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?

 

[BorinquenEclips]

I would do as the manual says, Im pretty sure that just means that the #1 piston has to be all the way up if you know what I mean. Someone correct me if im wrong.

 

[tenn-gsx]

Put a rag or shop towel tight in the plug hole. If you see it move up, pop out, or hear air escaping from arround the rag when you turn the crank then its on the compression stroke.

 

[brandnew161]

The piston is at TDC right now. However, as you may know, the piston will reach TDC twice in its 4cylces which is two revolutions of the crank i believe. One of those is compression and one is exhaust. Idk if it matters or not that it has to deffinately be on the compression stroke.

 

[delta448]

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Align the timing marks for the crank and the oil pump.

Once that is done, the rest doesn't matter since you'll be moving the cams and CAS to match TDC on #1.

 

[brandnew161]

Put a rag or shop towel in the plug hole tight. If you see it move up, pop out, or hear air escaping from arround the rag when you turn the crank then its on the compression stroke.

wow, . makes sense. thanks ill give it a shot

 

[tenn-gsx]

Yea sometimes the simplest solutions are the hardest to come up with on your own. An old OLD OLD OLD Chevy tech taught me that trick.

 

[delta448]

Put a rag or shop towel tight in the plug hole. If you see it move up, pop out, or hear air escaping from arround the rag when you turn the crank then its on the compression stroke.

That only works when the cams are correctly timed and the valves are known to be closed on the right stroke of the crank.

 

[brandnew161]

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Align the timing marks for the crank and the oil pump.

Once that is done, the rest doesn't matter since you'll be moving the cams and CAS to match TDC on #1.

ok ok. I'm new at this but i like to do things myself on the car so i'm still learning while I go. But what do you mean by moving the CAS? CAS is crank angle sensor right? Since I am working on my 95, it is stationary and it does not move correct?

 

[delta448]

In any of my posts, I use these abbreviations as I've found this to be the most common terminology among DSMers:

CAS = Camshaft Angle Sensor
CPS = Crankshaft Position Sensor

 

[tenn-gsx]

Are you going to actually REMOVE the cams or just the belt? On a 95 the cas is stationary under the intake timing gear.

 

[brandnew161]

I already installed new cams and gears. However, the motor was not at TDC when I did this and i feel more comfortable retiming the motor instead of testingmy luck. Thats why I cant use the cam gears as reference points

 

[tenn-gsx]

Ok so your JUST going to remove the belt and leave the cams installed then correct? I ask because it donr matter as long as its tdc if your going to pull the cams and start all over completely. Just make sure you get all marks correct or close as hell before you seat the cams completely and install the belt.

 

[brandnew161]

Yes, since the aftermarket ones are already in, i do not plan on taking them back out.

 

[LiquidX]

I may be wrong, but couldn't you just put the block at TDC, remove the cams, bleed the lifters and re install them at proper timing for TDC? You said you did a shoddy install so I'm assuming you were going to redo it.

 

[delta448]

On a 95 the cas is stationary under the intake timing gear.

The sensor itself is stationary but the pickup is actually located on the cam sprocket. As the triggers on the sprocket pass the sensor it produces the CAS signal's voltage bump that tells the ECU which cylinder is on compression and which is on exhaust. The 2G CAS produces a signal twice per revolution.

edit #2:
Scott, the 2G CPS sensor also produces a signal twice per revolution and the correct signal must match what the CAS is telling the ECU. If you get the CPS sensor set 180 degrees away from the CAS sensor the result will be an incorrect injector firing order. The engine will still start and run fairly well in this situation, but usually you experience some stumbling on acceleration, random knock and misfires.

 

[brandnew161]

The sensor itself is stationary but the pickup is actually located on the cam sprocket. As the trigger(s) on the sprocket passes the sensor it produces the CAS signal's voltage bump that tells the ECU which ignition coil to use.

Do aftermarket gears come with their own pickups or do you have to swap the stock one off? I never even looked into that..



As far as the cams, this is where I am at after i realized i f'd up. Belt is off. #1 piston is @ TDC. Cams are installed and the dowel pins are at 12:00. Tonight I will be getting the lower timing cover off

 

[tenn-gsx]

Can you post a pic? In my car I decided to use a 1G cas rather than deal with the stock position for the cas on a 95-96. I have link though so this isn't an issue for me. Not sure if you can really do that if you don't run link.

 

[brandnew161]

Can you post a pic? In my car I decided to use a 1G cas rather than deal with the stock position for the cas on a 95-96. I have link though so this isn't an issue for me. Not sure if you can really do that if you don't run link.

What would you like a pic of, the back of the cam gears?

 

[tenn-gsx]

the front of the cam gears. Im not 100% sure but I dont think you can use the 95-96 cas setup on aftermarket gears. I didnt look too far into it though I just changed to a different system.

 

[brandnew161]

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thats the only picture I have. it from a few nights ago. You can see how after they were installed, the timing was off because the motor was not at TDC. They are fidanza's.

http://www.dsmtuners.com/forums/ven...m-gears-limited-edition-black-back-stock.html

just found that. Is it worth just using the one adjustable gear on the exhaust cam? I'll probably just use stock gears for now since this is turning into a larger project than i originally anticipated

 

[delta448]

Do aftermarket gears come with their own pickups or do you have to swap the stock one off? I never even looked into that..

According to FFWD, the Fidanza gears you're using are compatible with the 2Ga CAS.

for the 95-96 cars out there, no modifications are necessary for the gear to work with your cam angle sensor. Just bolt 'er on!

Scroll to the bottom of this page.

However, on Fidanza's application guide, for some reason they have a footnote that claims only their exhaust cam fits a 95-96.

I believe that it would probably be fairly easy to modify the intake sprocket to accommodate the CAS trigger, but I don't have any first hand experience there.

 

[sophat34]

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.

 

[delta448]

Who said anything about a 1G CAS?
He's using the 95-96 CAS, and the signal it produces is inverted when compared to all other years.

 

[brandnew161]

If i can use the adjustable gears that I have then that would be great. If the car doesnt start, then I guess I'll know why.

So, to get the timing all lined back up where it should be after i messed up, I should follow these steps (correct me if i'm wrong please)
-put #1 piston @ TDC
-take belt off and readjust cams so that the dowel pins are @ 12:00

^^from there I should be all set and can go right into the vfaq tutorial right?