dirty_old_chevy

ok, I am sure this has been asked before, but can you use SBC connecting rods in an ls engine?? I have a set of Oliver 6.3'' rods for sbc, and I would like to use them. I'm hoping they would work in a destroker application using shelf pistons. LQ4 block, 4.8 crank (3.262 inches) and 1.3 comp ht. pistons give me a deck height of 9.231 inches. 9.235 inches with 1.304 comp ht. These rods are 1400 bucks to buy new, and I got them for $350 off ebay. So I would like to use them, and I'm not really interested in the SBC anymore. My machinist checked them out and said they are A-ok. Any input would be appreciated! Thanks.

nastychevelle

iTrader: (7)

I am not going to say yes or no, but i will say the rod journals on the 4.8 crank are 2.1" and if they are a SBC rod they should have a 2.1" big end. But, i dont know if the width is different on a SBC rod compared to a LS rod. Now i read somewhere that the LQ4's have a 9.230" deck height. So if the sum of your parts (crank throw + rod length + compression height) gives you 9.235" and you use a .051 head gasket you would get around .046" quench. Depending on the bore you plan on using i would pick up a .045" thick gasket to get right at .040" quench. You want the tightest quench you can reliably get.

Edit just found this:

dirty_old_chevy

yeah, you are thinking along the same lines as me. I dont want to put together another engine without optimising quench (.030- .040). I was pretty sure the big end matched in diameter, and most of weisco's pistons are made with a .927 pin which also matches. Big end width is another story. I don't know.

dirty_old_chevy

so it should be as easy as getting a pin boss width from the manufacturer and comparing it to the rods?

nastychevelle

iTrader: (7)

i have found that a SBC big end is 0.940" wide and Ls1 rods are 0.9449". The Ls1 crank rod journal is 2.0991-2.0999" from the factory and 2.0987" is the service limit.

dirty_old_chevy

so im wondering if this big end being narrower is something to worry about for a boosted build.

nastychevelle

iTrader: (7)

.940" + .940" = 1.84". so taking the middle of the production journal width (2.0995") that leaves you .2595" left after rods are installed. Ls1 rods give you .2097" left after rods. Now i think you would have to assemble it to check side clearance but i did find this:


i'd mock it all up and see what you get. so far it all sounds good if the rods dont contact the bottom of the bores anywhere.

Edit: i just read this in CircleTrack Mag

so if we go off that you have about .2595 left. even if you have to (i dont know) divide that to get clearance on both sides and in the middle your looking at .0865" on both sides and in between. i would imagine the bore placement in the block will hold the rods offset so the middle would have larger clearance but im not positive.

Edit #2: i just read this as well

Steve - Race Eng

iTrader: (1)

The small block rods have an offset big end to get the beam in the center of the piston and the small end of the rod centered between the wrist pin bosses in the piston. LS rods are on center.

You are better off selling your SBC rods and getting a set made for the LS engines.

Steve