Super Six frustrations

[oldskoolracer]

Hey there all, havnt posted much on here and I have looked all over for info but no luck so I need to ask a couple questions. Some of you may have an answer and be able to help me out...

Car is a 78 Plymouth Volare wagon. Factory 225 super six, a904 trans. Rebuilt the engine, trans, replaced all hoses, belts, gaskets, pumps, starter, alt, dist, HEI conversion, etc...

I have managed to get the car to run decent at best, but I am to the point of being beyond frustrated and am getting sick of pouring money into it. Heres the issue, if I adjust the carb/timing where it is idling nice and smooth, good vacuum (max I can get is about 18-19in) has decent throttle response and over-all decent driveability with the cost of it trying to run-on after the key is off. On the flip side, I turn the timing down till the engine is still fairly smooth but idles low it doesnt seem to try running-on as bad but throttle response and driveability is crap. Dies everytime the throttle is opened and has NOOOO power under load. Have tried several initial timing from 0*-12* btdc with and without vac advance hooked up.

I have thoughts/theory on the exhaust being partially plugged but feels to blow pretty decent at the tip so Im not sure. Can it be clogged enough to cause detonation/run-on and still blow out the tip, or should I be looking else where? Ive tried dialing this thing in everyway I can think and just replaced the carb all-together trying to remedy the issue with no luck... Any advice or info would be beyond appreciated. Like I said Im at my wits-end with it and just need some help!

 

[slant6billy]

Your run-on may be low octane gas. My last slant did almost a similar dance. It would start right up, but if I put it into drive it might just stall out. If I were to punch the gas pedal in park, it was ok, but in drive it would stall. I would have to Neutral drop on the down rev to keep from stalling and get going off the line. My carb was a store bought rebuilt. I switched to a more expensive new carb and problem solved. I put the so called bad carb in a box and a few months later put it on a friends D150 with super 6 and stickshift. That D150 is still running today. There may be a better approach and someone here might know if your carb is the issue, but I got to say it may just not be right.

 

[slantman]

For ANY Slant six advice...Slant six .org... The best/only place to go for slant advice!!!!

 

[oldskoolracer]

Ill have to browse their site a little more, tried joining a while back but wasnt accepted or something? Ive had the same issues with both carbs, the new one was a big improvement cause it has good throttle shaft bores and the bowl cover isnt warped. Also have tried running all grades of gas, tend to run 87+ a fuel treatment and doesnt seem to make a difference. There is NOTHING left original on this engine besides the exhaust. Thanks for the prompt replies and will do some more research and try to figure it out before I give up all together. Been dealing with this issue for about a year now and its just getting old...

 

[Jack Meoff]

Sounds a lot like my Volare when I got it.
But my initial issue was that the old timer I bought it from had the plug wires mixed up and was firing wrong...
Once I figured that out I got the carb rebuilt, as soon as I got it I did plugs, wires, cap and rotor and she's run like a champ ever since.
Owning two Super Sixes...I do know that they love ethanol free high octane.
Always puked on the 87 octane crap and in my opinion octane boost is snake oil.
Plus running 91 in mine means I can advance the timing a lot more and gives it a nice kick off the lights.

Amazing that the little sucker actually did run with the firing order wrong...that's what drove me nuts....before I figured that out...when I was setting it up it was either idle good....run like crap or run okay and stall at idle...made me nuts....
I'm figuring your firing order is correct....just thought I'd share.

 

[oldskoolracer]

Thanks, I am going to be sticking with 91 from now on, even a small improvement makes all the difference. I was worried about firing order too but have double and triple checked it, even went as far as looming the wires so none of them touch each other lol. Managed to tinker with it for a while yesterday, got it running pretty smooth with about 19" of vacuum. No idea what the timings at but it hasnt tried running on yet when I turn off the ignition, and the stalling is at a minimum. Have a 2.25" turbo muffler on order and will have it tomorrow so we'll see if that makes any difference.

 

[jasperjacko]

Timing is everything they say, Put a light on that thing to see where you're at. You have to get that right along with idle mix and idle speed before you can move on to drivability issues.

 

[Shorty Thompson]

Timing is everything they say, Put a light on that thing to see where you're at. You have to get that right along with idle mix and idle speed before you can move on to drivability issues.

True , and I feel his frustration . However . If the balancer's slipped a timing light isn't going to help .

 

[Jack Meoff]

True , and I feel his frustration . However . If the balancer's slipped a timing light isn't going to help .

Or a stretched chain....
I've always done mine by feel
But Jasper is dead on with dialing in the mixture and setting the idle speed first.

 

[oldskoolracer]

The chain is a new double roller, Im not 100% on the balancer though, its the original for 1978 lol. Seems like if I set the timing to the 12* its it runs like a raped ape, however thats when it tends to run-on the most so I just turned it back a little until it went away, thats why I dont know exactly what its set at.

 

[jasperjacko]

For what it's worth, my 360 runs 16 initial timing. I suppose each engine may be a little different. I don't believe timing would affect run on since the ignition is turned off. That may be a overtemp/poor fuel issue. May want to try a cooler plug as well. The plug could be so hot that it causes predetonation and run on. Don't give up.

 

[oldskoolracer]

I was just considering switching to the NGK UR5 plugs instead of the UR4 that is recommended. I know that having the timing too high could cause it due to high cylinder temps, but I really feel its the muffler causing excessive back pressure and keeping the cylinders hot. The engine temp barely ever even reaches 190* when fully warmed, going off of the stock gauge and aftermarket. Definately not giving up yet, WAY too deep into this thing. The exhaust is the only thing left on the car that hasnt been replaced/ upgraded yet.

 

[Shorty Thompson]

Or a stretched chain....
I've always done mine by feel
But Jasper is dead on with dialing in the mixture and setting the idle speed first.

Sorry Captain , I totally disagree since timing affects carbureation and carbureation affects timing . These 2 together can be very difficult .

 

[Shorty Thompson]

For what it's worth, my 360 runs 16 initial timing. I suppose each engine may be a little different. I don't believe timing would affect run on since the ignition is turned off. That may be a overtemp/poor fuel issue. May want to try a cooler plug as well. The plug could be so hot that it causes predetonation and run on. Don't give up.

Oh yes it does !

 

[Shorty Thompson]

The chain is a new double roller, Im not 100% on the balancer though, its the original for 1978 lol. Seems like if I set the timing to the 12* its it runs like a raped ape, however thats when it tends to run-on the most so I just turned it back a little until it went away, thats why I dont know exactly what its set at.

Smartalec question , but ! You are pulling the vacuum hose off the advance , right ?

 

[oldskoolracer]

Yep, pull the hose and cap it off at the carb, Ive tried setting the timing to 12* with and without the advance hooked up. Im not going to lie I really wasnt sure if it was supposed to be 12 with the vacuum hooked up or 12 without so I tried it both ways. Thats why I finally gave up with the light and set everything by ear and with a vacuum gauge. put a new dizzy in cause I thought it may be too rusted out, no difference and just put a rebuilt carb on it from Vapex. I have even gone through and double checked the valve lash a couple times, both witht he engine running and without, engine up to temp obviously. Set them to .012 in. and .022 exh. I know factory is supposed to be .010 and .020 so Ill re-adjust them to that spec if the muffler doesnt clear up the issue...

 

[oldskoolracer]

Again, thank you too all of your help folks, really just need some second opinions on it just in case Im overlooking something.

 

[Jack Meoff]

Sorry Captain , I totally disagree since timing affects carbureation and carbureation affects timing . These 2 together can be very difficult .

Understandable since my memory is beer soaked.
I did actually do my timing before I did the carb.
When everything was all dialed in and I ran a pile of fresh gas through it and took it for a good highway run I did do one final tweak on the timing....been running great ever since.

I stand corrected Sir...

 

[My imp]

Did you check your vacuum hookups vs. the sticker (hopefully still there) under the hood? Are all, some, none of the emissions still hooked up & working? This too can affect drivability.

 

[oldskoolracer]

...yea, I deleted all the emission stuff, all it had was the nox valve on the air cleaner, Hhot air door wich was a vacuum leak so I capped it off, egr and the vac solenoid that ran it, and a ported vac switch. All have been romoved and capped off, have the dizzy vacuum going to the port on the pass side of the carb. I did originally try having it all hooked up when the engine was first installed, it all matched and yes the sticker is still there! This car is imaculant, rust free, a little over 90k on it. The old engine was only replaced due to a dark morning and a water main stigging up too far and smashed the oil pan...