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Cam Belt was out one tooth.

Cubes

By Cubes,
in Forced Induction Performance

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Cubes Grand Master

Cubes

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I replaced my cam belt finally and noticed that the old one was one tooth out.

The crank was clockwise one tooth out.

So if I were right that would mean that the valves were opening late and closing late.

Hence maybe more exhaust getting out but less boost getting in?

I have noticed that there is heaps more down low off boost torque but I'm not sure if it goes any harder when on boost.

It also idles really smooth and with the copper 7's I am now able to idle her at 600rpm with out it missing and making the idle drop to 400rpm.

It also starts instantly as soon as you turn the key, before it would turn over for maybe 1-1.5 sec then start.

Even with the cam timing being the way it was before it still made 156rwkw on 12psi of boost with the fuelling perfect up top.

So what do you think ppls should it be slower or faster now?

Just a note I think the head has been off before as I can see marks on the head bolts which would coincide with the cam belt being a tooth out.

:burnout:

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Guest Stocker

Guest Stocker

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It was probably one tooth out deliberately. Retarding the cam gives more power upstairs, and advancing more downstairs. One tooth only is the limit though!

When I replaced my belt, it was REALLY stretched(so a bit retarded), so it made all it's power up high, and would rev to 5800-6000 rpm(stock RB 30), when I advanced the cam one tooth while replacing the belt, I picked up a fair bit of bottom end, and now only revs out to 5250 or so rpm, but that suits me better!

Regards, Andrew.

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Cubes Grand Master

Cubes

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It did run pretty well apart from the slight rough idle like a pop every now and again that is due to the colder spark plugs but it made the car almost stall if i didn't have the idle at around 800rpm.

Now the car still does actually pop a little on idle but it doesn't make the idle drop to 400rpm. It sits smack on 600rpm.

I noticed that it is pretty easy to knock it out one tooth if you can't see the lines on the belt as you can't really fit your head inbetween the front of the motor and the radiator support to line it up by eye level.

Grab a harmonic balancer puller from your local auto shop for around $18 then buy some M6 High tensile bolts and a couple of strong washers to suit, pull the balancer off then pull off the front covers and have a quick check.

Oh also you will need to pull the belts off which are pretty easy apart from the power steering pump that takes ages to wind out unless you have a ratchet ring spanner (:D

While you are there you may aswell do the waterpump and cam belt tensions ets.. Mine turned out ok I thought the tensioner was buggered but it turned out to be the AC tensioner bearing.

New bearing for that was $5 also :D

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  • 1 month later...
Ait Rising Star

Ait

Posted
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Hi guys,

I noticed you mentioned that the cam belt does cause rough idle and the occasional pop?

I just got my skyline from japan, it's low on Ks, about 45+ thousand (I'd bet it's knocked back), other then that it's clean. However, idle is alittle rough when it drops to about 500 or 400. I can hear the sound of the engine rising and falling. It gets alittle worse when I turn on the lights.

Any ideas? I'll have the plugs and fan belt changed soon, I hope it'll help.

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Cubes Grand Master

Cubes

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That sounds like your AAC Valve that has a solanoid attached to it at the back of your plenium near the firewall.

When you do the plugs make sure you slap the proper plats/iridiums in otherwise when the idle drops you will still get the slight pop.

Do a search on the AAC Valve and how to clean it.. ~$10 to do it your self.

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Ait Rising Star

Ait

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However, the strange thing was when the plugs were pulled out. They looked shiny and new. All that was done was a regap and clean. The idle wasn't completely eradicated (but better) but the engine rise and fall was still there. I dunno if it's due to the car sitting at the docks for too long (corrosion mebbe?)

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croat Mentor

croat

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Zoel i am pretty sure when your cam belt skips teeth it will lower your performance... i had the same problem but didnt know till my mechanic had a look. he told me that i had skipped 4 teeth. as a result i had a huge loss of performance and my exhaust was much much softer...

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Cubes Grand Master

Cubes

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I think that mine being a tooth out was an accident as i can see from the head bolts that the head has been removed previously.

But it did make 156rwkw on 12psi which isn't to bad i thought when the cam belt was out a tooth.

Especially when its only 1 or so psi more than std boost.

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puckish Rising Star

puckish

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This is way interesting Joel. Cos it relates to playing around with cam timing using adjustable gears, and how much you can get away with before piston finds valve:(

Does anyone know the number of degrees for each tooth?

BTW Croat ... Super Glory Super Glory ... sorry couldn't help it.....

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