Timing setting for Unleaded Petrol

[Scott Stephen]

Originally Posted by charlotte001

Ouch 4 teeth is quite major but not the end of the world. Did you start and run the car before you found the markings out?

The back fire may have been all the gunge clearing off the valves or yes it could have gone kersplat.

You have two options

1 Take the head off and check for damage
2 realign everything and rotate the engine on a socket with the plugs out

If the second doesn't work then you have to take the head off and check for damage which will probably be severe. When I say severe it will mean at least valves bent and signs when valves have met pistons, which is severe meaning new valves, pistons, maybe valve guides, rockers.

I'm hoping for you theres nothing wrong

Charlotte

Hi Charlotte, yes the engine did run before but didnt idle too good and occasionally backfired (No bloody wonder!!!) Now I'm even sceptical about the original timing marks! - I'm going to take the head off and have a lookie. Is there any 100% full proof way of aligning the engine correctly with the head on/off?

the only fool proof way to align the bottom end of the engine (Although not recommended) is to check the firing sequence of the engine which Is 1342 align the rotor arm to the firing sequence on number 1 cylinder, the piston should be at TDC (Top Dead Centre) going clockwise. A fool proof idea is then to use some white model enamel paint and mark where number one plug would be for future use.

Once you have this then check the markings on the crank timing marks the timing for the lower end will then be correct.

Once you have rebuilt the cylinder head simply place it back on the block without the cam shaft, tighten all the bolts back to 15lbft then tighten to 45lbsft and finally tighten all 1/4 turn in order

1=centre top
2=centre bottom
3=left top from 1
4=bottom left from 2
5=right top from 1
6=bottom right from 2
7=top far left
8=bottom far left
9=top far right
10=bottom far right


3,4,6,7 =1 bolt either way from taking 1 and 2 are centre bolts see below

7 3 1 5 9
<--Direction of engine
8 4 2 6 10

Replace camshaft it's upto you if you want to keep the top end timing sprocket on, you cannot get the valves out without removing the camshaft. Align timing marks making sure the valves have gone down in order and the bottom end hasn't moved.

Replace timing chain or belt, replace plugs, leads, cap and start

Charlotte

[Scott Stephen]

Originally Posted by charlotte001

. A fool proof idea is then to use some white model enamel paint and mark where number one plug would be for future use.

Once you have this then check the markings on the crank timing marks the timing for the lower end will then be correct.


Charlotte

Hi Charlotte, Thanks very much for all your input. I do understand the theory, but I dont quite understand what you mean on where to apply the paint!!

[pettaw]

Don't bother disassembling or removing the head just yet. Far better to get everything off, check alignment and reassemble very carefully. If it really was 4 teeth out then the engine would have struggled to run at all tbh, so it sounds like you've probably gone too far the other way, that's why I reckon you'd be better off getting it all off and putting it back 100%.

You'll have been unlikely to damage anything unless you were absolutely miles out eg: 30 degrees out.

[Scott Stephen]

Originally Posted by pettaw

Don't bother disassembling or removing the head just yet. Far better to get everything off, check alignment and reassemble very carefully. If it really was 4 teeth out then the engine would have struggled to run at all tbh, so it sounds like you've probably gone too far the other way, that's why I reckon you'd be better off getting it all off and putting it back 100%.

You'll have been unlikely to damage anything unless you were absolutely miles out eg: 30 degrees out.

Hi there, To my ability everything is exactly how it should be. Top and bottom marks aligned, (timing cover is off at moment) - Rotor arm is approaching no.1 at TDC, engine is turning freely, i'm so damn frustrated i just want to "rip it up and start again" as the song goes....... I surely must be missing something major but I cant see what?????

Hi Scott

Take the Distributor cap off align the rotor arm to number one Piston where the centre of the Rotor arm sits on the Distributor body put a white stip mark. it's a good idea to run it up the side of the body onto the lip where the cap would sit.

A great way to see if the piston is at TDC is to remove number one plug get a strong torch (one of these LED ones) shine into the port if the piston is at TDC you should be able to clearly see the crown (top) and valves. From memory 4 teeth on a 240 is around 10-20 degree +/- 5degrees.

You say the engine is rotating smoothly on a socket ? then damage is highly unlikely as if damage has occured then the engine wouldn't rotate let alone smoothly.

Try rotating the engine 5 times and see if the marks remain constant on around the 3rd turn if not then you are 180 ish out. Oh what marks are you going by ? paint or stamped ? There should be a stamped Slot or a circle on both sprockets.

I'd agree don't remove the head yet take the belt off, check that the Distributor is alignged to TDC or Piston 1 mark the Distributor lip and refit the belt. It's always a good idea to remove the plugs first to rotate the engine, checking that the marks alighn, before you replace the cover.

Charlotte

Charlotte

[Mike_Brace]

The B21A engine is a non-interference engine - you CANNOT damage the head by turning bottom seperate from top. We have a a case of the pin holding the cam pulley breaking off - this might explain your four teeth out situation. Worth checking non of the pulleys are loose! If I was a betting man I would put a large sum of money on it as I reckon this will be the problem. Aligning marks should then work.

Mike

[Scott Stephen]

Hi all. Took the head off today......all is well, Big sigh of relief!!! (Although when you rotate the cam pulley it is a bit sticky and then loose - Is it ment to be a nice smooth turn???)

The head could do with a decoke so i'll get it done at my local head shop

Is there only ment to be 2 locating dowels for the head both on the LHS of the block? the reason i ask this is when i lifted the head off i disturbed something and it fell down the side of the engine to the ground.

Thanks everyone for your comments

Hi there is at least one dowel. Not sure on the B21 engine as I had the B23 version.



Charlotte

[classicswede]

Originally Posted by charlotte001

I've seen some very impressive burnt out valves ok they're mainly from the older 144's and amazons and I agree plenty of valve guides


Charlotte

The reason the amazons burns valves has nothing to do with unleaded but a tiny little exhaust. I have seen a amazon compleatly melt a set of spark plugs and manifold gasket - in fact this car used to do it every couple of weeks!! The only way we resolved the problem was to fit a 2" bore sports system. All our B18's B20's and B30's run on unleaded or LPG.
The reason the ohv engines suffer from valve guide wear and the ohc engines dont is because of side loading. Tbh the main reson of OHC engines is for the use of unleaded fuel.