94 chevy truck runnin' like poo!

Hi all,

I have a '94 chevy truck with a 350TBI in it. I have installed an msd 6a ignition and corresponding blaster coil. they have functioned fine for a long time probably 20-30.000 miles.I recently had a blown head gasket and so I tore the motor down to the short block and as I replaced the head gasket I also put a comp cams cam in it,along with the correct valve springs and new comp cams lifters.I got the truck all back together and it ran pretty good for about 600 miles or so,just a little rough,like I had a bad plug wire or something. The truck died alltogether and I ended up replacing the distributor and it started up and runs again,but I still have another lingering problem.

The truck still runs rough, I called comp cams who recommended I time the truck between 10 and 20 degrees advanced for the cam they sold me. I have had the timing everywhere from 0 to 20 degrees advanced and it will run better or worse but never good no matter where the timing is set. There is a rough idle and a noticable vibration. The truck runs aweful when I am in the lower rpm ranges like cruising highway speed in overdrive or accelerating slightly. Also there is a wierd sound that has developed over the last few days that sounds like someone hitting the headers or the valve covers with a wooden hammer or something but it only makes the noise on cold startup and the noise goes away within 20 seconds or less of startup so I am having trouble tracking it down.Also if I remove the oil filler cap with the truck running I have what appears to be small puffs of exhaust gas puffing out. I am at a loss I have not had time or a break in the rain to pull the valve covers yet I plan to do that first chance I get. DOes anyone have any suggestions? Any help is greatly appreciated,Thanks.....Jesse

P.S. I recently added a new exhaust so the noise could be coming from that I'm just not sure.

Possibly a collapsed lifter? Have you checked to make sure you dont have a valve over tightened.

Are you getting popping outta the exhaust like you might have a burnt or bent exhaust valve?

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Doesnt sound very happy,, is your oil pressure ok , coz when i hear wooden mallet noises on start up and under warm run its big end ,, iff its only start up lifter noise ya got a bad lifter,,

The lifters are new they came with the cam kit,I soaked them in oil overnight and primed them.The noise goes away very quickly,I think it might me an exhaust leak or a part of the exhaust touching something I just can't tell yet I kinda wish it would start doing it all the time so I could track it down. The timing/rough running thing is what has me baffled. I could have a valvetrain problem though in addition to the timing mystery.Any other suggestions? I appreciate all you guys' input. Thanks....Jesse

My first thought is that one of your lobes may have gone flat

What would cause that?

Which particular Comp Cam did you install?

Part # 12-249-4

[size=3]Doc here:

Did you re torque the heads after breaking in the cam? If not you should check it.

You did run the cam at 2000 rpm for 5 minutes right?

Also put a vacuum gauge on any manifold source, and look for rapid fluctuation at idle that straightens out under throttle..If so, look, when you check the head bolt torque, for broken valve springs or slipped retainers.

Check your lifter hold downs and Valve lash.

Hope it helps!
Doc [/size]

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A compression test is always a great thing to do in a situation like this. It will let you know what cylinder(s) could be causing undue havoc of the power.

Hey Doc,

I did break in the cam as prescribed by comp cams and you,I did not however re-torque the heads. I will give a full report as soon as I get time to do it,Thanks for the help, Jesse

I'm undecided which heads to buy that's reasonable ' These are the parts I have already bought scat crank', KB 700 10:4:1 forged pistons Target Master block bored .030 over,288/296 ultradyne cam, roller tip rockers,performer RPM intake,scat rods 5.7 comp lifters and rods,hei distributor, all the rings, melling oil pump, rear end limited slip posi with 373 gears transmission th350c any help would be greatly appreciated Thanks in advance BLUE82