65 replies to this topic

[Cater_Racer]

My 998cc engine has a timing mark on the front pulley and a plate with one big peak and five smaller peaks. Using the strobe light on plug #1 the mark appears at the forth of the smaller peaks. Reving the motor cause the advance (vacuum) to move the mark off the scale.

About right?

Are these marks TDC then plus 5 per? that would give me 20 BTDC too soon?

Help please.

[duds_12]

My 998cc engine has a timing mark on the front pulley and a plate with one big peak and five smaller peaks. Using the strobe light on plug #1 the mark appears at the forth of the smaller peaks. Reving the motor cause the advance (vacuum) to move the mark off the scale.

About right?

Are these marks TDC then plus 5 per? that would give me 20 BTDC too soon?

Help please.

each timing mark teeth is 4 so it goes 0 4 8 12 16 20 etc

your 998cc should be at about 4 degrees before top dead centre (check the haynes manual) on plug number 1, with the vacum pipe off and the car idling at 1000 rpm

[Cater_Racer]

Thanks Duds, so I'm on 16 and I should be on 4, wow.

The engine has a 276 cam and 12g295 head with a pocketed block, that won't make much of a difference will it?

[duds_12]

Thanks Duds, so I'm on 16 and I should be on 4, wow.

The engine has a 276 cam and 12g295 head with a pocketed block, that won't make much of a difference will it?

don't think so it's just getting the dizzy to put the spark to the valve the same time the fuel mixture is coming in from the carb

what year is the car and i'll check cus i'm not 100% it's 4 degrees

[blacktulip]

that changes everything lol, the best thing to do is time the cam in to the instructions of the cam, im sure you can find the recommended timing spec on the cam manufacturers website.

[bmcecosse]

Don't waste 'time' - timing in that cam - it will be fine at dot to dot. But with that engine spec - you probably need to modify the dizzy advance curve - read Vizard. Meantime - just advance till it pinks then back off slightly. And do check the vacuum advance is working as it should.......

[Pauly]

Don't waste 'time' - timing in that cam - it will be fine at dot to dot.

.

If thats the case just fit a standard cam.

[Cater_Racer]

Well the vacuum is working fine, I can see that by taking it of( at tick-over) and giving it a good suck (sorry about that bishop) the mark swoops off the scale.

I'm not sure about this advance it until it pre-ignites then "back it off a bit", all well and good. But can't I just set it up right in the first place?

Should I aim for 4 8 or 12 degrees at 1200-1500 rpm?

[01smartc]

I dont like people giving bad advice, dot to dot the cam timing is nowhere near good enough. The dots on timing gear recently have been as far as 12 degrees out on some of our engines. For the extra 10mins it takes just time it properly! Why else would cam manufacturers spend load of money finding the optimum setting. Like someone above said you might aswell run a std cam if your not going to do it properly.

Anyway, to answer the actual question.

I would set your ignition timing at 10 degree's and see how that goes.

Chris @ Smart Performance

[lrostoke]

Factory settings are normally on the conservative side to stop engines melting, tuned for reliability not max power.

standard 998 timing a common setting is 8 degree BTDC @1500 rpm vac pipe disconnected

Stage 1 timing instructions say 5 degrees @ 1000 rpm vac pipe disconnected.

when set reconnect vac pipe

[Cater_Racer]

So around the third peak (8 degrees) the first being TDC second 4 BTDC etc.

So I was 8 too far advanced.

Thanks

[lrostoke]

Not neccesarily, it may have been set for max power.

Like mentioned engines can take more advance than they have as standard. If you google tuning A series, you will find 32 - 34 degrees mentioned at 4000 rpm. If doing it this way though you have to make sure you haven't got pinking. When setting for max advance though on a standard dizzy you will find the timing at lower revs is more advanced that standard which is what was meant by needing a different advance curve.

[Cater_Racer]

Not neccesarily, it may have been set for max power.

Like mentioned engines can take more advance than they have as standard. If you google tuning A series, you will find 32 - 34 degrees mentioned at 4000 rpm. If doing it this way though you have to make sure you haven't got pinking. When setting for max advance though on a standard dizzy you will find the timing at lower revs is more advanced that standard which is what was meant by needing a different advance curve.

So it will pink more readily if its too far advanced?

And if I back it off, what@s the down side?

Cater

[Dave33]

Why not just try advancing it a bit,then try retarding and see how it goes.
You dont always need to have it as far advanced as possible to get good performance.
if you retard it too far it will be sluggish to pick up,but if you only back it off and its still fairly responsive you will gain more top end power,and more overrev.
best to just slacken off dizzy to allow adjustement,start the motor and move the dizzy til you got a relatively smooth idle and good throttle response.Then test it,then try adjusting it til it feels best.
Check the plugs for any signs of detonation,or over advance timing after a a brief burst in say 3rd up a hill.
Im assuming the carbs set up fairly well?this needs doing before the timing.
Before doing any of this though i would check your cam timing is set accurately,as a few degrees out,if retarded will result in a very cammy motor and poor performance,it wont hurt and can be beneficial to have up to 4 degrees advanced.
So cam timing,
carburation,
Then ignition timing.
hth a bit
dave

[dklawson]

If the engine is already built and in the car why are we talking about cam timing? Yes... you can set cam timing with the engine in the car but it's a lot more work and if the cam seems to be doing its job, is it worth it?

As for the ignition timing, once you put on a stage x head and type y cam, the OEM tuning specs for the engine should only be considered a starting point.

I know of no situation where an engine performs "better" when the timing is retarded. My advice continues to be very similar to what BMecosse said. Bring the engine up to about 4k RPM then set the timing to about 32 BTDC. Return the idle speed to "normal" and test drive the car by putting it under load (such as accelerating uphill in too high a gear). If you hear ANY pinging and/or knocking, retard the timing about 2 degrees and repeat your test drive. Keep doing this until NO pinging or knocking is heard and you will have the max advance your engine can take for its state of build and the fuel you are using.

by the way, stop worrying about the vacuum advance. Its job is to give you fuel economy at part throttle (such as cruising). Under those conditions it does advance the timing. When accelerating (wide open throttle) vacuum advance is NOT happening. During acceleration the advance is purely mechanical and is handled by the advance weights under the breaker plate. (Mechanical advance for power, vacuum advance for economy).