question 4 walky or anyone with some cam smarts

steven95falc · 17-01-2007, 03:36 PM

Hey i am trying to help another forum member out by giving him a 977b cam what i am wondering is due to the longer duration and the higher lift will this all cancle each other out and therefor ehave no real differance in the angle of the lobe or steepnes of the lobe. i am familar with a bit regarding cams but not to this level and figured you may be ?
I have the specs for the 977b if you need them ?
we are trying to figure out if we need new valve springs to install it or if we can retain the original ones and save him some cash ?
My theory is if the lobe lift isnt any sharper than it wont get airborne on the back of the cam (valve bounce) and therefore we can leave the original springs.
Any help or advice would be awsome thanks

Mr_4.0 · 17-01-2007, 03:54 PM

977b needs at keast xr6 spings.

steven95falc · 17-01-2007, 03:59 PM

Sorry forgot to mention they are ef xr6 springs and its obviously a regrind and it was a virgin cam before regrind.

10secondET · 17-01-2007, 04:03 PM

will also need shims fitted to rockers

steven95falc · 17-01-2007, 04:11 PM

Rocker shims are no worries ive done mine before however i just went the hog and bought springs the car we are puting them on has a ef xr6 motor in it
I am him the cam so if he has to buy bits and peices it defeats the whole cheap upgrade idea.
Thanks for the help guys

poomba · 17-01-2007, 04:22 PM

i think you have the wrong idea about the specs...

lift and duration do not cancel eachother, and do not refer to the gradient of the lobe.

Basically, the more of these two, the more agressive the cam and the more power, but they must coencide to a degree...

More lift suggests that the valves opens further, and duration suggests the valve opens longer. how fast it opens (gradient of lobe) is different again, and can be proportional to the lift, as it has to reach a higher distance in a short amount of time. this grind, i would reccommend going better than xr springs, and you will need to put an extra set of shims in the rocker arms..

This cam will produce a lumpier idle, and more power higher in the rev range (i.e. 4000 - 6000rpm).

This will really come into play pending on where the lobes are situated on the camshaft, and likewise, how well tuned your system is to the cam. the ecu will only tune itself to a degree. for this cam you will need to reset it, if not a chip will be needed to get the most out of the cam.

steven95falc · 17-01-2007, 04:30 PM

When i am refering to the gradient of the lobe i simply mean if for example you had 200 thou lift and 220 degree cam (figures out of my a$$) it would have say a 45 degre gradient angle if you had the same 200 thou lift on a 240degree then the gradient angle would be less and therefore less prone to falling of the back of the cam
sorry for my poor description it is just hard to explain in a post

Rollin · 18-01-2007, 01:35 AM

Don't reset the ECU - if it has already learned an aftermarket exhaust's requirements resetting it after you put a cam in is going to make it harder for the computer to learn.

If he has an XR6 already, put the cam in and see how it goes, if it valve bounces put some crow springs in it - removing the rocker cover and gear isn't that hard, and you can leave the cam in the head when doing springs.

Note: I'd recommend getting stiffer springs for any cam, just for piece of mind, they generally make a bit of a mess when you drop a valve...

Walkinshaw · 18-01-2007, 01:05 PM

XR6 spring should be ok with the 977b (crow's 7993 single springs are XR6 replacement items anyway). 512" lift is ok (i run 524" with crow 9773's)

gthofan · 18-01-2007, 07:37 PM

you are correct walkinshaw. the 977B has 256 lift at the lobe, and 512 at the valve. you can even get away with standard springs, but to be safe, and you might as well. just put heavier ones in there. it means you can upgrade the cam at a later stage if you wanna.

cheers
scott

poomba · 18-01-2007, 10:28 PM

Quote:

Originally Posted by Rollin

Don't reset the ECU - if it has already learned an aftermarket exhaust's requirements resetting it after you put a cam in is going to make it harder for the computer to learn.

i dont agree at all. i have many mods (exhaust, intake, worked head), and didn't reset the ecu when i put a big cam in. took ages to adapt. then i reset the ecu, and followed the correct relearn procedures, and in 15 minutes i had a car running better than it was for weeks. including idle, shift patterns, and ISC adjustments.

just ressetting the ecu will take ages, but following the correct technique will take 15 minutes...

reset the ecu

Rollin · 19-01-2007, 12:23 AM

hxxp://www.fordforums.com.au/showthread.php?t=79382

Your car may be a magic car and learn straight away, (possibly ford fitted a WB02 sensor to it at factory by accident or something?) but they all (from Lamborghini to Deawoo) learn over a period of time, the EEC has "short term fuel trim correction" and "long term fuel trim correction" as part of it's strategy to take into account blocked air or fuel filters, sensors getting a bit erratic in their readings, resistance increases in connectors and harnesses and general wear and tear of the motor.

It's a bonus to us, as it means that we can get away with a few changes to the VE of the engine without needing to retune it, unless we have gone above and beyond the limits the factory ECU can cope with.