Timing question

[86chevyk20]

Hey guys,

So i have my 86 k20 with a 355 that i built. 600 Edlebroke card. HEI system.

I never timed it with a light . I have a comp cam extreem energy250 cam with flat tappet set up.

My question is. What should my timing be at and what is the best way to time it perfectly.

Thank you

Liam

 

[chengny]

You have created enough variables by modifying the original engine that no one can give you a precise/correct degree of timing. You'll have to do it yourself by ear.

Start with a reasonable number like 8 -10 degrees BTDC. Keep advancing until you hit a point where either:

1. The engine pings/knocks when a heavy load is rapidly applied

2. The engine attempts to kickback while cranking the starter (this will not generally occur on a cold start - use this limit only when the engine is hot)

As a general rule, you will get a ping under load well before you get the kickback effect.

Once you have reached these limits in the advanced direction, start to slowly retard the timing in tiny increments. It can take a while to finally find that "sweet spot" where you get the best engine performance without pinging or kicking back.

This is just my method -there may be other (quicker) ways of doing it.

For example, I have seen posts where people suggest locking up the drive train and stomping down on the accelerator while an assistant sits atop the engine and adjusts the timing to most advanced without the engine knocking. Sounds good on paper but...?

 

[rich weyand]

Advance the timing a couple degrees at a time until you get knock under heavy load at low rpms, like starting out from stop on a steep hill, then back off 2 degrees. That will give you some headroom. You will probably end up around 18* BTDC.

Or you can do what I did for a similar setup. I just set mine right off the bat to 17* BTDC and no knock, so done.

BTW, connect the vacuum advance to the driver's side manifold vacuum port, not the passenger's side timed vacuum port, for best performance.