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Originally posted by bloodyangel1
i will check all of that when it warms up around here. i also have adjustable cam gears, but slowboy wouldnt use them because the marks were off, and i had to remark them myself, and they werent sure how close they were to stock, even tho i told them i put the stockers on, aligned them, took them right off and put the adjustables on, and the lines i made matched up, but no one listens to me anyways. maybe ill just buy another set and put them on myself, but you say i have to overlap the gears to fix the vacuum, but how much would you say needs to be overlapped, or whatever? i remember the first time i did my timing before the tensioner came loose and bent my valves, the cams were slighty off, about half a tooth or less, and thats when the car ran perfectly, and i also remember reading about that on here somewhere, where with bigger cams, you need to offset the cam marks to adjust to the proper ignition timing and vacuum as well, so maybe i need to mess with the timing and increase or retard the cams a tiny bit to fix all that.
Originally posted by bloodyangel1
i will check all of that when it warms up around here. i also have adjustable cam gears, but slowboy wouldnt use them because the marks were off, and i had to remark them myself, and they werent sure how close they were to stock, even tho i told them i put the stockers on, aligned them, took them right off and put the adjustables on, and the lines i made matched up, but no one listens to me anyways. maybe ill just buy another set and put them on myself, but you say i have to overlap the gears to fix the vacuum, but how much would you say needs to be overlapped, or whatever? i remember the first time i did my timing before the tensioner came loose and bent my valves, the cams were slighty off, about half a tooth or less, and thats when the car ran perfectly, and i also remember reading about that on here somewhere, where with bigger cams, you need to offset the cam marks to adjust to the proper ignition timing and vacuum as well, so maybe i need to mess with the timing and increase or retard the cams a tiny bit to fix all that.
Woah hold on. First off do you have aftermarket cams? USe your existing adj cam gears and mark them accordingly as you stated. Has your head been milled?
For the record the correct and proper way to get your cams just right is to Degree them with a degree wheel. Since you have the motor in the car and have no idea what i am talking about then we will go about this another way.
A decrease in Vacuum is most often caused by too much overlap of the cams. Some overlap is required for scavanging. Look that up on the internet and learn a little. its good info to read.
If you think to the antique cars you will think about how the modified motors lope very agressively, this is due to a very high valve lift, duration and overlap. As duration increases in your valve lift the overlap will also increase. This is why most antique cars with aftermarket cams have very low vacuum. To give you an example, my superbee has around 7in/hg of vacuum idling and the cam i have is the second to largest lift/duration that can be used without smashing valves.
So what do you do? Start with checking your timing and get it to "0", if the head has been milled the cams will most likely be off. Basically you want to get the centerline of the cams matched up at TDC of piston 1. If you have aftermarket cams they prolly will not have the dowel holes in them like the factory cams do.
<b> If you still have factory cams </B> then remove the VC and rotate the motor till you see the dowel holes in the cams. Both dowel holes need to be facing up and perpendicular to the head while the piston #1 is a tdc. Bring the piston to TDC and adjust the cam gears till the dowel holes are where they are supposed to be.
<b> If you have aftermarket </b> the only way to accurately is t degree them. So for now what we will do is remove the bolts that hold the cam gears on and use the dowel pins as reference points. As you know one dowel pin is down while the other is up. With the piston #1 is at TDC check the location o the dowel pins. Make sure one is at 6 o'clock and the other is at 12 o'clock. If they are not the adjust the cam gears accordingly. Re-intall your cam bolts and tighen accordingly.
Now lets verify your work. Take a ratchet and socket and rotate the crank by hand with the spark plugs removed. For the first 2 full rotations, do this slowly. you are looking to make sure you didnt make an error and the valves with hit the pistons again. After 2 full turns go ahead and rotate the crank a little faster by hand. you should not hear anything fromthe cylinders other than air and there should not be any resistance other than the valves springs.
Put your motor back together and start it up. If you have aftermarket cams and your vacuum is still low and you have a poor idle. Then try retarding the intake cam 1 or 2 degrees and advance the exhaust 1 or 2 degrees. Try this 1 degree at a time. this will reduce the overlap of the cams. If 2 degrees does not make things even a tiny bit better then report back here. If it makes it worse reverse your adjustments and report back here.
Keep in mind if you have aftermarket cams you will not have a perfect like stock idle.
Also if you have aftermarket please post what cams you have already so others who have these same cams can chime in.
For the record a collapsed vacuum line will not react like a vacuum leak and if you have access to a scanner or know someone who does check the operation of the Crank/Cam sensor as stated. I tend to overlook the synchronization myself since i have hardley ever seen it. That is a strong possability and if you have a 95 the ECU may ignore it and default to simultaneous injection as stated. Good info from Alain.
Terry
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