So just recently i put some 3" dyno max bullet mufflers on my truck and its starting feeling really wierd past 3000 rpm. Almost like its kinda of missing. Its a 355 built for a 150 shot. Here's specs

srp dome pistons
11:1
gm 441 heads, ported with 2.05/1.60 valve (284/237 @.600)
forged crank and rods
Comp 274NX nitrous cam (274/292 & .519"/.532" with 1.6 RR's) flat tappet hyd.
weiand axcelartor single plane intake with 2" spacer
speed demon 750 mech secondaries
Accel stock replacement distributer with HEI super coil
Cheap $100 headers

SUPOSED to be running around 450 hp. Thats what 2 different engine calculators have told me.

My previous exauhst setup was dual 3"x18" pipe to some very restrictive glass pack (2 1/2 pipe -> 1 1/2" inside the the pack) and now i've moved to dual 3"x18" pipe to 3"x12" bullet mufflers.

This weird feeling has also began to be accompanied by a slight ticking, and when i rev the motor, it almost seems like something coming from the right side of the motor, but i can pin it down. I'm going to pull the valve cover and check it out, but i dont have time to do that for about a week and a half.

Could this new noise simply be it running lean? because after i get on it, there is a strange smell, and its not a rich smell.I know the old exhuast was really really restrictive, but do you think it was causing the motor to need that much less fuel? After the swap i did notice that the motor idles much easier, and my previous off-idle bog has pretty much disappeared.

here is a pic of the plugs after 2 days with the exhuast.

 

that is weird. try running some autolite 103's and see if your problem is there there.

 

Also check for an exhaust leak! what do you mean by "wierd"? What doess it do and is it on or off the bottle that you hear it?

 

haven't put it on the bottle yet, still waiting for funds. And the "weird" sound sounds almost abrasive or vibrating. Its hard to explain, but you can just barely hear it on the right. I dont think its a leak, but i'm gonna change the gasket to copper when i get a chance. The left has a copper one right now.

Just to confirm i have not put n02 on this motor at all yet.

Will 103's work with old style gm heads?

 

If all you have done is put exhaust on it, and now it sounds funny with a "tic" then it's most likely an exhaust leak..... Those cheap $100 headers will most likely make a ticking noise anyways, cause they are made out of such thin gauge steel.... It could be leaking at the collector as well.... If the exhaust is that much more free flowing, it could run a little leaner now... By the looks of your plugs though, it doesn't look too lean... But if you idle rich, and full throttle lean, you're going to have to kill it right after you make a pass, then pull a plug... Letting it idle on them will throw you off...

Also, what are those plugs gapped at???

 

if you were looking at 104's they should the 103 is one heat range cooler. Just compare the thread at the auto part store.

I personally hate NGKs. Pressed Plug = garbage. Bosch is the same thing. My roommate decided to go NGK and only got a month of use before they took a dump on him.

 

gap is .038 if i remember correctly.
I'll see if we can lift it up and make sure the weld is ok, because i dont think its at the collector since we never removed it. Just cut off the old exhuast from the collector with 3 inches left, and welded the new pipe and muffler on.