Justhereforinfo

iTrader: (2)

I want to be absolutely sure about this subject before I move away from the 4.8 and go out to find a 6.0 engine.

Why cant the l92 heads (that are made for a 4.0 bore) be fitted to a 3.78 bore 4.8 or 5.3?

Is it because the valves might have very little clearance coming down into the cylinder? If that is the case, has anyone tried measuring the clearance and using a thicker head gasket with a 4.0 bore? Or will a 4.0 bore gasket not seal a 3.78 deck? (in sbf world I have used 4.125 gaskets on 4.030 bores)

Or does it have more to do with the valves being partially shrouded by the cylinder walls and effecting flow?

I know most people say it cant be done, but I'd like to know exactly why.

Thanks

KCS

iTrader: (20)

Valves physically won't fit.

Tainted

iTrader: (9)

The l92s still arent what id call 'ideal' on a 4.0 bore either

Justhereforinfo

iTrader: (2)

Alright alright, I'm moving on.

They will work on a stock bore lq4 though, right?

PREDATOR-Z

Why push the envelope?
Look, why do you want L92 heads?

ZONES89RS

iTrader: (25)

Just bore the 4.8 to 4 inches. Then you can say it works.

Tainted

iTrader: (9)

Yes, minimum of 4.0 bore

batboy

iTrader: (6)

The intake valve on the L92 heads will hit the cylinder walls. It will not fit. Also, the L92 head are not made for a 4" bore, they are made for a 4.065" bore. The minimum bore size is 4" although there is still a fair amount of valve shrouding with a 4" bore. If you do get a LQ4 or LQ9 and HAVE to use L92 heads, at least bore the block out to 4.030".

bww3588

iTrader: (49)

The l92's were designed for a 4 inch bore. The first engine they appeared on was the ly6 and the l76. They later appeared on the ls3 and l92.

batboy

iTrader: (6)

Yes, the L92 heads were used on 6.0 L engines like the L76. They appeared on the L76 only a few months before the L92 was released. That does not mean they were designed for the 4" bore. The L92 is basically a sibling of the LS7 head made for the L92/LS3 engines. I'm sure GM also wanted them to fit the 4" bore too, but that was probably secondary consideration.

PREDATOR-Z

Those heads were meant for 4.060 bore, yes they appear to work on 4.0 but shrouding becomes counterproductive.

MPFD

iTrader: (5)

I think that's speculative... Even shrouded the l92 head can flow more air.

Justhereforinfo

iTrader: (2)

Sorry, didn't realize this post got any attention. I was under the impression those heads were a good bang for your buck. I found a lq4 short for $550, and refurbished l92 heads for $700. I figured with the right cam and intake it might make over 400-450 at the tires.

Am I too far off?

redtan

iTrader: (5)

You can make that much power on an LQ4, although with a compression in the mid 9s it's going to be a dog down low. That's a good combo for a budget low boost FI setup as the compression is low and the slow lazy ports of the L92 will be overshadowed by the forcing of air into the engine by a turbo or supercharger.

If I were you, I'd stick with some milled 243s for less money and used the extra cash you saved over L92 heads for a fast intake. That will make just as much power and be an overall better driver.

Justhereforinfo

iTrader: (2)

Thanks for the suggestion. What is the minimum bore with the 243 heads? I'm asking because I see complete 5.3's for sale for less than the lq4 short block.

Can 400whp be made easily with a 5.3?

96capricemgr

iTrader: (1)

The 243/799s are stock on later 4.8 and 5.3l engines so the minimum bore is smaller than anything GM offered in the gen 3-4 blocks.