Mixture/Ignition Issue?

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Aug 22, 2009 | 11:06 PM

wheatpj

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Racer

Joined: Jun 2009

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From: St. James, NC

Mixture/Ignition Issue?

I have noticed that there is a difference in the exhaust tone between the exhaust exiting the right and left exhaust pipes on my 1971 LS5 Vette. Left side deep and choppy ...right side deep but very smooth. Also, the exhaust from the left pipe seem richer and the left exhaust tip looks a little sootier The vehicle is recently purchased and seemed smoother than it is now. It has manifolds connected to 2.5 inch exhaust system with magnaflows and Q-jet carb. I was considering turning the left metering screw in a quarter turn to see if it smoothed things out. Is this a viable option? I was also considering pulling the plugs to see if one was fouled or whether all the lift side plugs looked to have been exposed to a richer mixture than the right side plugs before I started monkeying with the mixture until, I remembered seeing something about reinstalling plugs to the correct torque specifications. Is it really necessary to tighten spark plugs to a specific torque measure? Sorry for the stupid questions. I'm just trying to work through my Vette issues. I didn't buy it to run off to the pepair shop for everything. Trying to do it myself with advice from those more knowing than me.

Thanks

Aug 23, 2009 | 12:21 AM

PuddleJumper

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From: Hayward Wi

PULL PLUGS first don't mess with the mix yet

also what kinde of cam do u have in it and whats the idle RPM

Aug 23, 2009 | 08:06 AM

7T1vette

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From: Crossville TN

Make sure that the heat riser valve on the right side is free and that it goes to "full open" position when engine gets warmed up.

Aug 23, 2009 | 08:11 AM

wheatpj

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Racer

Joined: Jun 2009

Posts: 409

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From: St. James, NC

I am told it is a stock cam. It ildes around 600 to 650 when warm. The engine is fairly low mileage for its age, 68K, and has not been rebuilt. It has a new timing chain set, hi volume oil pump, and new main bearing seal which, appears to be leaking. I will need a good dose of confidence before I tackle to one. Will a torque wrench be necessary to reinstall the plugs?

It will check the heat riser.

Thanks

Last edited by wheatpj; Aug 23, 2009 at 08:19 AM.

Aug 23, 2009 | 03:36 PM

PuddleJumper

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From: Hayward Wi

yah you should use one for them, but i would just rent one for it. from an good auto parts place that rents that stuff.

Aug 23, 2009 | 04:54 PM

7T1vette

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From: Crossville TN

You don't need a torque wrench for setting plugs. Just seat them firmly with a socket wrench and they should be fine. If you have a plug set with the metal 'ring' gaskets, just make sure that all of the "give" in the gasket is taken out when you seat them. Using a little anti-sieze compound on the threads makes them easier to remove when you change them next time.

Aug 30, 2009 | 12:33 AM

wheatpj

Thread Starter

Racer

Joined: Jun 2009

Posts: 409

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From: St. James, NC

I pulled the plugs this weekend, plug 3 and 4 (other side of engine) looked pretty fouled. Number 3 was the worst, really black and sooty, threads maybe a little oily too, same with number 4. The rest of the plugs looked like they had been run rich, kind of dark. Also, the plugs that came out were a cold plug ACR43TS. I replaced them with a standard plug ACR44TS. I then took her for about a 30 mile drive including a sprint on the highway. Better but still seems a sort rough, exhaust is pretty smelly. Any thoughts, time to take a screw driver to the carb?

p.s. I found a click style torque wrench at Harbor Freight for only $18.75. The price was so good I bought two, a ¼ inch and a 3/8 inch drive.

Aug 30, 2009 | 02:19 PM

7T1vette

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From: Crossville TN

Replace the plug wires on those two cylinders. If you have an oil leak in that area, oil-soaked plug wires can deteriorate. If that helps, you can follow-up with a can of Seafoam to clean out the carbon deposits from all that oil. There will be a lot of cr@p coming out the exhausts when you use the Seafoam, so don't aim them at anything you want to keep clean.