I'll correct him just a little here, it's only around a 5700lbs curb weight lol.

But still it's a heavy truck, you can max it to around 8600 GVWR because it's a 2500 though.

 

Yeah, weighed in around 6100 with me in it (225lbs) Do a lot of driving with all 7 seats filled with adults so I'm probably not far off max. Still outruns half of everything else on the road... somehow. New heads would be a good option, it does have 190k on it. Gives me a chance to inspect the rest of the block. I'd like to be at least 600hp at the crank if I do the stroker. Will the 243/799 heads support that?

 

imo no not unless you spend a tone getting them ported. 243/799 are probably the best oem heads that are out there right now but at that power level go aftermarket.

also the cams i said should be good for when you do stroke it later.

this is for the 5.3l but should be good reading for you too if you want to make power.

The "recipe" to 500 rwhp with heads and cam. - LS1TECH

 

Where will the compression ratio be at on a 6.0 with 5.3 heads? I'd prefer for this truck to run on 87, if it's all that's available. If they would work, there is a set of ls1 heads near me for a good deal in good condition. What would be my gains with those?

 

what heads you have now? im hoping 317's

stock you have about a 9.4:1 compression
with un-milled 243/799 heads (64.5cc chamber) would be around 10.2:1 compression with a .051 head gasket.

would recommend starting with premium gas and work your way down. this can highly depend on what cam you have.

from what i understand 317 heads are just about as good as the 243/799 heads flow rate but have a larger 72cc chamber to keep the compression down. i think they tend to be cheaper.

but with that compression bump of the 799 heads that's a solid 10-20hp/torque threw the whole rpm range.




with a 408 it would bump the compression up to 11.3:1 with the 799 heads. where as it would be 10.4:1 with the 317's

 

No if it's a typical 2000 lq4 it will have iron heads. 851s if I am not mistaken. Any aluminum heads will save a ton of weight and increase power. 317s should go for around $100-150 in stock form. 243/799s became much easier to get when they came on every gen4 4.8/5.3 from the factory. They should be around $300-400 on average while offering equal flow to a 317 with higher compression. The other option is to mill the 317s. I wouldn't use the 5.3 heads. Tons of headache and limited flow with those.

 

i agree i would go with the 317's if you plan on going with a 408 later. maybe mill them to clean them up and get them ported.

 

Well 10.2:1 would be workable. That article just gave me scares of searching for a shell and a bottle of octane booster in middle of nowhere. I'd be slightly concerned with 11.3:1. Where would the LS1 heads put me? Not sure if there is an easy to use calculator for CR or not, sorry if there is.

 

Stock heads are 873s and they are the same as 317s except iron according to the sheet I have. I'd rather not port the heads I have. Partly because they are very high mileage and there are no machine shops I trust nearby. Also because porting iron heads on an LS motor feels a bit like polishing a turd.

Casting Number 873
Head: 1999-2000 LQ4 6.0 Liter Truck
Material: ***Cast Iron***
Part Number:
12561873
Combustion Chamber Volume: 71.06cc
Compression Ratio: 9.5:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

 

i meant to get some 317 heads and have work done to them before you put them on. can always ship them out or buy them pre ported.

as for 706/862 62cc chamber would put your lq4 at 10.5:1 also with the 706 heads have the possibility to crack.... thats why i have 799 heads on mine now.