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: 5,229	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



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.