BLACKND

iTrader: (5)

Ok, someone has to know some of this stuff. I have searched all over the net and probably 3 dozen forums and websites. I have come up with a lot of useful knowledge on the new 07+++ Gen IV engines, but still looking for 2 or 3 bits of info.

Maybe one of you GM Tech guys might know.

My focus is mainly on the LY2--4.8 liter as thats what my truck is. I am trying to find out what the stock cam specs are on this truck, I know that it shares the Gen IV--LS2 Architecture, but has many of the same specs as the Gen III--LR4(4.8 liter)--so is the cam specs the same as previous 4.8's or have they changed them up.

Also, are they using a different intake manifold from previous years--I believe they are, but can't confirm or deny. And if so, are the new manifolds shared through-out the gen IV lineup a-la 4.8/5.3/6.0/6.2? I believe the 6.2 uses its own Intake manifold with the 90MM TB. And last What size Throttle body is being used stock on the new 4.8/5.3/6.0? I have read an article that mentioned use of a new 87 MM throttle body on the 5.3 and 6.0's, wondering if that was shared on the 4.8's if that is in fact truthful, the source where I found this was not from GM so I don't know that it is necessarily reliable.

Just trying to obtain as much technical info about them as possible to see what will and won't work.

nighthawk08

couldn't you go to your truck and measure your TB?

the cam specs would be a bit harder.

BLACKND

iTrader: (5)

Well, yeah as far as the TB I could do that, might not be quite as accurate, but would give me a general idea. But the cam would certainly be more difficult.

Bo185

I thought the 5.3L and 4.8L use a GEN III head with updated intake not L76/L92 based, but has a larger TB than the earlier.

nighthawk08

LS6 based heads

the 5.3 has the 90 mm TB/intake manifold. which is probably the same part as the LS2 TB intake manifold.

BLACKND

iTrader: (5)

You are correct on this thinking, but I haven't confirmed the larger TB size. Mine is equipped with 243 casting heads, Gen III LS6ers.

niugnep

I don't know what the previous ones were but the 07 is 0.283" lobe lift on both intake and exhaust. I have a pdf of all the 4.8L specs saved for you here if you want it PM me with your e-mail (it is GM service manual stuff).

Hope that helps...

RWC

iTrader: (5)

The same intake manifold assy is used on the 06 and 07 Trailblazer LS2, the new 4.8L, 5.3L and is a good improvement over the older truck manifold. The new 6.0L and 6.2L use a different manifold. I have not measured the new 4.8L 4 bolt TB yet but it shares the same intake as the 5.3L and should be the same TB. The 5.3, 6.0L and the 6.2L in the trucks use the same 87mm TB (measured across the blade along the shaft), including the TB LS2. I don't think they would need to have a different one just for the 4.8L. The car LS2 - LS7 TB measures 90mm. The "new" manifold assy seems to flow reasonably well when you look at what has been done with the modded LS2 Trailblazers using this same setup.

Bo185

So the L76/L92 TB is 87mm? I wonder if the 90mm one would fit?

RWC

iTrader: (5)

The L92 and the L76 truck are 87mm. Yes, the 90mm bolts up, the plug fits and it opens manually at least on the 07 LS2 TB manifold. I don't know if it will work without programming or modifications though. I have heard it will work on some Trailblazers but am unsure what it takes to make it work, if anything. I have both for a future project on my truck.