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Cams Advanced Timing and Octane


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11 replies to this topic

#1 Myxalplyx

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Posted 15 January 2005 - 09:52 AM

Hey all,

I know some people here have installed aftermarket cams (camshafts) with their EA81 or EA82 N/A cars. Usually, people who get aftermarket cams advance their timing to help with idle and to gain some extra hp/torque. This can vary between +5 to +10 more degrees advanced timing from what I've read.

My question is what octane have some of you folks used with an aftermarket cam grind and advanced timing? Is it necessary or advised to run higher octane (Ex: 93 octane) or is 87 - 89 octane usually just fine?

#2 archemitis

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Posted 15 January 2005 - 10:50 AM

ive never cammed a subaru but...

usualy when you cam a motor, unless its very mild cam, you loose compression, because the cam is open longer, and all that tech. stuffs.
so uless you bump your compression too, a cammed na motor will run crappy gas and like it.

#3 Myxalplyx

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Posted 15 January 2005 - 03:19 PM

ive never cammed a subaru but...

usualy when you cam a motor, unless its very mild cam, you loose compression, because the cam is open longer, and all that tech. stuffs.
so uless you bump your compression too, a cammed na motor will run crappy gas and like it.


Thank you!

#4 Do It Sidewayz

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Posted 15 January 2005 - 03:23 PM

these things really do like high octane.

We ran one once at 22 PSI, with 110 octane and the thing sounded like a bat outta hell

#5 Myxalplyx

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Posted 15 January 2005 - 03:43 PM

these things really do like high octane.

We ran one once at 22 PSI, with 110 octane and the thing sounded like a bat outta hell


This was in reference to one of my XT6s that has Delta Cams. :cool: Sorry! I should've been clearer.

#6 archemitis

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Posted 15 January 2005 - 03:52 PM

i havent seen it adressed too much with subarus for some reason. but id want a big cam, with 10.5 or 11:1 compression, with some adjustable cam gears.

#7 Snowman

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Posted 15 January 2005 - 04:20 PM

Here's the story of my engine(s) and their experiences with the Delta cams I've got in there right now. This is in my 86 ea82 wagon that started out carbed.

Stage 1: Completely stock engine before cams. Non-factory muffler, intake and coil. She liked running around 16 degrees of timing advance. (The factory setting is 8).

Stage 2: Addition of Weber carb. Basically the same timing setting.

Stage 3: Rebuilt engine, installed Delta cams. Ran better and better as I advanced the timing. I actually had to grind the distributor hold downs so I could turn it a little farther. I'm guessing it was around 25-27 degrees. At that point, I was just going by how far I could advance before pinging, and there wasn't any at that setting.

Then that engine threw a rod because of my stupid mistake when I put it together. Completely unrelated to ignition timing.

Stage 4: Rebuilt the SPFI motor out of my parts car, but used the Weber carb again and the Delta cams. With the higher compression, all it could take before pinging was around 18 degrees.

Stage 5: Converted to SPFI. With the electronically contolled timing, I'm running around 22-25 degrees of advance with no pinging. It actually feels like it wants a tiny bit more, so I'm going to experiment with that in the near future.

So, long story short, it seems that with Delta cams, you can and should run more ignition timing advance.

#8 Myxalplyx

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Posted 15 January 2005 - 04:46 PM

So, long story short, it seems that with Delta cams, you can and should run more ignition timing advance.

Cool, thanks for the info but what octane gas were you running during all of this? :)

My distributor is turned just about all the way up. I just don't want to go overboard with 93 octane when I could use 89. I've been using 93 octane ever since I advanced the timing so I wouldn't screw up anything. My hearing sucks so I don't rely on that for detonation detecting. :(

#9 All_talk

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Posted 15 January 2005 - 05:18 PM

...with some adjustable cam gears.


Not to let the cat outta the bag to soon, but I've got something cooking in this department.

Gary

#10 Subarutex

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Posted 15 January 2005 - 09:05 PM

Meow :-D

#11 archemitis

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Posted 16 January 2005 - 12:40 PM

fur da er27?

#12 Snowman

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Posted 16 January 2005 - 04:59 PM

I was running premium gas the whole time, which up here varies between 90 and 92 octane.




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