Compression Ratios

Well since im still trapped in my room i figured i would start ordering the new parts for the engine so i dont have the run the tire old heart in the new stouter body, since im planning on going with a forced indection setup i was wonder ing what kind of compression ratio's i would be getting with these pistons
10660 - Ford 347 -4.0cc Flat Top SRS Pistons
and these heads in a 72cc Combustion Chamber
http://cgi.ebay.com/ebaymotors/AFR-...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
thanks in advanced
 
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What thickness gaskets? That will change it a bunch. If you use a .05" compressed thickness gasket, you'll be at 9.22:1.

Engine Size and Compression Calculator

Wow, thanks for the link, i normally did all that stuff and scratch paper, saves me alot of work, and im not sure what hasket im gonna use yet it but 9.22:1 sounds like a safe compression ration to run a KB at 18psi of boost
 
My thoughts/rambling:

I'm not sure if you intend to do so on pump gas. If so, I personally wouldn't be interested in running that much boost on pump gas with my car, but there are plenty of '03 Cobra owners who do it. Their Static Compression ratio is 8.5:1. However, there are a lot of important factors to take into account, and static compression is only one of them. Total timing is very important, and if you retard it enough, you can prevent detonation at any boost pressure (within reason). However, hotter exhaust and coolant temps, less power, and burned exhaust valves will result as this envelope is pushed. Far more important than static compression ratio is your dynamic compression ratio, which has much more to do with your camshaft than your static CR. The efficiency and material of the cylinder heads makes a difference too.

In my case (a turbocharged, intercooled 331 with AFR heads, 8.5:1 SCR, a custom turbo cam, and more), I'm sticking to 15 psi, though the car has momentarily seen 17-18 psi and lived through it. I'm glad I had the built in wiggle room. If I check to see what psig-max is and it is more than 15 psi, I know that I have lost control of the boost, and can make adjustments accordingly. If I were already at 18 psi and got a boost spike, it might be too late to do anything about it at that point. However, with a blower, boost spikes are extremely improbable, I think. So, I can understand how one with a blower might be more inclined to push the ragged edge.

On the other hand, with those blowers, despite their relative efficiency, you don't have an intercooler to keep IATs down. I don't know man, my attitude is that even an extra 100 rwhp would still not be worth living with the worry that I'm going to break stuff.

Chris
 
My thoughts/rambling:

I'm not sure if you intend to do so on pump gas. If so, I personally wouldn't be interested in running that much boost on pump gas with my car, but there are plenty of '03 Cobra owners who do it. Their Static Compression ratio is 8.5:1. However, there are a lot of important factors to take into account, and static compression is only one of them. Total timing is very important, and if you retard it enough, you can prevent detonation at any boost pressure (within reason). However, hotter exhaust and coolant temps, less power, and burned exhaust valves will result as this envelope is pushed. Far more important than static compression ratio is your dynamic compression ratio, which has much more to do with your camshaft than your static CR. The efficiency and material of the cylinder heads makes a difference too.

In my case (a turbocharged, intercooled 331 with AFR heads, 8.5:1 SCR, a custom turbo cam, and more), I'm sticking to 15 psi, though the car has momentarily seen 17-18 psi and lived through it. I'm glad I had the built in wiggle room. If I check to see what psig-max is and it is more than 15 psi, I know that I have lost control of the boost, and can make adjustments accordingly. If I were already at 18 psi and got a boost spike, it might be too late to do anything about it at that point. However, with a blower, boost spikes are extremely improbable, I think. So, I can understand how one with a blower might be more inclined to push the ragged edge.

On the other hand, with those blowers, despite their relative efficiency, you don't have an intercooler to keep IATs down. I don't know man, my attitude is that even an extra 100 rwhp would still not be worth living with the worry that I'm going to break stuff.

Chris
well obviously pump gas makes things easier, there is 1 station aroud here that sells 100 octane at the pump so i can do that ($8 a gallon) but if i dont have that option thats fine, as far as the intercooler goes, well i'll have one of those as well when im done with the setup, meth injection will also be something else thats added and your right i doubt im going to see any major boost spikes, after moddifing the KB to have an intercooler i'll be lucky to hit 18psi, so i may even machine my own pulley wheel for it as well, what are some choices i have to drop the compression further?