engine backfire and loss of power

[Jeeperator]

Make sure your floats are adjusted right also.

[neilbyrd]

I drove up bee canyon to the big flat area above the shooting area and back to my house before checking them (about 10 miles). By the time I got back to my house it was barely running, thats when I pulled the plugs and saw all the dry soot. I will change the plugs and drop the jets 2 more sizes when I get them and give another go either saturday or sunday.

[RAT]

Hopefully he changed the plugs same time he changed the jets so he dont get a false reading from the previouse jet usage. Need to drive up a long steep grade in a higher gear 1:1 and at the top pull over fast and check the plugs. Driving around town is not goin to give you a good reading. Engine needs to be under a good load like it was on a dyno pull.

Yes, agree 100%.

[Jeeperator]

Hopefully he changed the plugs same time he changed the jets so he dont get a false reading from the previouse jet usage. Need to drive up a long steep grade in a higher gear 1:1 and at the top pull over fast and check the plugs. Driving around town is not goin to give you a good reading. Engine needs to be under a good load like it was on a dyno pull.

[RAT]

Well I jetted from 57 to 55 and now the soot is dry instead of wet. I had ordered 54 also so I guess I will try those next. I will need to get new plugs to because they are fowled now it wont run to much soot. I might order some 53 and 52 just in case.

Yup! Sounds like you're getting there fast. One more jet change and you should be pretty close. How far did you drive it before you pulled the plugs?

[neilbyrd]

Well I jetted from 57 to 55 and now the soot is dry instead of wet. I had ordered 54 also so I guess I will try those next. I will need to get new plugs to because they are fowled now it wont run to much soot. I might order some 53 and 52 just in case.

[RAT]

You guys sure it's not a timing problem?

If it was timing the engine would run rough at all altitudes. What he describes is that it runs ok at "home" but gets rough going up the hill.

[Roger]

You guys sure it's not a timing problem?

[RAT]

My pickup spent 8hrs on the dyno trying to jet an Edelbrock carb. We gave up on that piece of junk and went to a Holley.

I feel yer pain. Not a fan of Edelbrock carbs. Ran a Predator 1250 on a 351 cleveland in pro gas eliminator class (not sure what class that is these days, maybe pro comp) NHRA. Loved that carb set up; it made massive amounts of HP. In a '72 Vega it was a blast.

[chris142]

Ya that makes sense but his carb must be running extreemly rich and I don't think 2 sizes will make enough difference.

But I have acess to a chassie dyno too so I can see what the mixture really is.

My pickup spent 8hrs on the dyno trying to jet an Edelbrock carb. We gave up on that piece of junk and went to a Holley.

[RAT]

I don't think 2 sizes will make much difference. If it was mine I'd go 4 or 6 sizes leaner, check the plugs after a cruise and listen for any detonation.

holley almost always recommends changing no more than 2 sizes at a time. Just for the reason you mentioned; detonation. They have to play safe.

[chris142]

I don't think 2 sizes will make much difference. If it was mine I'd go 4 or 6 sizes leaner, check the plugs after a cruise and listen for any detonation.

[RAT]

Rat at higher altitutes, the engine will run richer. Less air makes a engine run richer.

I stand corrected. Note to self: Proof read before posting... Thanks kevin.

[1 Bad F N Z]

Awsome, but remember, going down two sizes at your altitude will lean out the engine at higher altitude, and too lean is not good. So even if the engine starts running better after the change, make sure to check the plugs a couple of times afterward to make sure they are burning correctly. And, don't make any other changes to the carb like changing idle mixture or anything. Change the jets and drive it for a while unless the change makes it worse. Always with carb; one change at a time. Makes going back easier.

Rat at higher altitutes, the engine will run richer. Less air makes a engine run richer.

[neilbyrd]

ok thanks. I should have the new jets in a couple days, install sunday and take it up the trail a ways see how it runs.