That's not a bad idea. But how can he differentiate good vacuum from bad? In other words, he'll pick up the PCV unless he plugs it off.
318 Idle issues
- Thread starter 67Dart440GT
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TT5.9mag
Two atmospheres are better than one
Yea you have to plug off everything and then test for vacuum at the dipstick tube.
Holley 670 ^^^ Street Avenger
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Yep........Just like I suspected they are calibrated to be lean. You can place your fingers over the Idle Air Bleeds partially blocking them as its idling and see if it improves it.
The Carter/Edelbrock idle design is better than the Holleys.
The Carter/Edelbrock idle design is better than the Holleys.
Cuda416
Well-Known Member
There is still the possibility of a leak underneath the intake.
I agree, although pretty small since he removed and resealed the intake.
Cuda416
Well-Known Member
Sure but it depends on a lot of things. He indicated he used the cork ends, which are a known problem. The intake could be machined wrong (we've all seen that). it's easy to miss the junction where the china wall/heads meet, especially of the corks are used , etc, etc, etc.
Could it be the carb? Sure but Occam tells me it's something simpler and more obvious (not that Occam has never been wrong). In both cases, the only way to truly know for sure is...
1. put an air cleaner on the thing, and spray brake cleaner around the sealing areas of the intake. If the idle changes, intake leak. If not, points to the carb.
2. take the carb apart and rebuild it (or find a test/replacement)
3. take the intake off and ditch the corks, use a bunch of permatex grey to build walls after scrubbing with brake cleaner, use gasgacinch on the intake gaskets, front and back, with extra around the water ports.
Yeah?
FYI I did not use the cork. Printo seals and rtv on the China walls.
Cuda416
Well-Known Member
Ah ok, I thought I'd read that you used the corks.
Inertia
Well-Known Member
Have you re-adjusted the valves yet ?
He's already sprayed all around the intake with no idle changes.
I was going to start with my compression test. Then the valves next. I've been really busy lately. Tomorrow I will have time.
Inertia
Well-Known Member
Vacuum gauge is your friend, - vacuum leak is constant, fluttering guage indicates fluctuating vacuum, a single, or many out of adjustment valves will cause that, as opposed to a constant leak, like a pcv = steady guage .
jmo
This site had vids of various guage symptoms, they don't load on this pad, hope it does on yours.
Vacuum Gauge is an Invaluable Tool when Diagnosing Engine Problems
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Cuda416
Well-Known Member
Vacuum gauge is your friend, - vacuum leak is constant, fluttering guage indicates fluctuating vacuum, a single, or many out of adjustment valves will cause that, as opposed to a constant leak, like a pcv = steady guage .
jmo
This site had vids of various guage symptoms, they don't load on this pad, hope it does on yours.
Vacuum Gauge is an Invaluable Tool when Diagnosing Engine Problems
www.secondchancegarage.com
Also,
Engine Vacuum Troubleshooting
Years ago, a good friend introduced me to using a vacuum gauge to diagnose engine problems, in fact, it was often the first tool he would reach for when confronted with a poorly running engine.
www.classiccarrestorationclub.com
Inertia
Well-Known Member
Also,
Engine Vacuum Troubleshooting
Years ago, a good friend introduced me to using a vacuum gauge to diagnose engine problems, in fact, it was often the first tool he would reach for when confronted with a poorly running engine.
Thanks, - site I posted has/had similar, great info for diagnostics, little used these days.
Cheers .
I agree with this. Every time I have ever tuned the carb on this engine, even before I did anything to this the vacuum guage has always been low, and bounced 2-4 inches on the guage. It is never steady.
Dartswinger70
Well-Known Member
Best to just swap a carb on and see if it runs. A regular old 600 Holley would do....
They don't understand. With the camshaft your engine has, a vacuum gauge will never be steady. Ain't happenin.
I wish I had one. He'd have it already. I have this Eddy 750 that I cannot get to run right no matter what I do to it, or I'd send him that.
Inertia
Well-Known Member
Not saying it'll be steady RRR, just comparing a vac leak to a intermittent or pressure return to the intake by a mal-adjusted valve.
The vids on the link demonstrate how to tell the difference .
Yes, wild cams will not be steady, but shouldn't be " irregular or choppy? "
Just saying check the simple stuff first, before pulling things apart.
He admits not being too familiar with valve adj. or if done correctly.
Cheers
I will have some more news tomorrow. I plan on finishing the compression check, then I will do the valves. Thanks for all the help so far!
Those 750s have their own problems
May be correct about the Avenger line but the post screenshot only proves the guy didn't know what he was doing and blamed the carb. Changing jets for an idle problem is silly, and that's being charitible.
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