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Discussion Starter · #1 ·
Developed an odd sound over the past week. It sounds like exhaust under water or when you run out of gas and it gets "fluttery"...??? Still runs ok but can notice a lack of power. New fuel filters and carb rebuild a couple months back.

80 CJ7 with factory 304. Only upgrades are headers, dual 3" exhaust, Epump, and DUI HEI ignition.

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I know it sounds unrelated, but (when cool) remove the radiator cap (could be trapped air in the cooling system, causing cavitation and hot spots in the motor)

Also, to rule out vapor lock, take off gas cap and go for a drive.

Check oil to make sure gas is not getting into the oil
 

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Discussion Starter · #3 ·
Na, that makes sense. I haven't had a vapor lock issue since putting on the Epump which was 15 yrs or so ago. I did however put in a new heater core a few weeks back.

But again it started this just this week.

I also zip tied up into a horizontal position vs a 45 degrees ish the fuel filter in the engine bay.

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Discussion Starter · #4 ·
Well drove it a bit more today. Running with gas cap off didn't help. It's intermittent too. Once while at a light it straightened out and ran fine then a minute later back to it. Same thing happened while cruising in 3rd, as soon as I clutched and went into 4th it cleared out but a mile later it started loading/fluttering.

I also noticed a soft "burb" in the exhaust at idle and low load cruising. Once above 50 mph it had a noticable backfire pop in the exhaust but wasn't constant.

Could this be timing chain stretch?

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"burb"?

Fuff fuff.......fuff fuff?........Mix Screws each side even (same number of turns) and adjusted for either max vacuum or max achievable needle on dwell/ tach meter?

Look for vacuum leaks

Insure carb mounting is tight as well as any carb bolts/ screws that hold it together.

Choke plate standing at attention?

Fuel pressure using a gauge?

----JEEPFELLER
 

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Discussion Starter · #6 ·
"Burp" I suppose... almost like a back fire pop but soft and subdued so to say.

I double check the carb settings and mounts. IIRC mixers are 2.25 or 2.75 out from seated.

I do have a vacuum gauge but not a fuel pressure one.

Where is best place to T into for the vac guage?

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Description of engine behavior........a "Hiccup"???

I have one on the dash for the exceptional pilot to monitor for abnormalities, or when the power valve comes into play!

When I tune, I can do it out here on my 258, EZ to see while messing with the screws

I prefer the Dwell tach for tuning, as I can see minute RPM changes better than the vac gauge needle---Of course someone will say

that this is all wrong!

I also like it in that I can tweak the RPMs (a teeny bit) with my idle screw to get the needle on a

"LINE/ increment/ segment" (Basically a "zero" or reference that I can see a "Change" when I tweak the mix screws).

Just something EZ to see and launch from, I sometimes zero up again as

I tweak. (if that all makes sense--in the end I do put my idle back where it should be)

I observe the "tip" of the needle as it is the most sensitive part for my tweaking.

Some of my pics show ways to not get confusing--tape/ cardboard/ and a marker. I mostly did this to teach others how to use the

stuff, as they would get overwhelmed by all of the different engine cylinders and numbers all crammed close together

on the meter. Modify it so that you understand where your "timing RPM" should be, as well as a reference for

your normal idle speed.....might make things quicker and less chance of "looking at the wrong line".

----JEEPFELLER
 

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Discussion Starter · #9 ·
No hiccup... as I see it, it doesn't miss, hesitate or stall. It still pulls just sounds loaded up and not as powerful.

The exhaust pop is either at idle or under low load/easy cruising. Almost like it's got an extra fire command thrown in to a cylinder when it's in exhaust stroke.

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Do you have CATS included on your exhaust setup, or just mufflers?

Years ago when unleaded gasoline/CATS came about, there was a lot of leaded gasoline still in use, and the new vehicles had issues with the CATS melting solid inside from the leaded gasoline. Hence there were a lot of welding shops making exhaust adapters, and huge piles of these melted CATS, so the vehicles would run. Your symptom description just clicked, so throwing it out there to see if this might be the issue.
 

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Discussion Starter · #13 ·
No cats. Headers, newish 3" pipes to "race" bullets just behind trans skid, then turn downs at the rear axle.

I'll double check all plug wires.



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Probably smoked a wire on the Headers....................Backfiring through some Carbs with Power Valves are a Killer also; do not know the Carb you are running.
 

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Discussion Starter · #15 ·
304 with factory MC2100. Headers, exhaust, DUI HEI, and solid state e choke from mikes carbs are only non stock components engine wise

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Discussion Starter · #17 ·
Haven't had time to really check anything. Sorry guys but I'm hoping to get on it Sunday. I put a carb kit in it a few months back from mikes carbs that had a new PV so hope it ain't that. Is there a better one to use versus anything else? I always had good luck with anything from mikes but I'm highly considering not messing with carbs anymore. A few EFI kits are being shopped

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