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Old 01-15-2014, 02:48 PM
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5.7 Chevy Vortec exhaust manifolds

OK I'm turning to the board for information. I have a 327 with 906 vortec heads. I want to use stock exhaust manifolds. This engine has a 600 CFM carb. (1406) What OEM part numbers will work? What exhaust manifold part numbers hooked up to the 906 heads? Please help.

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Old 01-15-2014, 05:11 PM
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You will need a Vortec style intake.IDK if you need to run an EGR system or not.If so,you will need the exhaust manifolds from a 96/99 truck.The drivers side has a threaded port for the EGR to dump into.If not,you can either plug the port,or,use an earlier model exhaust manifold.You can get the intake with or without EGR provisions.
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Old 01-15-2014, 06:30 PM
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Dorman Exhaust Manifolds 674-218 - Free Shipping on Orders Over $99 at Summit Racing exhaust manifold for a98 Chevy truck. Pay attention that they're left and right specific when buying. Why are you set on factory manifold? I wouldn't buy them new either, just go to the none yard. Probably ten or twenty bucks each. A side not......the exhaust bolt pattern on the vortec heads are the same as earlier non vortec Chevrolet's
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Old 01-15-2014, 07:55 PM
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I would only buy brand new and have them surfaced.. Those manifolds were known for tweaking and leaking.. A cheap set of headers costs the same as a set of cheap manifolds.. When I redid the exhaust on my old truck due to broken bolts in the manifolds, I elected to get stainless headers
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Old 01-16-2014, 05:44 AM
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First let me thank eveyone for their input. I have decided to use stock exhaust manifolds because of clearance and flow. If its good enough for that 350 it should work well with my 327. I understand it is a %40 flow increase over the old camel humps. It seems that OEM P/N's 12554973 RH and 12554974 LH but there is another that pops up. Sorry I dont have it available just at this moment. I may be nuking this out but is there a difference between the TBI and carb'd due to exhast tempature. I do not have to worry about the EGR so I will just plug the hole. My local U-Pull & Pay wants $30 each for the exhaust. I can find used on ebay for $45 + free shipping and I have even located new for around $45-$53 each. Shipping depends. So go with the new. But what I believe I need and hope to get from this board is where to get the information or can you provide the correct P/N's for these 906 heads. To be honest I'm starting to get lost with something as simple as this. Shorty headers are an option but is it worth it? I mean what am I gonna get maybe an extra 10 horses. Please see attachment photos.
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Old 01-16-2014, 07:56 AM
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What is this going into? If you can use the old GM rams horn manifolds, and you are only using this on the street for a cruiser; go with the rams horns. Shortie headers are a waste of time usually, any benefit over the rams horns, is most likely in the upper RPMs anyway. The cast manifolds will transmit less heat into the cabin usually as well.

If your choice is a log-style manifold or the shorties; Id use the shorties in that case. If this is a performance application, use a 1-5/8 long tube header from a reputable company such as headman or hooker. Your exhaust pipes should be 2.5" and mandrel bent
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Old 01-16-2014, 08:48 AM
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For a gm part number for the manifold you should be able to go to the Chevy dealer and ask them the part number for a 98 Chevy 1500 5.7l
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Old 01-16-2014, 09:50 AM
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The stock manifold were crap on a 350, and will be on a 327- not sure why you'd think they were good.

What cam are you running? the stock Vortec cam is very small, if you have a step up in cam (likely) and overlap, then you'd be a lot better off with decent headers, even a set of "shorties". The reversion stock manifolds cause can be a PITA to tune around- especially with a carb.
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Old 01-16-2014, 01:00 PM
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Quote:
Originally Posted by ap72 View Post
The stock manifold were crap on a 350, and will be on a 327- not sure why you'd think they were good.

What cam are you running? the stock Vortec cam is very small, if you have a step up in cam (likely) and overlap, then you'd be a lot better off with decent headers, even a set of "shorties". The reversion stock manifolds cause can be a PITA to tune around- especially with a carb.
because not everyone drives around at 5000 rpm..
they are fine for a cruiser.. and give up zero until you pass 4600rpm.. on a 350.. the 327 is less air in and out.. so.. unless it's a race ,more than street cruiser the factory manifolds will be fine.. ramhorns are better than the vortec logs.. but if it's a cruiser. it doesn't honestly matter.. other than packaging..
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Old 01-16-2014, 08:53 PM
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Depending on what they are going in as far as figment goes, they are one of your better choices for manifolds. I've personally used them on a metric chassis (g body) and I think the passengers side will touch the frame rail. They are fairly wide manifolds but pretty good. As was said by someone else, they have a habit of warping, so instead of junkyard shopping you may just want to order the doorman replacements and save headaches installing them.
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Old 01-16-2014, 09:35 PM
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Quote:
Originally Posted by gearheadslife View Post
because not everyone drives around at 5000 rpm..
they are fine for a cruiser.. and give up zero until you pass 4600rpm.. on a 350.. the 327 is less air in and out.. so.. unless it's a race ,more than street cruiser the factory manifolds will be fine.. ramhorns are better than the vortec logs.. but if it's a cruiser. it doesn't honestly matter.. other than packaging..
If you drive at part throttle you'll notice a difference. Not everyone uses a cam with no overlap.
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Old 01-20-2014, 08:43 AM
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Originally Posted by Plaintoast View Post
Depending on what they are going in as far as figment goes, they are one of your better choices for manifolds. I've personally used them on a metric chassis (g body) and I think the passengers side will touch the frame rail. They are fairly wide manifolds but pretty good. As was said by someone else, they have a habit of warping, so instead of junkyard shopping you may just want to order the doorman replacements and save headaches installing them.
I take it you are refering to the stock replacement log type manifolds. I am quite suprised that the old ram horns will work on this application. To be honest I find that hard to believe.
As far as what this engine is going into. Hopefully a 62-65 C-10 so I will have plenty of room for anything I choose. The ram horns have a built in bracket on the drivers side manifold for the alternator to pivot. If I go with the log manifolds I will have to make a bracket for the alternator to pivot. I also wonder about clearance with the starter. I believe a lot of the 5.7 Vortec engines use a Hi-Torque starter which is quite a bit smaller than the traditional stock 327 monster.
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Old 01-20-2014, 08:53 AM
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Yes I was referring to the log style, factory vortec manifolds. A ram horn should fit that chassis I believe, if you're in the stock location. I know the vortec would not fit a customers 70 blazer chassis and several others wouldn't either, so he had to go with the ram horns.
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Old 01-21-2014, 04:15 PM
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A truck manifold from a 1987-1999 5.0/5.7 will work. As stated, the only reason to get a 1996-99 Vortec 305/350 manifld is if you want to supply EGR gasses to the intake.

here is a set of 1996-99 truck or 1996-2000SUV or 1996-2002 van Vortec L30/L31 exhaust manifolds


Same but only the drivers side showing the EGR supply flange and fitting




And here is a 1987-1995 TBI 305/350 manifold, so no real difference from Vortec


You will notice better acceleration with a shorty header, oreven better a long tube header than any of these restrictive boat anchors. You do NOT have to drive around at 5000rpm to notice torque/power gains. Thats just misinformation.

The reason why the Vortec manifolds didnt get much of a rework, is because in 1/2 ton applications they are forced to deal with these restrictive dual 1 7/8" headpipes that use crimp connections that reduce the diameter to almost 1/2 of that.. The larger pipes are from Vortec 350 3/4 ton and 1 ton apps, much better.



Decent stock manifolds are these 94-96 Caprice manifold


And these LT1 F body manifolds


Dont the Rams hirns have issues with centerbolt valvecovered heads such as the Vortecs? Not that I suggest using them either.

peace
Hog
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Old 01-23-2014, 01:29 PM
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I suggested the "Rams Horns" as I have a colleague with them in his EARLY 60s vette. However, I failed to remember that they're the Bowtie small port Vortec-type head, which has provisions for the early valvecovers. I dont know if he had to do any clearancing or use spacers; but they ARE on there. Sad thing is, its a balmy ZERO out, and I can't get pics until March or so. So Hogg and I are both right to some degree.

Incidentally the Vortec Bowtie heads are bad *** iron heads, especially when I think he paid $700 for the pair
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