LS6427

iTrader: (2)

1) If I build my 390ci with 10:1 cr.......can it be hit with 18psi later on, if I use race gas full time and meth? Or just race gas.......

2) Later if I want that 10:1 cr dropped to say 9:1.....can I get that drop in cr by just changing the heads or re-working the chambers on the current heads to get that drop in cr?
Meaning....I won't have to remove the engine and change pistons to get that drop in cr.......???

I'm thinking of going 10:1 right now so its not such a N/A dog for the next 6-7 months, maybe longer, till my turbo kit goes on. I plan to spray it with maybe a 200 shot in the mean time.

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dschmittie1

iTrader: (64)

My AES 385 is 10:1 and I am running 13 psi right now and plan on going much higher next year like 18-20psi. I am running E85 for fuel. My last motor was a 347 and I ran 15psi on 93 and Meth with 9.9:1 CR

2 yes you can drop the CR by changing the heads.

Also I will say fireball ran ~10:1 CR at 35+psi on C16

LS6427

iTrader: (2)

Thanks for the info..........can I also drop compression by just working the chambers in the current heads, and doing nothing else?
Or will I need to change the heads totally?

It will probably be a good idea anyway for me to change to thicker deck heads when the turbo kit goes on. But I'm just curious in case my current heads work ok at 18psi....

.....what RWHP did you get with the 9.9:1 cr 347ci on 15psi and 93 octane + meth?

.....what RWHP for the S88 385?

RWHP numbers are important to me....roll racer only.....not a drag car. Street driven only.

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Sales@Tick

iTrader: (3)

Dynamic matters more than static.

I'm sure Fireball's cam dropped his dynamic compression well below 8.0:1 and quite possibly under 7.5:1.


Thicker head gaskets will increase quench which in a boosted application is a good thing not so much in a N/A deal though.

I would say anything 8.0:1 DCR or under you could run 10psi on pump gas+meth as long as you didn't try and get crazy with the timing. If you wanted to run 18-20psi on 8.0:1 I'd say it would take a better fuel than pump gas to do it with like E85, E98 or a unleaded/leaded race fuel.

LS6427

iTrader: (2)

If I go with 10:1 cr.....what dynamic should it have?

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LS6427

iTrader: (2)

I thought filling in space raised compression? I was thinking they would have to be ported out to remove material? NO????



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dschmittie1

iTrader: (64)

Not sure on rwhp of my old 347 combo enough to go 9.5@152 in a 3550 race weight so around 800 on 15 psi

385 s88 combo made 620 on 6.5 psi. Never got to turn it up on the dyno due to an alternator issues. This setup just went 9.4@149mph on 12 psi

Sales@Tick

iTrader: (3)

You are correct, disregard what I said.

LS6427

iTrader: (2)

Ok....but can material be removed from the heads to lower compression?

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Sales@Tick

iTrader: (3)

Are you going to be using the same cam you have now?

How far out of the hole or how far in the hole is your piston currently? What is the chamber size going to be on the new motor? Bore, stroke and rod length? Head gasket thickness? Dome or dished piston and how much volume on either?

These will all determine what dynamic you end up with.

I would want it to be 8.0:1 or lower. If you want to run pump gas on 20psi you'll need it around 7.5:1, but to get this DCR you'd have to run a cam that is not really correct for your application because it's going to have to be pretty big to drop the dynamic down that low. It would be easier to get the static compression down lower and then run the proper cam for your application and let the DCR be dictated that way instead of having to crutch it with a cam that is too big for your set-up.

I'm no machinist even though I'm taking machining classes currently at the local community college, but from what I've gathered from there and outside of class if you can re-shape the chamber and remove material from it then yes it will raise the amount of volume in the cylinder thus lowering compression.

LS6427

iTrader: (2)

Well, this is a new engine build. I can use whatever is needed.

I guess my builder will have all those answers......lol

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LS6427

iTrader: (2)

I've gotten mixed answers on this.....do I need Inconel exhaust valves for 18psi?

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LS6427

iTrader: (2)

Well...I have to go to my builder now. Order my Callies crank and drop off my heads to him.

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Sales@Tick

iTrader: (3)

They are good for high heat applications such as an application that will run a fairly large amount of boost.

I would use them.

98Z28CobraKiller

iTrader: (17)

OP, I think that you are looking at this from the wrong end. If you want to grow up to be a surgeon, you don't start off by going to the Truck Driving Academy. Set your goal and work backwards from there. If not, you will have the tail wagging the dog.

Stainless exhaust valves are fine to 1200+ rwhp. This project wont need them.

Here is my free advice that could ultimately save you a bundle. Send me 5% of what you save as my commission. LOL

-Don't get bogged down in cam dynamics and dynamic compression. First of all, it's a voodoo calculation and from the sound of what you are after, you will not want to drop in a monster cam that will drop your dynamic compression enough to bandage too high a static compression FOR THE APPLICATION. It's the equivalent of using a 1/2 drive ratchet as a hammer. It works, but it's not right FOR THIS APPLICATION.

-Set a clear goal for your final project power. Keep in mind that your goal will probably increase by the time you get there so pad it a little.

- What will you realistically be doing most with the car?

Get back to us with those answers and you should have better luck at being pointed in the correct direction.

LS6427

iTrader: (2)

Then I'll go stainless.

I want no less than 1,000 RWHP......I want to match a turbo to my engine that will make that power without the turbo being maxed out on the ragged edge. Any additional power above 1,000 will be a bonus to me. 4L80E tranny.[/quote]

100% street car. Roll racer only. Fun weekend car......
It will NEVER be set up to drag race at a track.

......Thanks.....

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98Z28CobraKiller

iTrader: (17)

Is this motor for the car in your sig? Do you have most of your old stuff to reuse for this build or is this a brand new project? Do you intend to keep A/C?

LS6427

iTrader: (2)

The new engine is going into the same car in my sig. Only difference will be a new engine and new 4L80E.

Keeping A/C is a must........

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98Z28CobraKiller

iTrader: (17)

OK, A/C is the big hurdle at this point. In order to make the kind of power potential (1200 rwhp capable turbo setup to operate at 1000 rwhp), you are now pretty much boxed in to a twin kit or a rearmount (which isn't an option IMO). I have not yet seen a big single turbo kit that can deliver that performance capability and retain A/C. It's not so much about fitting the turbo as fitting the necessary DP to support (assuming you don't want to go out the fender). So once you come to terms with that reality, you can now move on to the now.

So you build your 390 with the requisite good **** to make it a reliable 1000 rwhp bottom end capable of squeezing out a few more ponies in a pinch. What I would do is spec out my pistons to get me to a 9.0-9.5:1 with a standard .055 LS9 headgasket. But instead of running the LS9 headgasket, I'd run a thin .040 gasket Cometics. Just make sure that both surfaces are freshly machined on the block and the head before it gets put together. I would run that same cam in your sig in the nitrous motor along with all your other ****.

Come turbo time, Pop off the heads. Switch to the thicker LS9 Gasket and tune for the given fuel. I'm not a fan of meth as it sort of defeats the simplicity of not injecting a foreign substance by way of electronics, pumps, solenoids and plumbing that can all potentially fail or cause problems. But that's just me.

Sales@Tick

iTrader: (3)

Are you saying he should run that cam with the turbo or just while he runs it N/A?

If just while he is N/A I agree 100%.

I'd like to hear your thoughts on why DCR is a voodoo number?