header primary size on a 496
+4
dfree383
crittersf1
rmcomprandy
72mav
8 posters
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header primary size on a 496
Hi guys,
Whats everyones thoughts about this? 2-1/8, or 2-1/4?
Engine is a 496 with SCJ heads with a 780/720 lift cam, compression will be 13+, stock valves with a 30degree back-cut on the intake valves. and a light cleanup on the ports for now.
Also planning on step design headers with merge collectors. I don't plan on taking it over 7200 RPM
Thanks.
Al
Whats everyones thoughts about this? 2-1/8, or 2-1/4?
Engine is a 496 with SCJ heads with a 780/720 lift cam, compression will be 13+, stock valves with a 30degree back-cut on the intake valves. and a light cleanup on the ports for now.
Also planning on step design headers with merge collectors. I don't plan on taking it over 7200 RPM
Thanks.
Al
72mav- Posts : 1081
Join date : 2008-12-03
Age : 61
Location : central Michigan
Re: header primary size on a 496
72mav wrote:Hi guys,
Whats everyones thoughts about this? 2-1/8, or 2-1/4?
Engine is a 496 with SCJ heads with a 780/720 lift cam, compression will be 13+, stock valves with a 30degree back-cut on the intake valves. and a light cleanup on the ports for now.
Also planning on step design headers with merge collectors. I don't plan on taking it over 7200 RPM
Thanks.
Al
Header tube size is mostly reliant upon RPM level and the cylinder size.
That header is to big unless you intend to be above 7,000 RPM most of the time.
Re: header primary size on a 496
I'm with Randy. 1 7/8's are probably more than enough.
crittersf1- Posts : 521
Join date : 2009-10-28
Re: header primary size on a 496
2" or 2 1/8" IMO
The bigger stuff will make bigger numbers upstairs.
The bigger stuff will make bigger numbers upstairs.
dfree383- BBF CONTRIBUTOR
- Posts : 14851
Join date : 2009-07-09
Location : Home Wif Da Wife.....
Re: header primary size on a 496
Too much cam, headers too big, too much rpm.jmo
bbf-falcon- Posts : 8995
Join date : 2008-12-03
Location : Jackson, Ohio
Re: header primary size on a 496
bbf-falcon wrote:Too much cam, headers too big, too much rpm.jmo
Too much cam? The OP did not supply any duration figures.
13+ CR and almost 500" can support a reasonably "big" camshaft for 7000 rpm limit.
2" header primaries will certainly work fine.
68galaxie- Posts : 351
Join date : 2010-04-13
Location : Edmonton AB
Re: header primary size on a 496
Personally Al I like the 2 1/8 I figure it is always better to have to much header than not enough....
the Coug- Posts : 3055
Join date : 2008-12-02
Re: header primary size on a 496
bbf-falcon wrote:Too much cam, headers too big, too much rpm.jmo
No cam yet. That 780lift is a guess, somewhere 700 and 800 for sure though.
Another small motor member here was running a735 lift @7100 RPM. thought......
Btw, guys thanks for the info.
Regards.
Al
72mav- Posts : 1081
Join date : 2008-12-03
Age : 61
Location : central Michigan
Re: header primary size on a 496
2" Primaries IMO.
D. Sea- Posts : 2768
Join date : 2008-12-02
Age : 55
Location : Kentucky
Re: header primary size on a 496
bbf-falcon wrote:Too much cam, headers too big, too much rpm.jmo
Rick why you say to much RPM? I spun my stock offset crank 7800 for 10 + years, and still looked like brand new when it went East to Kentucky
the Coug- Posts : 3055
Join date : 2008-12-02
Re: header primary size on a 496
Not saying it won't spin that far,just sayin imo that a pretty much stock scj head doesn't need that much cam or rpm's.
bbf-falcon- Posts : 8995
Join date : 2008-12-03
Location : Jackson, Ohio
Re: header primary size on a 496
bbf-falcon wrote:Not saying it won't spin that far,just sayin imo that a pretty much stock scj head doesn't need that much cam or rpm's.
That ain't no big cam..... and shifting at 7200 is about right for an engine peaking at 6700....
dfree383- BBF CONTRIBUTOR
- Posts : 14851
Join date : 2009-07-09
Location : Home Wif Da Wife.....
Re: header primary size on a 496
I think he has aluminum SCJs
the Coug- Posts : 3055
Join date : 2008-12-02
Re: header primary size on a 496
That ain't no big cam..... and shifting at 7200 is about right for an engine peaking at 6700....
Now i know why you race dyno's instead of cars.
Now i know why you race dyno's instead of cars.
bbf-falcon- Posts : 8995
Join date : 2008-12-03
Location : Jackson, Ohio
Re: header primary size on a 496
bbf-falcon wrote:That ain't no big cam..... and shifting at 7200 is about right for an engine peaking at 6700....
Now i know why you race dyno's instead of cars.
A step header with 2" to 2 1/8" primary tubes 31 inches long with a 3 1/2" diameter collector 17 inches long is the correct size for a 496 engine at 7,000 RPM ... on a dyno OR a drag race car.
USE a 2" straight tube header primary if the RPM level EVER drops below 5,000 RPM.
Re: header primary size on a 496
rmcomprandy wrote:bbf-falcon wrote:That ain't no big cam..... and shifting at 7200 is about right for an engine peaking at 6700....
Now i know why you race dyno's instead of cars.
A step header with 2" to 2 1/8" primary tubes 31 inches long with a 3 1/2" diameter collector 17 inches long is the correct size for a 496 engine at 7,000 RPM ... on a dyno OR a drag race car.
USE a 2" straight tube header primary if the RPM level EVER drops below 5,000 RPM.
And that's what I learned from all the dyno time......
When's the last time your car was on the track Rick?
dfree383- BBF CONTRIBUTOR
- Posts : 14851
Join date : 2009-07-09
Location : Home Wif Da Wife.....
Re: header primary size on a 496
One thing I learned in 40yrs of racing is that just because my engine will rev to 8k, that's no reason to shift it there . and a dyno is not a racecar.
bbf-falcon- Posts : 8995
Join date : 2008-12-03
Location : Jackson, Ohio
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