I have checked for exhaust leaks, and intake leaks. Unless the manifold is leaking inside where the flange on the head is I can't find anything sucking vacuum. I broke my other Vac gauge so I got another one and it says I have 14" of vacuum where as other one said 12". These LTFT numbers just seem ridiculous to me for something not popping up so I can see it or hear it. STFT on both banks is prretty close to 128 but goes up or down from that some.

I know the ECM is supposed to learn but this just seems like to lot to cram for.

 

How far off are the numbers?

 

Oops, thought I put them in. Get ready.........






160 bank1 and 140 bank2.

 

It's obviously getting a lot of un metered air from somewhere. Would it be safe to assume the intake is leaking on the inside?

 

I've never heard of an LT1 intake leaking from the inside.

The 160 number has maxed out, so this solution probably won't cure your problem. But, have you reset the PCM since changing your fuel pressure, and does this same problem exist with your different tunes?

 

Disconnected the battery and rest the PCM. If anything it made it worse. LTFT are 160 and 170 now. STFT are about 131 or so on both sides.

Something is leaking somewhere that's for sure or there is something wrong with this PCM. I'm pulling the intake off one more time tomorrow. If this doesn't do it must be something with the headers.This all started when I put them on. Looks like I could hear it if it was them though.

 

Here are a few suggestions.

1) EGR valve stuck slightly open
2) Brake booster has small crack
3) Faulty o2 sensors
4) Valve adjustment too tight

Good Luck

 

#3 gets my vote.

 

(1) No EGR

(2) I'm going to plug every vac fitting on the intake and recheck BLM's

(3) Both 02's are Delphi AFS75. Bank 1 02 was put in on Friday. Bank 2 is older but going through the numbers just like bank 1 is.

(4) My springs are rated 155# on the seat. I did set the pre load at 3/4 turn this time with the engine running when I put these AFR's on. To much? BLM's get better when the motor is revved slightly. Could this be it? Maybe just not enough oil pressure at idle for the the lifters to work correctly? Once revved up some the pressure increases and that is why the BLMs improve dramatically. I should be so lucky...........Have I been chasing a Ghost? With spring pressure like this should I be running a thicker oil? I'm running Mobile 1 10w30 at the moment.

 

Just by chance could my MAF tables be off and causing this?

 

It appears the intake was leaking at the bottom of the ports in the lifter galley area. It's going back on tomorrow and you can bet it WILL be sealed this time.

AFR actually says to seal the port bottoms on their website. Did I see that the 10 times I read the instructions............NOT!

 

I had the exact same problem when I installed AFRs. I used a better way of installing the gaskets the second time. I used a thin film of RTV around the ports. I set the gasket on the heads and set the manifold in place. I torqued the intake bolts to 10 lbs and let it sit 24 hours. The I removed the intake, applied RTV to the top of the gasket and installed the manifold. I think the problem may have been that the gasket moves some when torqueing. Letting one side cure before final toque prevents the gasket from shifting.

 

Thanks for this. I didn't do it quite like you but it started me thinking of a similar way. I'll know this afternoon.

 

Ok, got the intake back on yesterday and torqued down @ 35ftlbs. That's scary in these soft heads! AFR recommends not even torquing them to factory specs. There was a flier in with the heads that said that. Just slightly better than good and snug whatever that means is what it said. I did it anyway though very slowly with no problems. I'm going to let it compress overnight and recheck the torque tomorrow morning. I'll fire it up this afternoon. I'm hoping this has it sealed. If not I have no idea what else to do.

Here's what I did:

I used the Felpro 1284 gasket. I put Black RTV on the head side of the gasket all the way across it and stuck them on. I let it sit about 30 minutes with the weight of the intake only on them. Then I removed the intake and sealed the upper side and the china walls. I then installed the intake again but this time torqued the bolts to about 10 ftlbs. I let that sit about 30 minutes then re torqued to 20 ftlbs. I let that sit about 30 minutes and re torqued to a little less that 30 ftlbs. Let that sit 30 minutes and finished it off at 35 ftlbs. We'll see how all of this plays out this afternoon. I used the stock intake bolts this time with high pressure grease under the head to help with torquing.

 

WOW, the AFR heads can make a simple intake install a PITA!!

 

Be sure to re-re check the final torque setting before you get too far along in buttoning things back up. Often times after the gaskets have taken a set for hours the torque setting will lessen.

This can depend on the material the gaskets are made from as to whether or how much torque will be lost but over the years I've just trained myself to check ALL of them - FelPro, Mr. Gasket and even GM gaskets.

I always use 35# and it doesn't scare me in the least. Don't have a clue why it is that AFR is so dramatically different from GM's aluminum head torque spec. Ae their heads poured from softer aluminum. Makes my wonder.

I know that Edelbrock heli-coils their bolt holes to offset the softer aluminum used in their heads but I don't believe AFR does that.

One reason I went with Dart's for my son's engine was they proudly claim the use of stronger aluminum in their heads. To me the quality of the casting comes first, with all the other bells and whistles - like valve sizes, flow numbers, springs, etc. - coming in like an after-thought. To me, if the casting is suspect, all the rest is meaningless.

As they say in the old adage "You can't make a silk purse out of a sow's ear".

Jake