Timing: This makes no Sence to me. Please Help

[Greg]

Ok,
I finally got the engine back together tonight. I installed an FSPP Cam (CSC-264-12-DHS), Milled the head 60/1000 for a CR of 8.7:1, ported the exhaust, installed an new FSPP balancer, adjustable roller rocker assembly, etc.

I had some trouble getting it to idle so while keeping it running I adjusted the timing by ear and it idled fine. When I checked the timing it was about 45 degrees advanced with vac and about 30 degrees advanced without vac. Going down or up in timing made the engine run poorly. I assume I might be able to get the engine to idle with less advance if I reset the carb, but the engine ran fine with these carb settings previously and I don't want to add any more variables. I used a timing light with an advance degree dial to get the measurements, and also verified the balancer was showing TDC properly and marked when the rotor passed the number one plug wire post and all point to accurate results.

Additionally when degreeing the cam I got some numbers slightly different from the cam card. I had emailed Mike and he told me to contact Clay Smith, but Clay Smith never got back to me so I figured I'd see how the cam ran. I never did get back in touch with Mike, but below is the Cam info. My gut tells me the cam is not theproblem since the lobe center was not off much.

Thanks,
Greg

I've re-done the lobe center procedure multiple times now at 50/1000 and 35/1000 from the lobe center (measured off the lifter) and consistantly come up with a lobe center of 112.5 degrees and an off set of 4.75 degrees advanced.
Additional numbers:
Lift multipled by 1.6 ratio: Exh 0.472, Intake 0.464
Duration at 0.050" measured at lifter: Exh 228, Intake 211.5

 

[mugsy]

What year engine, and what kind of dizzy?

Could be the dwell, it's too short. Check that. Too little dwell time will make the car run very rough. Don't ask how I know....

tanx,
Mugsy

 

[Anonymous]

Double check your firing order.

 

[MustangSix]

Greg,
One trick I use if I have a suspect cam is to degree it against #6. It will be 180 degrees out from #1. Just rotate your degree wheel.

If the results are consistent, then the cam might be ground to a slightly different spec than the card indicates.

Also, 45 degrees is a lotta advance. I'm surprised the engine can idle with that. When you think about it, 45 degrees advanced is 15 degrees retarded from the last cylinder. Verify that timing mark again with the rotor to see if that's right.

 

[Greg]

I'll see if I can find something to put in throught the spark plug hole to act as a bump stop and verify the balancer timing mark

 

[Greg]

P.S. I have a Dura Spark ignition and the fireing order was one of the first things I checked and double checked.

 

[Anonymous]

Also, 45 degrees is a lotta advance. I'm surprised the engine can idle with that. When you think about it, 45 degrees advanced is 15 degrees retarded from the last cylinder.

Jack, I was thinking in the same terms. But, wouldn't there be 120 deg (crankshaft) between cylinder firings. The firing order would encompass 2 engine revolutions or 720 deg of crank revoloution. So 45 deg advanced would be 75 deg retarded on the last cylinder.
Doug

 

[MustangSix]

Also, 45 degrees is a lotta advance. I'm surprised the engine can idle with that. When you think about it, 45 degrees advanced is 15 degrees retarded from the last cylinder.

Jack, I was thinking in the same terms. But, wouldn't there be 120 deg (crankshaft) between cylinder firings. The firing order would encompass 2 engine revolutions or 720 deg of crank revoloution. So 45 deg advanced would be 75 deg retarded on the last cylinder.
Doug

You're right. That was a poor way to describe what I was trying to say. Mixing apples and oranges again.

The distributor spins at half the crank speed. It take 360 degrees of crank travel to get 180 degrees of distributor movement. Advance the timing by 45 crank degrees and you get 22.5 distributor degrees. There's 60 distributor degrees between cylinders (120 crank degrees), so the firing event is taking place less than 2/3rds between cylinders, assuming the damper is correct, 75 crank degrees afte the last cylinder.

Still, 45 degrees is still a lotta advance.

 

[Greg]

Well Mr. Sherlock Holmes does it again. I think the timing mark is off. The piston comes up and stays at what looks to be its highest point then bigins to drop just about or after the TDC mark.