PI swap problem

[Booboo]

I just completed a PI head swap on my 97GT, stock NPI bottom end. I had a local machine shop do a valve job, install MMR stainless valves, guides and seals, BTR .600 springs. I used new lash adjusters, new timing chains. XE262AH cams that MHS degreed. The engine runs but is down on power. The tuner says the load is about 30% less than it should be. It’s loosing air somewhere. Comparession test shows 180 on all except #2 which is 170. Any ideas?

 

[Booboo]

Anyone? Any ideas before I start taking this apart?

To explain it better, We are seeing about 70% of the power we should for the air that is coming into the engine measured at the MAF.

 

[J_lope82]

Fuel pressure?

 

[Booboo]

That was my first thought, tested pressure and it was fine, even swapped out fuel injectors and the ECU. Wondering if the cams are somehow retarded.

 

[J_lope82]

What cam sprockets are you using?

 

[Booboo]

TFS adjustable and adjustable and OEM.

 

[Snorky]

TFS adjustable and adjustable and OEM.


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I wonder why the huge disparity in timing 107 vs 113. I would perform a leak down test

 

[96blak54]

Ive seen lash adjusters hold valves open. Engine was down on power, couldnt figure it out, pulled heads off and noticed closed valves were slightly raised off the seat when they should have been seated closed

 

[Booboo]

Ive seen lash adjusters hold valves open. Engine was down on power, couldnt figure it out, pulled heads off and noticed closed valves were slightly raised off the seat when they should have been seated closed

This was my next guess, I installed brand new lash adjusters when I did the swap. This weekend I plan to replace all of them with a set of known good ones off the old non PI heads.

When you had this problem did you do a compression test? The decent compression I am seeing is got me confused.

 

[96blak54]

Yes for some reason when compression checked, each cylinder fell inline numerically close. My only guess is the valves were hanging open close enough to the seat to catch when pressures in the cylinder. The valves hanging open when they should have been seated was only caught by luck. Granted removal of the engine, heads off, looking at everything it was by chance a keen eye caught the valves off the seat slightly.

Hind sight, thinking of a way to diagnose this scenario,...on a cold engine, apply low regulated compressed air into the cylinder thru the sparkplug hole. Remove the trottle body and do some listening.

Take the lashers out, holding them with pliers or in a vise and heat them up to engine temp and squeeze out the contents while working them. Take the old lashers and do the same. Who to say the manufacturing is the same. The new lashers could be different. Oil weights play a big role in lashers due to their microscopic tolerances. Who to say manufacturing oil or assembly oil isnt trapped in them screwing with you. Oil just doesnt flow through these things and typically gets trapped.

Im a fan of strong lashers on the intake valve and loose sloppy lashers on the exhaust valve.

 

[Booboo]

How much down on power was your engine?

 

[96blak54]

At the time, rpm wouldnt get beyond 4500rpm on the dyno. After correcting lasher crap, then on the dyno again, a 6000rpm pull was made and revealed more issues. Like serpentine belt failure, fuel air management, weak torque converter.