NB8A lacking torque after recon head & new rings

[greenMachine]

David, see illustration on 1-10-12 of the manual, 'Camshaft pulley installation note', while it is not super clear it shows the marks described by Dann at the 12 o'clock position - I on the inlet pulley, E on the exhaust, when the E/E and I/I marks at 4 o'clock and 8 o'clock are aligned.

In passing, it looks like the two pulleys are identical hence both the I and E on each, rather than some other less ambiguous notation.

[NitroDann]

I can confirm that they are identical to one another.

Dann

[DTH]

Thanks RS2000, that gives more detail about it. I'll look more closely. However, this still doesn't explain the loss of torque where the cyl head recon & new rings should have increased it

[DTH]

OK, thanks for the comments. So, if the pulleys have been installed correctly (& I still wonder about that) why the decrease in torque? The cylinder head has been reconditioned, new rings installed, the engine should be working much better. Why the decrease in torque?

[greenMachine]

... this still doesn't explain the loss of torque where the cyl head recon & new rings should have increased it

1. Have you checked the belt has been tensioned by rotating the crank clockwise (looking at it) and the crank is at TDC on the timing mark?

2. At the same time, the 'I' on the inlet pulley and the 'E' on the exhaust pulley are at 12 o'clock, with the E/E and I/I aligned?

3. And there is no slack in the belt between the inlet pulley, the exhaust pulley and the crank pulley?

If the answer to all the above is 'yes', the cams are timed correctly with respect to the timing mark on the crank pulley.

So far as timing is concerned, the only remaining thing we have not been able to do is to determine whether the TDC mark on the crank pulley is at TDC on No1 because the plug in there is stubborn (without a dial gauge, valve movement will only be an approximation). The next best way (that I know) is to pull the other plugs and find the other piston that will be at TDC on the exhaust stroke when No1 is at TDC on the ignition (compression) stroke. This will determine that the crank pulley timing mark is showing TDC on No1 (or not - unlikely, but possible). If not, either the key is missing/damaged, or the rubber between the two parts of the crank pulley has deteriorated allowing the two parts to move out of alignment.

If TDC on the pulley is TDC on the piston, my diagnostic skills have been exhausted. I will have to yield to others who have better skills than me.

[RS2000]

OK, thanks for the comments. So, if the pulleys have been installed correctly (& I still wonder about that) why the decrease in torque?

The pulleys are installed correctly (as others have said, they are identical), but I'm not saying the pulleys are timed correctly! They look close, but you can't tell if they're spot on or out a tooth by looking at your photos.

Take off the middle plastic cover & check that the E & I at 4 & 8 o'clock are aligned with the marks on the backing plate.
Good points by gM.

mx5 075 (Medium).jpg

[hks_kansei]

Crazy thought.

If the head has just been rebuilt, surely you shouldn't have a stuck spark plug?

They will have needed to remove them to reco the head, and surely would have checked the threads were ok and not stripped/crossed.

[DTH]

Another update: The cam gears lined up with the timing marks so it is all back together again and road tested this afternoon. It's better than it was tho part of that would be that i serviced the air filter (a Dann mod) a couple of days ago. However, according to a hill test & the bum dyno it's no better than before the head recon, new rings etc. Hmmm.... Disappointing.
Re the stuck spark plug: Apparently the plugs were replaced with the head recond. I tried to remove the #1 plug to check TDC but it is very tight & didn't want to risk breaking it.
Anyhow guys, my thanks for all your help, wisdom & time. I really appreciate it all.
Cheers, david