someone solve this one for me, or give me a place to start, anyway...'87 iroc 305 tpi converted to 350 tpi. 350 came from jasper as a class I motor (ONLY difference is it has a "towing" cam). don't have specs in front of me, but can get them. rest of motor is stock, along with the completely stock 305 tpi and computer. no afpr.
symptoms: detonation if the gas pedal is pushed beyond about 3/4 of max up to wot. if you stay in the gas, detonation disappears and you can feel the increase in power. the repair shop that did the swap played w/ timing- detonation went away, but had NO power. returned timing to stock. generally speaking, it only does this when it's warm; right after start-up, it won't detonate (or it's so minimal i can't hear it over the exhaust). my thoughts of possible causes/ cures:

1) did they use the 305 knock sensor? if so, i know i need to change it, but that wouldn't cause the detonation, right???? i'll ascertain which knock sensor they used tonight
2) stock ignition should be upgraded for more spark delivery (probably go w/ accel)
3) afpr
4) get computer modded for the 350

i know all should be done or checked out, but what do you guys think? you can literally feel the surge of power when the detonation disappears, so i know my 350 has more in it than what i'm getting out of it. any suggestions/ starting points would greatly be appreciated!!

other specs- jet hot headman headers, high-flow cat, 3-in after cat, flowmaster muffler

 

I know what your problem is...your PROM is way off. In the old days we'd tell you to bump the FP up to compensate, and this used to work for people. But in todays world, you may as well get to burning chips.
...ed

as to your questions, yes the 305 used a knock sensor, and your 350 needs a different one as they are specced to pick up different frequencies. This is not going to help you much though, your calibration is still way off.
As to the ignition upgrades...wait till you have the thing tuned/running right before you waste apenny here, it will not help your problem but will divert resources you need
AFPR - good temporary band aid, better to get into PROM burning though.
PROM - start reading the DIY PROM board if you want to make it run right for the least $$$

------------------
Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

[This message has been edited by Ed Maher (edited June 13, 2001).]

 

mucho gracias, as you seem very confident that it's the prom, i'll be digging into it...