• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

MGB MGB timing marks

Share this page

wkilleffer

wkilleffer

Jedi Knight
Country flag
Offline
Sorry if this question has been done to death, but I ran a search and nothing came up.

On an 18GK engine, the timing marks are a four or five (can't remember) pronged piece of metal up on the front of the engine on the side with the dizzy.

Is the bottom-most prong TDC, or is it the top-most prong?

Manual says I'm supposed to have the timing at 16deg BTDC at 1500 rpm, so where is that supposed to be on the marks? I just want to make sure I don't over-advance or over-retard the timing.

Thank you,
-Bill
 
The prong closest to the driver's side is TDC, each mark to the left represents 10 degrees in advance timing, I would suggest you use a dial timing light and time from TDC.
 
Ok, yes, I do have a Bentley manual. I just sometimes have trouble translating a drawn diagram in a book to the reality of what's under the hood of my car. At risk of going off subject and not to bash any of the manuals out there, but I've been a bit disappointed with all of them because they tend to oversimplify things. They make a carb adjustment and balance sound like a walk in the park with lots of identifiable landmarks, but reality is much more complicated. I read the manuals, and turn to the forum to get the real story.

I've heard of a dial timing light, but have never seen nor used one. They sound expensive. Now's not the time for me to be thinking expensive solutions. How do they work?

Thank you,
-Bill
 
Sears used to sell em. Basic timing light with the knob(dial) on the back. You check your timing at idle, as you advance the speed the timing mark should advance, you dial in the light to keep the mark and light aligned. Then you can read how many degrees you had to turn the dial. They weren't that expensive. But that's relative. I've had 19.95 timing lights all the way up to 300 dollar timing lights. Best one I ever had was about 150, but it got caught in a flood. You can get the advanced lights that use digital advance also. Analog dial is usually less expensive.
 
Sears has an analog one on their website for $69.99. I've got my eye on a couple of them on ebaby right now. I've been trying to pay the Sears card off, but oh well. It's always something...
 
Not to beat a dead horse or anything, but I may have it where it needs to be.

If TDC is closest to the driver's side, then the tooth on the timing marker that's closest to the ground should be 20deg BTDC. So, in order to get 16deg BTDC @ 1500rpm, the mark on the crankshaft should fall in between the 15 and 20 deg marks, closer to the 15. I accidently got it closer to the 20deg mark, and the car knocked under load even if I shifted the gears between 3000 and 3500 RPM. So, I got it home and used the timing light to move it just higher than 15deg.

There were two problems that interfered with this. The worst was that my previous efforts to set the timing had me aiming for the wrong mark, which had my engine running in a retarded state. Also, the ring clip that holds the distributor down and in place was not gripping it well, which meant the timing was never consistent. But those should be taken care of now.

I may start using 93 octane gas, and I'd already been using 89. Here's hoping this will be one step toward greater power and economy.

Thank you,
-Bill
 
Back
Top