New cam and idle

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valiant1966

valiant1966

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Hi all. First off, I would like to thank everyone on the forum who has helped with parts or info on my project. It's up and running and hauls butt. You guys have been invaluable. Now, on with my problem.

My project has been building and installing a 318 in my 66 Valiant with a /6. The engine has stock pistons with heads shaved .40 and gasket matched and minor polishing . I have a Performer intake and new 600 CFM performer carb. Running stock exhaust manifolds and dual exhausts.
Timing is set at 12 initial and I think 36 all in. The cam is a Summit cam and lifter set with .421/.444 lift and 278/288 duration. I think that does details.
Anything I have had with a cam before has been radical or stock...no in between. I kinda thought it would be almost unnoticeable. By the way, I have checked the carb and the floats are good and have fiddled with the mixture screws until I'm afraid I might wear them out.

My thing is that I cannot get the car to idle smoothly. Should it?

Sorry for the long winded post but details are necessary. Thanks. Dennis
 
Duration at 050 inch Lift: 204 int./214 exh. and a wide 112 LSA should be very tame. Probably slightly audible but probably not smooth like a baby's butt :)

edit: Summit's description says smooth idle, so maybe it is!
 
With a cam that tame and bad idle it probably has a vacuum leak or carburetor issues. While it is running, slowly close the choke plate and see it smooths up. If it does, it has a vacuum leak somewhere, or the carburetor is running lean for some reason.
 
Personally, I would bump up the initial. I run my "teen" at 18* initial.
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Were there any mods to the engine to run that much advance? Factory service manual only calls for 10 I believe.

While it is running, slowly close the choke plate and see it smooths up.
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I've checked for vacuum leaks and done this also. All it did was choke it out.

The idle is not horrible, you can just tell that it isn't stock. I don't mind really, just wasn't expecting this and I want to make sure things are right.
According to Edelbrock web site and the manual, these carbs are calibrated to run 4% lean. Would that be enough to cause it?
 
Its not a stock cam right? so you can't go with the stock timing. bump up the timing and if it likes it(at idle) then you need to do some dis mods. If not, try a different carb and see what that does. do you have a carb adapter on the manifold. sometimes the wrong one can cause idle problems.

Did you degree in the cam? if not that could also be part of the lope sound. and it my not be at its designated center line. Lining up the two dots on the timing chain could still have the cam out by several degrees.
 
According to Edelbrock web site and the manual, these carbs are calibrated to run 4% lean. Would that be enough to cause it?
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4% lean at sea level,... your probably close. if it was lean you would most likely get into surge at cruising speeds.
 
I have a slightly larger cam in a Chevy 350 and it's barely noticable depending on the idle RPM and base timing. I think depending on your RPM and timing you could "tune" it out also if you want it to sound smooth. Agree with Cudafever though, even though it's mild that's probably a lot larger than a lame stock cam, the FSM is giving you settings for a stock cam. From the initial post it sounded like the car was running crappy :p you should post a video of it idling, that would be a lot easier to tell if it sounds right or not.
 
In my initial post, I said

It's up and running and hauls butt.
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Once you take off, it runs fine. It's just the idle that I'm concerned about. I know it is a small(but quite a ways from stock) cam but just can' seem to get it to idle smooth. It sounds like a big cam. Only other thing I'm not feeling real warm and fuzzy about is when you stomp it from a standstill, it doesn't burn tires(no torque in other words). No. That is not my goal to see how many or much tires I can burn, just something else that I noticed. Even my slant smoked em from a standing start!
Unfortunately, my car is at a friends house and it is difficult for me to get to it other than weekends so I haven' had too much of a chance to try any suggestions so far. I did tell my friend if he had a chance to go out and bump the timing up and see what it sounds like and how it acts. No response yet.
Thanks for all the help and suggestions. I'm anxious to get this going and feel good about it too.
 
You could always throw in a set of Rhoades variable duration lifters to help tame it out. I know that you just put it together and it will be some more money, but they work well and can help with your problem.
 
For it to idle properly,you must have the 2 a/f screws on the Ede set properly.
For a starting point I always start with the screws turned out 1 1/2 turns.
Screw them all the way in by hand,Do Not Over Tighten them.
Then back out 1 1/2 turns.
This will get you vary close to the setting you will end up using.
To adjust the a/f, hook up a vacuum gauge,or tachometer. Trim the screws for either highest vacuum or highest RPM. Some people leave it there and some back them both off a 1/2 turn.

There are some really good videos on YouTube in regards to tuning Ede carbs.

This is assuming there are no vacuum leaks,cam is degreed,ignition is up to speed,etc,etc.
 
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