I’m needing to change out some manifolds on my cruiser that has dual 4.3lx motors. Looks like a set of Sierra manifolds and risers costs $650 compared to $850 for the merc manifolds. I run Imco on my big block, so no experience with the stock or other aftermarket manifolds. It’s a 90 cruiser, so doesn’t need to be the best of the best manifold, but I don’t want to be second guessing it either. Anyone with experience with the Sierra manifolds that can share comments? Thanks

I just did a google review and some info there for you. From post I read is just make sure castings are from US. Like heads, blocks etc. OEM style casting will benefit in salt water also. Damm to bad I've thrown away at least 3 sets of merc manifolds and risers or used them for weight on something in of need like front end of kabota tractor. Got sick of moving and or tripping over them. I'd put an ad in wanted section and I would think a member would send you for shipping cost. Sorry couldn't answer your direct question however after a quick search review I saw no negative post.
Good luck!

John

Agree put add in wanted section
I have a BBC set removed from my cruiser during repower and I would almost give them any (fresh water)

Sierra castings are zero from the USA. If want USA casted iron manifolds and or risers I can get them.

I just received the Ebay Sierra manifolds. So, I guess that's what i'm going with. Gotta be better than the rusted, seeping turds that are on my engines now......

Check for flatness on the mating surfaces, and use a large flat file if needed. You'll be ok

Roger that. Thanks.

Don't over heat the engine or get those manifolds hot cause they will leak water internally. Internal water jacketed casting thickness not even. Thin spots and thick spots internally. Plus core shifting during the manu process. If your in brackish or saltwaters - I would not used them after 2 to 5 years max depending how you maintain for that type of waters.

Funny

GLMs get better reviews than Sierras.
Whatever you get, though, be sure to flat-file the gasket surfaces until they are within 0.002" flatness. I've seen machining irregularities at the flanges and such.