Ls2 408 motor build- compression
Ls2 408 motor build- compression What is the max compression you would run this motor on with 93 pump gas? e85? Would you lessen the quench area to .040?
Cylinder Head Volume (cc) 59 Cylinder Head Vol (cubic in.) 3.599
Piston Head Volume (cc) 4 Piston Head Vol (cubic in.) 0.244
Gasket Thickness (in.) .051 Swept Volume (cubic in.) 51.086
Gasket Bore (in.) 4.060 T.D.C. Volume (cubic in.) 4.503
Cylinder Bore Diameter (in.) 4.0325 Gasket Volume (cubic in.) 0.660
Deck Clearance (in.)
Note: Neg. number above deck, Pos. number below deck 0 Deck Volume (cubic in.) 0.000
Stroke (in.) 4 Static Compression Ratio 12.345
OPTIONAL DATA
Rod Length (in.) 6.125 Adjusted Stroke (in.) 3.092
Intake Closing Point (degrees) ABDC @ 0.050 lift plus 15 degrees 66 Dynamic Effective Compression Ratio 9.770
Cylinder Head Volume (cc) 59 Cylinder Head Vol (cubic in.) 3.599
Piston Head Volume (cc) 4 Piston Head Vol (cubic in.) 0.244
Gasket Thickness (in.) .051 Swept Volume (cubic in.) 51.086
Gasket Bore (in.) 4.060 T.D.C. Volume (cubic in.) 4.503
Cylinder Bore Diameter (in.) 4.0325 Gasket Volume (cubic in.) 0.660
Deck Clearance (in.)
Note: Neg. number above deck, Pos. number below deck 0 Deck Volume (cubic in.) 0.000
Stroke (in.) 4 Static Compression Ratio 12.345
OPTIONAL DATA
Rod Length (in.) 6.125 Adjusted Stroke (in.) 3.092
Intake Closing Point (degrees) ABDC @ 0.050 lift plus 15 degrees 66 Dynamic Effective Compression Ratio 9.770
That's a lot of compression for pump gas. I think you're asking for trouble there.
Yes, certainly keep the quench as close to 0.040" as possible. Some people here advocate closer to 0.035".
Yes, certainly keep the quench as close to 0.040" as possible. Some people here advocate closer to 0.035".
The problem is that the cam is a fairly large cam. I am worried by running down to .035 quench that I will have ptv problems. I'm running a .625 dual pac spring am the motor won't see past 6800rpm, but still a tad worried.
Originally Posted by .boB
That's a lot of compression for pump gas. I think you're asking for trouble there.
Yes, certainly keep the quench as close to 0.040" as possible. Some people here advocate closer to 0.035".
Yes, certainly keep the quench as close to 0.040" as possible. Some people here advocate closer to 0.035".
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Dynamic compression is an imperfect predictor. The reason is, that it does not take volumetric efficiency into consideration. So, in the end it is just a mathematical expression of the camshaft's IVC and static compression. With volumetric efficiency not included, it cannot predict cylinder pressures at various RPMs.
With that said, a later IVC will still help.
With that said, a later IVC will still help.
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Verdad Gallardo Still kinda pushing it with pump e-85. The problem is the 15% gasoline. It's the worst and lowest octane fuel available. Kinda the dregs from the bottom of the barrel. It can cause detonation under the ring lands, and your pistons end up looking like this.
You can get away with high static and dynamic compression with E-85; it does have a higher octane and it will certainly run cooler. Just don't go too crazy. And make sure your cooling system is up to the task, too. If it gets too hot - like above 200* or so - it will detonate badly.
You can get racing e-85, with 15% high octane racing fuel. But it's not cheap and it's not easy to come by.
As said above, a later IVC point will lower dynamic compression. But it will increase cylinder pressures at higher rpm's.
You can get away with high static and dynamic compression with E-85; it does have a higher octane and it will certainly run cooler. Just don't go too crazy. And make sure your cooling system is up to the task, too. If it gets too hot - like above 200* or so - it will detonate badly.
You can get racing e-85, with 15% high octane racing fuel. But it's not cheap and it's not easy to come by.
As said above, a later IVC point will lower dynamic compression. But it will increase cylinder pressures at higher rpm's.
What ring gap were you running?
I'm going to be running Mahle regular ductile rings with gaps at .018 and .020. I think that would be alright on this motor running with e85.... thoughts?
I'm going to be running Mahle regular ductile rings with gaps at .018 and .020. I think that would be alright on this motor running with e85.... thoughts?
I don't remember the exact ring gap. It was whatever was recommended by the manufacturer. I set them on the wide side, though. I took the pistons over to Lanier's, and he knew exactly what it was caused by in one look.
