I bought a set of small block marine manifolds today at an estate auction. paid 3.00 for a lot that they were in. I had an idea to gut them and do a twin turbo setup. Any ideas? I think they would be perfect for the application. As soon as my pics download I'll post them.

Take the ends off and check out the insides. These look like they are wet exhaust manifolds, the fitting in the front and back is the clue. They can/will rust out or get thin spots from the water and exhaust gases/deposits. There can also be a whole bunch of scale on the inside and once you clean that away there may not be a lot of manifold left. Although looking inside the ports of that one, it looks pretty good.

Got nothing to add about using them as turbo manifolds but it is an interesting idea.

I'll pull the ends off tomorrow and check them out. They are very heavy. But with a twin setup who cares about a hundred pounds?

Seems like they would work, BUT, being very heavy, means they absorb a lot of heat (energy), and lots of surface area, and that's the opposite of what you want, besides, they are very heavy.

Looks like the plenum area is kinda big, I would craigslist em (lots of boat guys let em freeze and crack) and get some magnum manifolds and just reverse em if you want the turbo in front. Smaller volume and they flow really good. Like mentioned by jcc lots less iron to have to heat up also. I bet a turbo would be real soggy when cold and only slightly better when hot with those things on there.

Like this, this pic is from a member on the turbo forums (not sure if there a member here or not)but its one of my a favorite designs

I tried doing flipped manifolds on my TT440 back in 2001. They blocked the spark plugs when installed upside down and interfered with the engine mounts when swapped side to side. If it hadn't been for those issues I would have used the irons.

In a typical street turbo car the manifolds should do fine, assuming they're in good shape.

They will be really heavy but if there are no clearance issues go ahead and do it. The iron will actually keep heat in the exhaust and work the turbos a bit better than thin wall headers.

Pretty turbo headers make a bit more power but it's not an earth shattering difference in most rides.

If you do it, go EFI. You'll be much happier on the street.

You can't flip small block manifolds, bolt pattern won't allow it and the ports won't line up proper anyway.

Flipped over no, swapped sides yes.

Yeah, you can swap them side for side but that doesn't help much, too much stuff in the location where the exits will end up.

I think this is the way to go. If I were to do it, that's what I'd do. Unless you can find some "shorty's" like this.

If you want to do turbo, and can find a way to make those work, go for it. There are plenty of OEM applications with log manifolds that look worse than those marine manifolds and they do well. Hell, some guys are even rear mounting turbos by the trunk and getting good results.



As opposed to, say turbo headers that have long primary tubes and snake all over the place before they see the turbo. Way more volume to fill on those before the exhaust gasses see the turbo.

All but the most highly engineered overbuilt turbo systems see more backpressure in the exhaust manifold than boost pressure in the intake tract. Even those systems are tuned for a particular boost/rpm range.

So many people think that turbos are free horsepower. They are NOT free. The engine still has to work the turbos. That results in slower velocity in the exhaust manifold while the air is trying to cram it's way past the choke point in the turbine housing.

Fancy headers can make more power than a decent common manifold but the difference on a moderate street engine is not that big of a deal.

Unless you're planning on running more than 700 hp out of a common V8 then you're not going to see a 20 hp difference with pretty headers.

I don't ever recall seeing a purpose designed long tube turbo header as you describe. I agree that the volume might be similar, but I bet there is big difference in exhaust gas velocity when comparing a large log style ala the OP's latest bargain project vs an individual tube style tuned turbo header.

Im no expert, but long tube tuned length headers are tuned to length to promote exhaust gas scavenging. With the turbo being such a huge restriction on the exhaust system, causing a lot of backpressure, there will be no scavenging. I think this is part of why the oem still uses some basic looking turbo manifolds.

Correct.

Unless you are designing a system for a very specific rpm and boost range you will see very little gain from fancy tube headers.

They look pretty but looks don't make power.

Today I finally got around to pulling the ends off of the manifolds. Looks like the insides aren't as big as some may have thought. I do believe the volume would be ideal for a twin turbo setup. I'll be looking for a 360 for mockup soon. I'll post pics of the insides as soon as they load.

Here are the pics

another

Sell them to a boater. They'll get you plenty of $$ for a better set.

Otherwise, you'll overheat them, crack them, scrap them and then end up buying better headers after all.