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Another way to find TDC on AQ131A?

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film842

Contributing Member
I've reassembled my engine and now need to set up the initial timing i.e. cam belt, crankshaft pulley etc and in order to do so correctly I need to find TDC on number one cylinder.

Research says to put my finger over the sparkplug hole and turn the engine until I feel the pressure. Sounds good, but no matter how I contort, I can't get a finger over that hole. I can stick a drinking straw in there and feel the piston rise, but that doesn't tell me if I'm on the compression stroke.

Is there some other method to visually determine TDC? Any help appreciated. Thanks.
 
Use the factory TDC notch alignment on the crankshaft cogged belt pulley against the notch on the engine.
When aligned as per the OEM service manual, that will get you TDC, but not necessarily TDC on the Comp Stroke.
To find TDC C/S, the camshaft cogged pulley must also be aligned against it's corresponding notch.
Not only those two must be aligned, but all three must be aligned prior to belt tension being applied.

It's all there in the OEM service manual. (not Seloc... not Clymers.... use the OEM!)



.
 
Last edited:
RicardoMarine said:
Use the factory TDC notch alignment on the crankshaft cogged belt pulley against the notch on the engine.
When aligned as per the OEM service manual, that will get you TDC, but not necessarily TDC on the Comp Stroke.
To find TDC C/S, the camshaft cogged pulley must also be aligned against it's corresponding notch.
Not only those two must be aligned, but all three must be aligned prior to belt tension being applied.

It's all there in the OEM service manual. (not Seloc... not Clymers.... use the OEM!)

.
Click to expand...

There is no corresponding notch on my engine for the camshaft pulley. The pulley itself is marked with a white dot, so I assume that I will have to eyeball an approximate position for it? Can't think of any other way.
 
kimcrwbr1 said:
It is tricky to get it right as there is spring pressure on the cam. Once you tighten the belt rotate the crank a bunch of times and then confirm the cam and crank still line up.
Click to expand...

Hey, thanks for the advice, I appreciate it. I will try your method although I thought I read somewhere that either they will never line up again or you have to turn the engine a huge number of turns to check to see if they come back together.

I think I'll post some pics of my final lineup and post them here before I stick the other bits back on the engine. I could use the moral support...
 
film842 said:
I've reassembled my engine and now need to set up the initial timing i.e. cam belt, crankshaft pulley etc and in order to do so correctly I need to find TDC on number one cylinder.

Research says to put my finger over the sparkplug hole and turn the engine until I feel the pressure. Sounds good, but no matter how I contort, I can't get a finger over that hole. I can stick a drinking straw in there and feel the piston rise, but that doesn't tell me if I'm on the compression stroke.

Is there some other method to visually determine TDC? Any help appreciated. Thanks.
Click to expand...

You answered your own question, drinking straw will do it for the crankshaft.
Then rotate the cam till notch is center of valve cover.
 
All must be indexed correctly before full tension is released on the belt.
If the counter shaft is not indexed correctly, the limited slot in the distributor housing will not allow for much compensation.... if any at all!
Unlike many other engines where the distributor housing can be rotated more.
 

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Thank you for making this so simple. I swapped out my tired aq140a for a rebuilt 151. The person that did the work borrowed a crank shaft timing belt pulley. After installing the engine the belt timing was off. The timing marks all set and correct but noticed number one at bdc? How could the timing mark be 180 degrees off? !! I found your post, you saved the day and my sanity!! 10degrees before TDC Why don’t they just put this in the manuals?
 
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