Timing On Rb25/30

[Black R32]

Sooooooooo....

I'm having trouble setting the timing on my freshly slapped together RB25/30....

Tensioner has been relocated to above water pump.... 152 Tooth belt...

Lined up everything but and the first time engine started fine, idled fine, but no power AT ALL!!!

played with the timing a lot and thought it might have been one or two teeth out but couldnt get it to run any better.... actually made it worse.

So i'm starting again, and need to know the count of teeth required between each mark.....

I know that its supposed to be 38 teeth between the two cam gear marks, but what is needed from crank mark to exhaust cam gear?

I have searched many forums but to no avail!?!

Help!!

NEED IT DONE BY AUGUST WINTON!!!

[KiwiRS4T]

I think my relative lack of power might be timing related too. Does anyone know if the timing belt is absolutely symetrical on a stock RB engine i.e. the same length (same number of teeth) on the left and right side?

It occurs to me that this could be upset by the relocated second tensioner. Is it possible that this could mean that even though all the timing marks appear to be in the correct place the timing is out?

I know that Guilt Toy and others have said that valve timing is critical to getting the full power from the RB30.

Well just had a look at this thread

http://www.skylinesaustralia.com/forums/topic/73824-adj-camshaft-pulley-new-cam-belt/

and it sems to me that if the crank timing is set at TDC and the cam gears line up with the backing plate it should be correct. The marks on the belt (if there are any on a belt for a twin cam RB30) probably won't line up as the belt will not have been made for that purpose.

[Black R32]

great thread but unfortunately that is for a standard rb25... i need one for the extra height of the 25/30!

Help!

[KiwiRS4T]

great thread but unfortunately that is for a standard rb25... i need one for the extra height of the 25/30!

Help!

I don't think so! I've got a 30/25 too and the main information should hold true and I will check mine this weekend. I reckon that if the crank is set at TDC and the cam gears align with the dots on the backing plate (not on the belt) - as per the illustrations in the thread then the timing must be correct regardless of how many teeth there are either side. The height of the block is neither here nor there. Have you found the timing marks for the crank?

[HR31-PASSAGE]

What was the outcome? Looking to find out the same question you asked

[GTRPSI]

I don't think so! I've got a 30/25 too and the main information should hold true and I will check mine this weekend. I reckon that if the crank is set at TDC and the cam gears align with the dots on the backing plate (not on the belt) - as per the illustrations in the thread then the timing must be correct regardless of how many teeth there are either side. The height of the block is neither here nor there. Have you found the timing marks for the crank?

Exactly....

Stop counting teeth.

Find TDC by finding the top of the piston travel on Cyl 1 by removing a plug and feeling down the plug hole (if you dont have a dial indicator), then check your harmonic balancer mark to make sure the balancer outer wheel has not slipped and is lining up where its supposed to be.

Then look at your cam gears, intake side cam gear dot should be at the 9 o'clock mark and lining up with the mark on the cover, exhaust gear dot should be at 3 o'clock and also lining up with the dot on the rear cover.

If they are adjustable cam gears, the scales should both be at 12 o'clock.

[iruvyouskyrine]

So the extra deck height of the RB30 won't throw out the timing marks on the cam backing cover?

Looking to start my engine soon and i was worried about the timing being out. I have aligned everything perfectly (cam gears to backing plate and crank sprocket to oil pump markings) but just want to be absolutely sure that i have it correct.

Thinking about getting a professional mechanic to degree my (stnadard) cam gears just to make sure timing is 100% spot on.

[iruvyouskyrine]

Anyone confirm this? Looking at first start within a week hopefully, thanks guys.

[r33_racer]

Easiest way is to setup number 1 on TDC with a dial indicator down the spark plug hole and get that bang on and then line up the cam gears with the backing plate using the backside of the dimpled tooth on cam gears. Once that is lined up your belt should go on quite easily and your timing should be pretty close to right.

I have found that some backing plates have a little bit of slop in them and can rock left and right which can throw out your cam gear alignment, so try to get that centred. I haven't seen enough slop before that it throws it all out by a tooth when fitting the belt.

Extra height wont throw anything out if you are setting it up with number 1 at TDC. If you are counting teeth like a 25/26 then you will run into issues.

The way I outlined it and others have already is pretty well the only way to fit your timing belt and have it aligned correctly on an RB30det.

Degreeing your cams properly is a far more involved practice, which you need a degree wheel, cam card information, adjustable cam gears and dial indicator with usually a custom made indicator rod so you can do the job correctly. But for most basic builds this is not required and in most cases cannot be done because people don't have the required parts fitted or tools to do it.

[iruvyouskyrine]

This is exactly the situation I was in. I understand how to set up timing following the backing plate and crank timing marks, which I have done correctly. Was just wondering if they would be out due to the extra height if the block, but if it doesn't matter then it should be all good.

Like you say I don't have the tools/knowledge to properly degree my (standard) cams, and was wondering if it is worth getting a workshop to do it properly.

Thanks

[r33_racer]

If you have it done that way then you should be fine. Once you get the car going you will know if its out a tooth.

After I fit the timing belt and then set the belt tension I will turn the motor over a couple of times and make sure its all settled in and then re check that it all lines back up. Always a good practice to double check things, even more so when its a pretty critical part.

[XKLABA]

Using the marking on the crank belt gear against the oil pump and cam gears agaisnt maykings on cam backing plate is the best way, then turn by hand a few times ( as michael said ) then recheck they are lined up

Then while still set at TDC install crank gear cover and balancer and check theose markings line up for later when setting ignition timing with timing light

[jiffo]

Once you've fitted the belt and test rotated a few times, I suggest you prove TDC on the balancer.

Make a suitable piston stopper such that when it's screwed into No 1 spark plug, the crank stops slightly off TDC.

Rotate the crank clockwise until No1 piston hits the stopper. Mark the balancer referenced against the TDC pointer.

Rotate the crank anti-clockwise until No1 hits the stopper again. Mark the balancer referenced against the TDC pointer.

Remove piston stopper and re-fit spark plug.

TDC is now halfway between those 2-marks you scribed on the balancer.

That's sorted the crank but I feel there's so many variables associated with building these engines that as a minimum, you need an adjustable exhaust cam wheel.

[iruvyouskyrine]

I was pretty sure I had the timing sport on with the cam gears and the crank sprocket, but I took everything off and double checked it all and it was all perfect turned it over and everything lined up again.

I just want to get the thing started at the moment so I know it's going to run. First engine build so I'm hoping for the best but expecting the worst haha. Will get everything spot on with a piston stop etc once I know it's not going to explode into a million pieces on start up

[Easto]

RB25/30's ain't that hard I just recently threw a big end on mine and replaced it with one I had under the house.

If you have the right belt and line all the marks up, providing the tension is correct, confirm they meet up again after a number of rotations. No problem.

You then need to tune the thing,

Stock 25 computer needs a fuel reg to bump the fuel pressure up.

If you haven't touched the fuel pressure you don't have enough juice for the thirsty 30.

I have never used an adjustable cam wheel on either cam other than the standard oil activated one(which has a blocked off oil feed of course)

[Ben C34]

"Tuning" an engine using fuel pressure is so ghetto.