[MrSurly]

That's why you're getting the echo when I say it. It's deep in here,

Just in case anyone wonders what sort of collateral damage ensues when you select the "427" checkbox....
click my sig line.

 

[Rubber Duck]

That's why you're getting the echo when I say it. It's deep in here,

Just in case anyone wonders what sort of collateral damage ensues when you select the "427" checkbox....
click my sig line.

Yes, when you build the engine for 'Max / Peak HP' it can get very expensive..lol

 

[Rubber Duck]

Please see attached for head information. I only want to get 800whp. But if can make 850-875 easy, that’s what I want.

Depending on the camshaft & compression ratio you chose. . .
yes those heads should be more than adequate for your new HP Goals..

However, I have been suggesting that you lose the HP Goals, which require high engine rpm, which in turn generate a higher 'mean / average' piston speed. High piston speeds are required for high HP goals, as they generate a high depression across the intake valve required to fill the cylinder. Your going to use a roots blower to fill the cylinder. And roots blowers, because they are driven from your crankshaft, push a lot of air into the cylinders at low engine rpm. NA Engines 'don't'. So why not build a large volume engine, and fill the cylinders at a low engine rpm, and generate huge amounts of torque.

HP is simply Torque multiplied by Engine RPM. . . .

Make it simple with a big volume engine:
Put sufficient compression in it, close the intake valve so as to hold high cylinder pressures at low engine rpm, and your big engine will generate much low engine rpm torque. Now you don't have to spin the engine high, and now you don't have to invest in lightweight valves, high open pressure valve springs, etc.

But you might have to invest in a bigger & better tire.

Cheers

 

[Bigwilly1267]

Depending on the camshaft & compression ratio you chose. . .
yes those heads should be more than adequate for your new HP Goals..

However, I have been suggesting that you lose the HP Goals, which require high engine rpm, which in turn generate a higher 'mean / average' piston speed. High piston speeds are required for high HP goals, as they generate a high depression across the intake valve required to fill the cylinder. Your going to use a roots blower to fill the cylinder. And roots blowers, because they are driven from your crankshaft, push a lot of air into the cylinders at low engine rpm. NA Engines 'don't'. So why not build a large volume engine, and fill the cylinders at a low engine rpm, and generate huge amounts of torque.

HP is simply Torque multiplied by Engine RPM. . . .

Make it simple with a big volume engine:
Put sufficient compression in it, close the intake valve so as to hold high cylinder pressures at low engine rpm, and your big engine will generate much low engine rpm torque. Now you don't have to spin the engine high, and now you don't have to invest in lightweight valves, high open pressure valve springs, etc.

But you might have to invest in a bigger & better tire.

Cheers

Ok got it. Higher compression equals more torque. Lower compression equals lower torque and higher horsepower from a bigger engine but

Depending on the camshaft & compression ratio you chose. . .
yes those heads should be more than adequate for your new HP Goals..

However, I have been suggesting that you lose the HP Goals, which require high engine rpm, which in turn generate a higher 'mean / average' piston speed. High piston speeds are required for high HP goals, as they generate a high depression across the intake valve required to fill the cylinder. Your going to use a roots blower to fill the cylinder. And roots blowers, because they are driven from your crankshaft, push a lot of air into the cylinders at low engine rpm. NA Engines 'don't'. So why not build a large volume engine, and fill the cylinders at a low engine rpm, and generate huge amounts of torque.

HP is simply Torque multiplied by Engine RPM. . . .

Make it simple with a big volume engine:
Put sufficient compression in it, close the intake valve so as to hold high cylinder pressures at low engine rpm, and your big engine will generate much low engine rpm torque. Now you don't have to spin the engine high, and now you don't have to invest in lightweight valves, high open pressure valve springs, etc.

But you might have to invest in a bigger & better tire.

Cheers

ok got it. So high compression equals more torque and a longer lasting engine. You mentioned the individuals you worked with for 5-8 years and the compression they went with was 11.0 to 11.25 or so. If I wanted 12.0;1 compression is that ok?

 

[Karch]

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[Blades1_99]

^^^hahaha

 

[Bigwilly1267]

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Are you saying that compression is to high?

 

[Karch]

Are you saying that compression is to high?

Yes


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[Bigwilly1267]

So this chart is about right then.

 

[Karch]

Who is building your engine?


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[Bigwilly1267]

Who is building your engine?


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At this time i don’t know yet. I’m trying to get a better understanding of what to expect and to be pointed in the right direction

 

[Rubber Duck]

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It's a learning process folks.
Any of you can chime in with your thoughts.

Steve,
So, how much compression would you run.
Based on what variables.

 

[Rubber Duck]

So this chart is about right then.

Good Start; but the answer to your question is a bit more complex than that, as your engine has a roots blower on it. But let's start with; no you don't want 12.0:1 static compression in your engine..

Your HP & Torque goals will determine how much compression is required.

However, the Octane Level of your fuel, as well as the competence of the tuner will generally offer a resistance to how much compression one can really run.

This is especially so on the street, as heat becomes more of an issue than one normally sees on the drag strip, as runs down the track are only a few seconds long.

 

[Bigwilly1267]

Good Start; but the answer to your question is a bit more complex than that, as your engine has a roots blower on it. But let's start with; no you don't want 12.0:1 static compression in your engine..

Lmbo 10-4

 

[Karch]

It's a learning process folks.
Any of you can chime in with your thoughts.

Steve,
So, how much compression would you run.
Based on what variables.

Depends on engine size, blower size, and primarily usage.

Max of 11:1 on any street driven car…I rather leave money (power) on the table than parts on the ground.

But, if you are running races only and unlimited categories, have at it.

IMO, too many here of late get all caught up in big power numbers, and then, after 6-12 months of driving the car, realize while the car is really fast, it’s just not as much fun to drive a lot of hours in.

My gf’s Porsche 718 Boxter had a dead battery last weekend.

I was able to jump it and asked if she wanted to go for a drive? She said yes.

Now, it’s an automatic, but it’s a PDK…they are the shit.

I put it in sport mode, turned off the DRL and ac compressor, and went through some canyons, down to PCH (we had affogatos in Malibu…not a bad deal trying to charge the battery)…

I called her the next day and said that little car is a blast to drive.

It doesn’t overpower the tires (I did get a bit sideways once, at a lower speed), doesn’t overpower the roads like my V, and you can push pretty good without having to hit obscene speeds on the street.

Just my 2 cents from observing years of builds on this forum, talking to many owners, and having my own car.

On that note, I thought of more power, I have the resources to do it, but I realized I have no compelling reason to do so.

If the track was closer I might try hard to see if I could crack a 9.xx with some tuning and a lot of driving practice, but I’m already busy enough with other hobbies.


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[jcmgt]

OP, may be more efficient to pay Matt / PatG or other reputable builder a consultation fee. They would set expectations based on verified build experience.

 

[Bigwilly1267]

I think I’m going to go with the 376. I do want to be able to enjoy driving around town. As a matter of fact I hadn’t intended on going to the track with it.

 

[713V]

Great info. I would like to build my own one day. And good luck bigwilly on the process.

 

[Rubber Duck]

Depends on engine size, blower size, and primarily usage.

Max of 11:1 on any street driven car…I rather leave money (power) on the table than parts on the ground.

But, if you are running races only and unlimited categories, have at it.

IMO, too many here of late get all caught up in big power numbers, and then, after 6-12 months of driving the car, realize while the car is really fast, it’s just not as much fun to drive a lot of hours in.

My gf’s Porsche 718 Boxter had a dead battery last weekend.

I was able to jump it and asked if she wanted to go for a drive? She said yes.

Now, it’s an automatic, but it’s a PDK…they are the shit.

I put it in sport mode, turned off the DRL and ac compressor, and went through some canyons, down to PCH (we had affogatos in Malibu…not a bad deal trying to charge the battery)…

I called her the next day and said that little car is a blast to drive.

It doesn’t overpower the tires (I did get a bit sideways once, at a lower speed), doesn’t overpower the roads like my V, and you can push pretty good without having to hit obscene speeds on the street.

Just my 2 cents from observing years of builds on this forum, talking to many owners, and having my own car.

On that note, I thought of more power, I have the resources to do it, but I realized I have no compelling reason to do so.

If the track was closer I might try hard to see if I could crack a 9.xx with some tuning and a lot of driving practice, but I’m already busy enough with other hobbies.


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My posts, should, if I have done my job, stated don't go for big HP Numbers.

If you desire to make more 'Power' so to speak, from stop light to stoplight,
then simply increase the engines torque, at lower engine rpm.

Nothing is easier than making big torque, with a larger volume engine.
Also, one can add a roots type DD blower.

So a big motor and a roots direct drive blower, are something
from heaven regarding building big torque.

But the answer as to how much compression can be used, is much more difficult to answer.

-something to consider-
If the torque curve pretty much follows the VE% curve, then we can also
arguably state; the BMEP curve, also follows the torque curve.

Cubic Inches, VE% and Compression Ratios help to determine the Torque Curve.
So then, we would desire to first determine how much Torque the engine will make.

VE% is linked to engine rpm, induction system, etc.
This can be controlled.

Large volume engines tend to not have sufficient valve area.
Speaking here of CID divided by Valve Area.

So they tend to be self-limiting regarding VE%.
And this limitation also reduces the peak engine rpm.

Compression ratios can be varied during the engine build.

So then; how much compression can one use, with an inefficient
roots blower, on a hot day, on a long road trip, with pump gas.

Or, how much compression can one use, on a hot day, long road trip, with E85.
And how about adding some Toluene if one is serious about their torque. . . .

-not always practical, but-
Add sufficient Toluene to either pump gas, or E85
and one can run up to about 250psI of BMEP.

Finally; if the static / geometric compression ratio falls
below ~10.2:1, the engine becomes less efficient.

Conversely; if the Cr rises above 10.2:1, the engine becomes more efficient.

So then; it appears that we have many variables which
we can manipulate to build said engine.

But the 'Performance Goals' of any build must come from the customer,
the owner of the car in this case.

Let's remember; IC Engines are not efficient at pulling air into the cylinders at low engine rpm.

The Roots Blower, because it is a DD PD Blower, is a perfect, low dollar solution here.
But it raises the VE%, which in turn raises the 'Trapped Compression'.

How about starting here:
427 CID, 10.2:1 static CR.
Low boost, maybe 10psi.
E-85
Toluene added on race day.

More than that, and one would be required to add a heavy dose of Meth, via one
of the aftermarket companies that do this via an onboard ECU.

Cheers

 

[random84]

10:1 bro.



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