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#93098 - 01/07/18 05:46 AM 250, should I switch to a 292 exhaust manifold?
James1972 Offline
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Registered: 05/20/17
Posts: 11
Loc: West Virginia, Mercer County
Greetings to all:
I have a 1973 C10 with a 250. The motor has an Offenhauser 5416 intake with a Holley 8007 (390cfm). The 250 currently has the stock exhaust manifold.

I have seen where many people have removed the stock exhaust manifold and put headers on. My mechanic told me that with the headers every six months or so you need to replace the gasket. As I am not a mechanic I can't afford that.

I just saw a post where a Camaro owner had the same set up and opted to use the 292 exhaust manifold as the exit diameter is 2.5" vs 2.0" of the 250 exhaust manifold.

Should I go for the 292 exhaust manifold or just stick with what I currently have?

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#93100 - 01/07/18 06:54 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
panic Online   content
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Definitely better, 56% more area, will last 20 years if well coated. Run the larger pipe as far back as you can.

Also possible: a fabricated header made from sections of Schedule 40 weld ells, not as efficient as an actual tube header but extremely durable. Downside: $$$, difficult to make.

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#93105 - 01/07/18 01:46 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: panic]
mdonohue05 Offline
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Loc: pennsylvania
As for the gasket remark, use a rimflex gasket.

The big issue for some of the headers is warping of the flange. I have run the same set of Clifford headers since 83 or so. They warped within the first two years. Built up the sealing surface on the face of the header flange with weld, and ground it flat and parallel. Rimflex gasket, no leaks, if you decide to bite the bullet and get a set of tube headers.


Edited by mdonohue05 (01/08/18 08:29 AM)

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#93107 - 01/07/18 07:26 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: panic]
James1972 Offline
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Registered: 05/20/17
Posts: 11
Loc: West Virginia, Mercer County
Thanks for the sound advice.

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#93108 - 01/07/18 07:29 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: mdonohue05]
James1972 Offline
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Registered: 05/20/17
Posts: 11
Loc: West Virginia, Mercer County
That is some encouraging info to go the header route. I have a lot to think about.

Thanks mdonohue05!

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#93110 - 01/08/18 05:13 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
gbauer Offline
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Registered: 08/11/14
Posts: 816
Loc: Maryland
Look for a Langdon split header. It's cast iron and very durable. I also used high temp (exhaust) RTV to get a good seal. No problems.

You'll still need to heat the intake manifold. Keep that in mind whatever you do.

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#93111 - 01/08/18 05:32 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: gbauer]
James1972 Offline
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Registered: 05/20/17
Posts: 11
Loc: West Virginia, Mercer County
With the Langdon split header do you recommend air heat or liquid? I see both being talked about.

Langdon no longer manufactures for the Chevrolet 250, he recommends going to 12bolt.com and purchase from Tom Lowe.

Thanks for the input gbauer!

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#93112 - 01/08/18 08:10 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
gbauer Offline
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Posts: 816
Loc: Maryland
It'll have to be liquid heat. There isn't a provision for air.

That said it really works well and woke my engine up significantly. I had pretty much exactly what you have. You'll also need to either mate to the existing exhaust or make a new one. I went with bringing the two together downstream and running a single 2.5" exhaust through Flowmaster 44's. She sounded really good but it'll cost you about a grand once you're all done if you pay an exhaust shop to do the exhaust.

Also consider a mild cam at some point. After that the only non-FI things to do are lump ports, HEI, electric fan, etc. Try to take some load off the engine via the electric fan. The mechanical fan draws a lot of power up top. Another option is a fan with a clutch. That way it's not drawing so much power at the upper RPM's.

Short video clip of her driving away the last time I saw her: https://www.youtube.com/watch?v=lJdZDW0AiO8

Sad moment for me but you get a good feel for the exhaust sound.

You can see how I routed the coolant lines here:

https://i.imgur.com/wgDOX0i.jpg

Notice the brass T's at the fire wall. I T'd the heater hoses to get some flow over to the intake.

Missing some pics but here's another:

https://i.imgur.com/iMmgB2s.jpg

I made a flat plate that I put two taps into for elbows and ran the heater hoses to it. Had to made a gasket from rubber and used a ton of RTV to seal it. Had to re-do it 3 times before it sealed but once done I never touched it again.

One other thing about the cast headers: the flanges are a different thickness than the OEM manifolds. I had to grind off some of the spanners to equal things out (I mean the things that hold the flanges on via the studs in the heads). Not a huge deal but still something you'll need to do.


Edited by gbauer (01/08/18 08:12 AM)

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#93115 - 01/08/18 08:32 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: gbauer]
mdonohue05 Offline
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I am with the others, water heat. Works way better then exhaust heat. I also used a flat plate with elbows. Mine leaked every time. Weld the plate to the manifold and end the problem once and for all or switch to a Clifford manifold with the water chamber already cast into the manifold.

Also, look at the bottom of your manifold. If there are sheet metal plugs staked into the casting (for the exhaust heat, you will need to weld plugs over them as they will also leak. Otherwise, the hot water will do wonders for drivability.

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#93116 - 01/08/18 10:26 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
panic Online   content
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Water heat: more consistent
Exhaust heat: quicker after start-up

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#93117 - 01/08/18 01:02 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: mdonohue05]
gbauer Offline
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Posts: 816
Loc: Maryland
Originally Posted By: mdonohue05
I am with the others, water heat. Works way better then exhaust heat. I also used a flat plate with elbows. Mine leaked every time. Weld the plate to the manifold and end the problem once and for all or switch to a Clifford manifold with the water chamber already cast into the manifold.

Also, look at the bottom of your manifold. If there are sheet metal plugs staked into the casting (for the exhaust heat, you will need to weld plugs over them as they will also leak. Otherwise, the hot water will do wonders for drivability.


Forgot about the plugs!

I used a 2 part epoxy and then painted over them. They held for me but others couldn't get it to hold with epoxy.

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#93121 - 01/09/18 07:49 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: gbauer]
tlowe #1716 Offline
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I also agree on the water heated intake. I don't agree that Gbauer's method is a proper fix to the leaky plugs on the bottom of OFFY intakes. The epoxy is a quick easy method that is sure to fail over many heat cool cycles. The only sure method is to weld caps after removing the staked in steel plugs.

Originally Posted By: gbauer
Originally Posted By: mdonohue05
I am with the others, water heat. Works way better then exhaust heat. I also used a flat plate with elbows. Mine leaked every time. Weld the plate to the manifold and end the problem once and for all or switch to a Clifford manifold with the water chamber already cast into the manifold.

Also, look at the bottom of your manifold. If there are sheet metal plugs staked into the casting (for the exhaust heat, you will need to weld plugs over them as they will also leak. Otherwise, the hot water will do wonders for drivability.


Forgot about the plugs!

I used a 2 part epoxy and then painted over them. They held for me but others couldn't get it to hold with epoxy.
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#93134 - 01/11/18 07:46 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
James1972 Offline
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Registered: 05/20/17
Posts: 11
Loc: West Virginia, Mercer County
Thanks for all the great info. I am trying to understand how to heat the intake. If I use the stock exhaust manifold do I still need the heat the intake?

Does anyone know of a diagram or where I can find pictures and directions to properly heat the intake?

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#93135 - 01/11/18 08:33 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
panic Online   content
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If your Offy bolts to the exhaust use that, but I doubt it does.

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#93137 - 01/13/18 10:12 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
ACH57 Offline
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Registered: 05/21/07
Posts: 62
Loc: Clarkdale, AZ
I'm running an Offy intake with a 292 exhaust manifold. I got the combination to bolt together by doing some careful grinding on both pieces. On the intake I had to grind away at the coolant passage but since the 292 exhaust bolts directly to the intake there won't be any coolant in the passage.

Once they bolted together I took them to my engine builder and he machined the two gasket surfaces smooth. There was about 1/16" difference in the two surfaces.

Added benefit: a single 2.5" exhaust is easier to DIY than a split manifold. For my intended use the 2.5" exhaust is more than adequate.

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#93160 - 01/16/18 07:17 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: ACH57]
James1972 Offline
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Registered: 05/20/17
Posts: 11
Loc: West Virginia, Mercer County
I have opted to stick with the 250 stock exhaust manifold for now. Thanks for sharing your set up.

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#93161 - 01/16/18 07:27 PM Re: 250, should I switch to a 292 exhaust manifold? [Re: James1972]
James1972 Offline
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Registered: 05/20/17
Posts: 11
Loc: West Virginia, Mercer County
The split manifold and running the new exhaust needed is just out of budget at the moment. When the cash is flowing better with the knowledge shared on this forum and after corresponding with Tom Lowe I will go with a split manifold.

Thanks for all the great information everyone has shared. I appreciate all you Inliner aficionados sharing your opinions.

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#93162 - 01/17/18 01:01 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: ACH57]
Lifeguard Online   content
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Registered: 02/17/14
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Loc: Rockford, IL
Originally Posted By: ACH57
I'm running an Offy intake with a 292 exhaust manifold. I got the combination to bolt together by doing some careful grinding on both pieces. On the intake I had to grind away at the coolant passage but since the 292 exhaust bolts directly to the intake there won't be any coolant in the passage.

Once they bolted together I took them to my engine builder and he machined the two gasket surfaces smooth. There was about 1/16" difference in the two surfaces.

Added benefit: a single 2.5" exhaust is easier to DIY than a split manifold. For my intended use the 2.5" exhaust is more than adequate.



Were you using a factory HD 292 2.5" exhaust manifold, or one of the aftermarket replacement castings meant for use on tractors and generators?

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#93166 - Yesterday at 01:36 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: Lifeguard]
ACH57 Offline
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Registered: 05/21/07
Posts: 62
Loc: Clarkdale, AZ
Mine is an aftermarket replacement.

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#93169 - Yesterday at 10:21 AM Re: 250, should I switch to a 292 exhaust manifold? [Re: ACH57]
Lifeguard Online   content
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Registered: 02/17/14
Posts: 435
Loc: Rockford, IL
Originally Posted By: ACH57
Mine is an aftermarket replacement.


Ok, that's the experience people seem to have with those. Manifold lineup, at least with the Offy, takes some extra work to make it work. I haven't run into anyone talking about installing one they salvaged from a 292 HD truck, but I assume those are probably a good combo of cheap and minimal amount of elbow grease to install. But have not run across one yet.

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