SVTeeshirt

dammit you got me excited, i wish i knew if it would make a diff in different heads, but the cam specs look pretty similar so idk.

Xemeth

Those results posted above. Did he degree the cams? Or just install them?

SVTeeshirt

idk good question.


oh and do you have any how-tos or stickys etc on how to degree cams? im guessing you did yours when u did the 4v swap.

99BlackPonyGT

if you plan to go FI and start making big HP, i dont see why the GT cams would be worse than the 98 cams...people dont use them in high hp builds because theyre no good lol, i would check into them a little bit more..or maybe get some custom grinds

Xemeth

4.6L Camshaft Degreeing Process:

Preface: Aftermarket camshafts are a very popular and extensive modification for the 4.6L SOHC and DOHC engines. Often times people tend to install the camshafts without taking the proper time to degree the cams and just “connect the dots.” While this method did work on older pushrod engines, the 4.6L OHC engine has the distinct problem of machining tolerances of the cam sprockets from the factory. Due to these tolerances, your engine can have a 2-6* difference between banks, and can rob a considerable amount of horsepower from your engine as each bank is fighting the other. You need to consider as well, that many aftermarket camshafts are ground with an advance in the cam itself and cause problems such as piston to valve contact. Taking the time to properly setup the engine is vital to making the most power you can, no matter what camshafts are used.

Shopping for camshafts with certain specs (i.e. duration, valve lift and LSA) has no affect if you do not spend the required time to degree the cams.

In this how-to, you will not learn the basics of camshafts, as I expect you should have a general understanding of how they work if you plan to install and degree them. If you have questions regarding the nature of camshaft specifics, please contact one of the many camshaft manufacturers for a detailed explanation.


Tools Required:

Metric socket set
Wire
Degree Wheel
Solid lash adjuster, or modified stock adjuster
Dial indicator and base stand

Procedure:

1. The very first step is to install your degree wheel on the crank snout and install a wire pointer. The pointer can be used from a coat hanger, wire, or anything of the like.

2. The next step is to bring piston #1 to TDC (top dead center). Do not just eyeball TDC, make sure you use a piston stop or dial indicator to find true TDC.

3. You will now rotate the engine clockwise until the piston hits the stop. Record this measurement from the degree wheel. Now, turn the engine counterclockwise until the piston once again contacts the stop and record this measurement.

4. Now that you have both measurements, add the two together and divide in half. You have now found true TDC. (Example: You found 30 degrees one way, and 28 the other way. The median is 29 degrees.) You will now rotate the crankshaft to this new value. Once you have done this, DO NOT move the crankshaft, and just spin the degree wheel so that it reads “0”. Congrats, you have now found true TDC. You can repeat this step to verify that you indeed have found true TDC, as the rest of the procedure relies on this.

5. You will now install the modified stock lash adjusters, or adjustable lash adjusters into their respective bores. Rotate the camshaft so that the #1 intake valve is on the base circle of the cam (ie. No valve lift).

6. Adjust the lash adjusters such that you are set at zero valve lash. You can either use a set of feeler gauges to do this, or spin the adjuster by hand until you can no longer do so (same procedure as spinning pushrods in an OHV engine). What this does is simulate a set of solid adjusters/lifters. The stock lash adjusters are hydraulic and use an internal plunger to adjust preload.

7. Now, install your dial indicator and stand such that the plunger on the dial indicator rests on the valve retainer is exactly parallel to the #1 intake valve stem. This is extremely important, as you will be measuring true valve lift and if not completely parallel can cause false readings.
8. Rotate the camshaft until it has reached maximum valve lift (the dial indicator will begin to go backwards once it starts descending in lift). Once you have found max valve lift, make sure you zero your dial indicator.

9. Now, rotate the crankshaft counterclockwise until the dial indicator reads 0.100”. Now turn the crankshaft clockwise until you are 0.050” before max lift. Look at the degree wheel and record this number.

10. Now continue to spin the crankshaft until the dial indicator passes 0 (maximum valve lift) until it again reads .050” past max lift (descending side of the lobe). Once again, look at the degree wheel and record this number.

11. Now, take the two numbers you found and add them together. Take this new total and divide in half and you have now found the intake centerline of the camshaft. You can now compare this centerline with the specs provided on the cam card provided by the manufacturer. If the centerline as found does not match the specs listed on the cam card, you must advance or retard the cam timing until it’s set correctly.


There are a few options available for altering cam timing. The first option is to use the stock cam sprockets and file the keyway to allow for movement of the camshaft. This method is perfectly acceptable. To note: The stock 2000 Cobra R 5.4L engine used a set of cam sprockets with no keyways without any troubles. The keyway is only machined for use in the assembly plant. If the proper cam bolt and torque value are utilized, there will be no issues with the camshaft losing its valve timing events.

The other option is a set of adjustable cam gears. Mod Components, LM and Comp Cams are a few to name. These cam gears allow for a much easier and simpler way of altering cam events. They utilize a systematic set of lines in one degree increments for the average engine novice to easily advance or retard the camshaft.

After you have degreed the cams on your engine, it would be a wise decision to also check the piston to valve clearance. Many sets of camshafts use a large duration, large overlap that can cause issues.

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I think there's a sticky at the top of this section about it, too.

amoosenamedhank

I guess I would say that if you are really that desperate to drive the car, you will have to choose whether driving around a lower compression engine now is worth it. It's not like it's going to be a complete turd, but it really won't be much more than a stock cobra.

Personally I don't think this is a horrible idea. Gives you a chance to break the engine in under low stress and gives you a chance to work all the kinks out before boost.

boduke0220

not to thread jack but what are the limits of the stock bottom end of a 4v? rpm wise. i know the valves start to float around 7500-ish. just wonderin about the bottom 1/2 of the motor

SVTeeshirt

what would you suggest as a final CR? for a twinscrew car?

Im not too sure, stock redline is 6850, idk if its limited there b/c of the crank pulley or not.



and Xmeth thanks for that.

amoosenamedhank

Since you have boost damn near off idle some where around 9:1 would be ideal, I would think.

SVTeeshirt

thats what i was thinking as well.