2.25 Petrol cam timing

The S3 engine rebuild continues.

I have assembled the crank gear and cam gear. Both only have one keyway, so there's no adjustment apart from tooth by tooth on the cam gear. I set cylinder No. 1 to TDC using a temporary install of the crank pulley and the timing pointers, whipped off the front cover and with the timing chain taught on the RHS (pulling) side, the cam wheel marks do not QUITE line up as shown in the manual. The top mark is supposed to point to the stud at approx 11 o'clock position, but on mine, the mark is just to the right (or if I shift it around by one tooth) just to the left of the stud position. So I guess it is half a tooth out, either plus or minus.

How critical is this degree of misadjustment? I have the original cam gear which to be honest does not look to be in terrible condition. The original has six keyways so I assume will offer a degree of additional adjustment. I am just wary of installing an old cam gear with new chain and new idler.

Any wisdom on this? The manual says to get it right, but does not say what to do if it doesn't quite go according to plan.

Thanks

I'm also (slowly) rebuilding an engine for my LWB Ser 3, but haven't reached this stage yet, so was waiting to see what responses you got from the experts. A quick thought: are you sure that TDC on the crank pulley is accurate i.e. No 1 piston is right at the top of its stroke?
I'd be tempted to try the old cam gear to see if that aligns 100%. Unless the teeth are worn or hooked I would think it's okay. I'm planning on re-using mine - I don't recall anything in the manual about using a new one (and I don't want to know what a new genuine one would cost...)
If you can't get it 100% I'd be tempted to set it up on the advanced side, then the timing will get closer to normal as the chain stretches. But I'm not sure if a few degrees offset would cause a significant loss of power.

Kiwi Landie said:

The S3 engine rebuild continues.

I have assembled the crank gear and cam gear. Both only have one keyway, so there's no adjustment apart from tooth by tooth on the cam gear. I set cylinder No. 1 to TDC using a temporary install of the crank pulley and the timing pointers, whipped off the front cover and with the timing chain taught on the RHS (pulling) side, the cam wheel marks do not QUITE line up as shown in the manual. The top mark is supposed to point to the stud at approx 11 o'clock position, but on mine, the mark is just to the right (or if I shift it around by one tooth) just to the left of the stud position. So I guess it is half a tooth out, either plus or minus.

How critical is this degree of misadjustment? I have the original cam gear which to be honest does not look to be in terrible condition. The original has six keyways so I assume will offer a degree of additional adjustment. I am just wary of installing an old cam gear with new chain and new idler.

Any wisdom on this? The manual says to get it right, but does not say what to do if it doesn't quite go according to plan.

Thanks

Click to expand...

have the cam to the right of the mark if its best you can get as thats advanced ie the more clockwise cam is the more advanced,with a diesel the 6 slotted cam sprocket is essential not so with the petrol

Thanks guys. In the end I used the old cam gear as there was really very little sign of any significant wear. I set it very slightly advanced (maybe 1 or 2 degrees at the most) as that was the best fit with one of the keyways and I figured that a bit of stretch in the chain would result in it dropping back to a more correct orientation.

By chance (or error!) I had ended up with two crankshaft gears in the last big order I made from Paddocks. On closer inspection, the tooth/keyway orientation on both of these was different, with only one of the gears matching the original one. The other was about half a tooth out. So something to watch there with aftermarket parts. (Not that there was any guarantee that the original gear I pulled off was OEM. It (and all of the timing gear to be honest) looked to be in good shape and just about everything else on the vehicle was completely worn out so I am picking that it may have been changed in the fairly recent past by a PO).

ExMil109, don't worry about how long it takes to rebuild the engine! I had all my machining done about eight months ago and I'm only now putting it all back together! I assembled the rest of the engine at the weekend, masked it off and painted it last night. Looks a treat. Hopefully it'll run as well as it looks.....

The 17H rebuild continues (slowly)....

I've replaced the cam and chain, but like Kiwi Landie, I find I can fit the cam chainwheel either slightly advanced or slightly retarded. It's not that far off (about 6 degrees according to the marks on the crank pulley). As per Jamesmartin's advice, I'm going for slightly advanced, then as the chain stretches, the timing should get closer to the ideal setting.
The manual says to use a new "special micro encapsulated treated bolt" for the cam chainwheel. As far as I can tell, this means it has some locking compound pre-applied. Does that mean I can re-use the old bolt with some locktite? I don't recall that it was especially hard to remove when I stripped the engine down...
Pictures below show retarded and advanced

Yep - that looks to be about the same as mine. Either retarded or advanced but not fully correctable.
If I recall, I just used some Loctite and torqued the bolt up to the correct figure from the manual... Certainly I did not have a pregunked bolt.
I now live in fear of having got this wrong and needing to strip it down to fix it. I am still a mile away from actually starting the engine!

Cheers
Andrew

ExMil109 said:

The 17H rebuild continues (slowly)....

I've replaced the cam and chain, but like Kiwi Landie, I find I can fit the cam chainwheel either slightly advanced or slightly retarded. It's not that far off (about 6 degrees according to the marks on the crank pulley). As per Jamesmartin's advice, I'm going for slightly advanced, then as the chain stretches, the timing should get closer to the ideal setting.
The manual says to use a new "special micro encapsulated treated bolt" for the cam chainwheel. As far as I can tell, this means it has some locking compound pre-applied. Does that mean I can re-use the old bolt with some locktite? I don't recall that it was especially hard to remove when I stripped the engine down...
Pictures below show retarded and advanced
View attachment 210029
View attachment 210030

Click to expand...

yes old bolt and studloc is fine

The diesel wheel is the best solution, and using a dial test indicator to find TDC. But that will do fine. I'm doing this job at the moment with an ACR cam, that requires the valves on piston one to be exactly the same amount of raise in order to work!