ChevyNo1

I will be heading back to the dyno this week and want to know what the HP/boost limits are . . . I am bone-stock down to the valvesprings. I've already put down 533/567 to the rear on 10psi.

What is the max boost I can run before I have head issues? I've heard up to 12psi, but don't know for sure . . . and what HP can I see before issues? I'm of the understanding that as long as I don't see KR, I should be OK.

Also, can you spot KR on a dyno graph? Like obviously? My PCM thinks my sensors are not working ( P0327/P0332 ) even though I recently replaced both of them. I need to know if I can see it in the graph, and how easy is it to HEAR kr while on the dyno.

Thanks guys!

- Dug

Noyzee

iTrader: (37)

Vaulve springs dont realy care how much power, I believe it is more RPM they dont like.
Heads are lifting around 700 but all varry from each other. Stock head bolts will do less.
I would say a stock set up, push it till it wont take it. Much more then 10-12 psi, you should have to start tweaking your MAF, I would call that good.
KR on the dyno you can see. Power will become shaky or flatline for the period of time, if it hapens, then comes right back it is just a spike, then fall off. Not a big deal.
Ithink what you will see is Lower timing, Richer tune, and better Octain will net you beter/safer power.
MAF spike will probably ocur if i had to gues, you can see that by a didp to rich in your AF graph, then a sharp spike to lean.
Good luck.

ChevyNo1

Thanks Noyzee . . . I believe when I dynoed at 10psi I was pretty well at the limit of the MAF then . . . so I will have to get power from timing I guess. I'm currently running 15 ramping up to 17 at redline, so I figure I can get more power from there.

So head lifting problems have been more at a certain HP level than boost?

Noyzee

iTrader: (37)

I believe so on that head lifting. Dont quote me tho.
As for timming, Im close to you, I peek at 19*, but i run a little 104 just for safe keeping. i mix about 2 gall 104 with 8 gall of 93-94 all the time. This will alow more timming, hense making more power.
KR and AF is the most importaint part of tuning, and I notice if i tune for 9psi dyno, put it on the street, and boost goes up a pound, so tune conservitivly.
Good luck.
What do you rev the car to?

ChevyNo1

I take it right to redline, so about 6200 . . . I'm still stock everything motor-wise.

Thanks for your help!

Noyzee

iTrader: (37)

I hve duel springs, comp push rods,comp liofters, and i still shift at 6,200. No need to go higher then that IMO
Good luck.

Pro Stock John

iTrader: (34)

I'm thinking that almost 600rwhp might be doable but do you have a fuel system to support that?

I'd tune it conservatively, you can see what it does at 12.7:1 AF at WOT but you would not leave it at that number, I'd fatten it back up to to 11.7:1 so that you have keep it safe.

ChevyNo1

Thanks John . . . I have the 340 Walbro that came with the Incon . . . I have 42lb injectors in it. Stock fuel lines and rails however. I also have a Kenne-bell boost-a-pump installed and ready to use when I need it. Do you think that will be enough?

Also, my car is currently tuned to about 11.5-12.0 . . .

- Dug

Pro Stock John

iTrader: (34)

Did you use the boosta-pump when you last dynoed?

Noyzee

iTrader: (37)

42* wont take you to far, i see some people going to the 550 mark but much more is pushing it. But 600 could happen, but i dought with 91 oct, maybe 100 or 104.
PSJ when is your car going to be done???
Speed inc is doing you a sick car. I remember when i was there in nov last year I saw your car, it was the nastiest car i had seen!!! I coulndt believe it!
Good luck with it.

RyanJ

9 times out of 10 boost has nothing to do with 'head lifting'. its detonation. keep that down (as in non-existant) and you can max out those turbo's...like someone else we know.

ChevyNo1

No, I did not use it last time . . .

Noyzee, what difference would the 104 make in how much pump I have ( or injectors )?

- Dug

ChrisB

Boost will effect your valve spring pressure though - it will reduce your seat pressure by valve area * boost pressure. Say you had a 2.00" intake valve, that would have ~3" of valve area (depending on valve stem thickness and style - nailhead, vs. tuliped, etc.) and 10psi of boost - that is 30lb of pressure on the valvespring while the valve is closed - so if you have 80lbs normally closed (don't remember what stock are), with 10lbs of boost you only have 50lbs of actual pressure - since the seat pressure is going to be a primary factor in stopping seat bounce - well, you may have issues.

It would probably be a good idea to swap out the valvesprings if nothing else.

Noyzee

iTrader: (37)

I may have said that wrong. I mean, 104 is cheap insurance. But the 42* injectors might non push the higher power. Nothing to do with 91 or 104 octain, fuel in general.
Sorry.

Pro Stock John

iTrader: (34)

I would get a better set of valvesprings on there.

I think you could hit 600rwhp with 104 u/l.

IMO use Rod442 as a guide, his 6.0 heads drop compression a tad but they flow better too.

Noyz it's getting worked on right now but we can talk about it in another thread.

ChevyNo1

Thanks guys . . . 6.0 heads to drop compression are in my near future, I wanted to wait until I got the heads so I don't have to do the springs separately. I'm hoping February-March . . .

Thanks Noyzee, I just wanted to make sure I understood what you meant and wasn't missing anything.

So what I'm getting is that I don't have to worry about head lifting unless I get detonation . . . is that correct? So theoretically I could run 12-14psi with no problems as long as I don't have detonation?

- Dug

Noyzee

iTrader: (37)

I think that is false. Could be wrong. It is pressure that lifts the head. You can only dump so much into it befor it seeps out.
Someone correct me if im wrong

Noyzee

iTrader: (37)

chevy, why dont you add a bit of gas, (104) and try adding timming insted of boost? Might be a bit safer.

Pro Stock John

iTrader: (34)

You can lift a head from detonation or from the heads/head bolts not being able to handle the cylinder pressure.

I think 99% of the folks who have lifted heads in this section can attribute it to detonation.

I used to see folks post a lot of lean WOT AF's that were unsafe, like 12.7:1 - 13:1, that's like 13.7 - 14:1 on the track under full load.

I think you might run out of injector first but I don't know for sure.

ChevyNo1

Noyzee, I will do that as well . . . just trying to get the car maxed ( safely ) on pump gas first. I don't expect to go beyond 10-11 psi anyway . . . then I'll bring in the timing.

Thanks John, I should be safe with my 11.5 then!

- Dug