Popping & Banging Under Heavier Throttle... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Ford Assassin · 07-05-2008, 04:42 PM

Hey guys I recently picked up a '69 C10 SWB for a little truck project that me and the better half can do together.

Anyway, it has a late '70's 350 engine in it (junkyard special I am sure) and it idles and drives normal very smooth. However, anytime I get into the throttle past half way and the engine speed goes up it starts missing and popping/banging through the exhaust. I can feel the loss of power as well.

Its got a HEI distributor already, but I went ahead and changed the cap, coil, rotor, plugs, wires, etc. and I played with the timing (10* initial). I also swapped the carb out for another one and still nothing has improved. I haven't pulled any valve covers yet, but I don't hear any unusual valvetrain noise.

Ideas?

Thanks guys!!

caminokid · 07-05-2008, 05:29 PM

Cam. Thats what's wrong with the 350 I took out of my 69 fleet.

68gmsee · 07-05-2008, 05:38 PM

Quote:

Originally Posted by caminokid

Cam. Thats what's wrong with the 350 I took out of my 69 fleet.

I agree... It was a common problem with early 350's. The symptoms you give is what happens when the lobes are worn.

Be sure and check for any vacuum leaks also.

Wrenchbender Ret · 07-05-2008, 05:39 PM

Yes. Pull the valve covers & turn the engine. Watch for valve/s that don,t open very far. You probably have lobe/s worn down on the cam.

67shortie · 07-05-2008, 06:09 PM

that's the first thing that 'popped' into my mind when I read this too, bad cam.

I know, bad joke

Ford Assassin · 07-05-2008, 06:32 PM

Pulled the driver's side valve cover, its a flat lobe on the exhaust side on #5. Maybe more I haven't pulled the passenger side valve cover yet.

07-05-2008, 04:42 PM	#1
Ford Assassin Registered User Join Date: Jun 2008 Location: Jackson, Ca. Posts: 674	Popping & Banging Under Heavier Throttle... Hey guys I recently picked up a '69 C10 SWB for a little truck project that me and the better half can do together. Anyway, it has a late '70's 350 engine in it (junkyard special I am sure) and it idles and drives normal very smooth. However, anytime I get into the throttle past half way and the engine speed goes up it starts missing and popping/banging through the exhaust. I can feel the loss of power as well. Its got a HEI distributor already, but I went ahead and changed the cap, coil, rotor, plugs, wires, etc. and I played with the timing (10* initial). I also swapped the carb out for another one and still nothing has improved. I haven't pulled any valve covers yet, but I don't hear any unusual valvetrain noise. Ideas? Thanks guys!! __________________ Cable -K5 Blazer 2wd: 6.0 LQ4, 7875 Turbo, Tick Stage II Turbo Cam, Built 4L80e, RevMax Billet 3600, 9.5" 14 Bolt -Chevy 3+3 Crew Cab Dually: Cummins 12v P-Pump Swap, Compound Turbos, A2W Intercooler, NV4500HD, 4wd conversion, Radius Arms, Coilovers, Crossover Steering, etc Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=803608

07-05-2008, 05:29 PM	#2
caminokid Chevy nut Join Date: Jun 2007 Location: Springfield, Illinois Posts: 2,266	Re: Popping & Banging Under Heavier Throttle... Cam. Thats what's wrong with the 350 I took out of my 69 fleet. __________________ 84 Chevy Custom Deluxe 1/2 Ton Named Fade To Black II "Remember kids there is NO replacement for displacement!"

07-05-2008, 05:39 PM	#4
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,207	Re: Popping & Banging Under Heavier Throttle... Yes. Pull the valve covers & turn the engine. Watch for valve/s that don,t open very far. You probably have lobe/s worn down on the cam.

07-05-2008, 06:32 PM	#6
Ford Assassin Registered User Join Date: Jun 2008 Location: Jackson, Ca. Posts: 674	Re: Popping & Banging Under Heavier Throttle... Pulled the driver's side valve cover, its a flat lobe on the exhaust side on #5. Maybe more I haven't pulled the passenger side valve cover yet. __________________ Cable -K5 Blazer 2wd: 6.0 LQ4, 7875 Turbo, Tick Stage II Turbo Cam, Built 4L80e, RevMax Billet 3600, 9.5" 14 Bolt -Chevy 3+3 Crew Cab Dually: Cummins 12v P-Pump Swap, Compound Turbos, A2W Intercooler, NV4500HD, 4wd conversion, Radius Arms, Coilovers, Crossover Steering, etc Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=803608

07-05-2008, 06:09 PM	#5
67shortie Green club Join Date: May 2002 Location: Central CA Posts: 1,059	Re: Popping & Banging Under Heavier Throttle... that's the first thing that 'popped' into my mind when I read this too, bad cam. I know, bad joke __________________ 71 short/fleet ECE 4/6 drop, LQ4/700r4/3.42 gears 70 SS396 Chevelle 427/200-4R/3.73posi 61 Lincoln Continental, black on black Son you are going to drive me to drinkin if you don't stop drivin that hot rod lincoln



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