16R running on two pots! Bent valves???

[bnicho]

Hi,

Ths weekend I decided to change the head gasket of the ailing 16R in my Corona Coupe. I could not go more than about 2km without it boiling, and I wanted to buy some time before fitting an 18RG.

Incidentally I noticed the pistons on my motor have a pronounced "lump" on top and the chambers seem to be a different shape to an 18R.









While the head was off the motor the engine was accidentally rotated about 1/8-1/4 of a revolution which meant I lost the cam timing postion.

When I bolted it together I turned the engine over by hand (no plugs in, not cam fitted) and lined the cam up "by eye" with the engine at TDC. I turned the motor over one or two revolutions and it became obvious I had the cam timing out by one tooth too far clockwise on the top chain. I corrected this and reassembled the motor.

Now the engine only runs on two pots! Pulling the plug leads from cylinders 1 and 2 makes no difference to the running of the engine. Pulling 3 or 4 causes it to stall. This indivates to me cyl 1 and 2 are doing nothing.

Both cylinders 1 and 2 show about 120psi compression, cold.
I've tried swapping plugs and leads around, which made no difference.

The head and block were flat and were thoroughly cleaned before reassembly. Photos above were taken before I put the head back on.

Am I right in thinking I have managed to bend a couple of valves?

I haven't pulled it apart yet, I want to make sure I haven't missed something stupid first!

Thanks,

[legend]

Re-check firing order or cam timing

[thechuckster]

what he said ^^ i managed to get the 18RTE running with the leads in the wrong order (1342?) - rotate crank in correct direction and then note down dizzi rotation - then recheck leads.

is unlikely that you've bent a valve as the piston shape seems to accommodate the valves.

cam timing
- remove rocker cover

- rotate crank to TDC and check dizzi is pointing to where #1 lead connects (points should have just shut if you have timing around 10degrees advance)

- check cam is showing the two lobes for #1 are both pointing downwards and outwards at the same angle - if not rotate crank 306 degrees and check again, if still not good, rotate the crank to TDC where the cam is closest to the above mentioned position and do the following...

- remove cam chain tensioner

- remove cam chain & pulley and shift position of pulley and pin to align cam to as noted above

- refit tensioner and re-check position of cam

- reassemble and do skids.


query about those high-comp pistons (they're definitely not standard 18/6R pistons) - any chance you have pulled the motor apart and have pics of those pistons? i know someone who might be interested in that info/pics or the pistons after you convert to 18RG.

[bnicho]

Hi,

Thanks for the suggestions.

The engine has definitely had the head off before as it had a broken rocker stud and a missing intake/exhaust manifold stud! Cam chain is also non-standard with no "bright links". But there were no intake or exhaust mods when I bought it, so I suspect it's had just a head job and no mods performed. Being a high compression early 16R JDM engine the pistons may be standard. Before the BHG it was showing 175psi on all four pots and supposedly has done 130,000km from new. BHG dropped pot 2 down to 150psi. All the bores looked great but I did not disturb the carbon lip around the top of the bores, so I don't know if there is a metal lip hiding under there. Oil pressure is still good too.

When I was looking at the pistons I was wondering if they would be suitable for use with an 18RG head to create a 16RG. Yes, I know I'd have to change all the timing stuff as well, I have an 18RG I can rob for that.

Firing Order:
I labelled each lead when I fitted them a couple of months ago (new leads). So I am 100% sure the firing order is correct as I did not disturb the dizzy end at all. It has had a Crane Cams electronic ignition fitted for over 12 months with no issues.

Cam Timing:
After I "bumped" the engine I retimed the cam exactly as you suggested. Pin into cam is at the top when the engine is at TDC and dizzy rotor is at cyl 1 position. So no chance of having the cam 180 degrees out.

When I go 18RG I will be storing this motor away in case I ever want to put the Coupe back to original. So I won't be selling bits off it. But I can probably pull out a piston for viewing.

[roadkill]

Hi,

There is a small chance that you may have bent a valve but i'm not familiar with 16r so i couldn't confidently say they are a free spinning engine.

What were the symptoms of it having a BHG?? Was it just boiling over? Was there oil in the water or water in the oil?? What did the head gasket look like when you took it off?? Was there any water in the pots??? If you have a cracked cyl head it can cause "boiling" in the coolant system as the air gets pushed into it and can drop compression too!!!

I'd firstly run the engine with the radiator cap off and see if it keeps "boiling" and if it does i'd say that the head is cactus. Also, recheck the head tensions.

If it is running on two cyls then it shouldn't be anything to do with timing from the cam at all.

18rg time!

bEn

[bnicho]

Hi,

Prior to head gasket replacement it was chucking out water and slowly getting worse. The overflow bottle would fill up and could not take the pressure through the bleed hole in the top. So the rad cap would let off the excess and spray the entire engine bay. It would dump about 3L of water in 20km. There were bubbles in the rad neck at idle, let alone when you revved it. No water in the oil but the water looked like thousand island dressing! Also it puffed occasional white smoke, particularly after idling for a few minutes.

When I took the head off I didn't see any sign of gasket damage, but I assumed it HAD to be the gasket. There was no signs of water in any particular pot, but I had not run it for several days.

This afternoon it was not bubbling at idle and the rad water looked okay. But I just drove it 1km to get the air con gas recovered in preparation for the 18RG swap. It was chucking out water again in that distance and puffing some white smoke. When I got home the rad neck was bubbling again at idle again and the coolant was getting muddy already. So I think your suggestion of a cracked head may be accurate.

Oh well, spent some time balancing the carbs on the 18RG today, it's still fitted to another Corona. The 18RG seems to run a lot better now, so it looks like I'm pulling it out and cleaning it up next weekend!

Cheers,