BMR 9 SECOND PROJECT GTO BUILDUP - PAGE 3
By now we were smitten with the horsepower bug. It was obvious that the stock motor would only take so much nitrous and we wanted to go much faster so plans were started to build a new motor. After scaling the car at the last race and finding out it weighed over 2 tons now, we decided that more cubic inches were in order. Our first plans were to purchase a pre-built motor from one of our distributors such as MTI , Thunder Racing, or AP Engineering but everybody we called were 2-3 months backordered so in the end we decided to build it ourselves. An iron block was ordered from GMPartsDirect.com and a Lunati 4" forged stroker crank from LS1Speed.com. We also ordered a set of Carillo "on center" billet connecting rods. This combination, when bored .030" over, produces 408 cubic inches and should easily be capable of supporting 1000hp.
Up until now our goal was to get the car solidly into the 10's without compromising drivability. After running mid 11's with a stock internal motor, the new goal became low 10's. In order to get a 4000 lb car into the low 10's it takes about 750 rear wheel horsepower so we knew that the motor would have to make at least 450-500 on it's own.
Knowing this, we knew we would have to address the stock fuel system before we could ever install this motor. The OE pump is only capable of supporting between 400-450 peak horsepower according to the Australian Monaro forums and we didn't want to test this data firsthand. Since we were waiting on parts anyway, the fuel tank was removed. The stock pump was removed from the tank as well as the pickup assembly. At the stock pickup location that protrudes through the trunk floor, we welded a -10 AN fitting. This became our primary fuel pickup and we used the factory pickup as our return line.
|An Aeromotive A1000 fuel pump, A1000 regulator and -10 filter was ordered to handle the fuel delivery. This system is rated to handle up to 1600 hp which is completely overkill but these pumps are insulated well for durability and are suprisingly affordable.|
While we were trying to locate a spot for the fuel pump, our Stainless Works headers and 3" exhaust arrived. The timing could not be more perfect. The exhaust uses chambered mufflers that are much smaller in diameter than the factory mufflers. This allowed us to make a bracket under the passenger side rear seat to mount the fuel pump and filter. A braided -8 line was then run from the pump to the engine bay.
The headers and exhaust are top quality pieces. This is the first we have used this brand and I can't imagine anything better. If all goes well, they should add about 30-40 horsepower dropping us down into the low 11's.
|This image shows the fuel pump and filter mounted under the passenger rear seat. Generally you would not want to use any 180 degree fittings in a fuel system but space limitations made it necessary in this case. Our line size and fuel pump capabilities far exceed our requirements anyway so it will be fine in this case.|
|Since the exhaust was already off the car, we decided to install one of Harrop's differential covers at this time. This is another very nice piece that should have come factory on this car. Not only does it provide more gear oil capacity but it also has a much better rear mount incorporated into the cover. This will help stabilize the whole cradle since this mount doubles as the rear cradle mount too.|
|In preperation for the new motor, we installed a set of BMR 300M billet stub axles and CV shafts while we were changing the rear cover. Up until this point I think we were lucky that a CV hadn't failed. Typically CV's will fail on these cars once 60 ft/times get below 1.60 and our car is much heavier than it was originally. In the image to the right you can see how much beefier the BMR axles are over the OE unit. Besides the larger diameter shaft, the CV cages are machined from billet making this setup good to 1000hp.|
It's tight but the Stainless Works exhaust clears the new Harrop cover.
One of the pieces ordered for the new motor was one of the new FAST intake manifolds. We decided to step up the nitrous system with the more conventional fogger nozzles, replacing the original NXL nozzles used on the factory intake. Once again Jeff Prock from Applied Nitrous Technology was called on to plumb the intake. The new system is a work of art and we were hoping it performed as well as it looked.
A set of billet fuel rails and 42 lb/hr injectors was ordered from LS1Speed.com and installed on the new intake.
While the intake was being plumbed, we received our Stage 3 LS6 ported heads from CNC Cylinder Heads. These heads come with Manley 2.05"Int/1.6"Ex stainless valves, valve springs, locks and retainers installed. Rumor has it that they flow a little over 300@.600 lift. With our custom BRC pistons and these heads, compression was calculated to be 11.4:1.
We also ordered a set of Comp Cams roller rockers, lifters, and a custom ground Comp nitrous cam. Since the car is so heavy and we wanted to keep the streetability, the cam was kept somewhat consevative with a .595/.601 lift and 232Int/236Ex @ .050. The cam was ground on a 113 centerline.
While the new shortblock was being machined and we were waiting for more engine parts to arrive, we decided to bolt the new intake onto the stock motor. With a better fuel system, new intake, headers, exhaust, a different nitrous system and stronger rearend components we wanted to see if we could get some low 11's out of the car with a mild nitrous tune.
Once the manifold was installed, a BMR shocktower brace was modified to attach our fuel pressure regulator to. With the new fuel system now complete, we headed back over to Rev Xtreme to dyno tune the motor again. After about 10 motor pulls and computer adjustments we made 342.8 RWHP, an improvement of 44 horsepower to the rear wheels since our last NA dyno tune. A stripped fitting prevented us from dynoing the nitrous sytem.
With the car making more power now and the fitting replaced we headed to the track. Since we didn't have the opportunity to dyno tune the car with the new nitrous system installed, we jetted it conservatively and checked the plugs after each run. The entire nitrous system was flowed by Jeff Prock and he provided a jet chart based off his flow figures. With the smallest jets installed and a little too much fuel pressure (to be extra safe), our first pass down the strip got us an 11.44@119mph with a 1.67 60 ft. We were thrilled and decided at this point to jet it up a little and leave the fuel pressure high. We also dialed in a total of 6 degrees retard on the timing tuner. Our efforts payed off with an firstname.lastname@example.org and a 1.63 60 ft. At this point we started to wonder if the car could possibly run a high 10 with a bone stock motor and nitrous. Leaving the jetting alone, we decided to change the activation rpm to 3200 and see what happened. Unfortunately during the burnout, the car got sideways and one wheel went up in smoke. The posi unit was toast and the car would not hook up no matter what we did, our track day was over
After this last trip to the track, we contemplated purchasing a KAAZ differential for the rearend. The factory posi would probably hold up if the car was kept straight during the burnout but it just seemed pointless putting a stock part back in it knowing the car was only going to get faster. After learning that a new posi could not be purchased from Pontiac without buying the entire differential, the KAAZ posi suddenly seemed to be the only choice. The other option was the ultra high dollar Harrop 9" IRS. Since this was out of the question, a few people were called and we learned of a new Ford 9" replacement differential being offered by Diff Technics. This unit is very comparable to the Harrop differential except much more affordable. Affordable meaning still expensive but not 1/3rd the price of the car. Needless to say we ordered one. The kit comes with the housing, axles and axle bearings. We ordered the gear, Detroit Locker, pinion support, pinion flange, and the rest of the bearings from Moser Engineering.
With the new motor still 3-4 weeks from completion and the new rear 8 weeks out, it looked like the car was going to sit for a while. On a longshot, we removed the posi unit and decided to do the backyard hot rodders trick of welding up the spider gears so we could get the car back to the track and run that 10 second et. A few bolts were wedged in between the spider gears and then the whole thing was TIG welded together in various places - walah, el cheapo spool!
We headed back to the track that weekend not knowing what to expect. This time the car was trailered just in case the rear let go. With all of the nitrous settings left as they were, we made a pass right off the trailer. email@example.com! We couldn't believe it, 10's with a stock motor and 4000 lbs. At that point we should have went home but we decided to make one more run. Leaving the line, it was obvious something was wrong and the car felt weak all the way down the track. The car looked like a mosquito fogger coming back in to the pits and was barely running. It had still run an 11.26@118mph but something was definitely wrong.
|We got the car back and took it apart. The first thing we noticed was the aluminum in the oil pan and on the pickup assembly. The second problem noticed was the spark plugs in number 5 and 6 cylinders had no electrodes. Once the heads were pulled off, you could see the big hole in the number 6 piston. Apparently things got a little too hot. We're not sure if this was due to detonation or we finally just reached the limitations of the factory hypereutectic pistons. Either way we were not going racing again until the new motor was installed.|
Up until now we had been running a single nitrous bottle and carrying 2 or 3 extra bottles to the track. Even with our BMR nitrous quick disconnects, it's still a pain to switch out bottles every 2-3 passes plus the new motor would be taking even more nitrous so we decided to make a dual bottle mount. It was designed to fit inside the spare tire well and it can easily be removed by simply loosening the factory spare tire wing bolt.
We also installed twin bottle heaters connected through a relay to a modified NX Fire and Ice controller to regulate heat and pressure. Our modified system works much quicker than the heater that came with the kit. We used the controller and the pressure sensor from the kit, discarded the heater and used two traditional bottle heaters connected through a relay. The pressure sensor is monitored by the controller which turns off the heaters when the bottles reach 1050 psi. The controller constantly monitors the pressure and turns the heaters on and off automatically to maintain optimum pressure. The system works flawlessly and really should be an NX part number.
|With the motor out of the car we decided to modify the stock K-member to make the center removeable. This will allow us to remove the oil pan without pulling the motor. The center was cut out and plated and a 1.5" x 2" tubular center section was fabricated that bolts into place. The result to the right almost looks factory.|
|Here you can see the new motor awaiting final assembly. The original motor is in the background while it is picked clean of sensors, plugs, and miscellaneous covers and fasteners. In this image you can see the Comp Cams roller rockers that required machining the valve covers for clearance (shown below).|
|We had to clearance all of the high spots on the inside of the valvecover to make room for the roller rockers. Each of the protrusions are the bottom of the coil bracket bolt holes. Machining the bottom off of each one opens up a hole that will require siliconed threads to prevent leaking. No biggie, the alternatives are valve cover spacers or aftermarket tall valve covers.|