If you have been following this big-cube hydraulic roller LSX buildup at Late Model Engines in Houston, then you know this bad boy means business. A Callies forged and balanced rotating assembly, high-compression Wiseco pistons, carefully selected Total Seal ring package, fully blueprinted GM Performance Parts LSX block, baffled Canton oil pan, and tried-and-true ARP fasteners are just a few of the features the short-block utilizes to make it 1,000-horsepower capable. By the piston and cam choice, you probably now realize that this is to be a mostly naturally aspirated street setup with the potential for some gas down the road. That being said, you may be wondering what heads we were going to put on the big-bore stroker. Since this was to be primarily a street car, we were particularly torn on this matter. A large runner cathedral port (there are several to choose from) could offer some great performance right out of the box, tremendous torque, and take advantage of the LSX block's extra clamping capacity. On the other hand, the thought of a square or rectangular port had us giddy with flow number talk in the 380+cfm range.
Unfortunately there were few cylinder head options that we thought would give both the track and street performance we were looking for, except one. I picked up a set of LS7 bare castings that LME could massage to give the maximum flow and velocity we desired to make our 451 the best all-around combo. LME co-owner Pecos Loughlin also assured me that he could easily convert the heads to the LSX's bolt pattern and make room for a trick, adjustable shaft rocker system from T&D Machine. We had been aching to get a set of T&D rockers for quite a while, and this looked like the perfect opportunity. The folks at CV Products were also anxious to get on board and help us out with some PSi valvesprings, heavy-duty pushrods, and titanium retainers. Last, but certainly not least, Scoggin-Dickey got us a killer set of titanium intake and stainless exhaust valves to help this high-revving motor breathe with ease. In our final installment, we'll be bolting on a set of valve covers and an intake before heading to the dyno, so stay tuned.
| LIFT |
INTAKE |
EXHAUST |
| FLOW(CFM) |
FLOW |
| 0.100 |
89 |
70 |
| 0.200 |
183 |
121 |
| 0.300 |
272 |
181 |
| 0.400 |
329 |
225 |
| 0.500 |
361 |
241 |
| 0.600 |
383 |
251 |
| 0.650 |
391 |
253 |
| 0.700 |
399 |
256 |
| *According to LME's SF-600 at 28-inches of water, no pipe on exhaust. |
Robert Maenza is LME's in-house...
Robert Maenza is LME's in-house head porting guru, and we were happy to place our bare LS7 castings in his capable hands. Reworking the short-side radius and guide area on the intake can do wonders for the LS7s. About three days worth of porting was put into our heads using a carbide burr as well as 60- and 120-grit paper to polish the runners. Robert said the intake is best left a little rough for better flow and fuel atomization, while the exhaust and chambers are made "baby smooth." A circular pad gets the edge left by the factory CNC.
Robert stated that, "GM did...
Robert stated that, "GM did its homework when they designed the chambers." Instead of reshaping, he simply polishes them up.
Meanwhile, the exhaust runners...
Meanwhile, the exhaust runners need quite a bit of work to enlarge the openings to 1 7/8 inch, from 1 3/4 inch, since this engine will not be utilizing factory exhaust manifolds. The smoother transition to 1 7/8- or 2-inch primary headers should pay dividends on the dyno and track.
Co-owner and machinist/fabricator...
Co-owner and machinist/fabricator extraordinaire at LME, Pecos Loughlin, created these tabs from billet stock then welded them on prior to our arrival. These will take advantage of the LSX block's extra clamping force; the key is welding prior to resurfacing the heads as the heat can cause the aluminum to warp slightly. Pecos said he can do this with most any LS head, but those with them cast in already are preferable. The GMPP LSX-LS7 heads hadn't been released yet, or we might have used them instead.
The heads are resurfaced for...
The heads are resurfaced for optimum seal and compression. Though they were originally around 71 cc, after cutting the heads LME had the chambers at 66 cc. With the pistons and Cometic gaskets chosen for the build, compression should be 12.1:1. LME assured us that pump gas would be no sweat, though most likely we would be dumping in some race gas at the track.
Since we are going to be using...
Since we are going to be using T&D's shaft-mount rockers the valve cover rail needs to be clearanced, and the cast-in pedestals need to be machined off of the heads. These will be replaced by a sturdy chunk of billet steel that is integral to the shaft system, which will offer not only rigidity-but a huge amount of adjustability.
Scoggin-Dickey Parts Center...
Scoggin-Dickey Parts Center set us up with these lightweight, titanium 2.200-inch intake valves (PN X12591644) and solid stem, stainless steel 1.610-inch exhaust valves (PN 12618110). Both are serious upgrades over the factory valves, and well-suited to a potentially forced-induction application. LME was adamant about using titanium valves given our high-revving intentions, and knowing the implications that it could have on the rest of the valvetrain-we were quick to jump on board.