View Poll Results: Primary Size for my 402 ci?
1-5/8"
1
11.11%
1-3/4"
8
88.89%
Voters: 9. You may not vote on this poll
Help With Header Selection
03-12-2011, 10:16 AM
#1
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Help With Header Selection I don't want to spend money on header selection software so I am here seeking assistance. I am not of the mind that 'bigger is better' and want to make a realistic choice. I want Tri-Y headers to get a broad power band but they limit me on the choice of primary and collector size.
I have a 2002 ChevyTahoe as a daily driver and use it every weekend for mild off-roading and occasional towing. It is not a lite truck as it has aftermarket bumpers, winch, etc............. totaling about 5,800 pounds. I just completed a new motor and transmission that will drive a 14 bolt SF with 4:10 gears on 33" diameter tires.
Here are the basics:
Motor
402 ci. LQ9 iron block (4.005" bore X 4" stroke)
10.5:1 compression ratio
Stock L92 heads
L92 Intake manifold
92mm FAST air door
228/238 .571”/.585” 113LSA +4 advance cam spec'd by Guerra Motorsports
Transmission
Built 4L80E
2400 stall torque converter
There only appears to be three companies right now that make Tri-Y headers. Stan's, Thorley and True Image. They all are 1-5/8" primaries except True Image that will do 1-3/4" primaries on request. But they all have 2-1/2" collectors. I prefer ball flanges but don't know if they restrict flow.
I am not racing this vehicle and it will rarely see high rpm except when getting on the freeway or just showing off my stuff if you know what I mean.
Or should I stay away from Tri-Ys and just get some 4-1 LT headers? Anyways, I look forward to recommendations!
I have a 2002 ChevyTahoe as a daily driver and use it every weekend for mild off-roading and occasional towing. It is not a lite truck as it has aftermarket bumpers, winch, etc............. totaling about 5,800 pounds. I just completed a new motor and transmission that will drive a 14 bolt SF with 4:10 gears on 33" diameter tires.
Here are the basics:
Motor
402 ci. LQ9 iron block (4.005" bore X 4" stroke)
10.5:1 compression ratio
Stock L92 heads
L92 Intake manifold
92mm FAST air door
228/238 .571”/.585” 113LSA +4 advance cam spec'd by Guerra Motorsports
Transmission
Built 4L80E
2400 stall torque converter
There only appears to be three companies right now that make Tri-Y headers. Stan's, Thorley and True Image. They all are 1-5/8" primaries except True Image that will do 1-3/4" primaries on request. But they all have 2-1/2" collectors. I prefer ball flanges but don't know if they restrict flow.
I am not racing this vehicle and it will rarely see high rpm except when getting on the freeway or just showing off my stuff if you know what I mean.
Or should I stay away from Tri-Ys and just get some 4-1 LT headers? Anyways, I look forward to recommendations!
Last edited by Duntov1967; 03-12-2011 at 10:24 AM.
03-13-2011, 07:09 PM
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Wow. I am a bit surprised at the larger primary suggestions. A 402 ci. isn't that big of a motor. But I am listening and look forward to other responses. Thanks!
03-13-2011, 08:55 PM
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Go with your gut. The tri y is the correct choice for a truck because low-mid range is way more important than top end. The 1 3/4" tri y would be a perfect fit for your 402.
04-11-2011, 10:46 PM
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Well, I made my decision. I went middle-of-the-road with some American Racing headers with 1-3/4' primaries and 3" merge collectors along with dual non-cat mid-pipes designed for the 6.0 trucks. Thanks for all the input!
