Author Topic: engine surging? (Read 2659 times)

hooD · « **on:** June 20, 2012 - 04:05:59 AM »

When cruising at a steady speed of 45-50 mph or more, the exhausts make it sound like the engine rpms are surging....the tach shows no fluctuation at all and I'm holding the gas pedal steady. When my wife asked me what that sound was I knew that I wasn't imagining it. My mufflers are 17 years old with 4,000 miles on them, do you think they are the issue or is it an engine problem?

I've got headers with dual exhausts, no H pipe. Turbo mufflers.

Bullitt- · « **Reply #1 on:** June 20, 2012 - 06:54:33 AM »

Most everything I can find on the subject suggests a lean condition, check for vacuum leaks, turn out the mixture screws 1/4-1/2 turn, anther suggestion was to back the timing down a couple of degrees.
How is the car running otherwise?

Chryco Psycho · « **Reply #2 on:** June 20, 2012 - 10:21:23 AM »

jetting is probably lean or the advance is moving around in the dist at that speed , what type of ign & carb ?

hooD · « **Reply #3 on:** June 21, 2012 - 03:15:20 AM »

Quote from: Bullitt- on June 20, 2012 - 06:54:33 AM

Most everything I can find on the subject suggests a lean condition, check for vacuum leaks, turn out the mixture screws 1/4-1/2 turn, anther suggestion was to back the timing down a couple of degrees.
How is the car running otherwise?

The car is running great! Starts up on the 1st crank, but it runs very rich while choked. After the choke kicks out it accelerates and idles smoothly. I advanced my timing 2 years ago to 34� @ 3 grand. I'll try adjusting the mixture screws and see what that does. Thanks Wade.

hooD · « **Reply #4 on:** June 21, 2012 - 03:24:13 AM »

Quote from: Chryco Psycho on June 20, 2012 - 10:21:23 AM

jetting is probably lean or the advance is moving around in the dist at that speed , what type of ign & carb ?

The ignition is the factory original including the coil. New 9mm wires and new copper distributor cap.
The carb is the original TQ which has been recently rebuilt. 850cfm

I replaced the distributor in 1974. It was called a HI-PO distributor that Ramchargers sold back then. It was supposed to have been "curved".
They said to advance the stock timing to 10� after I got it installed. And that's where it has been for 36 years.
I set it to 34� @ 3 grand two years ago.
I'm running 93 octane.

Chryco Psycho · « **Reply #5 on:** June 21, 2012 - 10:44:43 AM »

advance it 2 more degrees to 36* , a cruise surge can be advance if the there are light springs in the dist but it is more likely to be fuel related , also try running it wth the vacuum disconnected . The TQ is virtually impossible to jet as there are not parts around to work with .

hooD · « **Reply #6 on:** June 23, 2012 - 04:27:39 AM »

Quote from: Chryco Psycho on June 21, 2012 - 10:44:43 AM

The TQ is virtually impossible to jet as there are not parts around to work with .

I'm guessing that adjusting the metering rods is NOT related to the jets.

Chryco Psycho · « **Reply #7 on:** June 23, 2012 - 08:26:48 AM »

you will get some adjustment from the metering rod depth , if the carb is still stock it should have the correct parts in it to work correctly so adjusting the metering rods up will increase the flow through the jets

Bullitt- · « **Reply #8 on:** June 23, 2012 - 09:54:48 AM »

Quote from: hooD on June 23, 2012 - 04:27:39 AM

I'm guessing that adjusting the metering rods is NOT related to the jets.

Turning the tiny screw in enriches the mixture out for lean....Info I saved from demonsizzler who's now gone.
Note that one turn is a lot.
"lightly bottom the piston and turn the slot counter-clockwise until the piston stops dropping, then turn the slot clockwise noting exactly when the piston starts back up, still lightly bottoming the piston, turn the slot 1 turn clockwise. This is the correct way to dial-in the metering rod tree/piston. For a richer setting, turn the slot 1/4 more at a time. For a leaner setting, back off the slot counter-clockwise 1/4 turn."

hooD · « **Reply #9 on:** June 24, 2012 - 03:19:51 AM »

let me get this right.....if i turn the screw � turn clockwise, i will be enrichening the mixture. I f i need to lean it out i would turn the screw CCW.

Chryco Psycho · « **Reply #10 on:** June 24, 2012 - 08:22:01 AM »

yes

hooD · « **Reply #11 on:** June 29, 2012 - 03:33:06 AM »

i turned the screw � turn CW, but have yet to test it. I made reference marks so i could accurately measure my turns and if needed put it back to where it was.

next i will re-check the timing.

Author Topic: engine surging? (Read 2659 times)

hooD

engine surging?

Bullitt-

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Chryco Psycho

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hooD

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hooD

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hooD

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Bullitt-

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hooD

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hooD

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