I just finished a 305 to 355 swap and I have some problems. The car will idle semi-decently(good enough to drvie and everything). The motor is a 355 with the HSR setup. The cam has like 510 lift(+1.6 rockers) and 234 duration which i know is big but i still think the car should be able to handle it. I and running the stock computer with a chip burned from PCMForless. The car is a factory 5 speed with a new clutch. My problem is that the car will pull through first without to much trouble and even 2nd most of the time but when i hit 3rd and stay in it(like accelerating semi hard maybe half throttle) through 3000 RPMs it literally falls flat on its face almost like it is breaking up or something. IT really is so hard to describe its like you are anticipating forward motion and it just like stops. The motor doesnt pull nearly as hard as it should. It backfires yada yada. Has anyone else heard of anything like this and what should i look at first. my timing is set at 6 advanced without the computer plugged in and advances to like 24 advanced when revved up. I am also ruinning the stock throttle body and intake setup for an 87 camaro. If you baby the motor it will drive but not well. any ideas or suggestions would be greatly appreciated.

Sorry for the spelling errors i am on my way to work. and if you need any more information just ask.

 

does it only backfire in the upper rpms? 3000? are you getting enought fuel?

 

It should be getting enough fuel it has 26lb injectors in it and good fuel pressure at idle but i have no way of checking it under load at like 3000 RPM.
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does anyone else think its weird that i am only getting 25 degrees of full advance?

 

I really need help on this one guys. Any help is appreciated. I feel like 24 degrees of full advance is way to little and even a base of 6 sounds too little. I am gunna try changing the spark plug wires because the ones i have now from MSD are way too long and could be fouling out but i dont think that will cure my entire problem. Please help its really starting to annoy me that the car is all show and no go. (This is me at this point )

 

try moving the base up to around 10, just listen for pinging, if you hear any back it down. and yes 24* is not enough, it should be around 30-34 at full advance. you might have to get back into the chip to fix that.

 

I think i will be going down the DFI path if i can find someone with a good used unit. If anyone can help please PM me. Thank you guys this site is great.

 

24 degrees is way too low. 6 degrees at idle is fine. What about the knock sensor? Any chance it's pulling out some timing?