine cold and it runs like an oversized Swiss watch. Don't over think it.
 
A compression check is in order. What year model is the engine and how many miles? If it is pre '73, has it had lead substitute to keep the valves from sinking? Have you checked valve lash yet? Could be anything from timing chain having jumped, a few exhaust valves not seating, or maybe a crack in the bottom of the intake manifold sucking exhaust gas into the engine (My last \6 came afflicted in said manner). Or vacuum leak, as mentioned by others.
Thank you!!
 
When I was having problems with my slant I wish I would have just started by verifying everything was at the correct 'settings' instead of trying to diagnose why it wouldn't keep running. It would have saved me days of frustration. I see you have replaced a bunch of things but have you verified that they are all correctly working? points gap? Old Fuel? Vacuum leak(s)? Valve lash? Distributor advance degrees? Whats your vacuum reading? Float height?
Thank you! Once I check valves and for leaks I’ll reply back!!
 
I am in 100% agreement on the compression test. It's the first thing that should be done and always the last thing people do after they spend a lot of money. I did it on mine right after I bought it. Compression was good so I plowed ahead. lol
 
Don't replace intake gasket until you do the valves and vacuum/compression test. I had one bone stock from 1967 and the gasket was still good...darn lash was still spot on too. 1st start, No fuel feed so it died. This one had no exhaust either, just a head pipe.
 
Thank you!
Don't replace intake gasket until you do the valves and vacuum/compression test. I had one bone stock from 1967 and the gasket was still good...darn lash was still spot on too. 1st start, No fuel feed so it died. This one had no exhaust either, just a head pipe.

okay thank you. I’ll do all the tests first and make sure everything is running as it should and go from there!
 
Don't replace intake gasket until you do the valves and vacuum/compression test. I had one bone stock from 1967 and the gasket was still good...darn lash was still spot on too. 1st start, No fuel feed so it died. This one had no exhaust either, just a head pipe.


Why do slant sixes make people smile?
 
1....If you can run it long enough to get it completely warm, adjust the valves. EOIC which means bump the engine until the EXHAUST just starts to OPEN, then adjust the intake for that cylinder

Bump the engine until the INTAKE has opened and is not quite CLOSED and adjust the exhaust for that cylinder

2....Check compression. While you have the plugs out, examine them, oily? Is one or two "burned white" IE burned valves or running lean, vacuum lean into that/ those cylinders?

3....Use your ohmeter to check plug wires resistance and inspect them all. Old school rule of thumb is no more than 1000 ohms per foot of wire, and they should really be less. Check coil wire too

4...Inspect rotor for damage, moisture/ dirt, arc "punch through" Inspect cap for arcing, dirt, etc

5...Replace points and condenser if used and set points. If you don't know how say so we can step you through that. BEST is with a dwell meter

6...Set timing, even if you have to "rough it in" on the starter.

Now see if it runs any better and recheck timing. Next, figure out if the mechanical and vacuum advance is working A few ways, first you can "flip" the rotor with your finger. Rotor should move against the spring CW as you turn it, then spring freely back.

Next see if you can figure a vacuum leak. Does it idle better? Try adjusting idle mixture screw. Turn idle screw in if necessary to attempt to get some idle RPM. if it has no affect, try unscrewing the idle screw, then put your finger over the screw hole while revving the engine. Sometimes that will knock some gum/ dirt loose. If you have carb spray try a little of that. It often won't help into the idle screw, but once in a while "does."

Check carb linkage for binding, figure out if the choke is working. Might be overchoking try blocking it open

Use water, wd40, there are others you can spray selectively around the carb mount and manifold joints to see if you have a vacuum leak. Check vacuum hoses, such as brake booster, PCV

There's a hundred things I do which I don't even think about, anymore. They just "happen" and get done.

Download the closest you can find for a service manual, from MyMopar. they are free
 
Keep the valves on the loose side warm .I set mine at 11 and 21 with the engine running warm. This lets the valves sit on the seat just a bit longer and helps them cool.With today's garbage gas you need to do anything you can to help the valves.Sounds like you have a serious vacuum leak .
 
Do 12/22 cold: if it starts and runs, run it till warm and readjust to 10/20. Ditch all vacuum lines except the carb dash pot and distrubutor feed. I bet that PCV line is the culprit. If it runs better with the PCV plugged, you probably have a bad PCV valve (if you have one at all) As they are supposed to be 99% airtight at idle and WOT.
Thanks for posting that.
 
If your going to throw money at it and plan to keep it, converting to HEI ignition is money well spent. Glad I converted mine.
 
I know this might be a silly question but it does have points and condenser setup right? My 71 valiant had a pertronix ignitor setup when I bought it and I was having problems just like yours for as long as I owned the car until I figured out my problem.

In several other posts I've made, I talked about tracking down a problem I had with bad idle and wicked (dangerous) stalling bogs when cold. I was fighting it for months, and I went through just about the entire ignition before I figured it out. One of the magnets had fallen out of the magnetic ring of my pertronix ignitor and I had no spark on the number 5 cylinder. I found it stuck to the bottom of the dizzy and I glued it back in and replaced the tape. Now the thing runs like new.

I went through plugs, plug wires, vacuum leaks, choke and pulloff, heat riser, carb rebuild, bigger jet, new float, air filter, valve adjustment, fuel filter and hoses, alternator, fuel tank sending unit, coil, cap and rotor, more cap and rotor, and all the wiring leading up to the coil. I bought an extra spark plug and put it on one of the wires and checked the color of the spark even. Eventually what I did was hook a timing light to each plug wire one after another and saw if there was any spark while the motor was running which eventually lead me to the number 5 cylinder misfire. The stupid pertronix rubbed the tape off one magnet because whoever installed it didn't adjust the plate the black module sits on properly.
 
adjust your valves, .012/.022 a little on the loose side of .010/.020. Also check your intake gasket. Where is that large vacuum line going? Plug it for testing purposes. Its PCV, not needed for idle testing. I bet you got low vacuum on a guage at idle, massive vacuum leak.
Had time in between work and class to plug that tube on the pcv end and it ended up idling a helluva lot better and stayed running. ordered the pcv and should be here hopefully by the weekend. Sadly the mechanics in my town are quite clueless... I’ve replaced part after part they “thought” were causing the problem but they never once brought up a vacuum leak. Sucks living in a fairly isolated area with no good mechanics. I thank everyone who responded. once I install need pcv, I’ll update again.
 
F'n A! That's great news, Almost a free fix! Now get those valves adjusted...:thumbsup:
 
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