79 K10 Back Fire

[crazy4offroad]

May be a long shot but if you have a propane torch you can turn it on unlit and move it around the base of the carb and the front & back of the intake gaskets and see if it suddenly idles up. That would indicate a vacuum leak. But honestly that would be backfiring through the intake, not the exhaust. We're back to earlier suggestions of checking the spark plugs to see if one is showing signs of misfire (discolored center conductor, compared to the others). You REALLY have to keep them in order and remember which one came from where. You also never ran a compression test or a vacuum test.

 

[Guardian]

You could use a laser thermometer to locate any misfiring plugs while it is running then just pull that plug or the cap depending on the results.

 

[HotRodPC]

Still need to do a vacuum test, and a compression test. I'm sticking with being the bearer of bad news and say it's a bad valve. I say that because you mention it's constant and consistent. I do believe you also mentioned it tends to go away at higher rpm too didn't you? A vacuum test alone can tell you the facts, and the compression test can confirm the facts.

 

[Kapdin]

Lol sorry hot rod as u can tell im going "LALALALALALA" when u talk about bad valves. I am taking it to a shop to do a vac test and timing test cus grandpa rly things its timing and would be sweet. but yes i know a bad valve is still a big possiblity. I have no clue how to do a vac test or timming so im admiting defeat for the time being.

 

[HotRodPC]

Lol sorry hot rod as u can tell im going "LALALALALALA" when u talk about bad valves. I am taking it to a shop to do a vac test and timing test cus grandpa rly things its timing and would be sweet. but yes i know a bad valve is still a big possiblity. I have no clue how to do a vac test or timming so im admiting defeat for the time being.

OK, makes sense. I'd love to be wrong and hope I am. And it could be a flat cam lobe too. Really, you can do the vac test yourself. Just hook up a vac guage, and by what it's doing will tell you what you need to know. We have a good thread here telling you how to read the actions of the vac guage and what they mean. I'd just hate for you to take it somewhere else and they be dishonest and make it out even worse than what it is. I would rather it be a bad cam lobe so you valves are good, heads don't have to come off, and everyone needs a good excuse for a cam upgrade.

 

[Kapdin]

Sooooo im rdy guys, time to rip on me. #4 & #8 plug wires were crossed..... I switched them as soon as i got home and cured. Runs like a champ. I cannot for the life know were i would have done that.... cus i took one off at a time to change them out but i must have. But wat ever its fixed and im very stoked. But now i noticed my oil pressure gauge is pretty low while driveing and goes up a little when parked but still seems kinda low it never goes over half on the gauge.... also my battery gauge is kinda doing the same thing..... but im sure the alternator is very old but looks clean and doesn't make any noise but when in park its up were that should be but low when driving. O and i also sprayed undercote on the wheel wells to try and stop/hide the rust and i think it turned out better than expected. What you guys think?

 

[HotRodPC]

Awesome. Much freakin better than a bad valve. Could have a bad ground and guages are not accurate that way. Guage actually work by measuring in milivolts, some do anyway, so when a good ground or voltage is not correct it can affect electric guages. This is why I always prefer mechanical guages for my crticial things like Water temp, and oil pressure. And OEM guages usually aren't 100% accurate anyway, so what you need to get used to, is what do they normally do, then pay attention if they aren't doing what they normally do to detect a real problem.

 

[Kapdin]

yea very happy its not a valve. Its just that oil pressure that scares me... is there any way i can make sure its fine? that gauge is fed by an hose is it not?

 

[HotRodPC]

Order that cheap SW Oil pressure guage off of Summit.com. I do not skimp on guages. When your motor depends on them, spend the money and get quality, but for some reason these SW's are cheap. Stewart Warner are one of the best know quality guages built. I'd imagine these are cheapies, but still SW isn't putting their name on junk. They've got a good reputation to uphold and they won't lose it selling junk, so I'd trust these things even at this price. May as well get the mechanical water temp to match it too for this price. I also prefer full sweep guages. A larger scale has better tendency to be more accurate.

http://www.summitracing.com/parts/SWW-122259/

http://www.summitracing.com/parts/SWW-122260/

 

[Kapdin]

Nice guages, deff going to get me thos. I don't suppose thos will fit right in to the oem bezzels? And how hard is it to hook thos up?

 

[HotRodPC]

Not sure if they fit or not. Being they are mechanical guages, you'll run the oil pressure tubing to an oil pressure tap on the block, and the water temp will bolt up to one of your head temp sensor ports, and some intake manifolds have provision for temp guage. I prefer to use one in the heads since the head temp gets hotter than the intake. But, even in the intake is good and that also lets you know if your Tstat is doing it's job. If you have a 180 Tstat, you can usually see it rise to 180, then it drops, gets to 180 again, and then drops, then you know where your Tstat is popping at. That usually only works for warm up. After a couple pops, the whole cooling system is the same temp and the Tstat pretty much stays open.

 

[crazy4offroad]

They fit if you mount them flush to the front of the bezel but you really have to gut the hell out of your actual cluster. You MIGHT be able to put them behind the bezel but it would take some work, and again, gutting of the instrument cluster.

 

[Kapdin]

Damn guys its slow as hell at work so im doing alot of google searches and now im scaring myself. People saying its the crank bearings and wat not and to run like 50-60 weight oils..... so now im already thinking about motor swaps and **** lol. We got that 91 k1500 yet i could pull and i think that has a 700r4..... any way other than waiting for that guage to show up to test? or ideas?