8.1 w/stainless works headers add crossover or not?
02-25-2015, 09:37 PM
#21
Staging Lane
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Descreened the MAF, a noticeable improvement, dumped the POS stock muffler, you would think that the stock dual 3" in and dual 3" out would flow pretty well, but its trash! The "outlet" towards the driveshaft side is simply a resonator chamber with little flow! Looked at the Magnaflow, but it only has 2 1/2" internal tubes! Why bother? I ended up installing my favorite mufflers, (Dynomax 3" Super turbos #17769 after flowing a bunch of promising mufflers that didn't deliver. The pair of them flow over double what the stock muffler flows. I made a nice two 3" into one 4" transition that goes into a universal Dynomax 4" diesel tailpipe. On the flowbench the transition/ tailpipe/ Dynomax combo still flows just a bit more than double what the stock muffler/ tailpipe flowed. The results were nothing short of dramatic!!!!! The muffler/ tailpipe gains were worth more than the headers!!! Total modifications so far: Air box sound deadening vanes removed, inlet to airbox opened up in box and fender, outlet radiused (generously), K & N stock replacement air cleaner element, MAF screen removed, air crossover tube heated and clearance notch removed(think airfow QUALITY into the throttle body), throttle body ported(gained about 100 cfm and will bore it later), Superchips tuner with 87 octane tune installed(I'm cheap! so what?), Stainlessworks 1 7/8" headers, 2 Dynomax 17769 mufflers, and 4" diesel tailpipe. Results, A TIRE FRYING S.O.B!!! I can roast them all through 1st gear and into second! If I leave it in drive, it will upshift to second and sometimes into third while spinning them, and while not moving too far! Not very scientific, but a serious improvement. Tires are 285-70/17s and the gears are stock 3.70s. I will be looking at wider tires/ wheels soon! I have some different ideas on the intake manifold mods and will report when completed (I live on my Superflow 600 Flowbench!) Others philosophy may vary, but I have had a hi-performance machineshop since the early 80s and been dragracing since 1968. I prefer to do all of the external bolt ons and mods first (on a running vehicle), then I go inside the engine. My experience is if you go inside first and don't do the external stuff you will always be disappointed. If you can't get the air into and out from the engine, what happens inside is not as important. I've seen many good engines strangled when the money ran out before the externals were finished. Just my opinion/observation. P.S. I couldn't spin the tires more than 8-10 feet before the mods. TIMINATOR (and I earned that handle)
Last edited by TIMINATOR; 02-25-2015 at 10:07 PM.
02-28-2015, 01:02 AM
#22
Staging Lane
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adapter
The stock intake manifold necks down after the throttle body flange from a 78mm opening at the throttle body to a roughly 55mm opening before opening back up into the plenum of the intake manifold. You can throw all the breathing mods (K&N, bigger MAF, ported throttle body, etc.) you want at the engine, but you're always going to be limited by the stock intake manifold.
Vortec 8100 8.1L Modified Stock Intake Manifold - Raylar Engineering
After you modify the intake manifold, you can run any 3bolt to 4bolt adapter to run an LS2 style throttle body. You will need a wiring adapter to make the 4 bolt style throttle body work with your existing wiring / computer.
We swapped our stock manifold for the modified stock manifold with the LS2 throttle body and made 25hp with stock cylinder heads. You'll make even more with aftermarket units. Here's a video with a dyno comparison of the stock heads with stock manifold versus with modified on our 540 suburban:
http://www.youtube.com/watch?v=cfu_c3XlAog
And just in case you have a lot more questions, here's Larry on the intake manifold options for the 8.1L engine:
Vortec 8.1L / 496 Intake Manifold Information & Installation - YouTube
Vortec 8100 8.1L Modified Stock Intake Manifold - Raylar Engineering
After you modify the intake manifold, you can run any 3bolt to 4bolt adapter to run an LS2 style throttle body. You will need a wiring adapter to make the 4 bolt style throttle body work with your existing wiring / computer.
We swapped our stock manifold for the modified stock manifold with the LS2 throttle body and made 25hp with stock cylinder heads. You'll make even more with aftermarket units. Here's a video with a dyno comparison of the stock heads with stock manifold versus with modified on our 540 suburban:
http://www.youtube.com/watch?v=cfu_c3XlAog
And just in case you have a lot more questions, here's Larry on the intake manifold options for the 8.1L engine:
Vortec 8.1L / 496 Intake Manifold Information & Installation - YouTube
03-02-2015, 05:22 PM
#23
On The Tree
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You can only flow as much air as the weakest link in the chain. There is no benefit to the 90mm throttle body (or even the 78mm for that matter) until your intake manifold has been internally modified. At that point, you will be able to run either the 78mm (stock) or the 90mm (modified) throttle body and actually see gains from the swap.
03-02-2015, 10:29 PM
#24
Staging Lane
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Im
Raylar Engineering, of course!
You can only flow as much air as the weakest link in the chain. There is no benefit to the 90mm throttle body (or even the 78mm for that matter) until your intake manifold has been internally modified. At that point, you will be able to run either the 78mm (stock) or the 90mm (modified) throttle body and actually see gains from the swap.
You can only flow as much air as the weakest link in the chain. There is no benefit to the 90mm throttle body (or even the 78mm for that matter) until your intake manifold has been internally modified. At that point, you will be able to run either the 78mm (stock) or the 90mm (modified) throttle body and actually see gains from the swap.
03-02-2015, 11:31 PM
#25
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Tb
Raylar Engineering, of course!
You can only flow as much air as the weakest link in the chain. There is no benefit to the 90mm throttle body (or even the 78mm for that matter) until your intake manifold has been internally modified. At that point, you will be able to run either the 78mm (stock) or the 90mm (modified) throttle body and actually see gains from the swap.
You can only flow as much air as the weakest link in the chain. There is no benefit to the 90mm throttle body (or even the 78mm for that matter) until your intake manifold has been internally modified. At that point, you will be able to run either the 78mm (stock) or the 90mm (modified) throttle body and actually see gains from the swap.
OK just picked up a ls2 ctsv tb 90mm and the adapter plate for it I found on ebay. Is this the correct wiring and adapter plate?
Harness Adapter for LS2 Throttle Body on LS1 Vehicle
http://www.ebay.com/itm/Manifold-Adapter-Plate-92MM-4-Bolt-To-3-Bolt-THROTTLE-BODY-LS2-To-LS6-/131420686948?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e99488a64&vxp=mtr
Last edited by d-bo71; 03-02-2015 at 11:38 PM.
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