502 MAG MPI to 516 - exhaust selection
 

Good morning guys,

I’m new on this platform and I’m typing from overseas. Glad to be part of this community.
I have a 502 MAG MPI 1999 with MEFI1 and I fully rebuilt my engine last year installing an Eagle internally balanced rotating assembly with H beam conrods and flat dome Mahle pistons 4,530” with 516 cid, 9,0 Compression ratio. I installed Edelbrock aluminum marine heads 61555 (intake valve is 2,25” and exhaust is 1,89”) and comp cams XM270HR kit:
112° lobe separation
110° intake center line
intake duration 270°(218°@0,5”)
exhaust duration 276°(224°@0,5”)
valve lift I&E 0,51”.
I also had a MEFI re calibration in order to fix the extra fuel which the larger displacement requires.
Last, I installed a pair of GIL 500 HP (higher riser) with turbulators on a permanent thru hull exhaust configuration.

35 Hours made last season on fresh water and no issues. I pulled my engine out to have maintenance and all was fine except for droplets inside 7&8 exhaust manifolds L. I also had to clean n.8 exhaust valve seat because of light rust formation which caused my valve not to have a perfect seal, valve cleaned and problem solved.
Now the question is, do you think the water I found inside the manifolds came from reversion caused by the configuration I’m running? Could it be caused by moisture formation from outside? My exhaust tips have curves which go under water level as mufflers.
In few words, do you think my GILs do their job considering my cam and the 516 cid or dry exhausts are strongly recommended on my motor?

thanks for your help

In my opinion that cam isn't too big for wet exhaust. I run a slightly 'bigger' cam in a small block without out reversion issues (stock manifolds and thru hull). Been doing so for nearly 300 hours run time. I would verify exhaust drop and make sure there are no internal exhaust manifold leaks.