Final word on tubular headers?

[fireroad]

Back when my SV motor was stock I read all the posts I could find on the tubular headers SS carries, which I believe were/are made by Falcon. Long story short most felt the stock headers were a good design and the the expense of the tubular headers would not be justified by a few HP gain.

Fast forward 10 years and my newly rebuilt motor is nearly complete. 20 over flat top pistons, kb grind cam, vizard mod, larger Datsun valves, Weber 32/36 with webcom manifold, and fly wheel lightened to Le Mans specs. Compression came out to 9.5 or so, will run on 92 octane non-ethanol. Now I’m wondering if the headers make more sense with the motor warmed up a bit. I live in the mountains so low end grunt is my goal over total HP, and I have factory OD in the car. For those that have rebuilt there motor for more power, did you go with the headers and was it worth it? Or do I put the money towards a TVR flywheel?

 

[alpine_64]

Back when my SV motor was stock I read all the posts I could find on the tubular headers SS carries, which I believe were/are made by Falcon. Long story short most felt the stock headers were a good design and the the expense of the tubular headers would not be justified by a few HP gain.

Fast forward 10 years and my newly rebuilt motor is nearly complete. 20 over flat top pistons, kb grind cam, vizard mod, larger Datsun valves, Weber 32/36 with webcom manifold, and fly wheel lightened to Le Mans specs. Compression came out to 9.5 or so, will run on 92 octane non-ethanol. Now I’m wondering if the headers make more sense with the motor warmed up a bit. I live in the mountains so low end grunt is my goal over total HP, and I have factory OD in the car. For those that have rebuilt there motor for more power, did you go with the headers and was it worth it? Or do I put the money towards a TVR flywheel?

The TVR lightweight flywheel is probably a better gain.
For headers the new set Jerry is working on would produce a gain, but mostly at higher rpm as they are a race design...4-1.

Collector headers 4-1 produce better top end gains, the stepped 4-2-1 will help with mid-range torque more than the single collector but slightly less power.

A better value engineering would be the lightweight fly and then carefully port match the exhaust ports in the head to your cast manifold.

That said.... headers look nice and make it sound better ..

 

[jdoclogan]

My two 1592 engine builds were just completed yesterday (18 month saga). One (a numbers matching production Harrington Le Mans) is similar to yours Fireroad except it is a 1592 with a slightly longer stroke, cometic gaskets for head water crescent weld and probably some oiling modifications. The second one is more of a racing engine (mainly a more aggressive cam, bigger bore [60 over vs std], higher compression and header will have a longer collector).

The 4-1 header I designed is adjustable for the desired rpm - peak torque by changing the length of the collector. 15" (shown) is for approximately 3000-3500 RPM (longer will increase rpm/peak torque). I'm working on making a bell housing adaption for my engine builder's dyno. If that is successful I will be able to get solid data on many configurations (I have virtually every combination) of intake and exhaust.

I utilized Vizards approach in developing my Sunbeam Alpine header. Mathematically smaller is better for tube sizing - 1.25" (1" ID) vs stock 1.5" (1.25"ID). However the critical component is the collector. 2" OD X 15" length for maximum scavenging. Note: the collector has a pulse reducer installed.