tatertot91

iTrader: (41)

Been back and forth searching and calculating but i have yet to get a definite answer on how exactly to figure out my compression ratio.
Going to be running a stock LQ9 and 243 Heads
Figure the heads to be around 63-64cc

Stock LQ9 specs
4" Bore
3.622 Stroke
Flat top Pistons
.052 Gasket
6.098 Rod Length

Cam Specs
230/238 .600/.603 112+3
Further details in the pic below


Appreciate any and all help
Thanks

ejbta2

google Wallace Racing Calculators they have all the calculators you need.

JakeFusion

iTrader: (7)

8.62:1 DCR and a SCR of 11.18:1 with 64cc chambers.

LSOHOLIC

iTrader: (3)

for future reference..........https://www.uempistons.com/index.php...tors&type=comp

4.0" bore
3.622" stroke
6.098" rod
.052"x4.010" gasket
.006" out of the hole
64cc chamber
0cc piston head
44* IVC

SCR = 11.146 and DCR = 9.25

note.....the way some of these calc use the IVC is suspect IMO.
.

JakeFusion

iTrader: (7)

You use IVC at .006 not .050, which is 68.5 degrees (which you calculate from the .006" numbers). That add 15 degrees is not the correct method to finding IVC at .006".

The DCR figure I provided is accurate.

tatertot91

iTrader: (41)

This is close to what I got but I calculated at 63cc. Got around an 8.7 DCR which is a bit high but I think will do well.

JakeFusion

iTrader: (7)

8.7:1 is about as high as I'd go on 93. So you're okay.

pantera_efi

iTrader: (1)

The IDEA for a "tighter" Lobe Center Angle on most STREET LS-1 style HIGH SWIRL heads is absurd though what COMP like to sell for that "rump-rup".

NOW we all know the LS-x heads love tight(small) squish AND small chambers.

The question is DCR reduction which is GREATLY enhanced with a wider 116-118 LCA.
The choice of this "wide center" camshaft will allow for the use of a higher SCR.

Results ARE better fuel mileage, better low end torque, greater top end horsepower.
The only loss is a small amount of "mid-range torque" though the average torque is much better.

There ARE exceptions like a DD Air Boat engine@3200 RPM Max.

Lance

JakeFusion

iTrader: (7)

It isn't Comp that thinks this way. It works with the cathedral port heads... and it's because of overlap. Overlap is power. It also kills fuel economy and drivability, but if you time the overlap correctly, it makes a ton more power upstairs, where most people want it to go faster.

Now, when you go with a wide LSA, you can throw more SCR at it. The benefit is a wider, flatter torque curve. The compression creates the low-end grunt, not the valve events. So you are correct there.

Ideally, you want the valve events to be right for the heads and intended usage. You then optimize the compression for those events.

A wider LSA is better on bigger cubic inch motors with longer strokes.

Tighter LSAs are better with carb style intakes.

Tighter LSAs work great with stock heads, because you are dealing with relatively low compression and need the cam events to overcome low static compression.

pantera_efi

iTrader: (1)

OK, Jake I believe we are in a 90% AGREEMENT though my work with Camless Engines may add dimension and use slightly different terms.
First, I have order a camshaft from COMP, paid for the camshaft, then have the order refused by their engineering though they use the same core (Engine Machine) as does Crower Cams that I then received three days later with no advance charges.

MY VIEW of Overlap Requirement IS based on the RPM of the engine, I your terms the time when both valves are "off seat". (Agreed)

Your statement "upstairs" is completely incorrect. (WRONG)
Your statement "where people go" is relative to needs. (Undetermined)
Your statements, next two, I agree
Your statement "wider for large cubes" is incorrect (WRONG)
My example is our customers that 572/632 BBC for Irrigation/NG pumping@102 LCA
Your statement "carbs" completely correct (AGREE)
Your statement "stock heads" completely correct (Agree due to lower low lift of stock head)

Lance

JakeFusion

iTrader: (7)

I say generally for the larger motors and larger strokes a wider LSA gives you what you want as part of the overall valve events - you still end up with massive overlap when you have a 254/266 115 camshaft. LSA is nothing more than part of the equation, balancing LSA and ICL with the intake and exhaust duartion based off of the intended usage, manifold design, weight of car, gearing, etc.

And you can change the characteristics of the cam by centering overlap over TDC or BTDC or ATDC. That will predicate how the torque comes on in the midrange (at the expense of power after peak) or design the cam to "hang on" longer after peak, at the expense of power in the midrange.

That's interesting on Comp refusing the cam. Why did they do that? Because they didn't want to cut a 118 LSA 240 duration cam? Who cares, it's your cam.

Kip Fabre

The problem with making a cam with a 118 LS is because the cores that cam company's order will come with about 236/ 310 in 242/310 ex on a 112 or 114 this cover most cams. On a core like this you can make 210/280 in 220/280/109 to 254/360/262/360/115 these are about and can change some. We make our own cores so we just made some test cams for a car company on 121 LS but it is a custom core.