Cold Start for PV

[Erich M.]

Re: Cold Start for PV

Les,

I am he original owner of my '72 LT1. The car is a 5-Start Bowtie and has received Top Flight awards. I have never PV'd the car though. I don't know what Stan will be looking for but let me tell you how my car starts from ambient temperatures around 50-70 deg F.

When the motor first starts, engine rpm is between 2500 and 2900 rpm, sometimes a little lower if it sat for more than 3 weeks. If I do not press the accelerator the rpm will actually creep up to about 3200 rpm as the temperature guage creeps up to the the first mark on the guage. If I press the accelerator while the temperature is below the first temperature mark, the rpm drops to about 2500 rpm. Continued pressing of the accelerator drops the rpm down successive detents on the fast idle cam.

This is the way the car has behaved since the day I bought it. I believe the 2350 rpm fast idle spec is an approximate number.

I would be interested in learning what Stan looks for during a PV.

Erich Meyer
Central NJ Chapter NCRS

[Les W.]

Re: Cold Start for PV

Erich,

I have not been able to make contact again with Stan. I have called and e-mailed ---it's a busy time of the year. Thanks for the info on you LT-1, it is very interesting. I take it that the high RPM's do not stop unless you depress the accelerator to drop them down to curb idle speed. I will get back with Stan's call on this as soon as I find out.

Les

[Erich M.]

Re: Cold Start for PV

Les,

The rpm's will top out at 3200-3300 rpm, even if I do not press the accelerator as the engine heats up. By the way, the '72 LT1 does not have a CEC solenoid. It has an Idle stop solenoid which has nothing to do with the Vacuum Advance TCS system.

[Dave S.]

Re: Cold Start for PV

Les,

I am he original owner of my '72 LT1. The car is a 5-Start Bowtie and has received Top Flight awards. I have never PV'd the car though. I don't know what Stan will be looking for but let me tell you how my car starts from ambient temperatures around 50-70 deg F.

When the motor first starts, engine rpm is between 2500 and 2900 rpm, sometimes a little lower if it sat for more than 3 weeks. If I do not press the accelerator the rpm will actually creep up to about 3200 rpm as the temperature guage creeps up to the the first mark on the guage. If I press the accelerator while the temperature is below the first temperature mark, the rpm drops to about 2500 rpm. Continued pressing of the accelerator drops the rpm down successive detents on the fast idle cam.

This is the way the car has behaved since the day I bought it. I believe the 2350 rpm fast idle spec is an approximate number.

I would be interested in learning what Stan looks for during a PV.

Erich Meyer
Central NJ Chapter NCRS

Erich,
My opinion is the 2300 idle speed would be after the car has run for a few minutes without touching the accelerator and would represent the maximum engine speed. This means the car would initially start at 1600 or 1700 RPM and work its way up to 2300. (assuming the 2300 is the recommended RPM).
Creeping up to 3500 RPM does not seem right.

[Erich M.]

Re: Cold Start for PV

Dave, Les

Don't know about the 2350-2500 rpm data intent in the CSM. It could just be a guidline, not a bible. You will get production variations. That's why I find this an interesting subject and responded accordingly to see what experience others have had. My car has never idled at 1700-1800 rpm after starting cold. As I've said, if I press the accelerator about 1-3 minutes after starting, then the rpm drops to 2500 rpm and the cam is at its fast idle indent (you cannot argue the difference between 2350 & 2500 rpm).

The purpose of my response is not to determine PV requirements but to see how these motors operated when they came off the line.

[Dave S.]

Re: Cold Start for PV

Dave, Les

Don't know about the 2350-2500 rpm data intent in the CSM. It could just be a guidline, not a bible. You will get production variations. That's why I find this an interesting subject and responded accordingly to see what experience others have had. My car has never idled at 1700-1800 rpm after starting cold. As I've said, if I press the accelerator about 1-3 minutes after starting, then the rpm drops to 2500 rpm and the cam is at its fast idle indent (you cannot argue the difference between 2350 & 2500 rpm).

The purpose of my response is not to determine PV requirements but to see how these motors operated when they came off the line.

The question is not what the car did when it came off the line. I'm sure many of the cars were different than the factory Specifications at that point in time. The PV is about making the car operate as it was designed to operate.
I have PV'd both a 70 and a 71 LT-1 along with other cars and thought I'd share what I did to prepare my cars. The Service manual will give you the "warmed up" high idle and I think that is what the Team leader will look for.
They will want it to start lower and work its way up over a couple of minutes.