poping noise from exhaust

[frankyjoet]

On my 73 350 GMC man tran ,timing set between 10 and 12 btdc . have rv cam, roller rockers dual timing chain, i have an after market dual exhaust , i don't know their size, the whole exhaust system welded. have 2 magniflow mufflers. at first i thought the timing was off, but after searching with google, it seems the exhaust system is at fault. what is the timing set with a RV cam, also have ceramic headers edlebrk 650 4 bl with an edlebrock intake. need help thanks for any help

[rich weyand]

The timing is fine if that is where it really is. Did you check it again since the problem started, or are you reporting what you set it at a while back? Reason I ask is that I have seen a rash of "distributor not fully clamped down, rotating retarded" issues recently.

Check the timing as it stands right now and report back.

[Wrecked1982]

what rich weyand said plus check if simply distributor is not one tooth aside

[Dead Parrot]

Other usual suspects include a stuck mechanical advance, cracked distributor cap, bad vacuum advance can, bad plug wires, and gummed up carb.

[bnoon]

Don't forget simple stuff too, like too lean of idle mixture or exhaust leaks. Post a video so that we can get a better idea.

[frankyjoet]

guys found 8 plug wire and 1 plug wire were crossed, the opposite cyl from plug 1 should be 6 mine was five on the dist cap. also found oil in the #1 plug. this engine has all new upgrade parts except the heads. when i checked the timing the mark on the damper it was moving erratically, i thought this was strange. i have to change those wires and re-time engine. don,t know why there was oil on the the #1 boot. you can help me there. thanks

[bnoon]

The timing will jump around if the idle moves up/down. The mixture on the carb and timing can be a dance back and forth, plus make sure your vacuum advance is disconnected while setting timing.

[frankyjoet]

the wires weren't crossed, after loosening header found a blown gasket above #1 plug. pulled the NEXT plug opposite #1 and found no oil in the plug hole. could oil form the blown gasket leak to the #1 plug boot? maybe this blown gasket caused the pop noise. i am installing new header gaskets and new plugs. also found plugs with black carbon deposits and gap not correct. with a RV cam can i gap these new plugs at .045? I attached some photos to view. thanks for the help joeyt


ps the dist is new bought from c white in Tenn. ebay

[Dead Parrot]

You shouldn't have oil leaking from the exhaust manifold unless you have a really bad oil issue with the cylinder. More likely suspect is the valve cover gasket or PVC valve. Another possibility is leakage from the PS system.

Yes, an exhaust leak there can sound like a lot of things. Especially if it is a small leak.

What are the plugs gaped at now?

[frankyjoet]

dead p, checked all plugs, gap on most at 032. they were gapped at .035 before installing rv cam. this engine has been sitting for quite some time. started it to move from garage to driveway. it is not broken in yet. intend to replace all plugs gapped at .045. all dist wires are new. also replacing the header gaskets. thanks for the help, joeyt

[esbstuff]

I had a truck that had a popping from the exhaust... turned out the intake gasket was bad. May check that too.

[frankyjoet]

esbstuff thanks for the tip, shall i take off the intake man or test it for leaks, like spraying soap water around the edges.

[50seven]

Sounds like possibly could be a bad plug, wire, distributor cap, or rotor or all the above just accumulating to an intermittent misfire. Check the temp of the headers on each cylinder just as they come out of the heads while the engine is running very simple way to find a dead cylinder.

You could also have a stuck or burnt valve. Pull the valve cover on the suspect head and watch the valve rockers while the truck is running for a stuck valve or even a flat cam?

Good luck.

(Have had poor success with brand new distributors and related ignition parts myself lately? Just cause they are new parts here and there don't rule them out as the issue.)

[donut]

Usually for me, popping in the exhaust is air being drawn in and combusting in the exhaust.

Not broken in yet. What's not broken in? Fresh engine, heads, stab a new cam and go??

I'm also assuming that you checked all valvetrain clearances etc.

[frankyjoet]

donut, this engine is not broken in. its been sitting in my garage for 4 years. now all new parts were installed. 3 of those years the engine was on an engine stand.. it was put in the truck about 1 1/2 years ago. the heads are good so i ground the valves installed new stems springs pushrods roller rockers new pistons a rv cam, the rods were serviced at a machine shop along with the crankshaft. i ride daily around the block to run it and test the power brakes. it doesn't pop all the time. only when started. the engine sounds good also have 2 magnaflow mufflers. i'll send some pics. thanx

[donut]

Was the cam broken in when it was installed or first run? (good oil, 1/2 hr 2500rpm+?)

[50seven]

I would say valves are not seating properly. Either sticking valves or to much lift on your rocker/push rod combo? Check your valve springs maybe one got soft sitting so long?

[frankyjoet]

Originally Posted by donut

Was the cam broken in when it was installed or first run? (good oil, 1/2 hr 2500rpm+?)

the cam is new installed. had 10-50 but changed to 10-40. i only drove around a block 4 x. i couldn't get to 2500rpm. the truck has no doors windows windshield prepping for paint job. the valves are not noisy oil circulating good checked with valve covers off. replaced the hdr gasket the old one at n1 plug and n2 had blown. these were individual gaskets that covered the in/ex holes. i think i have to drive on the street for 50miles using brkin speeds. maybe all the sitting caused this. thanx for the help

[donut]

Google or site search, cam break in. (should keep you reading for a month).
Good oil, I mean higher zddp content and a break in additive. Break in instructions should have been included with the camshaft.

If it was a roller cam setup, back to your regular troubleshooting steps...Flat tappet, no break in, popping in the exhaust could be a symptom or the least of your worries. Someone far smarter than me can guide you from here. You may get away with doing a break in now...