First, I am completely new to forums so forgive me for any mistakes.

Now to my problem, I bought myself a 89 IROC with a bad engine. I rebuilt the engine myself .040 over with flat top pistons, stock heads, resurfaced and vj. I believe my problem may lie in my cam selection. I got a comp cam xr270hr-10. It has gross valve lift I.495/E.502 with duration @ .006 being 270/276. It has 110 deg of lobe seperation. I installed my engine and set the base timeing at 6 before and it doesn't want to run right. The idle goes from around 700 upto 1500, back and forth constantly. I tried adjusting idle, but to no avail. Do I need to reprogram my computer for this cam to work or could my problem be else where? I am getting no check engine lights.

I hope this isn't listed somewhere else, and I am ignored. Like I said, I am new to this. I tried looking around to see if anyone had listed a similar problem, but did not see one.

 

Probably need to reprogram.
Mine did the same thing, and it was it was pig-rich at idle. I adjusted the VE table to lean it out and now it idles great.
For info on scanning and programming check out the DIY PROM forum.

 

Need more info - 1989 IROCZ isn't enough.