Snap Crackle and Pop

I had something happen this evening that caught me a little off guard. After leaving the carwash I was showboating a bit with the wet tires. Hit about 4500 rpm and the engine had a an irregular pop coming out of the exhaust. I can only hear it on the left side of course and it didnt seem to come back thru the carb. Got it on my home stretch of road, sitting still ( no load) it wont do it and it doesnt show up till the 4k and up rpm when kickin it. Okay some history, I have changed the plugs to 1 notch higher heat range as I noticed before they run a little black, they still run kinda black.Think Im running rts45 ac's, might have a letter wrong there. This thing rarely sees those kind of rpms but it is annoying knowing it there. What I have, typical 350 chevy, add ons edelbrock torker 2, carter 650 headers and it is a factory style HEI ignition.Possibly an old school RV cam . I believe I have the choke set Ok at this point, I have adjusted the carb by ear as to idle and air. The timing I have set at 8 btc. My intake is a 3.5 inch tube to cool air that is about 30" in length with a K&N type cone filter. no holes in the diz vac adv line. While I have to double check if its backfiring thru the carb or not, I'm leaning towards the sparkplugs not being right either gap or heat. Possibly the coil weak?? If it is backfiring thru the carb I would suspect the cap, but not sure there yet. Any thoughts on direction here??
Joe

Plugs 1st- dont clean get new ones!! then u say carwash?? get it wet under there = ?????? when dry a day or so -try all again - see if problem is still theer - The black on plugs is bad - likely rejet or get a carb u can jet?/ presonal preference? plug wires were new how long back? likely plugs will cure it esp.= if black & sooty??

Im pretty sure water wasnt the issue. wires were new MSD 8.5s. the dizz might be still original type parts, my memory lacks a little there as we used 3 to make 1 at the time. Any suggestions on Plug make and gap, by the book these only gap at .035,, seems tight to me for HEI?

I usually run 45 gap on hei plugs, the black is your
carb running to rich, timming sounds close enough,
almost sounds like you have an exaust valve floating or
the lash is set to tight on one or two exaust valves.
also might be a weak valve spring not getting the valve
closed fast enough. you might try pulling one wire at a
time get the engine at the rpm of the pop see if one wire
makes a change in the noise, that would be the cyl that has
the problem. make sense? kind of like puling one wire at a
time looking for the miss.

Hey RD, TV and one of the other guys at VCVC were talking about tube size to the carb, would it be possible the 3.5 tube could be causing a semi choke condition on the air draw ?, maybe upgrade the AF to a better flow also ?? I'll grab another set of plugs next week for starters and go to the jets from there. Ive floated valves in a 400sbc before , but that was closer to 6g's. Yup Ive done the wire trick before ,, but never at higher rpms. Thanks for the input.

I don`t think so on the tube diam, remove the tube assy
and put through the paces, see if the pop goes away.
just remember only try one thing at a time, then you will
know what was the problem and the cure.

Sounds like Rice Krispy's

If it is only on one side maybe it could be a valve out of adjustment.

I dont know if it is one side... Mine is alittle loud so I can only hear the driverside exhaust by my lonesome,,lol

Did you raise your dog house lid up and listen to it while you were going down the road? Also check all of your wires to make sure that they are not arcing any fire. I just had to take a set that I had bought new that was maybe 6 mths old.

No, I had the dog iwth me it would scared the crap out of him...

my first guess would be coil. make sure you have the correct coil for your ignition. for the most part, it will run fine on just about any coil but problems occur at higher rpm's if wrong resistance/impedance. rather than getting to technical here, just call summits tech line. my second guess would be valve springs. i would also gap NEW plugs at .045 or more. with a hotter ignition, you might be able to go .060. you want the biggest gap your ignition can handle.

Digz wrote:No, I had the dog iwth me it would scared the crap out of him...

Yea that's not the kinda dog house a dog would like for sure. My dog is a kinda skiddish riding in my van with me anyway. I think it might be the flo masters on it.

Well I feel stupid , but I found a boot on the distributor that was not all the way snapped down, how that loosened up I have no idea. I couldn't get it to do the pop the other day , but I will romp on it some to make sure next time out when I dont have passengers with me! If that cured that , I'll move on to the dark plugs issue.

One wire loose or off will do it. Maybe that was your problem. I have one wire that keeps popping off of one of the plugs on one of my vans and I have put it back on maybe 10 times or more. I think that it must have a bad end where it snaps on to the plug. It makes a popping sound to when it comes off to.

Glad you found the problem. If I had read this earlier would have suggested pushing down all the wires and boots and checking your diz cap at night while running (in the dark) to look for sparks. I remember those old clear diz caps that were fun to watch. Probably all made in China now so you might go thru 2 or 3 to get a good one. Remember: China puts the "C" in Quality! Also, those little proximity pens you touch to the wires next to the plugs are great to see if all getting spark.

One thing to remember is that single plane torques intake is killing low end power there designed for 25-6000 rpm and the poping could be a brokin valve spring but that intake needs to get swapped for a dual plane performer I would also say the dark plugs would clean up on there own if it wasn't running rich off that single plane intake plus run the timing as far as u can till it pings then back it off 2-3 deg don't use a 40 year old spec mine at 24 static no advance and never ever run a gap larger than 35 on the plugs even if u have msd and a huge coil But I would defiantly do a leak down test on the right bank and make sure the compression isn't leaking out the exhaust

Dbennet, You have hit on a subject that I have been discussing with some friends. MY Bolt Ons..lol..
I am in agreement that the Torker2 is a major factor as this thing rarely sees the rpms that this intake likes. The heads are for the most part new and reconditioned by a pro. I bought an RPM Air gap for my current project and am thinking of going that route on this one. The carb probably could use a freshening up. The loose wire did a quick cure of some of the popping , but at high rpm 4-6k it can show up again. Im thinking now this is just the result of the plugs running near fouled. Winter is soon upon me so I will get some time to mess with it some more soon.

Ive seen pros cut a bad exhaust seat and have leaked compression causing extra fuel burn off in the pipe like a crackle sound A quick leak down test will show any variance even a very slight leak will show But yeah a single plane intake pulls fuel from the whole carb causing a rich condition on low rpm engines. My poor nodoor runs about3100 rpm@65 mph. And it gets worse the faster I go but it's still a stock iron intake and a q jet Albeit an edelbrock q jet but the dual plane intake give best low end torque and my plugs are spotless and u can wipe your finger in the tail pipe and it's clean.

Also I seen an earlier response about running the gap close to 60 that's a little extreme gm called for a large gap on bigger motors during the 70s fuel crises to try cut back fuel usage and clean up the exhaust didn't work and the gap was called back to 35 if u want to expose more spark cut the electrode off at the turn and gap to 35 from there the larger the gap the more dwell and voltage is required and changing the mechanical advance curve more static timing and the gain isn't worth the effort I've had lots of dyno time and seen actual numbers your talking 1-3 hp at best