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Old 08-23-2009, 01:13 AM
xoliex xoliex is offline
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Default 9.4CR running on 87 octane?!?!?!

alright this is now my 2nd thread!!!

i've calc'ed my compression before and i came out with 9.4CR. c9ve heads, std head gaskets and -26cc pistons.

i'm putting 87 octane gasoline with this 466 with 9.4 and it doesn't seem to be pinging. on some old valve covers i once had, it said the stock timing was 12 initial and i try to set it to 12 and it just idles like poops, and it runs alot smoother at 14 and alot better at 16.

am i asking for trouble running 87 gas with 9.4CR? when i built the motor, i tried to build something that'll run off of 87 but if i have to jump up to 89, i guess i'll take the hit.
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Old 08-23-2009, 01:51 AM
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if it's not detonating I don't see the problem. I have a 9:1 360 mopar that'll run on just about any fuel I put in it. I've put as bad as 85 in it before and finally got it to ping going up a hill, lugging it at 1800 rpm in 4th with at least 6000 lbs of trailer and cargo behind it. This was at about 1500 feet above sea level. But the quench is set tight at .036". That makes all the difference in the world. Also had 35 degrees total timing in it too. It's now locked at 38 with no problems. What is your total timing, initial plus centrifugal, vacuum disconnected and at what rpm does it all come in at? You'll need a dial back timing light to get this figured out or a balancer with timing marks all the way up to 40 degrees or so.
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Old 08-23-2009, 11:21 AM
rmcomprandy rmcomprandy is offline
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Using a camshaft with enough overlap or late enough intake closing or both will easily allow that phenomina you are seeing.
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Old 08-23-2009, 11:31 AM
xoliex xoliex is offline
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I set the timing to 16. And no matter if I disconnect timing vac line the timing won't advance at idle. Street avenger says to set timing line here. For some reason the factory tach doesn't work anymore. Maybe the LSD tach adapter is bad now. I know I rev her up to 3k rpms or so n I know for sure it advances to 30. If I rev a little more it goes passed it. I have a stock 71 balancer so 30 is the highest number. So maybe a timing tape in the future?
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Old 08-24-2009, 05:26 PM
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what octane is everybody else running on 9.5 +/- CR?
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Old 08-24-2009, 06:20 PM
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Quote:
Originally Posted by xoliex View Post
what octane is everybody else running on 9.5 +/- CR?

the octane needs of a 9.5 to 1 iron headed 460 can vary from 87 to 93+ depending on cam shaft duration @ .050" and the intake valve closing point. Additional considerations are tight quench, vehicle weight and gearing along with timing curve.

With out knowing your cam specs and calculating DCR your questions can not be answered accurately.


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Old 08-24-2009, 07:21 PM
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i have a 73 mustang and i have the popular XE274 cam from comp cams. c9ve heads (roof raised and exhaust humps grinded out), 3.89 gears and i've set the timing to 16.

Quote:
Originally Posted by The Mad Porter View Post
the octane needs of a 9.5 to 1 iron headed 460 can vary from 87 to 93+ depending on cam shaft duration @ .050" and the intake valve closing point. Additional considerations are tight quench, vehicle weight and gearing along with timing curve.

With out knowing your cam specs and calculating DCR your questions can not be answered accurately.


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Old 08-25-2009, 06:27 AM
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I ran my 9.78:1 on 87 with no pinging. I spent two years on here learning about quench and other stuff tho
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Old 08-25-2009, 11:02 PM
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Quote:
Originally Posted by xoliex View Post
i have a 73 mustang and i have the popular XE274 cam from comp cams. c9ve heads (roof raised and exhaust humps grinded out), 3.89 gears and i've set the timing to 16.
What is your total timing initial plus mechanical?
When is all of the mechanical / centrifugal advance in. RPM
Amount of additional vacuum advance and at what vacuum level.
Quench distance?
Intake heated?

The XE274 H will run on premium pump fuel in the combo's we build at 10+ to 1 and iron heads. I have run c/r even higher with tight quench, squish trenches and a light vehicle with decent gearing...


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