Or something... First off the motor is a 70's model block with iron heads, victor jr. intake, 650 demon carb, msd6al igniton/distributor supposedly with forged pistons 10.5-1 compression and a mild cam.

When I first started driving the car it didnt act up too bad but after drving it recently it makes a rattle can noise if I go anywhere over 3000 rpms. It mainly makes the noise if I give it over half throttle. Is this detonation, it sounds like its coming from the bottom passenger side of the motor but not for sure. Someone point me in the right direction I would like to hear some opinions before I start wasting alot of money again.

 

Yep its detonation. Did the timing move, what octaine fuel are you using? Could just be a bad tank of gas.

 

Whats the total timing at 3000 rpm's?

 

Is it like a crackling/rattle over 3000 RPMs? I'm having something that sounds the same. It seems to happen when I stick my foot in it, either from a stop, or when at speed, like passing on the freeway.

 

10.5 compression and iron heads is alot to ask of today's gasoline. How about a cooler heat range spark plugs? Or 160 thermostat. You need to get the combustion chamber temp down. Even a EGR valve would help for regular driving. But they don't do anything at WOT.

 

QUOTE Is it like a crackling/rattle over 3000 RPMs? I'm having something that sounds the same. It seems to happen when I stick my foot in it, either from a stop, or when at speed, like passing on the freeway.QUOTE It is exactly that.

I am using 94 octane gas . Also I couldn't tell you the total timing on it, I am still learning. Could you point me to a thread where it explains how to tell timing on a car without a computer.(I have searched) I think I am going to go to the track and get a tank of race gas and see if it quits crackling, and check the plugs.
Any other suggestions.