Cam surge/Buck

[SargeZ06]

I tuned 2 cars with the same cam. A Thunder Racing RapTR 617/613 236/242 111 +2 LSA.

Any way I hear a lot of people saying big cams like a lot of timing at idle and low RPM but that's not what I'm finding. I found that reducing timing considerably below 1800 rpm gets rid of the dreaded bucking you get when creeping around a parking lot in 1st or 2nd gear.

Has anyone else come across this too?

[oakley6575]

Thats is what I'm going to try next with my 231/239 cam. It surges pretty bad. How much timing are you using? I have mine running at 22 right now.

[edcmat-l1]

Yes, it seems the bigger cams what lower timing in the real low airflow, low rpm range to cure bucking. But, the milder cams are almost just opposite.

Now, the bigger cams still want alot of timing at idle. That helps to keep the manifold vacuum up, makes them idle smoother and return to idle cleaner.

[oakley6575]

Yes, it seems the bigger cams what lower timing in the real low airflow, low rpm range to cure bucking. But, the milder cams are almost just opposite.

Now, the bigger cams still want alot of timing at idle. That helps to keep the manifold vacuum up, makes them idle smoother and return to idle cleaner.

Wait, are you saying the bigger cams want a lot of timing at idle, or low timing?

[edcmat-l1]

Wait, are you saying the bigger cams want a lot of timing at idle, or low timing?

Big cams, low timing. smaller cams, more timing. Although, I have tuned a few big cam cars that drove pretty nice without having to knock out the low speed timing. I only do that as a last resort. I try other methods first.

[SargeZ06]

In the idle cells I have the 27 degrees(1000 rpm and below), in the light throttle 1200-2000 rpm) I have 22 degrees. This is only in the light airflow areas i logged for the condition I was trying to fix. Used VCM controls and commanded the timing and kept moving it until bucking went away or at least was much better. For reference this was driving around my neighborhood at 12 mph.

[edcmat-l1]

In the idle cells I have the 27 degrees(1000 rpm and below), in the light throttle 1200-2000 rpm) I have 22 degrees. This is only in the light airflow areas i logged for the condition I was trying to fix. Used VCM controls and commanded the timing and kept moving it until bucking went away or at least was much better. For reference this was driving around my neighborhood at 12 mph.

That's the way to do it. Sounds like you got it.

[DSteck]

You're definitely on the right path.

I've found that LS1 stuff likes a lot of idle timing but newer stuff doesn't. Odd.