LQ4, LS6 cam, 706 heads, 317 Heads, Junk Yard Dog, AND LIES

[zgeezer]

What year was the 5.3? At one point GM went to flat tops in both the 4.8 and the 5.3, if you dont have the year of the block you can check the crank part number. You might have the LM7 H/O.

 

Stay away from 706 heads, some of the early ones have a bad casting that cause them to crack and leak coolant.

 

317s are comparable to 243/799s but with lower cr. If you mill 243s past .030 you need your intake milled to match, any competent shop can do that. I do not know what cr an lq4 and 243s make off the top of my head, but if you have access to a large wrecking yard sell off your lq4 and pick up an lq9. Same displacement but with flat top pistons.

Lq4 is fairly common; but the lq9's sell for a substantial premium down here.  I understand that the Lq9 crank is balanced for the flat top piston and heavier bushed connecting rods.  If I could find a good lq9 crank; maybe I could use the ls2 pistons and rods I have.

[zgeezer]

Really appreciate the comments.  The flat top LS2 pistons and rods will stay in their boxes for the time being.  The Lq4 will receive a 2004 LS6 (405 hp) cam with the GTO lifters, 7.425 pushrods, Ls2 springs (yellow..beehive equivalent to the z06 springs) and stock 317 heads.  Oil pan from 2006 Ls2 Corvette... looks like it will fit, if not; the price was right.  Stock 4l60E automatic transmission.  Recovered an oil cooler from a third GEN Rx7 that is a perfect fit between the Z's front "frame"horns.  Has a built in thermostat.  Once this is back in and tuned, I'll start shopping for a set of heads.  Either stock 799s that I can pass off as genuine truck castings or the other casting often found on LS2.  I calculate that the GTO stock LS2 heads will net about 10.4 CR.

 

Since I have a year to work on this charade, I should be able to sort it all out in time for a 500 mile trip from the low California desert up to Reno.

 

Thanks  G

[The Infidel]

I got a set of low milage 243s for cheap on TBSS owners website, all the prices there seem to be reasonable compared to Ls1tech and the website moves at a slower pace.

Edited May 16, 2013 by The Infidel

[zdlite]

GM rated their carb'd LS2 crate motors at 440 HP.  That is with 243 heads and a cam equivalent to the LS6.  The single plane intake picks up a good bit of both top end and believe it or not low end power over the EFI stuff.  so combine a carb intake with a slight cam upgrade and you will easily and cheaply exceed your power goals.

[Zzeal]

Car Craft (July 2013) ran a bunch of GM cams through a stock 5.3. Here's three notable ones.

           

                                         HP    TQ

Stock 5.3 w/ LM7 cam=  353 / 384

 

LS6=                                376 / 389

 

LS9=                                420 / 412

 

I'd be shoppin' LS9

 

I'm running a C6 oil pan ('05-'08 Vette) on my LS2 240. Good clearance, great baffling.

 

Steve

[zgeezer]

Car Craft (July 2013) ran a bunch of GM cams through a stock 5.3. Here's three notable ones.

           

                                         HP    TQ

Stock 5.3 w/ LM7 cam=  353 / 384

 

LS6=                                376 / 389

 

LS9=                                420 / 412

 

I'd be shoppin' LS9

 

I'm running a C6 oil pan ('05-'08 Vette) on my LS2 240. Good clearance, great baffling.

 

Steve

I just got my c6 oil pan... paid less for it than I did for my fbody ls1.  Looks like a better pan as it has at least one inch more road clearance than the fbody pan.  I think the Ls9 cam's sensor is upfront, not in the back.

 

So, now I'm shopping a good set of heads.  I've seen 799s for $250-300 a pair (might be cores only, but that price is in my range).

 

gg

g