View Full Version : Aftermarket Cam Ignition Timing

10-13-2015, 09:29 AM
I installed a hydraulic roller cam in my 390.

Should the ignition timing be set to the factory specs for a stock cam?

If not, how does one determine where to set the timing?


10-13-2015, 11:23 AM
This post looks identical to one you posted on another thread some time ago. Your engine STILL isn't tuned?:
The manual for the 390 engine has tables for ignition timing, but that assumes that the engine has a factory cam. My cam is aftermarket (Comp Cams FE XR282HR-10).

Comp Cams tech support could not specify optimal ignition points.

Do the stock timing specs apply to the new cam profile?The Ford manuals only apply to OEM parts. There is no way Ford could possibly anticipate someone would put a 282 degree duration cam in one of their engines.

Your particular cam has very little horsepower at idle speeds. That affects torque converter stall speed (stock converters will bog down the engine) and distributor centrifugal advance (as well as carb settings), etc.

It's very important, whoever works on your Ford engine, understands FE engines. Chevy builders have a difficult time to the point where some quit or overcharge to cover 'learning' costs. So, find an experienced FE engine build shop, one that have done many dozens of FEs. That's why your cam company couldn't help.

Since you have little power at low rpms, your distributor needs to advance much later than stock settings. There are many more considerations like; weight of your car, what fuel you are running, compression ratio, what rpm range you normally run at so you operate in the peak range of torque, etc. When you choose a cam, this should not be a 'blind' consideration but an experienced choice for the service of this engine. - DaveThere are three timing factors, Initial Timing, counterweight timing in your distributor and vacuum timing.
You have dramatically changed your camshaft torque curves. They happen at a much higher RPM, now. Is your transmission an automatic or manual shift? If an automatic, did you buy a stall converter?

Stall converters are a 'must have' if your camshaft has a long duration. All OEM converters lock up at relatively low rpm because even at idle speeds your stock engine still pulls hard. A stall converter lets the transmission slip until it gets to a high rpm to ensure you're in the power portion of the torque band. Stall converters come in different 'lock up' rpm ranges. The higher the converter is allowed to slip, the more costly they become. They also add heat from all that slip.

So stock converters on hot cams act just like you're letting the clutch out too soon. Even if you give a 'hot' engine more gas, the converter will bog the engine because the cam produces very little torque at low rpm. So, 'big cams' are designed to launch at high rpm and remain there through the gears.

Now, you're asking about ignition timing. Look at the torque curve for your cam and match your 'all in' timing to it. You can see why Comp Cams could not suggest your timing points because you have a custom build. An FE engine builder who is familiar with this cam will know where to time the engine. - Dave

BTW, we should move this thread and combine it with your cam timing thread.