I just want to confirm what approx number a person should be shooting for with timing their Subaru. And now might be a good time to share any of those Timing "tricks" for those of use who have only done it a couple of times.

 

I have been lead to believe the motor was the main factor in timing (as the title suggests). But with some of the more recent threads I have been reading it is suggested that fuel delivery is what determines what it should be. For example; models with SPFI = 20 degrees and those with a carb (ea81 AND ea82) would be closer to 8 degrees.

 

Can we get some clarification on this? It actually kept me up part of the night thinking about this.

 

Many thanks in advance!

 

-Keith

You are correct sir....

 

20* for SPFI

8* for carb

carb 8deg btdc. including ea81 thru 89 and ea82 thru 87

 

mpfi with mechanical disty 185-86 25 deg btdc.

 

spfi (1986 and up) and mpfi 1987 and up 20 deg btdc.

 

if, say, you swapped an spfi onto an ea81, the timing is still 20 deg.

Ok. Thank you! This means I have my '87 (ea82) a bit too far (approx 20). Surprisingly it seems to run fairly good (has a Weber carb though).

Awesome. Thanks again!

 

I have been lead to believe the motor was the main factor in timing (as the title suggests). But with some of the more recent threads I have been reading it is suggested that fuel delivery is what determines what it should be. For example; models with SPFI = 20 degrees and those with a carb (ea81 AND ea82) would be closer to 8 degrees.

 

Can we get some clarification on this? It actually kept me up part of the night thinking about this.

 

Many thanks in advance!

 

-Keith

 

The motor and timing...Compression ratio, combustion chamber efficiency are primary factors in base and total timing.

 

The fuel delivery thing...carb less initial timing because you're working with a vac advance and mechanical, spring controlled advance.

 

SPFI, the computer controlls the timeing, you're setting a reference point.

 

I doubt that the SPFI is at 20* advanced while cranking.

 

Just some thoughts off the top of my head.

 

Doug

Some real life experience with the EA81 I built - FWIW:) Ea81 with EA71 pistons, ported heads (shaved .020), Delta torque cam, SPFI conversion running about 35PSI fuel pressure. Timing makes a really big difference with this engine. It will run fine at 20 degrees but the sweet spot seems to be about 28 degrees. I had to mod the distributor mounting plate to do this. Can't push it any higher than that though.