New L31 low vacuum question

[PlayingWithTBI]

How did you bump the fuel pressure up to 20?

With an 18LB spring and an AFPR.

Like this one

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[Hoosierlong90]

Just curious, what temp of thermostat did you L31maxexpress and playingwithtbi use on your builds?

 

[PlayingWithTBI]

Just curious, what temp of thermostat did you L31maxexpress and playingwithtbi use on your builds?

I'm running the Mr Gasket high flow 180° with a few small holes drilled in it since I'm running TBI style heads on a Vortec block with no bypass.

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[Hoosierlong90]

I'm running the Mr Gasket high flow 180° with a few small holes drilled in it since I'm running TBI style heads on a Vortec block with no bypass.

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Is there a reason for the 180? I guess my question is how did you go about picking 180 and not 195 ect.?

 

[PlayingWithTBI]

Is there a reason for the 180? I guess my question is how did you go about picking 180 and not 195 ect.?

It helps to keep it a little cooler and I can run a little more timing.

 

[Hoosierlong90]

Gotcha, that makes more sense to me. Thanks for the quick reply!

 

[Hoosierlong90]

Update-

I had the wrong spark plugs installed. Reach and type were wrong. Installed right ones and bam she purrs with great vacuum. Ignorant me grabbed the wrong ones for some unknown reason. We can't all be perfect.

Next problem-

High idle, I checked and checked and checked for vacuum leaks. None exist, iac is working too. Anyways I ended up pinching the pcv valve hose and BAM she idles normal. No leaks around it either. I imagine the pcv valve iv got let's too much air pass causing what seems like a vacuum leak. I have aftermarket valve covers with 1 1/4 grommet holes.

I thought of adding another breather instead of the pcv valve. I also found an adjustable pcv valve that can be adjusted both for idle and cruise. Pretty cool really. Any insight gentlemen?

I also want to say, the truck runs pretty decent for no tune yet. Plenty of power to hold 4th gear at 70 mph going up a decent highway incline. My old motor would struggle bad, downshift all the way to second. I can't wait for for it to be tuned.

 

[Schurkey]

I ended up pinching the pcv valve hose and BAM she idles normal. No leaks around it either. I imagine the pcv valve iv got let's too much air pass causing what seems like a vacuum leak. I have aftermarket valve covers with 1 1/4 grommet holes.

I thought of adding another breather instead of the pcv valve. I also found an adjustable pcv valve that can be adjusted both for idle and cruise. Pretty cool really. Any insight gentlemen?

1. Pinching the PCV hose will drop airflow into the engine. Idle speed might decrease. Doesn't mean the PCV system is the problem. Just means that it's a source of combustion air.

2. I want to know what the IAC is doing to get the idle correct. Is it closing-down to try to compensate for the added air from the PCV? Has anyone dicked with the base idle screw on the TBI?

3. Even if PCV is the problem, why not get a correct PCV valve for your engine instead of screwing the entire system, the bearings, and the environment with an extra breather, or setting fire to a hundred-dollar bill with an "adjustable" PCV valve?

 

[Hoosierlong90]

1. Pinching the PCV hose will drop airflow into the engine. Idle speed might decrease. Doesn't mean the PCV system is the problem. Just means that it's a source of combustion air.

2. I want to know what the IAC is doing to get the idle correct. Is it closing-down to try to compensate for the added air from the PCV? Has anyone dicked with the base idle screw on the TBI?

3. Even if PCV is the problem, why not get a correct PCV valve for your engine instead of screwing the entire system, the bearings, and the environment with an extra breather, or setting fire to a hundred-dollar bill with an "adjustable" PCV valve?

The stock one just ain't pretty enough.

I still haven't scanned it yet, soon enough.

 

[Hoosierlong90]

Update-

I got the idle figured out, PCV is hooked up like Schurkey insisted. It's running good, idling good and Dave at Old School Efi is currently working with me making ***** happen!