guys i got an 85 z28 witht he 305 tpi motor in it. i just recently rebuilt it with a small comp cam, ported heads, roller rockers and some headers. now the car runs awsome has great power but seems a little choppy at an idle and my thinking is its prolly the cam talkin. but i have 0 problems with it so far. but i have noticed that the number 7 header primary will get cherry red on me.only number 7 will do this. what could be causing it? im at a loss with it right now because it only seems to have a slighht chop on idle it has good power and doesnt skip while driving? without looking at the header primary yourself you wouldnt think the car has a problem..

 

Try and search or "Ported Base". I dont know much about the problem, but that search should turn up some results.

From what i have read, theres usually a #5-#7 cylinder lean problem from where and how the fireing order is that causes the #5 cylinder on intake stroke to pull the air/fuel from the #7 intake port given that they are so close to the combustion stroke. When you port a base and cut back the divider walls it makes this problem even worse, thus allowing the #5 cylinder to pull more air/fuel from the #7 port with more ease.

Im not sure, and i cant tell you for sure. Thats why i said to search. That should lead you in the right direction. Just trying to help. Ill read alittle more on it and if no one else that knows for sure chimes in ill be glad to find a answer for you.

Brian

 

i would recheck the firing order
i crossed 2&4 in a 4cyl once it did run but i almost burnt up the car too
pipes was red hot
so always recheck firing order

 

Check to see if the rocker isn't over tighten. This happened to me on my old 305. Most of the back rockers were over tighten, that the valves would stay slightly open causing fuel to fall into the headers thus causing them to glow red. Car felt fine even though they were overtighten. Took me over a week to figure it out.

 

Valve sealing problem. The #5/#7 thing has been beat to death and hasn't really presented anything concrete. Add madmax to that search and you should pull up a thread or two in that regard IIRC.