Head Choice for LQ4 build

[Rhino]

I'm currently rebuilding an LQ4 for a heavy Avalanche DD. Since it's a DD, and I also due tow with it occaisionally I'm looking for low end torque. I'm not at all interested in the sound at idle, nor HP peak. I have a number of heads that I could use, and wanted to get a few other opinions as to what you'd run. I'm using the Vinci Butt-kicker (210*/218* @ .050 .551/.551 lift on 116 LSA), Ls7 lifter, and GM replacement MLS gasket at .051 compressed. My main concern is that mid-grade around my area is 89, premium is 91. I'm looking for something that could regularly use 89 without too much worry. Obviously I could knock a few degrees timing out of the low octane table, which I intend to do. My Choice of heads is as listed below: LE2 ported 853's - 2.02/1.60 valves, 63cc chamber - Net SCR of 10.41:1 Patriot Stage 2 5.3's 2.02/1.60 valves 64.5cc chamber - Net SCR of 10.23:1 Stock 241's - 66.7cc chamber - Net SCR of 10.0:1 317's cut .015 - 69cc chamber - Net SCR of 9.7:1 What heads would you run? I'm really tempted to do either the stock 241's or slightly milled 317's since I have other projects I'd like to put the ported heads on.

[180ls1]

L92's i know it is not in your option list but that would be my first choice. They are inexpensive and flow like crazy.

I would also look into a little bigger cam like a 224/224 on 114, you wont even know it is there and will gain a good amount of power over the cam you have now.

[novaflash2002]

smaller intake valve will yeild more lower rpm torque on average. id stick with thw 317s

[Rhino]

I would agree that the L92's aren't a great choice for this setup. I did actually look into it. If this motor were destined for a car, I think that'd be my top choice. In this scenario it seems I would get minimal gain and it would more than double the cost even before looking into intake and exhaust changes.

The one thing that I'm not certain of is if the added airflow of the 317's is worth the .3 drop in compression. As I've always understood it, an increase in compression will yield an across the board increase in torque.

[180ls1]

Originally Posted by Rhino

I would agree that the L92's aren't a great choice for this setup. I did actually look into it. If this motor were destined for a car, I think that'd be my top choice. In this scenario it seems I would get minimal gain and it would more than double the cost even before looking into intake and exhaust changes.

The one thing that I'm not certain of is if the added airflow of the 317's is worth the .3 drop in compression. As I've always understood it, an increase in compression will yield an across the board increase in torque.

ok, also added compression will help gas mileage because of the increase in partial throttle power.

[Rhino]

I hadn't really thought about it from a gas mileage perspective. That is a very valid point. My cam selection is pretty mild, so I don't think I'll be losing much, if anything, there.
I've also done a little further research on octane and compression on these motors. I think I may be a little overly worried. Looking at the newer Gen IV motors, they're pushing close to 11:1 stock in some applications.

With that all said, it does make sense to use one of these better sets on my current build where they'll be better utilized. Does anyone think running 10.2 or 10.4 on mid-grade pump gas would cause any issues?

[180ls1]

its all in the tune but you would be fine with that compression, and your cam will not effect your gas mileage at all. I remember reading about a guy who installed a 224/220 116 cam and actually increased his gas mileage over the stock cam.

[garygnu]

run l92 heads and a EPS cam,or consider comp54-455-11.you mite be able to tune for 89 oct,just watch the knock sensor and adjust timing to work.

[Beatdown Z]

Either mill the 317's and/or use thin head gaskets or get a set of 243/799 heads. That Comp cam garygnu posted would probably work good for you, even with cathedral port heads.

[Rhino]

The supply of 243/799's has totally tried up around my area. IMO, prices on here are a little over inflated compared to local prices. Due to that, I'm left with these choices. These are heads I already have sitting around, and I think at least one of them should work for my purposes.

I thought about a thinner gasket on the 317's, but the LQ4's piston to deck height is, on average, is .007 out of the hole. With a .036 gasket (Thickest Cometic I could find) my quench would only be .029. That's running it a little too close in my opinion.
I would mill the 317's further, but I haven't found a shop locally that's able/willing to also cut the intake side down for proper intake fit.

What gasket are you running on your LQ4?

[garygnu]

54-455-11 is a 5.3 lsr cam ,recomended for torque ,witch would be a ls1 head port.won't need much gears or stall .get the 241s if you are on a budget.