Cam Tech Questions...

[RacerX]

Anyone know if advancing the intake cam a few degrees (without modifying the keyway, I believe there's 6° of play) on the intake cam of the 98 Cobra cam works well with a short runner? Thanks!

[Krytin]

Advancing the cams tend to shift the HP curve up in the rpm range so the short runner intake should like that. Don't know how much is too much but back when dinosaurs still walked the earth and I was building my '68 302 I advanced the cam 6 degrees with good results - 325 rwhp @ 6500 rpm. There was a little bit more to it than just the cam!

[RacerX]

That's about what I'm thinking, 6° max. Ever use centerline method for degreeing. Sounds simple and pretty foolproof.

[Vortech347]

Advancing the cam brings the power down.........
Retarding the cam increases power up top....

However it doesn't change "Peak" numbers so to speak, just shifts the band.

[RacerX]

Yeah, I've decided to try and just worry about getting them spot on. I would rather not have to worry about trying to change timing later if something didn't work as projected. Well, heads are being decked right now and hot tanked. Cams and new valves will go in as soon as they arrive and the forged sb supposedly will be here next monday.

[MM_BKK]

Anyone know if advancing the intake cam a few degrees (without modifying the keyway, I believe there's 6° of play) on the intake cam of the 98 Cobra cam works well with a short runner? Thanks!


Are you trying to change the LSA (lobe seperation angle) or the intake centerline? There is a difference between the two. On a typical 2V camshaft, advancing or retarding the cam changes the intake centerline. The LSA can not be change on an engine with intake & exhaust lobes on the same shaft. However, on our DOHC head, the LSA & intake centerline can be changed independently.

You have to ask yourself, do I want more low end torque or high rpm horsepower? If you're boosted, I would just leave the cam timings alone as you'll have both. But if you're N/A the short runner will kill your your low-end torque but will allow better breating at high rpm due to less restriction. You could compensate and get some low-end torque back by advancing the cam or intake centerline. If you change the timing between intake & exhaust cam, that will alter your LSA and will inturn changes your valve overlaps. Small LSA will increase overlap and make power curve peaky while wider LSA will decrease overlap and make more broad power under the curve.

BTW - On the MM engine, the crankshaft drives the Exhaust cams and then the Exhaust cam drives the Intake cam. Also, I would not advise modifying the key by filing it down or using narrower key. Without a precision fit key, the sprocket or gear will eventually slip or move back and forth. I would use adjustable cam sprocket or multi-position crank sprocket or offset keys to change any cam timing.

[musclemerc]

^^^ Thats some good info right there.

Thanks!

[cougar9150]

Here's a good article from 5.0 magazine a few months back about degreeing a 4V motor cams. Good luck, I'm interested to hear how it turn out.

http://www.mustang50magazine.com/techarticles/m5lp_0912_degreeing_our_four_v alve_modular_motor_camshafts/index.html

[MM_BKK]

Advancing the cams tend to shift the HP curve up in the rpm range so the short runner intake should like that. Don't know how much is too much but back when dinosaurs still walked the earth and I was building my '68 302 I advanced the cam 6 degrees with good results - 325 rwhp @ 6500 rpm. There was a little bit more to it than just the cam!

Actually, advancing the cams will move the HP curve to the lower rpm range.
Intake & exhaust valves do their thing earlier therefore max power comes sooner rather than later in the upper rpm range.

[Krytin]

Actually, advancing the cams will move the HP curve to the lower rpm range.
Intake & exhaust valves do their thing earlier therefore max power comes sooner rather than later in the upper rpm range.
Yep - my bad.
Comp Cams actually has some very technical info on there web site about cam timing that will make your eyes bleed but is VERY good if you really want to play with cam timing from a tuning aspect.

[RacerX]

It's interesting that if you follow Ford's timing directions, it's idiot proof. There's timing marks on evrything. You may be off a couple degrees here or there, but, from the factory, it'll all work fine. Could explain why there are factory variations in HP right off the floor. If one MM was degreed better than another by chance...