ZL1Killa

iTrader: (17)

I want to take the stock block @the normal 5psi of boost with the STS kit...as you can see in my sig that I already got some power with bolt ons...

I would like to know some opinions on what all i would need to upgrade
go ahead and NOT say trash the 10bolt as that I already know.

need fuel pump, engine main girdle (shown at EPP), ARP studs, hrdnd pushrods, titanium retainers...etc

just need some help here in wanting to keep the stock block surviving the 5psi of boost for a good amount of time

magius231

iTrader: (8)

Upgrade your valvesprings, fuel pump, injectors, good tune, and if your an A4 consider a decent torque converter.

longrange4u

iTrader: (2)

Man.... if your only going to do 5psi and thats it (Hard to stay just there). Then you only need the upgraded fuel and tune. Thats all that is needed for 5lbs... an FMIC and Cam would be good too.. but not nessessary. You may want to read what that girdle is truly for... your stock pistons will give out LONG before you will need that girdle.

jyeager

At 5lbs you only need to supply enough fuel and have it tuned right. Nothing else mentioned is necessary...not even the ARP head studs (although they are great and a definite upgrade any time you unbolt your heads).

ZL1Killa

iTrader: (17)

Thank you greatly!!! that was a lot of much needed info. longrange4u thanks man, what are u running boost wise?

I would get the ARP head studs and if i unbolt the heads then i will also replace the gasket with the thicker one that is new and lowers the compression a tad

ZL1Killa

iTrader: (17)

now also I would be pushing 475+ to the ground.... something is gonna be under a lot of stress... i know i need to strengthen something up.

From what i hear though they say the stock block is good to 650+~700HP

I realize that it will be hard to stay @ 5psi but the thing is that we want 450 @ the wheels. I know how project cars go and they develop to be true beasts but its a father and son build and I caused my dad to have a midlife crisis and i got him back in cars. We want the car to truly last once we get to 450HP...the turbo will be fun and awesome to drive. Thats what we want. I would greatly appreciate any info on part to get to help make the block last at 5psi. I DO believe you when you say a good tune and getting fuel to it. I just realize that I'm still running the stock cam, stock pushrods, stock valvetrain and what not and see that from the 300 or so HP the car comes with typically those parts aren't meant for 500HP(at the crank)

jyeager

Nothing in the valvetrain knows anything about the boost, so forget lifters, push rods, rockers, valves, springs, retainers....those only need upgrading if you want more RPMs.

I don't recommend that because RPMs are harder on the engine than boost.

I could get in to the physics of the issue, but I'd need to scan and paste pressure graphs and whatnot. The fact is that boosting the engine at mild levels DOES NOT increase the load the crank and rods see. Why? Because the force from compression is not absorbed at the same time as tensile forces. The force that these parts see from compressive forces (at your power levels) are less than the tensile forces the car sees at 6000 rpms.

There's a chapter devoted to this in Corky Bell's book Maximum Boost. I highly recommend you get it. It's cheap if you consider it part of the cost of your turbo upgrade.

magius231

iTrader: (8)

well, sort of...

Valvesprings hold your valves down (duh ) When you push 5psi of boost into the intake, that 5psi is pushing against the valvesprings too, and if your valvesprings are weak it could push the valves open at the wrong time (not real likely with 5psi, but it could happen). On an otherwise stock exhaust setup your probably pushing 3:1 exhaust/intake pressure or more, so theres >15psi pushing on the exhaust valves as well and thats where the problems normally come in.

I've heard of enough people having issues that when I do mine I'm going to spend the extra money and make sure it doesn't happen.

ddnspider

iTrader: (26)

You should do springs and pushrods even if your staying with the stock cam because of the increased wear and pressure on them from boost.It takes more effort to close the valves.And you dont need Ti retainers,but they do help an engine rev a lil faster than the steel ones.Get a Walbro 255 intank fuel pump,your stock rails are fine at 450rwhp.You didnt state if its an auto or manual so either a stall or a clutch(for that power level id recommend a Spec 3).If youre positive your wanna stick to 450rwhp get 42# injectors,otherwise get 60#injectors so u dont have to rebuy down the road.Besides all that just make sure the tune is good and you should be fine at that power level.

jyeager

Wait a minute guys...You think the valvesprings have to work hard to push the valve shut against the boost pressure? Consider the pressure exerted by the valve spring. Think it compares to 5 psi? Think that pressure can just spontaneously push a valve open?

That's just plain wrong advice. Now if you were to argue that you recommend a spring replacement just because they fatique over time, then fine. But don't base it on a little bit of pressure pushing on the back side of the valve. Besides, consider the fluid dynamics. For the most part, the cylinder is filled with high pressure air before the intake closes...pressures were equalized when it opened.

Blackbird

no it's not wrong advice.

at 5psi he may be ok, but if he steps it up he will experience valve float and the associated power loss along with it.

jyeager

I'll be the first to admit the limits of my knowledge. I only know what I've learned from magazines, boards, and Corky Bell's book.
That being said, I find it interesting that I've never heard about this issue of boosting before. I would have thought Corky would mention it in his book devoted to turbo charging.
Add to that the fact that what you are claiming is contrary to intuition and I've got to politely ask if you can give me a satisfactory explanation for the phenomenon.

How can 5psi or 10psi or 15psi overpower the kind of pressures being exerted by a valve spring? Especially when the open valve results in a (at least partial) equilization of pressures before beginning to close.

Perhaps you are referring to a situation where the engine is being reved to the limits of the stock valve springs already, then adding boost results in valve float 100 or 200 rpms earlier than before.

ddnspider

iTrader: (26)

Id rather base my knowledge on experience and the experience of others who have already gone through this,(ie many have experienced valve float above 5k on stock springs then when they switch to comp 918's or doubles viola!it goes away).I like how u come in here and start posting in these threads contradiction others when u arent giving any real proof.Like in the other thread about "You have a misconception that you can use a smaller turbo if you use the 370 ci option. You talked about using the shorter stroke to run higher revs which means that with both engines you are talking about the same amount of air being consumed.Each one will need the same turbo." When in fact they wouldnt ues the same turbo because your failing to take into account efficiencys and that a turbo for a 370 would more than likely choke a 408 due to it being to small.maybe you should check out www.forcedinductions.com and read the turbo 101 section to get a better idea of how different turbos would work on diff motors.

Blackbird

Remember "5psi" is purely a measurement of back pressure, that is not the extra amount of force being placed upon the valve spring. I am not an engine builder or engineer and would have to go research to tell you how to calculate how much extra load is placed on the valve springs and why they float. Hopefully somebody with that knowledge can chime in.

I do know though thru experience and dealing with shops and reading the forums for years and years, that anything but the smallest amounts of boost will cause valve float with the stock springs on these motors.

jyeager

I appreciate any information you can give me to increase my knowledge and dispell any misconceptions I have. I included my reasoning so as to give you something to work with when responding. I asked honestly for you to explain the issue to me.
You are off-base getting testy about this.

If there is a body of experience that finds valves start to float dramatically earlier with a boosted motor, that's news to me and I'll be glad to find that out.

Thanks.

ps. I'm open to being corrected on the other thread I also.

ddnspider

iTrader: (26)

i apoligize if i came off a little cross,but from the posts ive seen u make today it at least "sounded" like u were meaning to correct others and make them sounds ignorant,which isnt appreciated by those whove been around for awhile.You can search the Dyno section and this section as well for problems with valve float on a FI engine and it is almost ALWAYS traced back to springs and pushrods.But seriously the turbo 101 is great info on that site.

jyeager

Peace.

Initially I did think I was correcting you, but done politely I figured that it was appropriate even if I ended up being corrected. I'm still curious to know why this phenomenon occurs. If it's just the extra pressure on the intake side of the valve I'm curious why from the standpoint of the physics involved.

I apologize if my tone was insulting, I never meant it to be.

As for the turbo 101 stuff, yes it's good. I've been there and looked it over and it confirms the same info I got from reading Corky Bell's book. If you still think I'm wrong on the other post (ala turbo sizing) I'd like your input. The Turbo 101 data doesn't seem to be disagreeing with me.

ddnspider

iTrader: (26)

Just a word of advice,dont treat Maximum Boost like the Bible like some do,its not 100% accurate from what ive experienced,ask Slowhawk as well.Anywho,ive never really had it down pat as far as the spring theory but im my mind it seems pretty simple.....picture an NA motor...air is DRAWN in correct?Now picture a boosted motor, the intake is now pressurized and air is FORCED in instead,at higher rpms the springs have more strain on them because the valves are opening and close 100 times a second,while air is still be forced in(trying to keep the valves open) which in tern adds more stress to the springs(stock ones anyways).Thats how i see it.
As far as the other thread,in the Turbo 101 part of the site,they give an example of 3 turbos to 1 motor and their efficiencys.After a certain point the 2 turbos are too small and wont work with the motor.You can put a turbo sized for a 408 motor on a 370 but its not too wise to put a turbo fit for a 370 motor on a 408.Longranges problem is that he has to find a setup that compromises power output with spooling,and the rear mount setup is making that tougher.

jyeager

Roger on the book. I'd like to know where the book is wrong for future reference (to anyone familiar).

The impression I'm getting is that the underlying reason for the valve spring issue is that stock springs are at their limit to begin with. Perhaps in some cases, the problem is first identified after the turbo is installed because it's the first time the car was on a dyno?
I know I've seen lots of threads about dyno sessions where the valves are floating at 6K on an NA engine.

ddnspider

iTrader: (26)

ill dig up my book and see what i can remember off the top of my head and maybe pm ya....
the springs are ok in stock form on a stock engine on a stock rev limiter but more than that and as you said theyre overworked and become damaged(ie once stretched the motor physically cannot rev as high as it used to).Many people do dyno their stock or bolt on car and theyre usually ok,but what ull find is that the ones who are having trouble are usually either
A) revving higher
B) using a higher ratio rocker
C) something else that affects them,normally an intake and exhaust wont just cause this problem.