Is my timing off by a tooth?

NEW SYMPTOMS/ISSUE HERE: http://forums.turbobricks.com/showthread.php?t=343102

Last post in this thread has details.

I was having issues building boost in lower rooms with my T3/T4 Turbo and someone suggested that it could be cause by my timing belt being off by a tooth essentially reatrdung the timing a lot resulting in me building boost rapidly above 4800rpm but very slowly below there. I would like to know what you guys think about what I have done and what you suggest I do next.

Alright so I've made a little progress with my boost issues by adjusting timing. What I did was I aligned the cam gear with the timing mark on the back plate by turning the crank via the crank bolt (this also aligned the mark on the harmonic balancer with the 0 degrees marking although it did seem to be off a bit like maybe half a tooth?). I then loosened the tensioner and removed the belt off the cam gear. I turned the cam gear a tooth clockwise and put the belt back on. I then realigned the cam gear spot with its timing mark. I then looked at the harmonic balancer, the mark on the balancer was as expected no longer in line with the 0 degree mark, but assuming I had corrected the skipped tooth, the engine should have been at tdc if the cam was ligned up which it was. So I marked on the harmonic balancer in line with the 0 degree mark to essentially make a new, correct timing mark (balancer may have slipped a bit. I couldn't use the crank pinion key to align for tdc because my lower timing cover is still on). I then used my new mark to set the ignition timing to 14 degrees btdc (didn't require much distributor rotation).

I've read that advancing cam timing should move the powerband down which is what I wanted (car was sluggish until 4800 suggesting I skipped a tooth). I assumed shifting the cam clockwise was advancing the timing.

So after performing this change I will list what has now happened so you guys can see what you think.

Good:

- acceleration is more consistent now. Boost no longer climbs super rapidly after 4800rpm and boost is now built consistently throughout the rpm range.
- vacuum is now 20mmHg warm where as it was only 18mmHg before

Bad:

-idle rpm is no longer consistent (climbs to 2000-2500 on its own and only a blip of the throttle will drop the it back down where it begins climbing again. This also happens driving while stopped) could this be part of the ECUs "learning procedure"?

- engine began misfiring at idle which was only fixed/improved by richening up the base mixture (wideband read 13.0 at idle once misfiring had stopped).

So what do you guys think? Had I skipped a tooth before or am I now running my cam advanced like 10 degrees? LOL

Set your timing up correctly instead of what you are screwing with. Set the crank, cam and intermediate gears correctly before you start changing anything

I had cam and crank set correctly to the best of my ability before, everything was aligned (cam and back cover, balancer mark and 0 degree mark). Intermediate shaft doesn't matter on 7/9. Forgot to mention it's an 87 740 Turbo b230ft. I was thinking the mark on the balancer may have been off due to a bit of slippage resulting in me timing it wrong. What I did above was to try and account for that.

I agree with apachechef.

To account for potential inaccuracies in the fabrication of the valve train components, time the camshaft off of valve movements using a dial gauge to measuring movement (valve lift) of the valve retainer (bucket in the case of an OHC engine). Good cam spec sheets will provide you with the valve events versus crankshaft angle. You will of course also require a degree wheel for the crankshaft to do this.

The official Volvo service manual for my ancient B20E sets out a procedure for confirming the correct timing of the camshaft itself. The bucket / shim arrangement on the later OHC engines precludes using exactly the same procedure; but, I expect that the manual probably sets out an equivalent method. Of course, this would only work if you retain the OEM camshaft.

I think I'll just use a piston stop to find true tdc and mark that on the harmonic balancer, then go from there.

You can also use the slot in the washer on the crank. That should line up against the mark on the aluminum timing cover. Remember, if you put a mark on a balancer that's spinning, your mark will never be right.

Pictures:

http://www.volvoclub.org.uk/faq/B230FTimingBeltAlignment.htm

Right I was thinking about that, I just don't have the tool to hold the crank pulley in order to remove the bolt so I can get the bottom timing cover off to look at the key way on the cam sproket. Is there any other way to do this?

An air impact. Breaker bar and the starter.

Rope trick.

wedge a prybar between a ringgear tooth and the block.

In case of a manual trans: fully apply hardbrake + put trans in gear. Most of the time that is enough to undo the bolt

culberro said:

An air impact. Breaker bar and the starter.

Click to expand...

^^^ works every time

I like the idea of the handbrake and being in gear being good enough. Now I should probably go out and buy some new accessory belts as some of mine are pretty crusty. How many belts aside from the t belt are there on an 87 b230ft in a 740? Are contitechs good belts?

Should be Alt, PS, and AC. They are all separate belts and all run off the HB (i.e. the AC does not run the PS like on a 240)

Go to FCPeuro.com, find belt part numbers and interchange them with local parts stores. Contitech is a good belt.

Sounds like you're getting close to solving your boost/rev issue

Thank you, so 3 accessory belts, got it. I'm really hoping this is the issue and that everything will be much better once I get it all timed correctly. First time I'm actually hoping the harmonic balancer slipped as it would explain a lot of my issues.

Look down from the top with the upper cover removed, don't need to pull the lower cover to see the notch.

gsellstr said:

Look down from the top with the upper cover removed, don't need to pull the lower cover to see the notch.

Click to expand...

Oh really!? That would make life a lot easier. I remember looking and only seeing the teeth for the crank sprocket. Could you possibly find a pic looking from the top? There's a lot of grime in there from who knows what so that only makes things harder to see.

Edit: didn't know there was an actual notch on the disc also.

Yup, there's a pic for ya. Should be visible from the top.

Alright, will check tonight in a bit.

Checked and my timing was indeed correct before, ugh. Corrected my wrong doing and now the search for the spool issue continues.