So the 440 in my demon is acting funny. Just took it out for a spin the other day and it drove OK... I noticed at steady state driving down the road it sputters and spits, not sure what thats all about. It idles fine and it doesn't pop or sputter when accelerating just when steady state or slowing down. Also I noticed when i let off the gas to slow down a pretty good cloud of smoke started following me down the road, but went away when it came down to idle or back on the gas. I've read somewhere that that might be worn valve seals? Anyone got any advice?
Spitting and Sputtering
- Thread starter Joep
- Start date
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bOb shingler
Well-Known Member
at steady speed it's probably the power valve. either is bad or the wrong size. the smoke is from a high vacuum when off the throttle. which could be that it need a need intake gasket or like you said, valve seals.
Purple Haze
Well-Known Member
Hook up a vacuum gage and see what vacuum your pulling at cruse when it is doing what you said.
Purple Haze
Well-Known Member
Not really, your vacuum is highest at idle and can still be low enough to open it at cruise.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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By any chance, do you have a vacuum advance? and is it hooked to manifold vacuum?
Where/at what rpm, the vacuum is the highest is determined mostly by the cam timing.
Stock 2bbl cams make their best very near idle, and will hold it in Neutral for quite a ways up the rpm range. My old 223* cam made its best around 1500 or thereabouts, again in N.
My 232* cam makes its best at about 1900ish
That wicked 292/509 cam was up around 2300,IIRC.
Cam-timing moves it around some. Ig timing moves it a bit too,but not much.
The peak vacuum rpm more or less stays the same in hi-gear; the numbers are just lower.
Where/at what rpm, the vacuum is the highest is determined mostly by the cam timing.
Stock 2bbl cams make their best very near idle, and will hold it in Neutral for quite a ways up the rpm range. My old 223* cam made its best around 1500 or thereabouts, again in N.
My 232* cam makes its best at about 1900ish
That wicked 292/509 cam was up around 2300,IIRC.
Cam-timing moves it around some. Ig timing moves it a bit too,but not much.
The peak vacuum rpm more or less stays the same in hi-gear; the numbers are just lower.
340doc
Well-Known Member
I would throw a timing light on it also and see what the timing is doing at the problem RPM
Right now its at my auto shop so i can work on it during school a little bit. The initial timing right now is set at 16. Before when it was skipping I had backed it down to 12 and that seemed to make it run much better. But I have been told that because it has such a high compression ratio (11-1) that backing off the timing is not a good thing to do. Should I put it back to 12 or leave it at 16? I really don't want to do any damage...
340doc
Well-Known Member
16 is not too high for initial, what's your total timing and what rpm is it all in at? Make sure the timing is steady all the way up. You gotta start with one thing and eliminate as the problem. JMO
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