a friend kept on splitting hubs I machined the timing to take a bbc seal and a new hub to fit it has been 5yrs no problem
Uuhhh...not being able to figure out everything in the formula (to figure out what I'll have for ECR), what does a 7.5 static compression ratio with 3lbs boost work out to? I'm looking to run my DeSoto on 93 Pump gas without detonation...
Wow, panic posted a useful formula for adiabatic compression. For consideration, the exponent of .74074 is the ratio Cv/Cp for the gas being compressed, where Cp is the specific heat capacity of the gas under constant pressure, and Cv is the specific heat capacity of the gas under constant volume. So the ratio is dependent on the composion of the intake charge, which is dependent on the air/fuel ratio and the fuel (gas, methanol, nitromethane). Has anyone figured out the effects of the different fuels on the Cv/Cp ratio, and if they are worth involving in the calculation? I suspect that the reason for blower motors are able to tolerate higher effective compression ratios is that the two-staged compression isn't truely adiabatic, as the intake plumbing allows heat transfer, and small amounts of temperature reduction in the first stage has large effects on the ending temperature.
Yup, there's some heat soak. The exponent is the inverse for a ratio of variable heats, making a guess at the reduction as from 1.4 to about 1.35 - but it will vary based on heat transfer through the cylinder, overlap cooling etc. and of course the charge temperature isn't included at all - which is a very big deal. BTW: not my formula, developed by TFX Engine Technology Inc. ( http://www.tfxengine.com/ ) and generously furnished to me by Clint Gray.
It's not especially good at predicting between engine designs. Wedges with closed chambers are good, open chambers not so good. The hemi is pretty bad for knock tolerance because of very limited quench area (you only have the narrow band between the bore diameter and the chamber diameter, and even then only if the piston's upper deck surface is within perhaps .060" of the head @ TDC). This is a good argument for using the head from a smaller engine in the same family (if the ports will support this) not only because the chamber volume is smaller but because a smaller chamber diameter makes the quench area larger.
As to the drive: I agree, 2" keeps the leverage on the nose down vs. 3", which has to help. Chain or gear drive is even more compact (leverage right next to the block), but they present other problems. As to whether the belt drive is as effective as a real damper in suppressing crank harmonics - my opinion is that's it doesn't do the same job, but it may be enough that you'll never have a problem.
I'm not trying to stir the pot, but with that low of static compression, regardless of chamber design, I'd think you could get away with a lot more boost. Maybe as high as 10 lbs w/premium. But at that point I'm worried you may be generating a lot of excess heat with your restrictive intake set up and the blower having to work that much harder. If you want to play it safe, shoot for 7 lbs. and you'll still make gobs of power.
I just stumbled across this discussion,, originaly was about pistons,, I built a 327 with 350 pistons to drop the compression ratio and used the 461 heads and a 471 blower,, It was for a friend that was running cc/gas in a 57 chev AHRA. Ran the car hard for 2 seasons with only sparkplug problems. I think it was 10% over. This was done on a shoestring budget and lots of fun.
Thats what I like to hear! Love to hear storyies of, 'we threw some parts together... ...and it worked!....... WELL!' Can you remember what the chevy ran?
check through my old threads about the 6/71 motor im building. I got ALLOT of good advise!! I Am just waiting on money for my crank and pistons but It will be a 383 stroker with -31cc forged pistons!!! Im looking at 8.1-8.2 CR. the car is 1400 pounds!! my buddies think im nuts!!
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