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Topic Review (Newest First)
03-24-2015 12:23 PM
BogiesAnnex1
Quote:
Originally Posted by kevenj View Post
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.
You don't want nor need the Vortec exahust manifolds on the 327. They are unique to the needs of the Vortec's externally fed EGR valve. Regular Chevy exhaust manifolds for the chassis the 327 is mounted in are suitable as are headers from block huggers, shorties, or long tubes. The L31 Vortec does not change the location of the exahust ports nor their bolt locations with reguard to other small block heads. The original 327 heads were most likely for the short water pump engines that mounted accessories off the exhaust manifold. The Vortec heads are dsigned to support front mounted accessories with the long water pump, but with "period" exahust manifolds they will support side mounted accessories with the short water pump.

Bogie
03-24-2015 11:43 AM
55_327 I need to update my post above, because I've just seen some pictures of Vortec heads where a line drawn through the header bolt holes runs right through the vertical center of the ports. A friend of mine says he has used standard 1.38" x 1.38" Fel-Pro 1444 gaskets on both 906 and 062 heads and they fit perfectly.

Go figure.
03-23-2015 04:42 PM
55_327
Quote:
Originally Posted by AutoGear View Post
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.
I know this is an old thread, but wanted to add what I learned first hand today about Vortec exhaust ports, gaskets, and using rams horns manifolds.

First, the Vortec ports (at least on my new 062 heads) are positioned approximately 1/8" higher relative to the bolt holes, compared to conventional OE Chevy heads. However, I can't find a gasket that is cut properly for the for the raised ports. Fel-Pro says their MS94054 and 1404 gaskets fit Vortec heads, but the bolts holes are not relocated. They did make the port cut-out 1.5" x 1.5". So at least the top of the port is uncovered, but barely.

As for rams horns, the only way they will work is to remove approx 1/8" of material from the top of the ports. Otherwise, you will obstruct the part of the port with the highest exhaust flow. (Think about it: The exhaust gasses are being forced to make a turn out of the combustion chamber, so the flow naturally wants to continue upwards.) As for clearance, my 2" rams horns clear the heads and valve covers by a bunch.

Below are pics of the MS94054 gasket installed on a head and a 2" rams horn manifold. Also of an OE gasket installed on a head, which is exactly how an unmodified rams horn manifold port would line up. You can see the dilemma. Now if you're using 1.5" x 1.5" gaskets with headers that have tall port openings, you're probably OK, but check anyway.





01-23-2014 12:29 PM
AutoGear 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
01-21-2014 03:15 PM
Hogg 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
01-20-2014 07:53 AM
Plaintoast 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.
01-20-2014 07:43 AM
kevenj
Quote:
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.
01-16-2014 08:35 PM
ap72
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.



01-16-2014 07:53 PM
Plaintoast 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.
01-16-2014 12:00 PM
gearheadslife
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..
01-16-2014 08:50 AM
ap72 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.



01-16-2014 07:48 AM
crussell85 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
01-16-2014 06:56 AM
AutoGear 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
01-16-2014 04:44 AM
kevenj 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.
01-15-2014 06:55 PM
matt167 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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