Project V8 RX-7: Part 3 – Inside the GM LS3 Cylinder Head
By Mike Kojima
In the last edition of Project V8 RX-7 we looked into the bottom end of our EROD LS3 engine to find that the modern Chevy V8 is a far cry from the old small block Chevy of years past. Lately on some forums that cater to import performance, there has been a huge backlash against the LS swap, particularly into Nissan S chassis and RX-7’s. All sorts of bleating noise from uninformed sheep decry putting “NASCAR” engines and the like into the S chassis. Purists claim that putting in a domestic engine somehow is making their favorite cars all the same and causes them to lose their soul and other things not defined by logic. Such is the garbage cluttering the net these days. Like many FFF facts on the interwebz, their are many fundamental inaccuracies to these statements.
|This is a NASCAR SB2 engine. It is very closely related to a small block Chevy. Many of the parts will interchange except it has a few major differences. The distributor is in front instead of in back for less spark scatter at high RPM. The heads are actually pretty sweet and have canted splayed valves with ah high quench and turbulence combustion chamber. The camshaft is much higher in the block for crank clearance with big lobes and for shorter less flexy and lighter pushrods and everything is beefed up and more suitable for racing. It has an iron short skirt block. It is not even close in design to an LS motor.
One, the LS engine is not a NASCAR engine or anything close. NASCAR engines have evolved from the venerable small block Chevy and do not share any parts or engineering with the LS other than bore center dimensions. Although they are not really small block Chevys anymore with different block castings–with relocated camshafts and way different main web dimensions, cylinder and deck thicknesses–they are at least recognizable close relatives. The LS is very different from these engines, if you were to simply look at the bottom end you might think it was a European or Japanese design.
|This is not a NASCAR motor. The only things the same between an LS and a small block Chevy are the bore spacing and the fact that they are both V8's and have push rods. Examining the cutaway diagrams closely should show that there are no similarities in architecture between the two engines at all.
Two, LS motors are are not all the same, they are many variants of the LS engine and there are more LS tuning options than any import engine. In fact, tuning an LS is probably more intellectually stimulating that figuring out many power solutions to popular imports. It's typical youth trying to make a statement in non conformity by conforming to a youth norm!
|Lighter than a Nissan KA24, almost as light as a 13B-REW or SR20DET with way more power than any of them makes the LS a good swap choice. GM Performance's EROD swap kit can make it all smog legal as well!