Need to get my Corona back on the road again

[71coronadlx]

Just recently I had a valve job done on my Corona. It has an 18r engine...Ive finished putting the head back on replaced the carb with a rebuilt one and just last week got it to turn over. It doesn't want to stay running and sounds as if it is backfiring from the carburetor? I know it has a leak in the exhaust manifold I have to have a couple of holes rehtreaded and bolts replaced to fix the leak. So my friend tells me that if I dont fix this my valves will burn up again. I do know that the 18r engine was known to burn valves since they didnt have hardened seats and used to use leaded fuel. So the problem is keeping my car running. If I time it and properly adjust the carburetor will it run better? If anyone could help me to figure this out it would be greatly appreciated. I figured that my friend was just burnt out on trying to get it to run and didnt want to mess with this anymore? Am I wrong? Well any input of any kind would be greatly apppreciated. I am very anxious to get her back on the road and running properly again.

[robakun]

It sounds like your cam timimg is off.

[Carlyn Dinkler]

As Robert suggested, since the head was worked on, the timing chain may have been installed a few teeth off. However, it could be another problem(s). If you do not have a good 8/18RC manual, you might want to get one. I suggest the 00402-10500 manual as the best. I can supply a good used one for $20 including postage, or look for one on ebay. I can include my parts listings for the RT8#/9# and for the 8/18RC engines with the engine manual if you want them.

Try a few simple checks first. Check your compression: remove all spark plugs, open the carburetor, & a hot engine is best. The readings should be 128 to 164 psi, and all readings within 14 psi. Check the wires to the spark plugs which should be in order 1-3-4-2. Remove the valve cover, put cylinder no.1 on top dead center, and check that the piston is on top dead center (I think you can see using a light thru the spark plug hole), check the line-up of the slot on the pulley & the pointer, and see if the cam shaft looks in the correct position for cylinder no.1. Check the valve clearance on each cylinder, cold the intake valves should be 0.007" and the exhaust 0.013".

Some of the 18RC heads had inserts, but there was a big change-out of heads by Toyota about 1975 to a head with stelite valves, no hardened seat inserts, and better water flow around cylinder no.3 which was bad to burn valves. The head was to use only leaded gas. Using unleaded gas, adjust your valves each time you change the oil & filter, and when the valves eat in the head far enough to run out of adjustment, have seats installed.

I have two rebuilt 18RC long blocks + manifolds and other parts not normally supplied on a long block, at $1475 in stock that I build for my own use but have never needed them. Carlyn Dinkler [e-mail]

[71coronadlx]

Thanks for all the help. I have a Toyota 16r/18r manual. The valves were adjusted and the firing order is correct. I did notice that my carb was not adjusted right and I went back and adjusted it the way the book said. I started and it started right up, but I still have those leaks to fix and it needs to be timed. Other than that it didnt sound bad. My friend kept messing with the carb adjustment and I think that was one of the problems. I appreciate the help. Thanks.

[71coronadlx]

Well I took my corona in to get the leaks fixed that I had mentioned earlier...well the mechanic calls says its ready and its been timed the leaks are fixed etc. So I go to pick it up and they tell me they got it running but the timing chain is rattling. When I had started it the week before it sounded fine other than the leak from the manifold. So I go to drive it from the shop it runs really rough when I put it in reverse and when I go into drive. I would really like to figure this out. If anyone can help me on this it would be great. Why is it that when I started it before I could hear no rattling and now when I get it back it sounds like a diesel? Then I drive it down the road and it shifts back and forth between gears (it was very low on tranny fluid) But the shop told me they drove it around for a half an hour, but yet they failed to mention this? This is very irritating..all I want is to fix this problem how difficult of a job is this? Why all of a sudden this rattling? If anyone knows what the problem is or what it could be maybe you can give me some advice? I would appreciate all the help out there. Thanks.

[Carlyn Dinkler]

As the timing chains & tensioners wear, there is some rattle when the engines starts but as the oil pressure comes up, the rattle goes away. At the end of their life, the chains will break and come thru the side of the aluminum timing gear cover. This might be the time to check the oil pressure the see if the engine may have serious internal problems.

The other source of the rattle might be spark knock if the timing is too far advanced. You need to determine whether the noise is from the timing chains or is spark knock.

If the transmission fluid was very low, start looking for leaks.

To determine the source of the rough running engine, you still need to do the basic tests of compression & vacuum & checks to see if the timing chain was put back correctly. Perhaps the problem is more difficult than you think. I suggest that you find an older Toyota mechanic that remembers these engines and actually worked on them. Carlyn Dinkler

[79corona]

If your timing chain is off even one tooth, sometimes it won't even start. But let's say it's running, rough, it could be the distributor gear is off. If your timing chain is rattling then maybe the tensioner is not working. I'm assuming that there is an oil pressurized tensioner, right? When you first started it, didn't you run it without the coil wire attached to get the oil circulating first? I agree with robokun that severe backfiring through the carb is a sign of the cam being off. What's the mileage on this engine? If you have a lot of mileage, it would have been wise to replace the timing chain, guides and tensioner also. Did you change your spark plug wires on the distributor cap?

[justin]

On one of my old datsuns the problem wasn't that the chain was installed incorrectly, the problem was that the chain STRETCHED from years of use. This resulted in a vehicle that COULD NOT EVER be timed correctly, but could be timed well enough to run (shittily).

So yea, I bet your timing chain stretched.