Engine Noise

[VDOG]

Ok it sounds like a bad miss or exhaust leak.
At idle, or in Park if I rev the engine is sounds normal. Once I put the truck in gear, D or R, and put a load on it, then it sounds like a bad sputter or miss, and its loud. It sounds like its coming from the passenger side of the motor by the head but I cant detect any air leaks.
Had my exhaust checked, and there are no leaks.
Help

[Stocker]

Flat cam lobe??

[Sinister]

Ignition?

[cdowns]

if you have the original type exhaust i'd think the donu where the manifold meets the pipe is burned out

[Wrenchbender Ret]

Sounds like an exhaust leak around one of the ports. If it shakes at idle when in gear it's probably a bad valve.

[2tons of fun]

burned head gasket between the cyliders.

[68gmsee]

Just to get the symptoms straight.

A miss is caused by a misfiring from the ignition or fuel system and you can here it as an intermittent sound. A sputter is similar but is a rapid sound almost like when you put your lips together and blow air threw them. At least that is the way I would describe it.

But, regardless, I don't have a clue.

I'd first check what's been recommended and maybe see if you can have someone put the parking brakes on and you stand by the engine while they shift it into gear.

Maybe even use the NDD tool (noise detecting device). I use a 3 foot piece of hose garden hose but any hose will do. You may be able to isolate it further to a certain location.

[VDOG]

Stocker how would I check for a flat cam lobe?

Sinister It only gives me the noise when Im moving, not at idle, in park or when I rev the engine. But since im not sure cant rule anything out.

cdowns I have headers and turbo mufflers, and just last week to eliminate exhaust leak, I had the donuts welded together. Not what I told the guy to do, but for now I will leave it that way. no exhaust leaks.

Wrench Bender If you mean engine shake like rough idle, then no it does not shake in gear.

2Tons of Fun When I first notice this, I took it to my friends shop, I said head gasket in the begining, after driving my truck he said exhaust leak. Now he said maybe its a piston slapping a valve.

68gmsee Sputtering is more of what its doing when you put it that way.

[Stocker]

Originally Posted by VDOG

Stocker how would I check for a flat cam lobe?

Good question... I guess maybe pull the valve covers, check when engine is idling -- you would need a way to measure the movement of the rocker arms....

All I know is many years ago my wife's '68 Camaro (327) started sounding/acting like you described. I took it to a mechanic who said "Flat cam" and he was right -- lobes at the front of the engine were badly worn down, he said it's typical for SBC engines to have insufficient oiling to the front of the cam.

[2tons of fun]

Originally Posted by VDOG

2Tons of Fun When I first notice this, I took it to my friends shop, I said head gasket in the begining, after driving my truck he said exhaust leak. Now he said maybe its a piston slapping a valve.

how would a piston be smacking a valve? you would either have had to drop the valve all together which would cause a hell of alot more racket than you have, or the timing and stroke for that one valve would have to change/increase and that just cant happen.


do a compression check.

pull the valve covers.

check the pushrods.

take off the exhaust and look for a leak.

[2tons of fun]

[69GMCLonghorn]

Classic case of header leak at the head... To test it, you need to have a friend that you can trust, get in it, drop it in drive with the foot on the brake. Have him do a "slight" brake stand to get some load on the engine while you stand off to the side of the vehicle and try to hear exactly where the noise is coming from. I'll bet you discover a bad manifold gasket... or loose header bolts.

[Stocker]

Originally Posted by 69GMCLonghorn

Classic case of header leak at the head... To test it, you need to have a friend that you can trust, get in it, drop it in drive with the foot on the brake. Have him do a "slight" brake stand to get some load on the engine while you stand off to the side of the vehicle and try to hear exactly where the noise is coming from. I'll bet you discover a bad manifold gasket... or loose header bolts.

Yes -- and this works best with a stone cold engine.

[VDOG]

Bad Mainfold gasket, never thought of that. Header bolts are tight but I will check again. Manifold gasket did have a large amout of oil on top passenger side.

[pat 70/71]

sounds real basic so forgive me, change out the spark plugs& then the wires if needed i have had the same thing kick my butt in the past only to find it was a fouled plug not a pro just trying to help ...Pat

[echo72]

When I bought my truck, I had the same problem. My manifold exhaust gaskets were shot to the curb. After I replaced them, the problem went away.

[wzuke]

Maybe a spark plug that is loose or not seated properly.

[VDOG]

Changed the plugs 3 weeks ago due to the plug in the picture. They were only 3 months old. With the new plugs installed, its like it runs smooth when its reved, but when in drive, its almost like a seperate noise.

[2tons of fun]

stupid but did you gap and check the plugs when you installed the new ones?


my dumbass noob buddy bought new plugs and wire and went to town, didnt know aboutthe the gap or even basic concepts of how the plug works and didnt even look at them :laughing:

got mad a called me over and after about 30min i asked if he had xxxxxxxxxxx.

by the blank stare i got back i knew it was time to pull it, 7/8 were folded flat to the stem/electrode.

a motor under load will never act the same as a free reving unloaded motor. just like fuel issues. runs great till you put a load on it then it coughs sputters and fails.

[VDOG]

Originally Posted by 2tons of fun

stupid but did you gap and check the plugs when you installed the new ones?
a motor under load will never act the same as a free reving unloaded motor. just like fuel issues. runs great till you put a load on it then it coughs sputters and fails.

I gap the plugs. I had this problem even when the old plugs were installed. In fact, thats the reason I changed the plugs because I thought that was the problem.

[VDOG]

Found the problem, I think. Where the two center header pipes meet the head, the flange just under the valve cover is contoured out. So when im on the gas, exhaust escapes from the top of the header flange.
So I need to bend it back with heat or replace the headers. Going to a different muffler shop tomorrow to make sure.

[Sklptrljay]

Originally Posted by VDOG

Found the problem, I think. Where the two center header pipes meet the head, the flange just under the valve cover is contoured out. So when im on the gas, exhaust escapes from the top of the header flange.
So I need to bend it back with heat or replace the headers. Going to a different muffler shop tomorrow to make sure.

Dredging up an old thread. I'm having an issue just like this. VDOG, did it turn out to be the header gasket?

[haysonj]

Buy these gaskets (http://catalog.remflex.com) and you will never have a problem. They are expensive but they work. I've had mine two years and never had a problem

[VDOG]

Originally Posted by Sklptrljay

Dredging up an old thread. I'm having an issue just like this. VDOG, did it turn out to be the header gasket?

Wow I had forgot about this thread. Heres what happened. I bought a new Edelbrock cam. Did not know I did not have to take the heads off. On the passenger side head 4 bolts were finger loose by the plugs. That was my exhaust leak. So check those too before you change anything.

After that I upgraded to a 91 TPI out of a camaro.

[tcrist]

One thing that I have always done on headers with the thin flanges is cut the flange between the first and second, third and fourth cylinders (I.E. for a SBC, between 1&3, 5&7. 2&4, 6&8). Thin flange headers tend to warp after time then it is hard to keep them tight. You can also use the locking header bolts http://www.jegs.com/p/Stage-8/Stage-...49275/10002/-1 .