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Old 11-24-2012, 06:02 PM
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Big Block Chevy Mainfolds Upside Down?

Hey gents,

Is there any mechanical issue that you can see that would prevent the use of log style big block Chevy manifolds being mounted upside down and forward for a turbo build?

The turbo will not be directly mounted to the exhaust manifold so it / they will not bare the brunt of the weight. Just trying to see if there was anything I was missing that would prevent me from taking stock exhaust manifolds like this one and mounting them upside down with the exhaust outlet pointing forward.

1973-1975 BBC 454 LH & RH Police Interceptor Exhaust Manifolds 353030 3994045 | eBay

I was also thinking, if I can use these, to maybe cut the cast iron between each exhaust port to help with expansion and contraction issues (I have seen that done before), but didn't know if it would weaken the overall manifold design to much / more than it would help with expansion and contraction.

Thanks in advance for your responses.

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Old 11-24-2012, 06:19 PM
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They might end up in a strange angle. But should work. Are you using single or twin turbos.

Alot of times it easier to buy block hunger style headers and just bring the pipes forward in stead of back. Not sure what the goal is and how much hp you are looking to get in the end. Big blocks need to breath if you use bad manifolds and Tight piping you may have trouble with heat soaking and poor combustion leading to detonation. Its also usally easier to mount the turbos down lower on a street car as you can get top mounts for accessories. Leaving lots of room for some big turbos.
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Old 11-24-2012, 07:14 PM
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Thanks for the reply. I am actually using a PT106. It's going in a 1984 1/2 ton Chevy Truck so I have tons of room under the hood.
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Old 11-24-2012, 07:21 PM
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$250 for crappy manifolds? I'd just find a set of hugger or shorty headers, and make those work, you'll have an easier time making power and they're cheaper. the ONLY drawback is that they MAY not be as durable as cast iron manifolds- then again they could end up being just as good depending on what you buy and how it built.

Heat can kill any manifold or header so don't think a cast iron one will be bullet proof.
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Old 11-24-2012, 07:44 PM
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Quote:
Originally Posted by ap72 View Post
$250 for crappy manifolds? I'd just find a set of hugger or shorty headers, and make those work, you'll have an easier time making power and they're cheaper. the ONLY drawback is that they MAY not be as durable as cast iron manifolds- then again they could end up being just as good depending on what you buy and how it built.

Heat can kill any manifold or header so don't think a cast iron one will be bullet proof.
Who said I was buying those particular manifolds? I just used that pic cus it was the first one that popped up. Chill.

I can pick up a set for $40 bucks locally so I just wanted to know their viability. I also never said they would be indestructible; again just wanted to know if they could be configured correctly.
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Old 11-24-2012, 08:36 PM
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Having them thw same on both sides would be easier to plumb up. The one in the picture looks good but the other one will be pointing oddly straight up. Not sure if the set you are thinking of has the same Outlets as the picture. Block huggers and some turn outs and a few pieces of pipe and the turbo will be hanging off the headers in an afternoon. Stock manifolds may be just as easy but i would think it better to run some headers. Even if they are equal length. I have seen them installed upside down and turn and turned around.

Also the block huggers headers from headman and hooker are cheap all the time. The manifolds may get more costly further down the road. And will give better performance. Turbos will need to be supported either way but less with the cast manifolds.
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Old 11-24-2012, 09:52 PM
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Thanks hcomp.
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Old 11-25-2012, 09:50 AM
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They will not bolt up upside down.
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Old 11-25-2012, 10:06 AM
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Originally Posted by S10 Racer View Post
They will not bolt up upside down.
Good catch i think you are right the bolts on bb are not in line like sbc. They are offset bolt pattern in the picture. Once you turn them upside down they will not fit. You could use a few tricks to make them fit if this was a rare engine and parts were hard to find. But for chevy i would not waste the effort to make them work since other options are pretty cheap.

Do you have a wire feed welder. You can buy kits with manifold flanges and header primary pipes included if you need them but i would think a log manifold would be ok in this case. It would need to be pretty big but not to hard to make your own. I have had to do it on several cars. It seems to be easier than trying to weld to the old cast iron it will resist all efforts to weld up correctly and stay that way for any length of time.

You can also buy manifolds and pipe kits setup for bbc and sbc. Bbc might be costly because a bbc with twin turbos is almost always a big build up in the 1500 hp range. Mild turbo builds for big chevy have a smaller market. But imsure so,eone has a nice kit out there if you want to buy one and be done.
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Old 11-25-2012, 10:12 AM
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If all else fails I can take a exhaust manifold gasket or make a pattern and take it to my laser cutter guy and have a manifold flange made and then get some ready bent tubes and make an exhaust header that fits my particular needs. Sometimes guys try to save some cash which is fine but then wind up screwing themselves..learned that lesson..

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Old 11-25-2012, 11:08 AM
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Ok thanks a million for the replies guys. Guess that answers that question. I just didn't want to spend $$$$ on an aftermarket header designed for turbo applications.

I do have a good wire feed but just not that good at using it yet. Good friend of mine is an expert welder so I guess we will just get a good kit and get after it.

Thanks again.
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Old 11-25-2012, 01:55 PM
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Quote:
Originally Posted by S10 Racer View Post
They will not bolt up upside down.
If you swap them side to side and THEN flip them upside down, I believe you'll see they bolt up.

The outlet may not be where you want it. There may also be a slight mismatch between the manifold and head ports, but this can be taken care of w/a die grinder and/or slotting the holes.
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Old 11-25-2012, 03:57 PM
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Cobalt,

As alway I appreciate your insight. Looking at the manifolds if I switched sides and turned them upside down, wouldn't one collector be facing upward and the other collector facing forward with a slight upward tilt? Please correct me if I'm looking at them incorrectly.
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Old 11-25-2012, 06:14 PM
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Quote:
Originally Posted by 31fordcoupe View Post
Cobalt,

As alway I appreciate your insight. Looking at the manifolds if I switched sides and turned them upside down, wouldn't one collector be facing upward and the other collector facing forward with a slight upward tilt? Please correct me if I'm looking at them incorrectly.
Like I said earlier, the outlets might not be where you want them...
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Old 11-25-2012, 06:29 PM
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I tried switching block hugger headers for the BBC S10 I built and the ports are too far off to correct with a die grinder. I actually cut the flanges off the tubes and flipped them 180* and welded them back on to get them to fit. Not saying it's the best way but I didn't want to fork out $1500.00 for a set of Lemon headers. The way mine came out, it would be so easy to install turbo's on.
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