Manifolds
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Pro
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From: Austin Texas
Manifolds
I'd like long tube headers but I've heard emissions forbids them. So how about manifolds from older vettes onto an LT1 ? Is the bolt pattern the same on the exh side of the head on a 93 than a 1968 model 350 ?
These guys claim 20HP better on a ram horn manifold than any other stock manifold.
http://www.castheads.com/faqs_exhaust_manifolds.php
20HP is comparable to some (but not all) headers I've seen numbers on and these ramhorns if they fit might be a good way to keep it looking somewhat stock while gaining exhaust flow ?
http://www.castheads.com/corvette_systems.php
Or maybe they won't even fit on the C4 chassis with the modern routing of other items present under the hood ?? ......
These guys claim 20HP better on a ram horn manifold than any other stock manifold.
http://www.castheads.com/faqs_exhaust_manifolds.php
20HP is comparable to some (but not all) headers I've seen numbers on and these ramhorns if they fit might be a good way to keep it looking somewhat stock while gaining exhaust flow ?
http://www.castheads.com/corvette_systems.php
Or maybe they won't even fit on the C4 chassis with the modern routing of other items present under the hood ?? ......
Safety Car
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From: Made In America
St. Jude Donor '10-'11
Port the hell out of your stock manifolds. Cut open and gut your mufflers. Looks stock and very free flowing. Yes, you can get aftermarket mufflers or muffler eliminators, but nobody would expect that.
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From: O'Fallon Missouri
What type of emmisions' testing do they have in Texas? When Missouri was still testing the OBDI cars I passed with long tubes and high flow cats. At the time there was no visual test unless you failed the tail-pipe sniffer.
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From: Austin Texas
I'm not sure of the laws, was basing my opinion on what I've read from others from Texas writing that long tubes aren't permissible, whereas shorties are; however shorties don't do as well as long-tubes .......... and I thought that if it were possible to get a 20HP increase from a factory-made manifold that would fit under the hood then I'd be happy enough with that.
I once had a 454SS pickup and a visual was part of the initial inspection - they wouldn't pass it because the fifty-cent aluminum flex tube from the heat riser to the air diaphragm on the filter housing was missing.
I once had a 454SS pickup and a visual was part of the initial inspection - they wouldn't pass it because the fifty-cent aluminum flex tube from the heat riser to the air diaphragm on the filter housing was missing.
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From: Austin Texas
Also contemplating having comp grind a cam with 2002 LS6 profile onto an LT1 stick. The 02 LS6 shows nice torque, is rated 425 HP and such a profile, I would think, would provide good idle, decent economy and valvetrain longevity. any thoughts ? I realize the rod's a bit longer in the LS6 (and stroke a little too) and wonder how much difference that would really make if the grind in the link below were put in an LT1....
http://www.corvettemuseum.com/specs/...haftvs2001.pdf
Last edited by ChrisWhewell; Jul 6, 2009 at 10:29 AM.
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From: altered state
St. Jude Donor '05
That claim is bull imo. Ive ported the daylights out of those rams horns and I highly doubt youd get 1/2 that amount of gain at redline.
You cannot get all the way through the passages from the two farthest cylinders, only the middle two and partway back in them..
think the stock LT1 manifolds are way better. just my .02
You cannot get all the way through the passages from the two farthest cylinders, only the middle two and partway back in them..
think the stock LT1 manifolds are way better. just my .02
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From: O'Fallon Missouri
Next question is whose guideplates / 7/16 studs to use. I'm thinking ARP studs and Manley guideplates, the raised ones. If its not too much trouble, would you share which studs / plates you used ? I see GM 14011051's out there but believe the raised Manley's should provide a little more stability.
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From: Kempner Texas
On my son's 96 LT1, I went with ARP 7/16 rocker studs and CompCams guide plates. I used the slightly longer studs that ARP offers.
Even with Scorpion 1.7 RRs, the 96 stock valve covers fit without any modification.
I didn't modify the stock exhaust manifolds.
Jake
West Point ROCKS!
Even with Scorpion 1.7 RRs, the 96 stock valve covers fit without any modification.
I didn't modify the stock exhaust manifolds.
Jake
West Point ROCKS!
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From: O'Fallon Missouri
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I seriously think they are comapring to an era with those ram horns. Like what was out there in the 60's/70's. but I dont have the time to read the whole page
I think you are light years ahead with the stock lt1 manifolds you have now.
The l98 manifolds... not sure. unless someone ported them to death. out of the box, ports are clogged up.
I was looking into manifolds for ages... for a turbo set up. whern I came across the ram horns, it is stated in every hot rod engine building book out there. the 2.5" ramhorns were the ones to get... Opposed to the 2" I believe they were. Thats all I get out of that web page.
I think you are light years ahead with the stock lt1 manifolds you have now.
The l98 manifolds... not sure. unless someone ported them to death. out of the box, ports are clogged up.
I was looking into manifolds for ages... for a turbo set up. whern I came across the ram horns, it is stated in every hot rod engine building book out there. the 2.5" ramhorns were the ones to get... Opposed to the 2" I believe they were. Thats all I get out of that web page.
Last edited by bill mcdonald; Jul 7, 2009 at 05:39 PM.
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From: altered state
St. Jude Donor '05
Chris you are correct on the thurbp/rams horn thing; there are 2.5" repops out there to be had as the originals get ridiculous $. Problem is the logs that connect the 2 outermost cyls are small in dia and have large bolt bosses protruding right in the path of the exh, they create a problem. about all you can do is extrude hone which imo wont do much....Iron you dont want to get too thin as it will crack getting red hot and all.
The L98s all you can do is go in about an inch and mess with the bottom but taht wont help the rest of it flow any better.
Heres an example. You can see the middle two cyls should pick up some (wish I had taken "befores") but the log parts were all about impossible to do anything worthwhile on. (plus the heat riser tube is in the way but the guy wanted his # matchign C2 t stay that way. Fun experiment though .
Keep the LT1 pieces
The L98s all you can do is go in about an inch and mess with the bottom but taht wont help the rest of it flow any better.
Heres an example. You can see the middle two cyls should pick up some (wish I had taken "befores") but the log parts were all about impossible to do anything worthwhile on. (plus the heat riser tube is in the way but the guy wanted his # matchign C2 t stay that way. Fun experiment though .
Keep the LT1 pieces
Last edited by cv67; Jul 7, 2009 at 07:56 PM.
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From: Austin Texas
Thanks alot for posting that, it should get a marker since this is an important area. man, that's a lot of work grinding and I agree with you about the thickness issue. I'm just trying to look at potential alternatives before I do the head swap after the weather cools (probably september) and you've helped me eliminate one of the options. Hey, lets talk about porting, I'll start a new thread and hope it turns into a real good one. 
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St. Jude Donor '08 thru '26
Check the TXC DMV web site...
....for emissions testing rules. Sorry to jump in as I have no idea about the specifics of the DMV rules in TX. However in the People's Republic of NY we have two parts to emissions testing.
Visual inspection of smogg equip, is the first; and that part must be passed before the sniff test on the rollers for OBDI cars.
In NYS you will pass the visual if your headers have all the smogg connections, EGR, A.I.R., and anything else the mod yr calls for as OEM. Or if the headers have a CARB # it makes it even easier.
I would also say this, in NYS we don't have State Inspection Stations run by the DMV. The DMV licenses repair shops & dealers to be NYS Emissions Inspection Stations...soooo in theory you could cozy up to a shop and bend the rules a bit.
Tom
btw, you threads about heads and porting are
Visual inspection of smogg equip, is the first; and that part must be passed before the sniff test on the rollers for OBDI cars.
In NYS you will pass the visual if your headers have all the smogg connections, EGR, A.I.R., and anything else the mod yr calls for as OEM. Or if the headers have a CARB # it makes it even easier.
I would also say this, in NYS we don't have State Inspection Stations run by the DMV. The DMV licenses repair shops & dealers to be NYS Emissions Inspection Stations...soooo in theory you could cozy up to a shop and bend the rules a bit.
Tom
btw, you threads about heads and porting are
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From: Austin Texas
Dang ! Was grinding on a port wall earlier and it punched a hole through to where the pushrod is on one of the ports. Was a fluke in the casting. Now I need to weld that baby closed. Arrrgh. and these are castings 10207643, supposedly the "good" ones with lots of "meat". sheesh.
I like the look of your motor. Have a good afternoon.
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From: Conroe TEXAS!
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Tx goes by county. If you are in Travis County, Id really check all the laws first. They do make shortys that you may be able to get by with. If the car is registered in a surrounding county of Austin proper, the laws may be a little less harsh. Check the local smog laws.