LQ4 Exhaust
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Teching In
Joined: Oct 2016
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From: O'Fallon, MO
LQ4 Exhaust I am building a 55 Chevy truck. A stock LQ4 is now mounted in there. I am contemplating using the stock manifolds. I am possibly considering installing a cam with a mild lope. I am reusing the stock intake with the injection.
How much gain would there be with long tube headers compared to the stock but ported manifolds?
How much gain would there be with long tube headers compared to the stock but ported manifolds?
Teching In
Joined: Nov 2016
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Changing the cam requires tuning on the ECM. I'm sure there are a few threads in here about a 6.0 and LS6 cam.
tfi racing said it, 15-20 with some 3" exhaust pipe out the back. Your engine is a big air pump, so with some free flowing exhaust there is some power to be gained.
I'm a bit behind you, just pulled the donor LQ4 from an 06 van. The end sound is more of a concern with me then the extra HP as mine is going to be for cruising, maybe a drag or two just to know what it will do. I like the idea of the Dynomax VT muffler, get the open pipe when needed and no drone when cruising.
Need to find someone that is using them before I go that route.
tfi racing said it, 15-20 with some 3" exhaust pipe out the back. Your engine is a big air pump, so with some free flowing exhaust there is some power to be gained.
I'm a bit behind you, just pulled the donor LQ4 from an 06 van. The end sound is more of a concern with me then the extra HP as mine is going to be for cruising, maybe a drag or two just to know what it will do. I like the idea of the Dynomax VT muffler, get the open pipe when needed and no drone when cruising.
Need to find someone that is using them before I go that route.
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I am building a 55 Chevy truck. A stock LQ4 is now mounted in there. I am contemplating using the stock manifolds. I am possibly considering installing a cam with a mild lope. I am reusing the stock intake with the injection.
How much gain would there be with long tube headers compared to the stock but ported manifolds?
How much gain would there be with long tube headers compared to the stock but ported manifolds?
Mine will be stock as I plan to use it as my daily driver when I retire at the end of 2017 (we'll see). Using stock exhaust off a C5 Corvette, they ought to flow plenty since a stock Vette runs a lot more horsepower than my engine will. We're guessing somewhere over 300hp, but that's plenty compare to the little 283 (with a weak cylinder) that was in there!
Here are mods made to the exhaust manifolds. We'll be using 2-1/2" all the way back with flow-through style mufflers and an "H" pipe or "X" pipe. I'm going stock but if there's much advantage to be gained with the X over H approach, please let me know.
Here's a photo of one exhaust manifold. I plan on doing some clean up, remove the EGR mount and will have them Jet Hot coated. I've no experience with it but I hear it won't discolor with het cycles even after time.
Last edited by Dan Estrada; Nov 19, 2016 at 10:37 AM.
for what its worth my dad races a 74 gto with 98 5.7 ls with a mild cam with manifolds it ran 11.98.....with stainless long tubes it ran a best of 12.19, mostly 12.20s, weve tried jets timing ect, the stock manifolds arent bad!
ok another example,1970 chevelle my friend had 454 auto stock manifolds, he had me put on hooker super comp headers 2 1/8 primary tubes 3 1/2 colectors 1 tube goes outside frame $730 .........it ran no faster et, or mph not at all. it was a mild motor but nothing?
Launching!
Joined: Jul 2016
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You can read a little bit about that right here - and, if you want to see an example of that being taken to an extreme, you can see that in this article. (Wild, huh?)
Going from memory, the test results for LS headers I've seen over the last few years is this:
- Shorty headers seem to be roughly equivalent to manifolds - sometimes a small gain (on the order of 4 or 5 HP) sometimes none;
- Mid-length headers (depending on the design) will sometimes provide a gain of 7 - 10 HP - and not infrequently, more like 5 - 8 HP;
- Long-tube headers provide the best return for your money/effort - those gains seem to be around 20 -25 HP.
Personally, I'm not sure that I'd even bother with the shortys or the mid-length headers (unless maybe it was a mild street build where space was really a factor, like a Vega/Chevette/Monza/etc.)
(EDIT: Another mildly-technical header design article from Hot Rod magazine is available right here.)
Last edited by Cheese Weasel; Nov 21, 2016 at 11:29 PM. Reason: Added another link
