Header upgrade

gumper said
Thinking of upgrading my 1 5/8 Hooker Competition headers while my engine is pulled. Curious if there would be a significant power increase by using a larger primary tube setup. This is what I have:
408, around 11.6:1
Ported Performer RPM heads
65cc chambers, 270/232 @.500, 280/240 @.600
Solid cam, 250/254 @.050, 588/600 lift, .010/.012 lash
Rons toilet injection on alcohol
Timing set at 35*
Manual VB 727 with ~4800 stall 8” converter
4.30 gears, 28x10.50 tire
Weighs 3250 with driver

It had a Mopar purple .557, [email protected], .028/.032 lash solid cam that I am replacing with the new one listed above. The old cam was running at 4* retarded. Hopefully the new one works better. Best the car ever ran was 11.01@119 in Seattle. We mainly race at a 1/8 mile track with a 5300’ elevation running 7.20-7.30. Want to run 7.0-7.10.

Like I said it has 1 5/8 hookers into 3” collectors connected to a 3” x-pipe dumping in front of the axle. Was looking at TTI stepped headers, or their 1 7/8. Using a manual steering box, and not using the factory shift linkage. Also looking at ditching the torsion bars for coil overs. Don’t want to cut out the inner fenders.

There was a set of 1.875 TTI headers for sale here on FABO.

I have tested step headers, merge collectors and step headers with merge collectors until I was sick of it, and neither the step or the merge collectors did squat.

You didn’t mention the LSA...I hope it’s not more than 109. Even with those heads, 109 is about as wide as it should be before you start giving up ET in the gear changes.

IMO, if you are going to do a step header, or use merge collectors or use a 4-2-1 header, you have to develop and make everything work with those styles of headers and collectors. I know the 4-2-1 headers use a very small primary tube and that design with a merge collectors will seriously over scavenge the chambers. So you need to know that and make the cam timing for that system. I think a 1.875 primary with a 3.5 inch collector is a must. A 3 inch collector is way too small for use with mufflers.

Also, keep in mind almost every header has a collector that is too small and way too short. If you are running full exhaust, it should be collector diameter all the way back. If you aren’t running full exhaust the collector should be about 18-24 inches long as a start and test from there.

That’s what I’d do. Also, if by some stretch of luck, you can find a set of Hooker 5303 headers i would buy those. It’s what I run, on 340 inches. They are like hens teeth, but I’ve used enough of them that I know they work. I’ll also be on the dyno hopefully by June, and I’ll test the 1.875 headers against a set of 1.750 headers I have access to, just to show that big headers dont kill torque.