aaron101m

iTrader: (2)

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

aaron101m

iTrader: (2)

dynamic compression: 9.770
static compression 12.345

.boB

iTrader: (1)

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".

aaron101m

iTrader: (2)

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.

aaron101m

iTrader: (2)

Do you think e85 would be a problem instead of pump gas?

speedtigger

iTrader: (16)

15 degrees would be some very short seat timing. 25 to 28 would be more realistic for most LS street cams. So, if you have a 51 IVC at .050" then you would be looking at using 76 to 79 IVC @.006 for input into the dynamic calculator.

aaron101m

iTrader: (2)

So with that being said.... The static compression may be too high for pump gas but the dynamic is feasible in my opinion. Would you agree?

speedtigger

iTrader: (16)

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.

.boB

iTrader: (1)

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.

aaron101m

iTrader: (2)

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?

.boB

iTrader: (1)

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.

imma_stocker

iTrader: (19)

I think it'll do fine on E85. Not like you're running 13+ compression.

OR keep some race gas handy and figure out how much you'll need per tank to hit the right octane.