Truck running bad after exhaust work give me a couple ideas.

[stx4wheeler]

So i got my exhuast re done a couple weeks ago. I went from headers/dual 2.5 inch pipes and turbo mufflers, and dumps to stock manifolds/single 3in.to a flowmaster 80 series, and ran it all the way out back.

Well now it seems one that i have lost a lot of power- i realize i was gonna lose a little power. But the main problem is that the truck is running like crap. Before it would take 30 seconds or so to warm up and be good to run like a top all day long. Now it is taking more like 15 minutes to warm up. When i stop at a light i have to keep my foot in the peddle slightly so that it will stay running.

Also the worst part is it is back firing, and sputtering badly when going at speed with your foot in the gas, does it worse around 40 mph. I do have a small exhaust leak on manifold collector that just needs to be tightened.

I attribute the running bad to the truck having so much more backpressure. Do i possibly need to jet the carb up or down?

[stx4wheeler]

anyone?

[agjohn02]

lean it out some with smaller jets.

[Reckless]

My thought exactly

[KrazyKarl02]

Couple of things to check, Check your spark plug wires, I know it sounds simple, but they might not have seated them properly after putting new headers on, plus they might now rub against the manifold causing a short. My brother toasted a $100 set of MSD wires like this! A good way to check this is if anyone in the club has an optical temperature gauge (pyrometer I think) shoot each of the exhaust ports and see if one is running cold, could just be a spark plug. Or if you are like me, spit on the exhaust ports and see which one is cold!

Next if you think it is the carb, there are a couple of things to do. Putting a more restrictive exhaust will make the mixture fuel rich (less air is flowing). Backfiring through the exhaust indicates rich fuel, through the intake shows lean. To counteract this adjust the idle screws at idle. I do this by setting idle speed then adjusting each barrel's screw. I hook a tach up and set it for where the engine is running highest. Next if it is back firing when you are stomping on the gas consider changing the lever or pump on your accelartor pump. Third if it is just while cruising change the jets, go down in size on the jets.

I really doubt on a motor as big as a 460 the changing of the exhaust would cause this kind of problems. I would look closer at the ignition, did your truck sit up for a while, maybe the carb is gummed up? If the problem continues you might need to rebuild the carb, or since no one has said it yet in this thread, ditch the land anchor you call a 460 and put a EFI 351 in. Better yet put a chevy motor in it.

[agjohn02]

A good way to check this is if anyone in the club has an optical temperature gauge (pyrometer I think) shoot each of the exhaust ports and see if one is running cold...

these dont work very well on shiny things like ceramic coated headers... but wait, even the frick knows that would be a waste of a pretty set of headers. sounds like karl knows carbs better than me. as a matter of fact i know he does, just look at that belly.

[KrazyKarl02]

these dont work very well on shiny things like ceramic coated headers... but wait, even the frick knows that would be a waste of a pretty set of headers. sounds like karl knows carbs better than me. as a matter of fact i know he does, just look at that belly.

They work on chrome motorcycle pipes, so as usual you have shown you are a dumba$$

[robertf03]

they work great on stainless steel

[agjohn02]

karl, i bet you're one of those people that think you can shoot a laser sized dot from 6 feet and tell what the temp of it is too.

below me


http://www.raytek-northamerica.com/cat.html?cat_id=9.5

Emissivity of Most Common Materials
Emissivity is the measure of an object's ability to emit infrared energy. Emitted energy indicates the temperature of the object. Emissivity can have a value from 0 (shiny mirror) to 1.0 (blackbody). Most organic, painted, or oxidized surfaces have emissivity values close to 0.95. Some of our portable thermometers have adjustable emissivity to ensure accuracy when measuring other materials such as shiny metals. You can choose units with adjustable or preset to 0.95 emissivity.

If you are using a thermometer with a fixed, preset emissivity of 0.95, and need to measure a shiny object you can compensate by covering the surface to be measured with spray oil, flat black paint or masking tape. Measure the temperature of the taped or painted surface. That is the true temperature.

[BMFScout]

When looking for a dead cylinder I don't think we need to worry about "Emissivity" levels or whatever. I really don't think we need a laser anything. How about a squirt bottle of water, or as Karl mentioned (my favorite) spitting. I bet I can hock a loogey from 6 feet and tell which cylinder is dead.

[KrazyKarl02]

karl, i bet you're one of those people that think you can shoot a laser sized dot from 6 feet and tell what the temp of it is too.

below me


http://www.raytek-northamerica.com/cat.html?cat_id=9.5

Emissivity of Most Common Materials
Emissivity is the measure of an object's ability to emit infrared energy. Emitted energy indicates the temperature of the object. Emissivity can have a value from 0 (shiny mirror) to 1.0 (blackbody). Most organic, painted, or oxidized surfaces have emissivity values close to 0.95. Some of our portable thermometers have adjustable emissivity to ensure accuracy when measuring other materials such as shiny metals. You can choose units with adjustable or preset to 0.95 emissivity.

If you are using a thermometer with a fixed, preset emissivity of 0.95, and need to measure a shiny object you can compensate by covering the surface to be measured with spray oil, flat black paint or masking tape. Measure the temperature of the taped or painted surface. That is the true temperature.

[KrazyKarl02]

When looking for a dead cylinder I don't think we need to worry about "Emissivity" levels or whatever. I really don't think we need a laser anything. How about a squirt bottle of water, or as Karl mentioned (my favorite) spitting. I bet I can hock a loogey from 6 feet and tell which cylinder is dead.

This is true Jimmy, I have however used one on a motorcycle to compare things. Most motorcycles have one carb per cylinder, so you can see which cylinders are running hotter. One example, I compared those bosch 4 prong plugs to regular spark plugs on a bike. The 4 prongs ran about 30 degrees cooler, indicating to me that they are not firing as hot and are crap!

[BMFScout]

Well if you didn't compensate for the emissivity it was probably actually 28 degrees, so the jokes on you dumbass!

[KrazyKarl02]

Well if you didn't compensate for the emissivity it was probably actually 28 degrees, so the jokes on you dumbass!

God, I am so stupid, I wish John would have been there to show me with his infinite wisdom....

[CheapJeep]

Too rich, lean it out a bit and it'll run good. I had the same problem with the jeep.