marine02ss

iTrader: (3)

Whats the most compression I can run for street motor on 408?Trying to decide on wiseco -8cc 11.1 or diamond flat top 11.8,Will unshrouding AFR205s,enable me to lower compression down closer to 11.1 while still keeping .040-.045 quench.What size gasket? Trying to decide to order parts tomorrow and get the build done by x-mas!!

white2001s10

iTrader: (4)

Without knowing many other details it can't be called, and even then it would be a guess. I'd error on the high side. If it turns out to be too much it's not that hard to just pull the heads and open the chambers a bit.

marine02ss

iTrader: (3)

What other details do I need to provide,maybe I can help to figure this thing out.

white2001s10

iTrader: (4)

Well temperature makes a big difference. Keeping the intake charge cool and running the engine cooler can make the difference. Other things can help you get away with more as well. Things like polishing the chambers, valves and piston tops, running cooler plugs, and running a very tight quench.

The cooling passages formed in your headgaskets are not neccessarily designed to handle a higher compression 408 cube engine. A stock tstat and bypass is also not designed for that. How much you get away with may depend on how much you are willing to modify.

The dish in the wisecos is another question. If the dish takes away from the quench, then they aren't such a good choice.

It may also come down to the tune in the end. With a very good but conservative tune you shouldn't have a problem with the higher compression except for instances when the engine is running hot. A good complete tune should cover this as well.

JC5

Talk to Tony Mamo @ AFR before touching (unshrouding) The chambers.

DanZ28

iTrader: (5)

Choosing the right cam and figureing out your DCR can determine how much SCR you can run. Try using the VE calculator floating around to help figure out what your SCR and DCR would be if you know all your engine specs. (ie...You could run a 12:1 CR if your DCR was in the 8:5 or less area, again, just an example).

Dan

white2001s10

iTrader: (4)

His sig says he has a LS6 cam.
It shouldn't be giving up too much DCR

marine02ss

iTrader: (3)

Sorry but what is DCR,Im not running the LS6 cam Its going to be a 244/248 with the AFR 205's,fast 90/90

white2001s10

iTrader: (4)

#1 DCR = dynamic compression ratio and is more akin to cylinder pressure.

#2 You should've said about the cam from the start. With that cam you'll probably want the more compression. Consult about this with the cam manufacturer.

There are some simulators you can run to map your DCR, but you have to know your exact valve events from the cam-card.

marine02ss

iTrader: (3)

So what would be anybodys opinion flat top or -8cc The wiseco does have a quench pad Of couse with the flat top thers going to be more compression

MadBill

Here's a spreadsheet that does dynamic compression ratio. There are several threads in the Advanced Performance Tech; just do a search for DCR.
http://users3.ev1.net/~black_ops/ca...0calculator.xls

Brandon Boomhauer

iTrader: (10)

I'd get the 8cc dish rather than a flat top considering you want to stay around 11:1.
To get the SCR low enough with the flat top you'll end up running a larger gasket, and a larger chambered head.
8cc will get you the compression you want, and has a nice quench pad.
plus you can run a smaller gasket and smaller chamber if you need to.