BJ8 engine timing

[BOBBYR]

Hi Guys,
I hope everyone is well.The other night, I replaced the points and plugs and thought it a good idea to check the timing. I think this could be the beginning of a drinking problem. Timing this motor is not an easy job. As I see it, the manual spec for idle timing is 10 deg.BTDC at 600 rpm's. Getting this motor to run at 600 rpm's is next to impossible. Also, the pointer on the timing gear case only indicates top dead center. Any help in timing this beast would be appreciated. Meanwhile, I'm going out to the garage to read the manual and have a cold brew.
Bobby R

 

[fwtexasbj8]

Bobby,
Get yourself an advance timing light, you can get them everywhere (mine came from Sears), so you can set the dial to the desired degrees BTDC. Then all you have to do is set the dial and rotate the distributor until the needle lines up. My manual shows 15 degrees BTDC using a timing light. I too have a hard time getting the engine to idle at 600, but the advance with RPM that low is not great so 15 degrees is probably close enough at any reasonable idle. Be sure to plug the vacuum advance line before you time it.

Doug

 

[tahoe healey]

Wine cork works good to plug the vacuum. I go to 18 degrees. Runs great.

 

[GregW]

Hi Bobby,
A quote from Dave.

It is very important to make sure that the total advance, static plus centrifugal, vacuum disconnected, does not exceed about 34 to 36 degrees at 4,500 rpm.

Over advance can get into silent detonation which will rapidly damage an engine. It's silent because at higher rpm other engine/car noises are covering it up.

The safest way is to set the maximum advance to 35 degrees at high rpm with a timing light. Let the lower rpm advance fall where it may. There are just too many variables in a distributor's calibration to assure that setting static or low rpm timing to a given value will assure that the maximum advance is not exceeded.
D

So if you were to buy a dial-back timing light, you might also want to get one that reads RPM. Set the timing light for 35°, aim it at the mark and rev the engine with your other hand. I would make adjustments either while the engine was off or at idle, then retest.

 

[GregW]

Wine cork works good to plug the vacuum. I go to 18 degrees. Runs great.

Looks like you solved the vacuum <span style="font-style: italic">and</span> drinking problem in one swoop.

 

[tahoe healey]

I have no problem drinking.

 

[Keoke]

I have no problem drinking.

 

[GregW]

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[Keoke]

HEY !! What do they mean when replay comes on the screem??

 

[Keoke]

Hi Bobby, What equiment do you have at hand to set the timing.---Keoke

 

[GregW]

HEY !! What do they mean when replay comes on the screem??

You've already watched it?

 

[BOBBYR]

Hi Guys,
Thanks for the input. I used a snap-on timing light, but it's seen better times, if you know what I mean. Anyway, I'm sure it's time for a new one.So who has a good suggestion on what to get? I think you are right about timing this engine to 34 or35 degrees total advance. Also I've noticed the timing mark is a bit erratic at a set rpm. I'm wondering if I have too much slack in the timing chain. Oh well, thanks again for all your input and if anyone has a good suggestion on what to get for a timing light, please let me know.
Bobby R

 

[Keoke]

Hi Guys,
Thanks for the input. I used a snap-on timing light, but it's seen better times, if you know what I mean. Anyway, I'm sure it's time for a new one.So who has a good suggestion on what to get?
---------------Sears Top of the line dial back .

I think you are right about timing this engine to 34 or35 degrees total advance.

Also I've noticed the timing mark is a bit erratic at a set rpm. I'm wondering if I have too much slack in the timing chain.
Most likely Distributor wear. Get a Pertromix installed.

Oh well, thanks again for all your input and if anyone has a good suggestion on what to get for a timing light, please let me know. Sears, Sears, Sears.--- :laugh:
Bobby R

 

[GregW]

Also I've noticed the timing mark is a bit erratic at a set rpm. I'm wondering if I have too much slack in the timing chain.

Possibly a worn out dizzy too.

 

[vette]

Hi All, As posted on this forum many moons ago, I don't have the exact date. And I will give this credit to John Loftus for this info: ( my appologies John if I'm wrong)
"timing should be set at 15 degrees BTDC. at 600rpms.
15 degrees translates to 51/64 inches. (.796875 inches).
-Maximum advance is 34-38 degrees at 6400rpm.
-Dwell is 35+ - 3 degrees.
-remember there is a micro-adjust wheel on the side of the dizzy.
5 degrees - 17/64 inches
10 degrees - 17/32 inches
12 degrees - 21/32 inches "

My words, (15 dregrees = 51/64 inches = 3/4 inch....BTDC )
Also, this suits my BJ7, so should be good for others of same ink.

 

[BobHorvath]

Having blown up a couple of high performance boat engines, I believe in setting the total advance and letting the low speed fall where it may. I have used this method with the vac. advance attached. Is this wrong?

 

[Bob_Spidell]

Maybe, but you'd probably be setting the timing somewhat retarded (if your car seems to lack some power or overheats easily this could be part of the problem). On a "normal" (e.g. American) car, the vacuum is taken off the intake manifold, and is only effective at part throttle (4,500 RPM would be almost WOT). The vacuum on a Healey is port vacuum, caused by the airflow past the vacuum port, which is located about where the throttle plates are so, theoretically, vacuum hence timing increases with throttle opening.

At least, that's how I think it works; feel free to correct if I'm wrong (I know you will :wink:.

 

[BobHorvath]

I don't know if you are wrong, but here is my thinking: The vacuum advance does exactly that and I believe the vacuum is max @ a high RPM no load condition, therefore advance (centrifical plus vacuum) is max under those conditions. High temps are a product of detonation (too much advance not too little).

 

[RonMacPherson]

I would like to add an input. Use a vacuum gauge!

Yup, use a vacuum gauge to set your ignition timing.

Connect the vacuum gauge to manifold vacuum(where it's reading vacuum at idle-possible tee into the booster line if your car has one).

Set the timing to maximum vacuum, you'll probably be able to get up around 20-21 inches. Then retard the distributor 2-3 inches of vacuum.

Vacuum is a good diagnostic and adjustment tool. Old school, and these engines are definitely fitting that category.