ptuomov

You should have worked a boroscope in somewhere in there.

AO

That's funny. Kurt, the man-*****!

auzivision

Hey now… I ain't as good as I once was. But I'm as good once as I ever was. LOL

auzivision

I’m trying to comprehend the whole time gear crank concept and am a little murky on the relationship between crank revolutions and cam gear revolutions.

Here is what I understand so far. A four stroke motor means two revolutions of the crank to complete 1 engine cycle. So one crank revolution means the valves are only halfway through their cycle.

Theory:
To keep an engine in ‘balance’, the left side is doing (for lack of better words) the opposite of the right side. They are in essence 180 degrees out of phase with each other. So at the 45 mark now versus the 45 mark one revolution from now, wouldn’t that put the valves in the same but opposite positions? Left is right and right is left.

Conclusion:
If that is true, then why the need to mark an alternative 45 indication on the cam gear to do a belt change, when the one 180 degrees out of phase will already match up with the notch? One would think that if the cam gears can be rotated without valve piston contact at one 45 degree mark, they would be le to do the same at the other 45 degree mark.

Does this make sense or what am I missing something here?

Since I’m not only changing the belt, but also the gears this weekend. I’m trying to get my hands and mind around this concept before digging in this Saturday.

John Speake

The two banks are 90 degrees apart.

Bill Ball

Kurt: I think you understand that the crank rotates twice for each cam revolution. So, with the crank at 45 degrees BTDC, the cams can be both either 22.5 cam degrees (3 teeth) BTDC or 180 degrees off that. So, without creating any problems you could put the belt on both cam gears at 3 teeth before the TDC mark or 180 degrees off from that, as long as both cams are the same in that regard.

auzivision

90 degrees apart relative to what… are you talking about relative to the crank, engine cycle, physical geometry or ???

In my analysis, I was referring to one complete engine cycle equaling 360 degrees (which is 720 degrees on the crank and I have no idea how many on the cam gear, but it’s not really relevant).

I know I might not be using proper engine lingo when I stated they are 180 out of phase. I haven’t really thought through one lagging the other by 90 degrees, but it sounds plausible since there are four phases (breath out, breath in, compress, and bang)

Bottom line… my real question is if I line up the 45 crank mark when the cam gear align with the v notch on the tower back, is that a safe place to lock my crank and R&R the belt and cam gears?

auzivision

Thanks Bill... I think we are in agreement.

I do understand that the crank goes through two revolutions for each cam revolution. I haven’t cracked open the cam covers yet. Is the Cam gear directly connected to one of the cams or is there some sort of internal gearing?

This is my first time working on an engine other than changing fluids or plugs.

auzivision

Okay, sounds like there are 48 teeth on a cam gear. If one crank 45 degree mark is 3 teeth short of TDC, the other one would line up at 21 teeth after. That would mean at no time does the crank set 45 will the cam gear notches line up with the groove.

Part of my confusion stems from helping Hans button up his TB WP (delete) job last night. His belt was already on and his cams were lined up with the TCD notch and his crank was at 45. Now I’m more concerned that he didn’t get his belt back on correctly. He said he didn’t move the cam while the belt was off, but not I’m wondering if he isn’t “3 teeth off”.

Bill Ball

The pictures of your cam gears with the crank at TDC looked to both be at the TDC mark. Now, if you rotated the crank around to the next 45 degree BTDC, yes, the cam gears would end up 21 teeth AfterTDC. If you locked things like that and did the TB job, the belt could be put back on in the same position OR both cams could be moved around to 3 teeth BTDC. Most people just lock the crank at 45 degrees BTDC when the cams are 3 teeth BTDC before they remove the belt, then leave the cams in that position. Yes, the intake and exhaust cams are connected inside by a chain.

If Hans ended up installing the belt with the cams at zero TDC while the crank was still locked at 45 degrees BTDC, he is going to have a problem. I hope your memory is just a bit off. What most people do is install the belt 3 cam teeth BTDC, then unlock the crank and rotate it a few times and verify that the cams are zero TDC when the crank is zero TDC. So, you may remember the checks at TDC and be confusing them with the belt install when the crank was still locked at 45 crank degrees BTDC. It's all a little tricky because you are installing the belt untensioned, so it is easy to get the belt off a tooth from when it is finally tensioned unless you are real careful to pull hard on the belt as you work it back on the cam gears, right side first, while in some way holding the cam gears so they do not rotate.

auzivision

I helped install the damper and I’m certain it was at 45. Then I installed the rotors and caps and I'm 99.9% positive they were set to TDC.

I had an Oh $h!t moment while lying down to sleep and called Hans last night. He convinced me it was cool and I was trying to rationalize it. Now I’m convinced his is not right.

The lock is still in place and the engine hasn't been cranked, so at this point it just rework.

Bill Ball

If the cams are zero TDC while the crank is still locked 45 degrees BTDC, you are completely right and Hans needs to think this over again. There are some people who lock the crank at zero TDC. In general, this is not kosher, but on non-interference OB cars it doesn't matter and as long as you don't let the cams rotate too much it could be done that way on a 32 valve.

AO

Caps and rotors can only go on one way.

hans14914

Ok, since this involves me more than Kurt, here are the facts. My timing is off. I know its off. Its advanced on the drivers side cam, and retarded on the passenger. I know this from the static compression test, as well as looking at the cam marks. The cams have not moved any from when I installed the lock. They are in the same place they were prior to removing the belt.

That said, they are off, and I was planing on setting them correctly shortly.

So, If the flywheel was locked and the cams havent moved from the place they were previously, I deduce there should be no problem, but I have been wrong before.

Thanks,
Hans

auzivision

False, I saw first hand last night a rotor that was not installed correctly. Three screws equals three differenct posible positions. Only one is correct.