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Exhaust Manifold/Header  Rate Topic 
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 Posted: 07-24-2019 03:23 pm
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Dakota123
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I think I understand that only later JH engines ended up with cast iron exhaust manifolds.  Somehow 10628, a Mk1 from 1972, has a cast manifold.  (Not noted in the service records, of which I have every one up until about 1990.)  I'm finishing up my 2.2L, should be ~200 hp trim when all is said and done, and wondering if I'll be leaving much on the table by not going to a header.  The cast manifold has been trouble-free, and doesn't seem like a horrible design, really.
TIA

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 Posted: 07-25-2019 01:17 am
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Esprit2
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I don't know which cast manifold was used on the JH, but the one used on the Lotus 907 was actually very free flowing and efficient. A good tuned length tubular header could still deliver more horsepower, but not much. On the order of 3-5 hp more. Not a big deal.

Regards,
Tim Engel

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 Posted: 07-25-2019 03:04 pm
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Dakota123
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Thanks, Tim -- from what I've seen from online images, it looks like the same part, or very similar - 1 and 4 joined and 2 and 3 joined, with separate tubes running down to a 'Y'

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 Posted: 07-26-2019 12:49 pm
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Brett Gibson JH5 20497
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This is the later version of Delta's header, really has a nice free flow. http://www.deltamotorsports.com/products/pg15d-jensen-healey-headers.html

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 Posted: 07-27-2019 01:50 pm
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Dakota123
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I may get it, or the one from the club store, just because they look so freakin’ cool — but then again, you can’t see it when it’s installed...

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