TBI masters, have a cam question...

[PlasticBoob]

Can anyone tell me if I'll be able to get a decent idle (or any kind of idle) with the Comp Cams 256 Xtreme Energy cam? I'm pulling around 18" at idle, and from what I have read, mild cams are okay. But I just want to verify. The cam #s are:
Intake Duration at 050 inch Lift: 212
Exhaust Duration at 050 inch Lift: 218
Duration at 050 inch Lift: 212 int./218 exh.
Advertised Intake Duration: 256
Advertised Exhaust Duration: 268
Advertised Duration: 256 int./268 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.477 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.484 in.
Valve Lift with Factory Rocker Arm Ratio: 0.477 int./0.484 exh. lift
Lobe Separation (degrees): 110

[Bill USN-1]

212 duration is about on the edge for good idle TBI applications.
However it is fairly easy to just set the chip up with an open loop idle.
GM did this from the factory on the 454 TBI engines.
This allows for a smooth idle with out the O2 sensor becoming confused by the valve overlap dumping raw fuel into the exhaust.

OH, I'm not a TBI Master but I did stay at a Holiday Inn Express.

[Serious Johnson]

Rob:

I'm running a K8600 (214/224 - .472/,496 - 112) with GM TBI, and it idlles quite well -- not silky as stock, a little muscle-car-ish, but certainly not a problem. It's been years since I checked, and I don't recall the vacuum numbers, or whether or not it idles in closed loop.

S.J.

[PlasticBoob]

Thank you both, it's much appreciated. That's another check in the "go" column. I forgot to mention that mine is going to be Megasquirted; that'll be fun to tune. :eek:

[dusty]

i believe he ment 112 lobe seperation yeilds good idle. 114 is smooth

110 can be a little lopy. but with that short a durationa dn lift you should be fine.