Harley engine timing

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Idiocracy
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Harley engine timing

Post by Idiocracy »

First, I hope this is the place for this. I didn't get any responses on the Harley forum (not surprised). For context, I am rebuilding an Evo HD motor, with 10:1 compression (up from 8.5:1), EV-27 cam and a Crane HI-4N ignition.

I set the base timing to where it was at disassembly as a starting point but I am looking for some insight on what advance curve might be good to start on. I am set to Mode 6, which is Dual Fire, Multi Spark, Race Curve, Electric Start. Crane says to use the Race Curve for high compression engines, per the instructions. Now for the advance curve, Crane never defines the advance curves, but says mode 9 can be used for stock ignitions with 93 octane, BUT when using race curves, less advance might be necessary.

I am still looking for the specifics regarding the differences between the different advances. Is there a standard amount of retard per point of compression increase? With this combo, my DCR will be about 188psi, so I know timing is critical.
SupStk
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Re: Harley engine timing

Post by SupStk »

Probably shouldn't respond to this since it's been so long back my memory may not be accurate.

Bought a '96 FXDL new. At 800 miles installed the better cam bearing, the EV-27 cam, taper-lite pushrods, Mikuni 40mm carb on a Ness intake, K&N filter and 2-1 Supertrapp. The Supertrapp had 15 discs and an open cone. I set my old style single fire HI-4 with the electric start performance curve at 35 degrees total with -3 on the rear cylinder. I played with carb and timing, judging performance by the butt dyno.

Wasn't very scientific but a vast improvement over stock, being better for performance, driveability, and fuel economy.
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hoodeng
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Re: Harley engine timing

Post by hoodeng »

An EV27 [36° close] is a too small for 10:1 comp, something with a 48/50°inlet close will work a lot better, you will be pulling timing out just to stop it detonating.
If you haven't already you will need to change springs and set the squish as these engines are usually miles out.If you go over .530" lift you will need to address the rear inlet lobe to case clearance and lifter roller at full lift clearance.

As for optimal ignition and fuel setting, get it on a dyno. The final timing will be whatever the engine asks for.

Cheers.
HDBD
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Re: Harley engine timing

Post by HDBD »

I do a cheap pocket port and nice valve job on those evos and they run well. I mill the heck out of the heads and zero deck the barrels to get to 9.8 with the EV27. At 9.8 compression releases are needed but the timing can be dealt with by the dials and the initial. Single fire is a better way to prevent detonation. No releases then drop it back to 9.3. Will make about 80hp and 90tq. even with the stock carb.
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Re: Harley engine timing

Post by FuelieNova »

When in doubt look up Pacific Mike on youtube. He is a heck of a harley craftsman and gladly doles out help to anyone who ask.
Tom
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