I am in the middle of an LSX Dr headed build and am finding out about the difficulties of getting information and putting these engines together!

Our goal is an all out race, NA, carbureted, high compression, drag engine specifically built to be used in a sand drag Jeep. Running only 300', obviously we can put this monster on the edge and plan to, with regard to compression and cam.

We already have a new LSX block (9.240 deck height)

New CNC ported DR heads

GM 4500 series intake

Rotating assembly 4.125 stroke, 6.125 rods and domed pistons to achieve 15.3 : 1 compression

We know that rockers are available from Jesel or T & D and the valves, springs, pushrods are also easily available.

In fact, having FINALLY gained possession of the correct piston for our needs, we kinda feel we have rounded the corner. (They are bad A$$ looking pistons!)

The next challenge is the camshaft. How big can we safely go with regard to lift, duration and clearances?
How much duration do we need to overcome the 430 cfm intake flow vs the relatively small 454 cubic inches?

Is the stock 50mm cam journal size adequate?

Lifter bore? Offset?

We are looking at a custom grind cam with numbers of over 770 lift, 260 intake dur and 274 ex. (1.8 rockers) This cam is available, and all we need to do is make the call.

Any red flags here????
We plan to stay under 8000 RPM's, coming off the brake at between 3600 and 4500 depnding on track conditions.

A couple more ????'s, Can we get a stud kit for this engine cheaper than it is availbale through GM? Were looking at almost a grand for studs!!

Has anybody used the MSD computer on one of the carbureted LSX engines? How about with DR heads. Sure would be nice to have a little idea what kind of a timing curve to set up initially!

I have tried to contact Robin Lawrence many different ways, with no luck. Any advice or help would be greatly appreciated. We are spending a ton of jack on this project and I would hate to hurt it due to our ignorance. I am not afraid to say I do not know everything about this set up. Hell, I don't know if there are very many people who do!

Thanks for any advice!! Brian

 

duration looks too small on the cam.shawn at v.a. speed can design you one.if i was too guess it would be around 28x 29x

 

that intake makes for a good paper wieght above 4500.. call beck intake's.

 

Mike I think he's talking about the DR carb intake, not the regular GM carb intake for ls1 and 7 heads. That's the one (if I have it right) that has the shorter runners and the larger plenum, I would think it would be more of a top end orientated intake...


The cam to me looks somewhat small. I would be aiming for 800 lift on something like you're doing and with the carb the lsa can be pretty low, 104 or so.

I have a buddy that runs a sand rail, I know that when they dyno the engine, they only hit it for about 4 seconds because that's all the time it ever runs for... and what they do to get the instant power is somewhat off the wall with alot of stuff (probably would never stay together in a drag car that sees a full 1/4 that's for sure)

Oddy's performance would be someone I would call on that, just becuase I know that they do alot of sand drag engines and probably can steer ya in the right direction cam wise... or at least give you an idea what they do with other engine platforms which can't hurt to know.

 

BES Racing Engines has built one. Check GMPP facebook page and you'll see some results of it. They learned a lot, and I can tell you they didnt use the CNC DR heads, they did their own port from a pro port head.

some other tricks learned along the way, but it was a 420 cube, single 4500 carb 9400 rpm.

 

I think if you're looking max effort you wouldn't be posting here, but rather calling someone like Kurt Urban, Shawn Miller, Billy Briggs, etc. They will steer you in the right direction for sure! For a distributor setup Kurt Urban has an absolutely sick package I would recommend looking into.