Chugging like symptoms?
Thread Starter
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5th Wheeling
Joined: Aug 2017
Posts: 36
Likes: 0
Chugging like symptoms?
I rebuilt my 390 and threw in a big cam and re did all my internals. I had to take my head and intake off because I had a thread fail me and helicoiled it. Put it all back together with new gaskets. Did my best backyard tune on it and I have one issue I didn’t have before. When I’m cruising around 30-35 mph I’m at 1,600 to 1,800 rpm(4speed manual) but I have a chugging like feeling going on? I accelerate and there’s no hesitation and she doesn’t die at idle or seem weak. I have messed with my timing and Air to Fuel ratio for two days now and can’t seem to fix it. Any help?
many thanks in advance guys!
many thanks in advance guys!
Logistics Pro
Joined: Jun 2018
Posts: 3,550
Likes: 441
Do you know the RPM range your cam is happiest in? 1600-1800 RPM is not in that range for a "big cam". Myself I try to run 2-3K RPM with my 410. That's it's happy torque range, none of this hyper miler stuff. Sounds like you have a lively set-up. Try keeping the R's up.
More Turbo
Joined: Nov 2019
Posts: 542
Likes: 72
From: Point Washington
Also, what ignition system are you using?
Points? HEI? Some other type of electronic ignition?
Weak spark, timing off, any one of these can cause issues.
Also, check for a vacuum leak, you may be leaning out a cylinder and dropping it out at high vacuum (low load cruising).
Points? HEI? Some other type of electronic ignition?
Weak spark, timing off, any one of these can cause issues.
Also, check for a vacuum leak, you may be leaning out a cylinder and dropping it out at high vacuum (low load cruising).
Cargo Master
Joined: Oct 2011
Posts: 2,238
Likes: 299
From: Kenner,La.
Chug a lug
If there is no balance tube joining the exhaust together adding one should help. Just as the other posters, a big cam needs to turn up and if you have a manual transmission makes it even worse.
What is the vacuum at idle? Which intake manifold are you using?
What is the vacuum at idle? Which intake manifold are you using?
Thread Starter
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5th Wheeling
Joined: Aug 2017
Posts: 36
Likes: 0
Also, what ignition system are you using?
Points? HEI? Some other type of electronic ignition?
Weak spark, timing off, any one of these can cause issues.
Also, check for a vacuum leak, you may be leaning out a cylinder and dropping it out at high vacuum (low load cruising).
Points? HEI? Some other type of electronic ignition?
Weak spark, timing off, any one of these can cause issues.
Also, check for a vacuum leak, you may be leaning out a cylinder and dropping it out at high vacuum (low load cruising).
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Thread Starter
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5th Wheeling
Joined: Aug 2017
Posts: 36
Likes: 0
I don’t have a balance tube. And vaccum at idle seems low to me. Like 7-8hg. And an Edelbrock performer RPM
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