/6 help, need some guru's

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bignick

bignick

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Ok, first off I've been building racing mopar for over 20 years. So I buy a 75' /6 for my gf. Got it running new carb, plugs, wires, cap & rotor. But this is where Im stumped. It starts and runs well. Before a shift into 2nd gear it pops thru the exhaust. Also when idling not always but every few mintues it will pop thru the exhaust. Other than that is has been great. Fast forward to yesterday I took it on a long cruise and it would creep up in temp at idle and popped thru the exhaust going down the interstate at 60-65mph. This morning when I shut it off after a short ride to work it dieseled and puffed smoke up thru the carb. Im thinking timing not advancing or ignition box going out? Whats the initial timing supposed to be on these little alien motors? Any help steering to fixing it would help. System is still stock and has a vacuum boost and heated switch in the radiator.
 
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Exhaust valve hung open or you lost a cam lobe.
Pull the valve cover and look for any rockers that don't move as much as the others.

Timing should be around 12 initial and 35 total, that's a typical mopar factory advance spread.
 
MOPAROFFICIAL said:
Exhaust valve hung open or you lost a cam lobe.
Pull the valve cover and look for any rockers that don't move as much as the others.

Timing should be around 12 initial and 35 total, that's a typical mopar factory advance spread.
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Wouldnt you agree if it was a cam lobe it would happen all the time and not just every few minutes or a different RPM. It you put it to the floor there is no isssues. And very rpm based popping.
 
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Pull the valve cover and take a very close look at the valve springs I would bet you have a broken valve spring most likely an exhaust spring. You may also have a burned valve.

Brian
 
MOPAROFFICIAL said:
Exhaust valve hung open or you lost a cam lobe.
Pull the valve cover and look for any rockers that don't move as much as the others.

Timing should be around 12 initial and 35 total, that's a typical mopar factory advance spread.
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12 is way to much without limiting mechanical, try 3 to 5, 0 was usually specced for emissions. I run a smaller mechanical advance and safely run 9* initial.

Get it hot and check the valve lash, you do it running. Procedure is on here somewhere


Is there any other emisiions stuff on it?
 
bignick said:
Wouldnt you agree if it was a cam lobe it would happen all the time and not just every few minutes or a different RPM. It you put it to the floor there is no isssues. And very rpm based popping.
Click to expand...
bignick said:
Wouldnt you agree if it was a cam lobe it would happen all the time and not just every few minutes or a different RPM. It you put it to the floor there is no isssues. And very rpm based popping.
Click to expand...
Or you have an exhaust valve hung open....letting gas into the exhaust tract, lighting off here and there, you could call it a burnt valve...either way it's the same effect.
Not everything is text book
 
cdnEHbody said:
12 is way to much without limiting mechanical, try 3 to 5, 0 was usually specced for emissions. I run a smaller mechanical advance and safely run 9* initial.

Get it hot and check the valve lash, you do it running. Procedure is on here somewhere


Is there any other emisiions stuff on it?
Click to expand...

Cylinder pressure dictates wether or not it is "too much".

Slant 6 engines are not special, they do not require a slant guru engineermosexual to diagnose, tune or repair them.
 
cdnEHbody said:
Still mis information , 9r, 11r, 15r, governors all came in slants. With a 15r and 12+ initial seems a bit more than 37 doesnt it
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There are more than that fyi, I have boxes full of those pos distributors.
Im seeing a pattern here, so ill tell you this... If you're so smart, why don't you know what the solution to his problem is? And I'll ask you again, it diesels and pops up in the rpms... so what does that tell you? Defintley not too much timing ehh? Do you know if it's the 2 brl egr version...? That might be important huh...
Misinformation is what you post as fact.
So may I simply conclude with.. i think everything you say... is utter horse ****, and it's embarrassing to even read.
I'm guessing you parrot from .org, I'm sorry for you...just kidding, im not.. in fact I'm putting you on ignore so don't go blind reading your **** anymore.
 
Max power timing(initial+mech.) recommended for a 225 is 32* or less, long stroke, small bore, and good spark plug location, + decent swirl #'s..........the 300hp build
not too many threads away used 30* I believe. Sounds like Charrlie_S said, small vacuum leak somewhere, or as mentioned a small valve leak/hang-up. How far open
is the throttle blade,and are You able to adjust the idle mix w/o a problem? I'll admit I'm not familiar with '75 era stuff, is there a throttle stop solenoid on that carb &
is it working? I won't automatically assume both symptoms are caused by the same issue even tho' they can be.
 
As a follow-up to the above, is the dizzy shaft tight, and is the reluctor gap to spec w/the brass feeler gauges? Also unfortunately these days, having new parts doesn't
always = having good parts, so beware substandard ignition parts failing You...............................
 
cdnEHbody said:
Yup, as i have said, i buy new old stock made in usa caps and rotors, bit pricey, but worth it in the long run
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Well, its alot more simple than most have thought. I changed the thermastat to a high flow 180. Stopped dieseling after shut down when it stopped getting hot. Im assuming it was vapor locking. Then I changed the control module and bam. Popping misfire issues are all gone. No more idling pops or driving. I never knew this leaning tower of power had this much power. All that over $30 worth of parts.
 
bignick said:
Well, its alot more simple than most have thought. I changed the thermastat to a high flow 180. Stopped dieseling after shut down when it stopped getting hot. Im assuming it was vapor locking. Then I changed the control module and bam. Popping misfire issues are all gone. No more idling pops or driving. I never knew this leaning tower of power had this much power. All that over $30 worth of parts.
Click to expand...
You wouldn't be the first to get bit by a bad ECM, glad You didn't have to chase any obscure gremlins!!
 
Could have just been the case ground on the ECM. Make sure you have that cleaned up and use some dielectric grease where the ECM bolts go through to keep it clean.
 
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