Texas_WS6

iTrader: (9)

I am wanting to know what everyone thinks the best engine compression ratio is for a 408 Iron Blocked Turbo charged engine. I want to make at least 15psi to 20psi at full boost. TSP is going to be building the short block here pretty quick and I need to let them know what my target CR is so we get the right pistons for it. The turbo kit is air to air intercooled. I am wanting to be able to drive on pump fuel. I will be putting racing fuel in it at the track, but I would like to make the compression ratio low enough to not need the racing fuel. I was thinking around 8:1. What do you think? Can I get away with more without pulling alot of timing out of it? Would seam to be useless to put too much compression ratio in it if I would have to pull lots of timing out of it. I have not yet decided on a cam so if you want to spec one out for me too that would be good. What ever cam I go with it will be a solid roller lifter cam. I am trying to achieve 800 rwhp, so if you think I can do that with less boost and more compresion then let me know that too.

Thanks guys.

98turbls1

iTrader: (17)

8:1-8.5:1 would be a safe bet...With that bad boy you'll probably be getting into some boost pretty early...Dude with a 408 you could definitely hit 800rwhp by 15-17psi on low 8 compression...you could be closer to 1000rwhp at 20psi if you have a proper sized turbo...Why run a roller setup?? Are you going to be revving this thing to the moon?? Hydraulic is easier and you can run some major rpms with it...You may come into some problems running higher rpms with the 408 because of the longer stroke and those big slugs in the cylinders...

98turbls1

iTrader: (17)

ARe you going to be upgrading the rear and if so what gears are you going to be going with?? Also with the boost realize that when compression goes down the psi that you see will be less too at a given setting...If it's 12psi for example at 9.5:1 then it will be more like 10psi at 8.0:1...So you're going to have to get a big fat turbo on that thing to actually see the 15psi that you want...

Texas_WS6

iTrader: (9)

No, 800 is all I want at this time. If all it takes is 15psi then thats were I want it. As for sollid, I am running the MS3 Hydrolic right now, and I am having a few lifter pump up problems at idol and high rpm. Its not the cams fault. Its the dam Factory lifters. I use to run Roller solids in my ols school stuff and realy I love them. My hydrolics make enough noise to be solids and if its going to sound like a solid, then I want a solid.

Yes it will require more Periodic tunning (checking the lifter clearence) but thats fine by me too.

98turbls1

iTrader: (17)

You may want to look at some Comp R's but these days solids can be made to be a little more tame then old school solid lifters...Also being roller doesn't hurt...With all of those cubes and everything else upgraded like some massaged heads and a good size intake 800rwhp will be pretty easily attainable...Speed Inc made 995rwhp through their 370ci with a T88 turbo...It's a clean car too

Texas_WS6

iTrader: (9)

I guess I should have stated it this way, I want to make 800rwhp, not sure what the actual psi will be, but need a good idea on what I should shoot for with the engine copression ratio so I can safely run on pump fuel.

The rear end is the next thing to work on. Right now it is pretty much stock with 3.73's in it. When I scatter it I will get something worthy for it. When that time comes, I am thinking of going to 3.23's or maybe something lower to help incress the top end speed on a road course. I am more conserend in out running a few of my friends turboed vippers in all aspects then quarter mile ET's alone.

98turbls1

iTrader: (17)

Yeah I hear you...I'm making my car in fear of the new z06's...they may run low 11's in the quater stock but people that have that kind of money and want a car that bad will probably mod it all to hell...Plus I'm sick of these damn 03-04 cobras...I'm shooting for 9's but am also concerned for streetability to kick some major ****... ARe you going to be running a meth kit?? It's really hard to say if you WILL on pump gas..I mean we can speculate but it's easier to yes or no if we have more of the pieces to the puzzle to work with...You will probably be able to walk all over your buddies Vipers when this is done...

Texas_WS6

iTrader: (9)

As far as the rest of the peices go, TSP is building the shortblock for me. The turbo kit will be installed next month and be running on the present engine with less turbo. I will upgrade the turbo once the 408 goes in it. I could go with a methanol kit but would like to try and stay away from it if the intercoolers work right. I will still have my Nitrous kit on it too, but I will window switch it to go off after 4000 or 4500 rpm and only shoot a wet 25 to 50 horse shot just to help get it off the line and help spool the turbo quicker. May play with that a little. Its probley going to come off once the 408 gets finished. As for camming the 408, I have no idea what to run. I lick my MS3 but I am not sure it will work good on the turbo, so I expect to change it out even in the 346. I have yet to decide on the heads. I am wondering just how much a set of aftermarket heads will help me, or if I can achieve what I want with the factory heads, maybe a little port work done to them or something. I might be wrong but it just seems to me I could force the air threw them the way they are, and they would help on the bottom end.

98turbls1

iTrader: (17)

Personally I would go with some good 6.0 heads and port them...Aftermarket heads will work better if you're going to be running a tremendous amount of boost because they have thicker decks than factory...If you start playing with some stock heads you can make them flow as well but if you're not careful then you may be spending as much or just shy what a good set of AFRs or ETs will cost you...then you'll be kicking yourself because you could have just went ahead and paid a little extra flow and got the thicker decks and a piece of mind...Shooting the juice would probably be good in small amounts but with the bigger turbo you want to get that tune EXACTLY right because if you're not careful you'll get the dreaded ping...I"m thinking of doing the same once I have everything dialed in on mine...As far as the cam I would either talk to your engine builder or maybe call speed inc. It's going to be a bitchin car man...Oh, what kind of turbo kit are you going to be running?? turbo headers or log?? I don't know if I caught that...

Texas_WS6

iTrader: (9)

The heads are going to be the last thing I get. I do want a set of AFRs. The other is a good custom intake. I was talking to my head porter in Midland Texas today, he was telling me about some custom intakes he's been working on. I bet I will go with his intake and a set of AFRs from him. Thats probly when I finaly pick the cam too. I like to wait until the heads have been flowed threw the intake to make the final cam choice. Jason at TSP does all me tunning. He has done alot of good work on my car over the last year. I will get most all the rest of the stuff for the engine from him as well. Plus they are right down the road from me, so I get to drop in from time to time. As far as the kit goes, you will think I am crazy, but I am building it myself. It will be a rear mounted setup. The turbo suppliers believe I can make the power I want even with the turbo in the rear. As far as any extra lag time, thats were the nitrous comes in. The only thing I have not comitted to yet is the were to place the intercooler or intercoolers. I think I will settle on daul intercoolers mounted in the same location the Procharger intercoolers are mounted. I am also seriously thinking of going threw the trouble of running the filtered fresh air from the present whisper lid all the way to the rear of the car instead of pulling the air from the back of the car. I just do not like all the road dirt kicking up. I know were to get some oval shaped pipping to help reduce ground clearence problems.

nick y

iTrader: (1)

[QUOTE=Texas_WS6]I am wanting to know what everyone thinks the best engine compression ratio is for a 408 Iron Blocked Turbo charged engine. I want to make at least 15psi to 20psi at full boost. TSP is going to be building the short block here pretty quick and I need to let them know what my target CR is so we get the right pistons for it. The turbo kit is air to air intercooled. I am wanting to be able to drive on pump fuel. I will be putting racing fuel in it at the track, but I would like to make the compression ratio low enough to not need the racing fuel. I was thinking around 8:1. What do you think? Can I get away with more without pulling alot of timing out of it? Would seam to be useless to put too much compression ratio in it if I would have to pull lots of timing out of it. I have not yet decided on a cam so if you want to spec one out for me too that would be good. What ever cam I go with it will be a solid roller lifter cam. I am trying to achieve 800 rwhp, so if you think I can do that with less boost and more compresion then let me know that too.


DUDE DONE IT HERE!

i run 347, 205 afr out of the box, 228 224 (from tsp) PTK te44, A4, TCI new bad azz billet 5 clutch stall, 3:15 .....compression 8.37
see my vid...www.nck.neptune.com see atco vid
i ran no alchy, pump gas on 17DR!!!! look at that MPH.
i got hammered on vette board for running low compression but aint heard sh*t now!

Texas_WS6

iTrader: (9)

My stupid Nortine internet security(slowitdowntodialupspeeds) will not let me veiw it. What did it run? Hell, how do I uninstall this Norton crap? This thing has LS1 Tech going slow and I can not see most all I want to look at!!!!

CarolinaWS6

i have the same goal as u but i have a 408 with 9:2:1 ported polished AFR 225s my motor goes in this week hopefully ill have some numbers soon

jyeager

8:1 - 8.5:1 is the range (as someone above said).

You can get your power goal easily and shouldn't really need to go solid roller, but if that's what you like why not?

This looks very much like what you want, so look at this: http://www.fuelairspark.com/Articles...p?ID=505885251

Pro Stock John

iTrader: (34)

Target 8.5:1 and you will never second guess yourself.

When you FI something you can end up at a total compression in the 12-17:1 range. Focusing on another point of compression NA is pointless when you are trying to hit a big number on pump gas.

Texas_WS6

iTrader: (9)

Thans guys. I spoke with my engine builder today and he strongly recomends 8.5:1 too with good intercooling. So I think that is the route I will go.

Thanks

Texas_WS6

iTrader: (9)

Thanks man, that brightens my spirits and makes me think my goal is very realistic. I am starting to think the boost level I will need to get were I want won't be as high as I was first thinking. I might get lucky and only need about 12psi. I hope that is the case.

Thanks guys!!!!