New 440 Build - Ignition Question
I am building a 12 to 1 440 and wanted to know what I'll need to spark the fire of this motor...Ignition, octane fuel? etc...
440 .30 over motor w\516 closed chambered heads, pocket ported, gasket matched with 2.14 intake and 1.81 exhaust valves. The heads have been cc'd to 73cc's. The KB pistons I am using say that this combo should yield approx 11.3 to 1 compression ratio using the felpro blue .040 head gasket. I would like to use the steal shim .020 head gasket that should yield approx 12.02 to 1 compression ratio.
Thanks in advance...
Rob
Timing is not an opinion, timing is calculated with a Physics formula based on the speed of flame front, distance it has to tavel and some other variables. If you do the calculations on just about any mopar wedge motor you'll always come out to 34* (there is some circumstances that will alow more).
You can run more timing but in most cases the carb will be flooding fuel into the engine to keep the combustion chamber cool and out of detonation. The optimum point for max expansion within the combustion chamber is 13.7* of crank rotation from TDC, normally if you can get it to about 12-15 you'll make peak HP and not risk detonating the engine.
If you run an Orange box they will retart the timing 8* starting at about 3200 and by 5200 they'll have you retarded the full 8* so some guys think they're running big timing but it actual fact when the system is put on a load bench what they think is 40* is actually only 32*. Just be aware that what some guys run may not apply to your application. A good ignition box and 38* of timing could put you into full detonation.
When tuning an engine it's always "Ignition 1st then carburetion". The timning events can be set on a distributor machine to exact numbers, once that is achieved then jetting and tuning of the carb is fairly simple, always jet to max MPH.
If you have a zero deck piston you CAN NOT run a .020 or even a Cometic .027 (Thinnest they make), rule of thumb with steel rods is .038 piston to head clearance, you have a closed chamber head so this is important or you'll train wreck the pistons into the head. have you ever wondered why the industry standard for head gaskets is .040? Did you clay this engine? You need .080 on the intake valve to piston and .100 on the exhaust valve again you don't want any train wrecks.
S/E guys will run much tighter but they run on the ragged edge and life expectency is not that long on a S/E engine. They run them so tight you can see on the piston where the intakes have been pushing the piston down and the piston has been pushing the exhaust valve closed....I don't think you want to go there, especially with a KB piston.
You need to carefully measure and calculate the actual compression ratio to determine what fuel you'll need, most importantly don't go by what the piston manufacturer says on a set of off the shelf generic pistons, are their calculations done at zero deck or 20 in the hole??? Call and ask, then measure where your piston is and do the calculations.
11.3 should run on 105 octane but at 12.2 i'd be running 110.
Many times head portng and big valves are over rated, you must always consider the Air Speed over the intake valve. this is another one of those pesky Physics formulas, bore, stoke, cam lift, valve size, peak RPM....etc. when it's all put on a chaulk board ideally it should come out to .600 Mach or about 400 MPH. Now engine builders vary on this opinion some like more some like a little less I always work to as close to Mach .600 as I can get, works for me.I run high 10's with a 1.94 valve in a ported Iron head with 381 CID.
Nothing will kill power quicker than too much valve, too large of port and too much cam lift, be careful in selecting the correct cam for the combination and consult with a real Cam Engineer, I always refer to Jim at Racer Brown he really knows his S**t.
Email me direct from my web site and I'll send you a FREE email version of our 47 page "Tuning to Win" book. I think you'll find it very helpful in achieving your goals.
