Wayne or other gurus: Help me with my timing
 

Looking at the Engine Rebuild book it says for the Euro 2.7 RS engine the timing is 0 degrees at idle.

My engine is similar configuration being 2.7 9.8:1 JE Pistons and Modified S Cams by Elgin. I have timed it to 0Degrees and it seems happy. Is this correct?

Thanks
Tristan

Seems right - which distributor are you running? Also, did you check total advance?

-Wayne

Tristan,

That spec is only correct if you have an RS spec distributor. If you are using the original 2.7 distributor then you should set it to the spec for that original engine. All the cars specify a window of 30 to 35 degrees advance at 6k rpm. Most 2.4/2.7 engines are set to 5 degrees ATDC with the vacuum retard connected. This will give the 30-35 degrees at 6k. If you measure at 6k be sure to disconnect the vacuum retard. If you set one of these to zero you may have too much advance.

-Andy

Thanks Wayne and Andy.

I believe I'm using the original 2.7 distributor with the vacuum hose.

I'll set it to 5 ATDC. That's the second mark after the Z mark right?

Thanks

Tristan

So what is an ideal initial advance for a hot-cammed motor? Say you had an electromotive setup where the initial advance is free. I have been told 10-12 deg is ideal, I have found that to be too much.

I thought the critcal ignition timing measurement was at 6K, not idle, and should be in the 30 to 32 degree BTDC for a hot-cam single plug engine. Could some of the pros jump in on this question?

Thanks,

JP

What mark on the pulley do i need to align it with at 6k?

Thanks
Tristan

On most pulleys, there is a 30 and 35 degree BTDC marks. (See pic). BA once told me "start on 30 and see how it runs"

http://forums.pelicanparts.com/uploa...1085780050.jpg

Good luck,

JP

Total Advance
 

When working with performance engines, it would seem reasonable to set the engine at TDC when you first start it. Once the engine is warm, run it up the where you're certain total advance will be achieved . On a 911 6000 rpm is a good number. set the engine between 30 and 35 degrees depending on engine specs and fuel availability. Allow the engine to idle down. If the engine returns to idle you win. If not adjust your idle adjustment as necessary. If it won't return to idle you have two choices. Replace/Recurve the distributor or give up performance by retarding the timing.
You Choose

Off of which 2.7 engine?

-Wayne

Yes, this is a critical mesurement - you want to make sure that your engine doesn't exceed the total advance at these higher RPMs, otherwise you may experience detonation and engine damage.

The lower end is also important for maximizing your power off of the line. The good thing about programmable ignition systems is that these two measurements are independent of each other. On a distributor-based system, the advance on the low and high end are related via the distributor weights.

-Wayne

my factory Calif 2.7 dizzy used a vac advance. I set to zero and disconnected the vac permanently. It runs cooler and sharper at low and mid rpms w/CIS. it's also doable for carbs because you'll have more lower rpm advance .. many other 2.7s in the US and Canada had the same dizzy vac hose plugged at new delivery. I now run the 2.7RS dizzy.

By way of reference, the early S distributors produce about 25º of advance via the centrifugal weights. The initial timing specs are 5º BTDC for a total of about 30-32º of total spark advance. The S timing curve provides more spark advance at lower rpm for added torque (something the 2 liter S needed). Like Wayne and others suggest, be aware of excessive spark advance at max rpm.

Since all engines are slightly different, the best method is to perform a spark test on a chassis dyno. That way, you will know the best spark advance throughout the rpm range (with some headroom), then recurve the distributor or ECU accordingly.

Sherwood

PS: Early S distributors don't use a vacuum unit.

So you rev your engine to 6000 rpm to check the 30-35 degrees?

Yes. It's noisy, but you don't hold it at that speed very long.

Sherwood