Those running pump gas.

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340Dust-her

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What's your highest compression ratio without any use of methonal or any cooler. With a somwhat aggressive cam and 10:1, think it'll be fine on 93 octane?
 
416 11.9 to 1 compression running on 93 pump gas...........

360 10.7 to 1 compression running on 93 pump gas...
 
360 running 11.0-1 on 93 and octane boost.

Every now and then I fill er up with 110 octane for the lead.
 
340 9.4:1 SCR .474/280([email protected]) advance 4*
Total timing set at 36* when at the track(4400 feet)
Premium fuel + 1 gal 108 octane race fuel w/ a half tank, Or will ping at top of 2nt gear........In hot weather.

I have seen engs with just over 8:1 ping! and 12:1 that didn't!

Cam shaft really make a huge difference in running compression or DCR
 
You need to be much more specific. Regardless of piston, stroke, chamber, material, timing, pump octane, etc... The guide I follow is:
Iron open chamber - no higher than 180psi and dynamic ratio no higher than 8.3:1
Iron closed chamber - no higher than 190psi and dynamic more than 8.5:1
Aluminum open - no higher than 190psi and dynamic more than 8.5:1
Aluminum closed chamber - no higher than 205psi or higher than 8.75:1

Those basics havent failed me yet. they allow pump octane of 90 or so.
 
340Dust-her said:
What's your highest compression ratio without any use of methonal or any cooler. With a somwhat aggressive cam and 10:1, think it'll be fine on 93 octane?
Click to expand...

In general, the more cam you have the more comprsion you'll need to run. As a general rule, nothing in stone here, for a street car;

10-1 iron head

11-1 aluminum head

with the said beefy but not radical cam and 93 octane. With these numbers, you should also have an adjustable vacuum advance on the distributor as to limit the amount of advance.

Personally, I like to run it alittle less around a 1/2 point down from each example. On my aluminum headed 360, it is 10.79-1 and I was running a Purple 292/.509 cam.

9.76-1 on the iron headed version with 93.
 
My magnum headed LA 360 has 10.58 to 1 running a Comp Cams Magnum 280H. I run 91 Octane and can run 89. My cylinder pressures run 185 to 195 psi.

Jack
 
11.25 cr, 360 with j's, 205 cranking psi.

71 Demon 340 (45).jpg
 
moper said:
You need to be much more specific. Regardless of piston, stroke, chamber, material, timing, pump octane, etc... The guide I follow is:
Iron open chamber - no higher than 180psi and dynamic ratio no higher than 8.3:1
Iron closed chamber - no higher than 190psi and dynamic more than 8.5:1
Aluminum open - no higher than 190psi and dynamic more than 8.5:1
Aluminum closed chamber - no higher than 205psi or higher than 8.75:1

Those basics havent failed me yet. they allow pump octane of 90 or so.
Click to expand...

Did you mean dynamic NO higher than 8.5:1 or HIGHER than?

Iron Closed and Alum Open same requirements?

My 360 magnum build (virtual for now) is clocking in at 10.614:1 SCR with 9.153 SCR with a .040 quench
 
My stock '69 440 Magnum is over 10:1 with open heads (no quench) and stock timing, and it doesn't ping on pump gas.
 
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