[SickSickSick]

i'm a first year bracket racer trying to figure out the in and outs of positive and negative pressure waves. i'm good at turning a wrench and shoving my foot through the floor board but, i'm not an engineer. can anyone tell me a fairly simple way to tune my exhaust so i can get peak performance from my rod. my engine is a 305 , bored .060, 305HO flat top pistons, 467/480 lift 304/287 duration cam, heads have been milled .20 thousands and pocket ported with 1.94 valves, MSD ignition, tunnel ram with holley 600 VS and long tube headers. had other plans when i built it so i had 3" exhaust with glass packs dumping in front of the rear tires installed. right now it's running the mid 13's without a stall. the engine is in an 85 IROC and i'm gonna have to do some cutting on the exhaust just to get the tranny out to put the stall in. since i've learned a little about the positive/ negative pressure waves, i figured this would be a good time to investigate it. thanks in advance. Sick

 

[onovakind67]

Is this an all-out race car? What are the complete cam specs? What are the specs on the headers you have now?

 

[runn141]

what are your head casting # ? are they original 305 heads ? because i cant see them being 1.94

 

[xntrik]

3" sounds awfully large for 305 cubes. Header tube diameter should be 1 1/2,,, or 1 5/8 max if you are into rpm power.

In PHR Popular Hot Rodding Magazine, David Vizard did an excellent article about exhaust scavenging and exhaust systems a year or so ago. You might go to their web site and search the article.

You might find that he recommends 1 1/2 headers, 2 1/4 exhaust, and a totally different type of muffler and expansion chamber.

You could also look into FlowTech 4 into 2 into 1 headers. They work.

Viz is one of the top engine engineers in the world and he specializes in hot rods...... He actually gets paid to play........ yeeee hhhhaaaaawww. :thumbup: