OBX LT1 headers on L98
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
The bolt pattern is the same for the headers and they are at the same height for both heads. The difference is that the roof of the LTx ports is about .100" higher than the regular d-port heads like the 113's. The LTx manifolds work just fine on the 113's - I ran mine that way for a few months before swapping the engine.
I don't know how the OBX headers are built, so the test would be to get a stock LTx manifold gasket (under $15 at your local auto parts store) and compare it to the header. If it fits correctly, then you should be good.
I don't know how the OBX headers are built, so the test would be to get a stock LTx manifold gasket (under $15 at your local auto parts store) and compare it to the header. If it fits correctly, then you should be good.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Here is a question for you guys....are the early iron head stock L98 manifolds the same as the later D port 113 headed L98 manifolds? I have Pacesetter shorty headers for a LT1 (uninstalled) and Performer RPM D port heads, the LT1 gasket fits these heads perfectly. The D port gasket partially covers the bottom of the port of the iron heads. So, just wondering if there is an "early" and "late" L98 exhaust manifold?
Thread Starter
Racer
Joined: Nov 2006
Posts: 379
Likes: 7
The bolt pattern is the same for the headers and they are at the same height for both heads. The difference is that the roof of the LTx ports is about .100" higher than the regular d-port heads like the 113's. The LTx manifolds work just fine on the 113's - I ran mine that way for a few months before swapping the engine.
I don't know how the OBX headers are built, so the test would be to get a stock LTx manifold gasket (under $15 at your local auto parts store) and compare it to the header. If it fits correctly, then you should be good.
I don't know how the OBX headers are built, so the test would be to get a stock LTx manifold gasket (under $15 at your local auto parts store) and compare it to the header. If it fits correctly, then you should be good.
does that make a difference? as I understand these heads does not have the D ports...
Instructor
Joined: Jul 2004
Posts: 137
Likes: 0
From: CT
Not sure if this has been said, but the LT1 OBX driver side header requires an LT1 steering shaft that has the flex (rag) joint low by the steering box. Ask me how I know... Not sure if all L98's had the flex joint in the middle like my '86.
On the passenger side, wiring running down the bellhousing might have to be lifted over the A/C evaporator housing (I think '85 were that way) to clear the rear exhaust tube.
You can compare the Stainless Works L98 vs LT1 headers (bent the same as OBX) on their website and see how the pipes are bent differently.
I have the LT1 OBX headers on my '86 project with T56, F.I.R.S.T intake and Vortec heads; the OBX work (Vortec exhaust ports might be raised by 0.200" over L98 heads), but adding (reasonably priced) cats was a PITA, then connecting everything to a Magnaflow #16837 cat-back. Been driving it for about a year but I want to quiet the exhaust down so am going to try out factory LT1 manifolds and cats.
On the passenger side, wiring running down the bellhousing might have to be lifted over the A/C evaporator housing (I think '85 were that way) to clear the rear exhaust tube.
You can compare the Stainless Works L98 vs LT1 headers (bent the same as OBX) on their website and see how the pipes are bent differently.
I have the LT1 OBX headers on my '86 project with T56, F.I.R.S.T intake and Vortec heads; the OBX work (Vortec exhaust ports might be raised by 0.200" over L98 heads), but adding (reasonably priced) cats was a PITA, then connecting everything to a Magnaflow #16837 cat-back. Been driving it for about a year but I want to quiet the exhaust down so am going to try out factory LT1 manifolds and cats.
Thread Starter
Racer
Joined: Nov 2006
Posts: 379
Likes: 7
Not sure if this has been said, but the LT1 OBX driver side header requires an LT1 steering shaft that has the flex (rag) joint low by the steering box. Ask me how I know... Not sure if all L98's had the flex joint in the middle like my '86.
On the passenger side, wiring running down the bellhousing might have to be lifted over the A/C evaporator housing (I think '85 were that way) to clear the rear exhaust tube.
You can compare the Stainless Works L98 vs LT1 headers (bent the same as OBX) on their website and see how the pipes are bent differently.
I have the LT1 OBX headers on my '86 project with T56, F.I.R.S.T intake and Vortec heads; the OBX work (Vortec exhaust ports might be raised by 0.200" over L98 heads), but adding (reasonably priced) cats was a PITA, then connecting everything to a Magnaflow #16837 cat-back. Been driving it for about a year but I want to quiet the exhaust down so am going to try out factory LT1 manifolds and cats.
On the passenger side, wiring running down the bellhousing might have to be lifted over the A/C evaporator housing (I think '85 were that way) to clear the rear exhaust tube.
You can compare the Stainless Works L98 vs LT1 headers (bent the same as OBX) on their website and see how the pipes are bent differently.
I have the LT1 OBX headers on my '86 project with T56, F.I.R.S.T intake and Vortec heads; the OBX work (Vortec exhaust ports might be raised by 0.200" over L98 heads), but adding (reasonably priced) cats was a PITA, then connecting everything to a Magnaflow #16837 cat-back. Been driving it for about a year but I want to quiet the exhaust down so am going to try out factory LT1 manifolds and cats.
Then its probably easier just to wait and modify the OBX L98 headers (removing the air tubes).
I have already bought the complete OBX exhaust and have a FIRST intake on the way
Instructor
Joined: Jul 2004
Posts: 137
Likes: 0
From: CT
Waiting for the L98 headers is a good move! 
There might be a clearance issue with the alternator bracket, I had a problem to work around and it may not be unique to my setup. The A/C side bracket needed a spacer (had one welded on).
http://forums.corvetteforum.com/1579328997-post2.html
I used Moroso spark plug wire brackets and did some filing of the header flanges to clear the threads in the side of (Vortec) heads but I like the end result, and a flexible Lokar (fleabay clone) dipstick tube is easier to work with than the stock tube. Also have a Hitachi PSL100 mini starter and no clearance issues, don't know how a stock starter would fit.
That's a nice exhaust. A couple of years ago the Magnaflow 16837 was the only reasonabley priced alternative. My biggest gripe is the center resonator ground clearance and reworking the exhaust if forced to remove it. Another issue is Magnaflow used steel wire and if the OBX exhaust is like their headers than the welds sould be all stainless. If the Magnaflow breaks over time like some have reported then I'll jump ship to the OBX.
There might be a clearance issue with the alternator bracket, I had a problem to work around and it may not be unique to my setup. The A/C side bracket needed a spacer (had one welded on).
http://forums.corvetteforum.com/1579328997-post2.html
I used Moroso spark plug wire brackets and did some filing of the header flanges to clear the threads in the side of (Vortec) heads but I like the end result, and a flexible Lokar (fleabay clone) dipstick tube is easier to work with than the stock tube. Also have a Hitachi PSL100 mini starter and no clearance issues, don't know how a stock starter would fit.
That's a nice exhaust. A couple of years ago the Magnaflow 16837 was the only reasonabley priced alternative. My biggest gripe is the center resonator ground clearance and reworking the exhaust if forced to remove it. Another issue is Magnaflow used steel wire and if the OBX exhaust is like their headers than the welds sould be all stainless. If the Magnaflow breaks over time like some have reported then I'll jump ship to the OBX.
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Thread Starter
Racer
Joined: Nov 2006
Posts: 379
Likes: 7
Waiting for the L98 headers is a good move!
There might be a clearance issue with the alternator bracket, I had a problem to work around and it may not be unique to my setup. The A/C side bracket needed a spacer (had one welded on).
http://forums.corvetteforum.com/1579328997-post2.html
I used Moroso spark plug wire brackets and did some filing of the header flanges to clear the threads in the side of (Vortec) heads but I like the end result, and a flexible Lokar (fleabay clone) dipstick tube is easier to work with than the stock tube. Also have a Hitachi PSL100 mini starter and no clearance issues, don't know how a stock starter would fit.
That's a nice exhaust. A couple of years ago the Magnaflow 16837 was the only reasonabley priced alternative. My biggest gripe is the center resonator ground clearance and reworking the exhaust if forced to remove it. Another issue is Magnaflow used steel wire and if the OBX exhaust is like their headers than the welds sould be all stainless. If the Magnaflow breaks over time like some have reported then I'll jump ship to the OBX.
There might be a clearance issue with the alternator bracket, I had a problem to work around and it may not be unique to my setup. The A/C side bracket needed a spacer (had one welded on).
http://forums.corvetteforum.com/1579328997-post2.html
I used Moroso spark plug wire brackets and did some filing of the header flanges to clear the threads in the side of (Vortec) heads but I like the end result, and a flexible Lokar (fleabay clone) dipstick tube is easier to work with than the stock tube. Also have a Hitachi PSL100 mini starter and no clearance issues, don't know how a stock starter would fit.
That's a nice exhaust. A couple of years ago the Magnaflow 16837 was the only reasonabley priced alternative. My biggest gripe is the center resonator ground clearance and reworking the exhaust if forced to remove it. Another issue is Magnaflow used steel wire and if the OBX exhaust is like their headers than the welds sould be all stainless. If the Magnaflow breaks over time like some have reported then I'll jump ship to the OBX.