How do you know whether the #1 piston is @ TDC on it's exhaust or compression stroke?

[brandnew161]

I'm going up to work on my car in an hour or so and something just popped into my head as i was sitting here reading the haynes manual. I'm retiming the motor after a shotty cam install and in the manual it states that the #1 piston has to be at TDC of its compression stroke prior to removing the belt. I understand that this would be simple if the cam gears were in time. However, they are not, so I cannot use their timing marks as reference points. Does it matter if the #1 piston is at TDC of its compression stroke or exhaust stroke? If so, how do I know if piston 1 is in its compression stroke?

 

[tenn-gsx]

hang on a min. the cam gears have absolutely nothing to do with the cam angle sensor or crank angle sensor period. with the 1g cas the keyed slot is on the opposite end of the intake cam cam with the 95 and 96 the crank angle sensor is on the crank, behind the crank timing belt gear.

What I said was that I did not know for sure if he could use the 95-96 cas with aftermarket gears. Then I told him I PERSONALLY just went with the 1G cas rather than deal with it.
The cas on a 95-96 is mounted behind the intake cam gear. There is a trigger plate attached to that cam gear. This is why I dont know if he can use the 95-96 cas with aftermarket gears.

CAS= Camshaft Angle Sensor
CPS= Crankshaft Position Sensor

We are talking about the CAS Not the CPS

 

[Tanro]

Easiest way to tell if your on the compression stroke is to thread a compression test hose into the spark plug hole the cylinder you are testing and put your thumb over the end. On the compression stroke you will feel pressure build up in the tube.

 

[tkelly27]

It's very easy to get the dowel pins in a position that looks like 12 oclock, but be a tooth off. If your adjustable cam gears do not have notches across them to make a straight line AND a zero line that you KNOW is good, do not use them. Put them in a box, read the "degreeing camshafts" guide until you feel you can do it with your eyes closed then do it.

Odds are good nothing will break, but you don't stand to gain much, but you are increasing the odds of problems, and the consequences are big. Fidanza may or may not be dialed in from the factory, but a lot of cam gears are not because they assume you will be doing it when you get them.

This is the nicest way I can put it. If you have to ask when you are at TDC, you should not be using adjustable cam gears yet. That doesn't mean you can't, but you're going to save yourself a lot of headaches going back to stock cam gears. It's kind of like saying "I've loaded this gun, got rid of the trigger guard, can you tell me where the safety is?"

 

[brandnew161]

It's very easy to get the dowel pins in a position that looks like 12 oclock, but be a tooth off. If your adjustable cam gears do not have notches across them to make a straight line AND a zero line that you KNOW is good, do not use them. Put them in a box, read the "degreeing camshafts" guide until you feel you can do it with your eyes closed then do it.

Odds are good nothing will break, but you don't stand to gain much, but you are increasing the odds of problems, and the consequences are big. Fidanza may or may not be dialed in from the factory, but a lot of cam gears are not because they assume you will be doing it when you get them.

This is the nicest way I can put it. If you have to ask when you are at TDC, you should not be using adjustable cam gears yet. That doesn't mean you can't, but you're going to save yourself a lot of headaches going back to stock cam gears. It's kind of like saying "I've loaded this gun, got rid of the trigger guard, can you tell me where the safety is?"

I understand what you are saying. The fidanza gears that I have DO have timing marks at the 9oclock and 3 oclock position on each sprocket. So i'll be able to get a straight edge and really make sure they are aligned. If they did not have the timing marks then I would agree 100%, they would not even be out of the box

 

[tkelly27]

Ok, then make sure the 0 marks are aligned and follow the VFAQ guide. The camshafts define when TDC is the compression or exhaust stroke. You need to take the lower timing belt cover off if you haven't done it yet. Then put the #1 cyl at TDC with the crank indicator, align the oil pump, then turn the camshafts to the 12 oclock dowel position. Viola, TDC on the compression stroke.

 

[brandnew161]

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bottom end marks look good? Thats how the crank sprocket is supposed to line up right? I dont have to do anything fancy with the oil sprocket except align the marks right? The balance shafts have been removed. I havent put the intake cam gear back on yet. I accidently broke the angle sensor so i'm waiting for that to come in the mail.

Thanks for all your help guys. I'm not saying that retiming the motor was fun... but it was a learning experience for sure and it honestly wasnt as bad taking all of those pulleys off as i had thought.

 

[white92talontsi]

Ok, then make sure the 0 marks are aligned and follow the VFAQ guide. The camshafts define when TDC is the compression or exhaust stroke. You need to take the lower timing belt cover off if you haven't done it yet. Then put the #1 cyl at TDC with the crank indicator, align the oil pump, then turn the camshafts to the 12 oclock dowel position. Viola, TDC on the compression stroke.

Correct, the bottom end knows no difference between TDC on compression or exhaust.

 

[2gGSXEclipse]

Pull the valve cover. When the 4 valves go into over lap(when exhaust and intake are both open to let exhaust gas out and new air in) you know its starting its next stroke...intake.