 Header sizes for /4 |
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| stownsen914 |
 Feb 19 2020, 04:55 PM
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#1
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Senior Member  Group: Members Posts: 912 Joined: 3-October 06 From: Ossining, NY Member No.: 6,985 Region Association: None  |
I'd like to confirm the proper header primary size for a high performance, small bore 914/4 engine. I recall that 1 5/8" OD is what was recommended back in the day. Is that correct?
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| yeahmag |
Feb 19 2020, 06:31 PM
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#2
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Advanced Member Group: Members Posts: 2,421 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California 
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That's a good universal size.
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| wndsrfr |
Feb 19 2020, 07:55 PM
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#3
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Senior Member Group: Members Posts: 1,428 Joined: 30-April 09 From: Rescue, Virginia Member No.: 10,318 Region Association: MidAtlantic Region
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QUOTE(stownsen914 @ Feb 19 2020, 02:55 PM)  I'd like to confirm the proper header primary size for a high performance, small bore 914/4 engine. I recall that 1 5/8" OD is what was recommended back in the day. Is that correct? PM Len Hoffman on that with info on bore & stroke & what you're doing with valve springs for redline limit...he'll know. |
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| HAM Inc |
Feb 20 2020, 05:19 PM
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#4
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Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
5/8's is a good all around size on a 4-1 header. The collector size and shape is waaaaay more important than primary size, though.
CR and revs and cam impact size selections greatly. How much power do you expect to make? |
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| stownsen914 |
Feb 20 2020, 10:01 PM
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#5
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Senior Member Group: Members Posts: 912 Joined: 3-October 06 From: Ossining, NY Member No.: 6,985 Region Association: None |
Thanks guys for the input.
Len - I hope to get 150-160 hp. If you have any wisdom to share about the collector, I'd love to hear about it. Thank you. Scott |
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| HAM Inc |
Feb 21 2020, 08:16 PM
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#6
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Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
I'd run a 2-1/4 collector with a nice taper and experiment with tail pipe lengths and shapes.
I was able beat sound readings without a muffler by running a tail pipe that ran from left to right under the trunk tucked up tight with a downturn that pointed at the track. The outlet was out of the line of sight of the DB gun so they never got a good sound reading. The car was louder than they thought. The tail pipe length was ~ 3' long with 2 ~ 90* bends. Not saying that's optimal for your car (or even ours) but some variation of that is what we ran. |
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| Charles Freeborn |
Feb 22 2020, 12:43 AM
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#7
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Member Group: Members Posts: 244 Joined: 21-May 14 From: United States Member No.: 17,377 Region Association: Pacific Northwest |
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