| Known good BBF combo's dyno proven |
| page 4 |
| this next combo belongs to Darryl Manalo of Tacoma, WA. this is easy to duplicate and is very nasty !!! |
| Darryl is running a 4.39 bore and 4.150" stroker crank for his 500 inch combo. K&B flat tops with the single eyebrow, The rotating assembly uses standard machining practices and a high volume oil pump. The cam is the comp solid roller XR292 and specs out at 254 / 260 @ .050" lift .671" / .678" lift on a 110 degree LSA C/R is 12 to 1 Heads are my ported iron CJ's flowing 390 / 205 at .800" intake is the offy port-o-sonic with a holley 850. Ignition is MSD and total timing is about 34 degrees on race fuel. headers are the CJ flange hooker super comps 2 1/8" primarys and 3 1/2" collectors. Dyno says: 626 HP @ 5,800 and 666 pound feet at 4,200 RPM This is an easy build to duplicate guys... An edelbrock victor ported here with a 1000 BG demon is also on the testing menu. I will update you on this one. |
| One of the consistancies I see in poor running combo's is too low a C/R for the chosen cam specs. another is having the piston too far below deck killing quench. Keep these important issues in mind when putting your combo together. A poorly curved ignition system is another culprit. A good running combo need be concieved as a total system and not a bunch of individual parts and pieces. All parts must be coordinated and work well together. |
| One really lame combo I had used ported D0VE's on a stock 75 460 with the grand canyon pistons. I had chosen a comp 274 EX and used a no name double roller.Un known to me at the time was the fact that the timing set was not indexed correctly so cam timing was badly off. This combo would barely offer 300 RWHP |
| I wanted to share some rather new information with you folks regarding C/R and it.s effects on the residual pressure and gas volume in the cylinder as blowdown occurs. A high compression combo has a lower residual gas pressure and volume at the end of the power stroke which doesn't work the marginal exhaust ports as hard. This is one reasons the early engines didn't choke at 4,000 RPM .It is quite important to allow for increased exhaust pressure and gas volume in a low C/R combo and adjust your exhaust accordingly. High velocity with reasonably sized header primaries and exhaust system diameters will maintain velocity and torque production. An "H" or an "X" pipe will help low to midrange torque on a street combo. Lesson is to use as much C/R as is practical for your combo, intended use, cam specs and fuel avaliability. More C/R equals better mileage and thermodynamic efficiency. |
| Another seeming debate is the issue of primary pipe diameter size and length. When in doubt go smaller on the street. The larger the primary diameter the higher in the RPM window peak torque occurs. when you are looking for a max rpm combo use the monster primaries of 2 1/8" or 2 1/4" but the 1.7/8" and 2" styles are good for the portly street terrors. |
| Percent increase to be expected when upping compression ratio. |
