L-92 Cylinder heads, best bang for the buck for your LS2 block. - F-Body Online

SpecialK · 12-23-2006, 05:38 PM

Quote:

When he LS7 was first being developed, it's cylinder bore was not 4.125 inches. We kind of grew into that diameter as we pushed the envelope further and further and learned more for theC5R guys. We finally decided that more cubes would be needed to meet the 500 hp goal, and it's at that point that we divorced ourselves from teh smaller bore prototype casting.

Here are some flow chart numbers.

Lift Intake Exhasut
.1 79.2 57.8
.2 153 114.4
.3 225 147.2
.4 276 170.3
.5 309.6 183.1
.55 323.2 186
.6 332.2 189.5
.65 327.7 191.1
.70 330 192.6
.75 317 195
.8 317 195.8

The L92 heads are the initial design for the LS7 to be short. Although they are cast, and not machined in any way normally. They will bolt up to any LS block without many changes. And if you have a LS2 block there are even fewer changes to be made. But there are thing that need to be changed so you can make them fit, as they aren't a direct bolt on replacement.

First the head was designed for a 4.065 cylinder diameter and were designed to fit on bores as small as 4.00 (so us LS-1 guys have to bore our cylinders out) so they would be compatible with the current truck offerings. Also before you bolt these heads down make sure you have a set of gaskets sized for a 4.065 bore this is thanks to the l-92 head overhanging slightly on the cylinder liner on a 4" bore so you don't want to cook your gasket so just buy the right sized gasket's and you won't have a problem.

The only drawback to using these heads though. is you will HAVE to use a dedicated L76 manifold (Lets hope FAST gets on the ball here and makes a intake for these heads.) because the hight intake prort floors mean they won't match up on the with your conventional LS intakes. Also you'll need to make sure your exhaust ports match up thanks to the L92's slightly taller port.

Finally you will have to purchase a set of offset inlet rockers (PM part #12569167 less than $10 a piece) and all your original hardware otherwise can be reused on a set of bare heads. Which should go for $175 a pop. (PN 12582714 ) and assembled heads are $400 a piece. ( PN 125582713 )Also be aware that the assembled heads use a LS-1 style valve-springs, retainers, and locks. So any kind of aftermarket cam will wreak havoc on the top end keeping up unless you spring for a set of stiffer springs. The L72 intake is off the Holden V8 or part number 12590123 for those of us that don't live in the OZ.

Slowass · 01-30-2007, 04:30 PM

Was considering these until I read up on the intake manifold not fitting the same.
Almost cried.

SpecialK · 01-30-2007, 08:42 PM

Quote:

Originally Posted by Slowass

Was considering these until I read up on the intake manifold not fitting the same.
Almost cried.

Yea, that really killed me too. I don't want to have to give up this wonderful intake I have now.

BaD AZz Z/28 · 01-31-2007, 10:36 AM

An LS1 block would need more than a bore to be able to use these heads, you would need to have it resleeved to get it big enough. They just didnt leave enough meat in those stock liners. Not worth the price on an LS1, better off buying a new 6.0 block.

The L76 intake is actually a killer deal. It will flow LS6 level or better (FAST is usually a waste of a grand anyway), and it comes with 42lb injectors and a 90mm TB. The price is practically worth it for the injectors alone. The throttle body it comes with is drive by wire though, so sell it online to some GTO/Vette guy and buy a normal 90mm one.

They also make an L92 carb style intake that you can get direct from GM, but despite what the magazines say, the numbers Ive seen support the idea that the L76 plastic intake flows MUCH better until 6800+ rpm

The intake to exhuast flow on these heads is a bit unusual, over 140cfm difference at its max intake flow, but some porting has brought the exhuast up to where it needs to be, so atleast it is possible to straighten them out. Definately a killer deal for the money.

SpecialK · 02-01-2007, 03:44 AM

Didja not read my post Scary :P I stated you had to bore out to 4" to get them to fit.

It might be an option for guys rebuilding their LS1s tho cause that's a lot cheaper than buying an entire 6.0 block.

BaD AZz Z/28 · 02-01-2007, 11:22 AM

Quote:

Originally Posted by SpecialK

Didja not read my post Scary :P I stated you had to bore out to 4" to get them to fit.

It might be an option for guys rebuilding their LS1s tho cause that's a lot cheaper than buying an entire 6.0 block.

A 6.0 block is still going to be much cheaper. To rebuild an LS1 with a large bore, its $1400 just for the new sleeves, plus the labor for a machine shop to do it, and not many have the ability to do it.

Then you may still have other machining costs, cam bearing install, etc depending on what you need done.

You could get an iron or aluminum block brand new for well less than that. And since you may want to have it gone over at the machine shop anyway, buying a used one may get you some extra goodies thrown in (crank, gaskets, covers)

If you have an LS1, its best to sell it off whole and get a new block to run L92 stuff because the LS1 bore is just too cost prohibitive. But with 6.0 blocks becoming so available now, GM is making it way too easy to go fast with this L92 stuff. I already have some AFR 225s for my 6.0 block, and Im sticking with them because they have a thick deck and great exhuast flow, but we'd like to build another 6.0 with L92 setup to see what its got