Sweptline.ORG

NO, I DONT WANT TO DEAL WITH HEADERS.

Pulling my hair out a bit. Planning to redo the exhaust on the D300. Found a set of the sought after Magnum manifolds that measure 2.125" outlet. Thought I was good until I went to fit the driver side. Knew it was questionable so I started with that and even with a mini starter, there is no way the driver side manifold will work.

I'm at a crossroads of trying to find a different manifold to use or just reuse the stock ones that came on the truck? The stock ones are very small, noticeably small compared to the later magnum manifolds.

Does anyone know of the later (75- mid 80s) have a bigger port and/or passage? Waiting to hear back from a couple ebay sellers who I asked to get me a measurement but thought I'd ask here as well.

This is a stock 318 but I only want to build the exhaust once. I'd even entertain running a passenger side magnum manifold on the driver side and run the exhaust around the front of the oil pan like the factory did...but these Magnum manifolds I have, the passenger outlet is too far forward to be used as a driver side (puts the exhaust really close to the lower radiator hose).

Anyone with any insight as to what manifolds work best? Stock 318, mini starter, 4-speed (z-bar in the way of things). Any input is appreciated.
Thanks!

I'm not sure what your "Magnum" reference is to. I'm going to assume it is to the later model pickups whose model name was Magnum. Chrysler really over used this word, calling big block high performance engines of the late '60 and early '70s "Magnum", as well. I don't believe small blocks ever were, but I'm not sure if you weren't referring to them.

Any way, my thoughts would be to utilize exhaust manifolds from late '60s through early '70s 340 engines. They had the bigger outlets, 2.5"?, and better flow characteristics. I don't know if anyone is reproducing them and finding a used original pair will be challenging, but not impossible.

The "magnum" manifolds are for the later 360's. 92-93 year Dakotas had "the best" ones with a 2.125" outlet size.

I will use the "magnum" manifold on the passenger side as originally intended. Today I stopped at the local wrecking yard and pulled manifolds from a '98 Cherokee (one was actually already removed and laying in the engine bay, other had 1 bolt holding it in place). I think I've decided to go with a passenger side Cherokee manifold (also a much larger port and outlet compared to the stock manifolds), on the driver side, which means it exits down and out the front (just under/in front of the forward most exhaust port).
This allows plenty of room for a starter, will need a 96 degree sweep to point it back towards the rear of the truck, and away we go. Im excited about the manifold being figured out but probably more excited about the fact that I can put the stock, old school starter back in it. I put one of the newer mini starters in, thinking I'd need all the clearance I could get, but I really dont like the way it sounds and honestly I think the truck started better/quicker with the stock style starter in it.

Overall plan is 2.25" tubes back to the rear of the cab, where the driver side will cross over to the passenger side. Going to use a merge 2-1 collector (should help scavenge a little) to bring them both to a 3" single inlet muffler, 3" single out of the muffler.

So dumb, so overkill, so..."why am I even doing this?" but its fun and it brings me joy to tinker with this old stuff.

ardentindustries wrote: ↑

Sun Jul 30, 2023 8:56 pm

This allows plenty of room for a starter, will need a 96 degree sweep to point it back towards the rear of the truck, and away we go.

How did you measure 96° to that precision?

ardentindustries wrote: ↑

Sun Jul 30, 2023 8:56 pm

Overall plan is 2.25" tubes back to the rear of the cab, where the driver side will cross over to the passenger side. Going to use a merge 2-1 collector (should help scavenge a little) to bring them both to a 3" single inlet muffler, 3" single out of the muffler.

This is close to what I planned for my big-block truck but with the addition of a crossover (with flanges). Shuttleworth has good 2-into-1 mufflers btw. If you go with them, I'd like to hear what you pick. shuttleworthexhaust.com If you know of any better, I'd like to hear that too.