Just got done with my 355 rebuild with a cc503 cam and a MadZ28 tune. The problem is under 2000-2500rpm in any gear the car wants to buck like I am going too slow for that gear. Is this cam surge? Could the tune be off at low rpm? It pulls hard up top and feels very strong. The only thing I can think of is that the tune is for a car with longtubes but I never had a chance to get them on before I had to get the car out of the shop so it still has stock manifolds. Could this cause the problem?

 

check the gap on the plugs, i had #6 and #8 plugs with no gap in my car at one point due to a ****ty shop and the car bucked pretty bad

 

Wouldn't that cause a problem at all RPMs though?

 

It is most likely a little bit of cam surge. How strong is the bucking?

If it is pretty faint, then that is normal. If it is knocking your teeth out, then that is a problem

 

Its harder to tell in higher gears but in first and second its pretty bad. Think maybe the tune has something to do with it?

 

Is it more like bucking or missing? Can you hear or feel the driveshaft or rear end catching then loose, then catching then loose, like any z28 will do if it's in first and you don't apply the pedal? Any time I've had a miss it's been a distinctly different feel than bucking.

 

I can hear and feel the clutch and rear catching and releasing. I know that it will do it in first gear, I am saying it does it in all gears below 2000-2500rpm.

 

This is a perfect description of my car at around 1.5K RPM and very, very light throttle. With my stock motor I could easily drive in 4th down my long street at 25 MPH. Now if I do this on my new engine (see sig) I get the bucking as described, I would not characterize it as a miss. If I drive in 3rd gear the bucking is totally gone.

I am not sure if this is the description of cam surge or not, I believe whatever it is its the nature of the higher performance cam. I would imagine that its harmless. Hopefully others will chime in.

 

Maybe it is your tune if you didn't have the problem before your rebuild. I would try reloading the stock tune and if that fixes it contact MadZ28 and ask him to tweak your aftermarket tune. It might just be where the idle is set. The only way I know of that a car will buck is when the engine pushes the car for a split second until the car is going faster than the engine, then the car slows down until it wants to go slower than the engine and the engine hits it again because it wants to maintain its idle speed.

 

Welcome to the wonder full world of cam surge, but that cam shouldn't have that much cam surge, maybe under 1500, but not at 2500.

 

Yea thats why it was bothering me. I was expecting some but not this much. I do have an exhaust leak from the manifold so it might be throwing off the O2s and causing it to buck. I'll hopefully have time to fix that on Tuesday.

 

yea i have the same cam and a set of GTP heads and it will surge a bit in 1st or 2nd at real low speed with almost no throttle, but not at 2500 and it does not take much throttle to get rid of the surge. But i have stock cubes, and all cars react differently, maybe that is just the way it is going to be. If it was a miss that bad at low rpm, it would only magnify as rpm increased so i would say a miss is pretty unlikely.