Center section of manifold cracking..

[marek4792]

It started around this time last year possibly earlier when the mpg dropped off, it still had the mandate Uni and you had tweaked and RR's tune with stock 565/1850 fueling, would randomly blow out the turbo flange gasket found the flange itself was cracking on the oem manifolds tried the aftermarket one and same deal except it did on both sides of the turbo flange at the 90° bends
Always installed to spec and slip joints lubed with light film of antiseize. Cac was replaced at that time too. The white smoke on start up was around that time when I chose to inframe it due to oil consumption and cooling system starting to pressurize. Been running it across the RPM band 14-2000 rpm with varying loads. Based on this the injector is the only variable we hadn't messed with. Either going to cap each cylinder until I find the offending ones or just do a 6 pack and do the break in overhead. I'll update when I know meanwhile I'll get the file sent to you, I agree this is very odd.

[marek4792]

So another update went back to the stock 505HP file Rawze sent me, power was very comparable and mpg went up at least 1/2 mile a gallon and 100 degrees cooler EGT wise, did the cylinder cutout test and #5 when cut out would tick tick tick then stop and then come back intermittently. Took the cracked aftermarket manifold off, fired it up and idled fine, but as soon as I snapped the throttle #5 was dumping fuel out, replaced said injector and tube and put the OEM manifold back on it with a new center section because it would crack on the turbo flange sealing surface, aftermarket would crack on the corners where it met 3 and 4 above the turbo flange. Idles smoother and seems to run and sound better and more responsive, but I know the other 5 injectors aren't far behind. No white smoke when snapping the throttle so far..

My conclusion, injector was leaking between pulses creating uneven heat in close proximity to the turbo flange, and the fact the tune was a 565hp in a Volvo despite being OEM correct (just not for this truck in particular, this truck maxes out at 525hp from factory) besides some alterations by RR (no fault of him) creating the ripe conditions for cracking it. I know Haggai ran into an issue of injectors leaking like this and still pass a leak-down test and made a tool to spot ones that do this.. I'm really hoping this was my case and is the end of the cracking manifold saga..

[Rawze]

make sure your torquing those manifold bolts properly too. they are a specific torque to allow for expansion.

[marek4792]

(01-31-2025 )Rawze Wrote:  make sure your torquing those manifold bolts properly too. they are a specific torque to allow for expansion.

Tightened everything down a few times after love tapping the slip joints, then torqued to 44ft lbs twice over. Fingers are crossed!