|Posted: May 30 2008 at 12:08 | IP Logged
Thank you for bringing this up!
Yup. In my opinion, the riser/exhaust manifolds are one --if not the weak link on the american (GM, Ford) V8 based marine engine. The mating surfaces of the riser/manifolds castings always seep, rust and generally need constent attention. Also, the two center exhaust ports on the heads are always vunerable to rust errosion/intrusion. Frankly, I cannot tell if all of this errosion comes from exteror or interor seep sorces or what. Certainly a moisture source is the riser/manifold mating surfaces, but I suspect that may be only part of the story. Of course, it's the critical point where heat, vibration, salts/chemistry for the entire raw water cooling side. I suspect it's a nature-the-of-the-beast sorta thing. I beleive it's rooted in no real historical design effort to deal with this glaring shortcoming. There is little incentive for Mfgr's as they benefit from failures. They have not really been the target of public scrutiny or criticism and it's been easy for them to blame the aftermarket sector for not doing better. The Austrailian Hitec system is of interest. I can collect no reliability data so far- anybody have anything on this? It's expensive, around $2500 per engine. The concept is solid: one piece stainless steel sheeting- stamped/welded (very light, probobly pretty noisy due to less mass) assembly combining riser and manifold into one piece. I have a real interest in installing this system when I redo my single 305. Till then, vigelance replacment or taking the darn things apart for cleaning, reseal and fresh gaskets is the only alternative I see- a real pain.
Further info on this subject would be greatly appreciated. The entire forum could benefit.
Again, Thanks for bring this up...well done
Roy & Laurie, S.F. Bay Area
'83 280, hardtop, single 305