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10:1 bro.



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10.2..:)

Actually, it could be either.
We simply need to understand that anything around10.1, will generate
an efficient engine, capable of converting the mass charge brought into
the cylinder, into power, at a rate favorable for good torque and hp.

Up around 15.2:1 on NA Engines, we are looking for a %VE (not VE%) of over 128% when
the intake valve closes, when the piston has begun moving past the intake cycle, and is
moving into the compression cycle.

The trapped compression on these engines is ~17.2:1.

Actual VE% is above 150%.

So an engine spinning 10,500 rpm, is inhaling air as if it was spinning ~15,500 rpm.

This then provides for an NA Engine the ability to produce about 3-fwHP / CID.

And here, with these FI Engine platforms, it's a big thing to produce 900 HP
from 376 CID. That's 2.39 HP / CID, using a blower.

Why?

Because these engines, including the roots blower, are very inefficient.

Raising the Static Compression Ratio will help, but we desire to do
that without moving the engine into self-detonation.

This then depends on the customer / owner making rational decisions. . . .

Cheers
 
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9.2 for me
And your engine will be spun to a higher RPM.

Therefore, along with a higher engine rpm and the resultant increase in piston speed, along with your larger blower, your engine will have a higher trapped compression ratio.

To increase either peak torque, or peak horsepower, within a given engine volume, it gets real expensive.

Engine rpm needs to be increased, and the entire Induction system needs to be replaced with highly sophisticated and expensive parts.

Would you like to speak regarding that.😆
 

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Its good to read all of this and makes more sense to me why my builder went with 10.5:1 on my 427. Although going turbo and not supercharger.
 

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To be fair, I run 93 most of the time.



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Determining the correct fuel, is so much more important than most understand.

A simple change in combustion chamber, piston design, engine cooling etc. can make differences in what fuel will be the correct fuel, for any given Engine being pushed to its limits.

With these engines heat is particularly the enemy.

The mass flow recovery system on these engines is most important!

The two rear cylinders need much help regarding reducing heat.
 

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Determining the correct fuel, is so much more important than most understand.

A simple change in combustion chamber, piston design, engine cooling etc. can make differences in what fuel will be the correct fuel, for any given Engine being pushed to its limits.

With these engines heat is particularly the enemy.

The mass flow recovery system on these engines is most important!

The two rear cylinders need much help regarding reducing heat.
thats why i have gone hardcore on the thermal coatings within the head and piston as its ment to stop hotspots accruing and stop the exhaust heat getting into the head and thus intake temps should be least affected i hope, was hoping to get mine done by end of this year to be able to see if all my efforts have paid off but we got flooded out last month went foot thru the house and lucky i had my car up on jack stands couple feet off the ground which saved it but its made things a bit slower :(
 

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thats why i have gone hardcore on the thermal coatings within the head and piston as its ment to stop hotspots accruing and stop the exhaust heat getting into the head and thus intake temps should be least affected i hope, was hoping to get mine done by end of this year to be able to see if all my efforts have paid off but we got flooded out last month went foot thru the house and lucky i had my car up on jack stands couple feet off the ground which saved it but its made things a bit slower :(
On NA Engines we attempt to retain heat in the primary tube, until the tube bends.

The heat keeps the velocity up, which in turn helps to pull the intake charge into the chamber, before the piston moves down on the intake stroke.
***However, this wastes about 30° to 40° of cam duration.

On these engines, since most do not use any, or minimal overlap, and we donot have to rely on the exhaust pulling the charge into the cylinder, I believe we Should desire to keep everything as cool as possible.
***With maybe only 5° degrees of overlap @ 0.050" of lifter rise, and pressure behind the intake valve at all times, these engines require a very different cam and rocker arm ratio, and different con rod to stroke ratio in order to make power.

However, since we can't redo the coolant passages within the cylinder head, or extend the exhaust port further to help cooling, we must rely on the mass charge to do this. This is where E85 or Alcohol helps.

But consider this; a somewhat overly large roots blower, with a sufficiently sized TB.

Now, we no longer have a restricted InFlow Engine, and we could now look at the camshaft from a different perspective.

Since our current camshafts limit power on the intake cycle, this
would I believe, allow for these engines to provide more power,
while simultaneously helping to keep the chambers cool.

Here, assuming the engine might be on a Trans Brake, where the converter does not limit the engine rpm to some engine rpm, far under peak torque, we could move a greater percentage of mass charge through the chamber, thereby helping to cool the cylinder down.

----------------------------------------------------------

Hope the damage to your home is limited, and you can get it repaired soon.. :)

Cheers,
Bruce
 
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Discussion Starter · #53 ·
Thought on this short block number
 

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1. I will say that AMS Racing built my LSX and it appears they do great work (though mine isn’t on the road yet, nothing to do with AMS) and they will happily build the engine with ANY special components you prefer and of course the price adjusts as you make upgrades… but they are just charging the difference vs the K1 or Compstar or whatever was in the advertised build. I started with their advertised LSX 427 and then spec’d EVERY internal part my way including special ordered rods and pistons. In my case they had the block and the Brodix crank in stock.
2. The m311 heads are built for a 4” bore and work just fine on bigger bores, but some will say that they don’t really take “full advantage” of say a 4.125 hole.
Since you aren’t shooting for the moon, that’s fine.
3. The m311 heads are SIX-BOLT heads and it would make good sense to consider taking advantage of that when buying a block. The LSX 376 for example would provide six-bolt security. Or Dart, RHS, LSNext etc.
 

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1. I will say that AMS Racing built my LSX and it appears they do great work (though mine isn’t on the road yet, nothing to do with AMS) and they will happily build the engine with ANY special components you prefer and of course the price adjusts as you make upgrades… but they are just charging the difference vs the K1 or Compstar or whatever was in the advertised build. I started with their advertised LSX 427 and then spec’d EVERY internal part my way including special ordered rods and pistons. In my case they had the block and the Brodix crank in stock.
2. The m311 heads are built for a 4” bore and work just fine on bigger bores, but some will say that they don’t really take “full advantage” of say a 4.125 hole.
Since you aren’t shooting for the moon, that’s fine.
3. The m311 heads are SIX-BOLT heads and it would make good sense to consider taking advantage of that when buying a block. The LSX 376 for example would provide six-bolt security. Or Dart, RHS, LSNext etc.
All good advice.. :)

I would like to add to a comment of yours, if I may..

------------------------------------------------

You wrote:
"2. The m311 heads are built for a 4” bore and work just fine on bigger bores, but some will say that they don’t really take “full advantage” of say a 4.125 hole?

The M311 Heads come with a 2.165" Intake valve, and
therefore, cannot be used on a 4" Bore.

The smallest bore recommended is the 4.065" bore.
Both the LS3 and the LSA come with the 4.065" bore.

These heads come with a 273 CC Runner Volume.
They are then capable of easily reaching HP Levels of +850 fwHP.

This is again verified by the fact they flow about 350 cfm, at or around convergence lift, or. . .(2.165 * 0.25)= 0.541" of valve lift.

If we desire to make 850 fwHP, then we simply divide that by the value of 4,as 4-Cylinders fire in a 90° V8 every 90°.
Where 4 * 90= 360°.
***Actually, a 376 cid engine, is only a 188 cid engine, per revolution / rpm then.
***It takes 720°, or two full revolutions to fire all 8-Pistons.

So we would need to make (850 / 4 = 213 hp / cylinder.
Let's assume the engine is going to be efficient.

We can then multiply 213 * 1.5, and we can surmise that we
will require a cylinder head that flows 319 cfm, by convergence lift.
***an efficient engine requires a ratio of ~1.5 cfm, per each fwHP.

These heads flow 350 cfm at convergence lift. . .
And they flow 322 cfm at just 0.500" of lift.

That's a 'Ton' of air..;)

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Now, since those heads were meant for a 4.065" bore,
the issue Mr. Big might decide to look into would be,
if he might desire to have the combustion chamber
modified to fit the 4.125" bore.
***I believe these heads were flowed using a 4.125" flow plate. . .

-he should at least look at this-
But I would think not, as then he would have to make up the
difference in the volume removed from the combustion chamber,
by choosing a different piston, decking the block, surfacing the head, etc.

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Your scenario as I recall:

1000 fwHP goal. . .

Divided by 4 = 250 fwHP / cyld.
Heads must flow 375 cfm by convergence lift.

And 2.250" * 0.25= 0.5625" of valve lift.

Your heads come with a runner volume of about 295 cc, as I recall.
Along with the 2.250" valve, your engine is scaled for ~1000 fwHP.
Might also break 900 lbs feet of torque. . .Depends!

1000 fwHP / 427= 2.34 fwHP per cid.

850 fwHP is a 'Cake Walk' for your engine..;)
850 fwHP / 427= 1.99 fwHP per cid.

But to make 1000 fwHP. . .

Sorting out fuel versus tune, piston speed versus absolute
pressure ratio of the blower, versus mass flow recovery system
efficiency, will be where you find that extra 50 fwHP to 100 fwHP
you might want to find, after your first dyno pull..lol
***Your manual transmission also helps. . .

***All valve lift values are consider to be 'Net Lift' Values,
after all flex and geometric issues are removed.
 
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Discussion Starter · #57 ·
Ok how about this one. I am calling tomorrow to inquire about compression
 

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FWIW no one with any smarts builds a performance engine with a combination like that.

FWIW 2.165” / 4.00” equals 54% and shrouding will cause choked flow at peak valve lift with that cylinder head.

GM also attempted to use the 1 5/16 valve with the 283 CID back in 1961, having a 3 7/8ths bore, and it didn’t work then either. They quickly took the heads off the market. Next year, in 1962, they worked real well with the 327 CID, having a 4 inch bore.

—————————————————————————

-some physical examples-
434 CID engine.
2.165 inch intake valve.
4.155“ Bore
8,000 rpm
15* Intake valve angle

2.165” / 4.155” = 52% Ratio & equals ideal inline 2-Valve performance ratio.

Made 898 fwHP.
We built that engine over 12 years ago.

NHRA Pro Stock 500” cid.
2.555” Intake valve
4.750” Bore
8* Intake valve angle; means intake ports are virtually pointing straight up, not low entry level, as with what you proposed as being okay above.

Splayed valves, where both intake and exhaust valves are angled towards the center of the cylinder.

2.555” / 4.750= 53.8%, but with an 8° valve angle, splayed crossflow heads, also having a very shallow combustion chamber.

1500 fwHP from NA 500 cid on gasoline.

I am really surprised you would come out with that statement Matt.

You’ve seen me give that same information out here, many times before. This time though, I forgot to say they would bolt on, but not perform well.

Same issue with a 4.065 inch bore, and the 2.204 inch intake valve.
Here GM agrees, and use the 2.204” valve with a 4.125 inch bore.

They flow OK on the bench with the 4.065” bore though.

Head will bolt on OK.
But car won’t perform well at the track.

You know all that, and I wonder why you would make such
a statement on a performance forum like this?
 

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Looks to me like Mr. Big has a great combination.

Usually, the reason to increase valve size, is because you
need more flow in order to hit your horsepower goal.

And typically, that raises the intake valve to bore ratio as explained above.

When that happens, the intake valve becomes shrouded, and flow becomes choked as the valve lift is increased.

—————————————————————————

-mr. big’s combo-
2.165” / 4.125”= 52.4% Ratio, which is the ideal inline 2-Valve, wedge chamber ratio.

And Mr. Big’s cylinder heads flow more than sufficiently to hit his HP goal.

And since Mr. Big’s cylinder heads flow so well, he can go to a smaller duration camshaft, thereby increasing low end torque and drive ability.
 
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