Spoilt said:
Yes it is the cleveland main size and I am running the Chi manifold compression is 12.5/1 to be honest i dont now the exact specs on the cam will find out though the builder said it is one of the smallest cams he could find because i wanted it to be streetable as well. with a bigger cam he reckons lots more power and then also if we run it on methanol lots lots more power. It was run on avgas they reckon with that vpw racing stuff it will go more but i dunno. You seem to have one friggen tough motor what you got it in and how does it go???
Mine is relatively low compression at 11.25:1 (flat tops with 66cc heads). It has a decent amount of camshaft in it, but certainly not a BIG cam by drag racing standards. 274*/274* @.050" and .697" lift (with my 1.7:1 ratio rocker arms). This is an off-the-shelf cam, too. I did a lot of estimating and couldn't find a really that much better camshaft. A few grind profiles I modeled had maybe 5 more HP on the top end, but for $395 compared to (something like) $145 that I paid for this cam, I wasn't about to spend the extra money.
Here are the specs:
Factory '72 4-bolt block filled 1" below WP
Aftermarket main caps on 2, 3, 4 w/ARP studs throughout
4.030" bore SRP 11.28:1 (calculated) flat tops
Scat 3.85" 4340 forged/profiled/lightened crankshaft
6" H-beam rods SBC sizes big/small ends w/floating pins
FMS "A3" aluminum cylinder heads with flow @28"
Lift--int-/-exh
.200 152/100
.300 217/146
.400 266/194
.500 305/217
.600 341/232
.700 357/242
2.19" titanium intake x 1.71" stainless exhaust (+.100" each)
Isky dual coil w/dampner springs, titanium retainers 10* locks
Comp Pro Magnum roller rocker arms w/Jomar stud girdle
JP Performance billet timing gear/chain set
Mechanical roller 274/274 @.050" .709"/.709" lift 105 LCA
Lunati solid roller lifters
Edelbrock aluminum waterpump w/Moroso electric drive
Professional Products SFI rated harmonic damper
Milodon oil pump driveshaft, oil pump pick up and full length wet sump pan.
Mellings HV oil pump w/Moroso oil restrictors.
ARP head studs, oil pan studs, header studs, carb studs, more
MSD billet mechanical advance distributor (advance locked out)
MSD 7AL-3, 10mm wires, Pro Power HVC coil
Motorsports B351 4150-style ported intake manifold
Holley HP 1000 CFM carburetor
Stahl 2.125" primary tube headers (open) 4" collectors
7500 RPM redline
(Note that peak HP and peak TQ were taken from two different pulls)
RPM CBTQ CBHP
4500 443.3 379.8
4600 452.7 396.5
4700 454.8 407.0
4800 464.3 424.3
4900 472.4 440.7
5000 479.0 456.0
5100 490.0 475.8
5200 492.6 487.7
5300 492.0 496.5
5400 491.0 504.8
5500 494.5 517.9
5600 490.8 523.3
5700 490.1 531.9
5800 488.1 539.0
5900 487.5 547.6
6000 487.0 556.4
6100 484.5 562.7
6200 481.0 567.8
6300 482.1 578.3
6400 480.6 585.7
6500 475.9 589.0
6600 472.7 594.0
6700 468.4 597.5
6800 464.2 601.0
6900 458.7 602.6
7000 456.6 608.6
7100 445.6 602.4
7200 442.2 606.2
7300 435.2 604.9
7400 431.7 608.3
7500 421.3 601.6
7600 418.9 606.2
If you're looking to run methanol, then the 12.5:1 compression will be fine. I wouldn't run avgas (assuming it is 100LL) at 12.5:1 at the track, but on the street with say a 6000-6500 RPM pill in the ignition should be fine. A good thing about methanol is that it will make your engine run a lot cooler. However, it is really not a good fuel for a street car.
I prefer to run lower compression than most other drag racers. It makes the "finer" tuning less appreciable. Meaning...you don't have to be exactly on for the weather conditions to run well. Higher compression, especially the guys running 13.5:1 and higher, is "finicky." A bit off and you're burning things up. A bit too rich and you're off your ET.
12.5:1 is great for a hot drag car, IMO. Over that and you're wasting your time playing with the tuning every pass. The problem with running that much compression in a street car is that underhood temperatures get really warm. You need to devise a serious strategy on getting rid of the heat. Coated extractors, air ducted to your inlet, massive radiator and high flow through it. Also, consider cutting louvers into your bonnet to let more heat out from under it.
What's worse, IMO is that the heat from the engine bay gets into the cabin. Of course, making power in an automobile means making more heat. Insulating the cabin is usually something few consider because of the added weight it brings to the package.
You may be able to get a bit more out of it with racing petrol all right. The deal would be to add more timing because of the added octane to start the burn a bit earlier due to the slower burning fuel. However, if the engine isn't rattling with the avgas under full dyno loads, then it is unlikely that a higher octane fuel will do anything but further slow the burning process and result in less power. The one area where it might be a help is in uncontrolled temperature/air flow situations consistent with under-bonnet conditions where the heat is more concentrated and you don't have as consistently good supply of cool, fresh air. You're likely to find that the higher octane fuel takes a bit of heat out at the same timing or lets you run a bit more timing without pinging.
:davis: