Help with 18R Engine

[sadboii]

Hi guys,

I recently bought an RA28 Celica and it has an 18RG engine in it. I was just wondering if anyone could help me identify which 18RG variant I have. I am having trouble with the engine misfiring at idle, and upon inspecting my spark plugs they are covered in carbon.
I have just done a full service on the engine to which I put brand new spark plugs, reset timing, brand new voltage regulator, new oil & filter and new points. Engine still missing at idle but is smooth as day under load. Rarely ever a hiccup or stumble cruising at about 3k rpms on the highway. So I'm thinking its either the carbs, or the spark plugs are wrong, or I set the timing wrong. This is why I want to identify the 18RG I have so I can make sure everything is bone stock and according to factory service manual, just so I can get everything running right first.
The block stamp is 11411-36040
Head 11111-88250
Intake 17111-8823
Twin Mikuni Solex Carbs

I am currently using BPR5EY-11 plugs. I had the mechanic do the timing for me, not sure if he set it to 12 degrees or something else.

I have done quite a bit of googling, but haven't found anything specific to my case.

Thanks

[checksix]

Hi,

My 18RG has the old heads 88210. My green book makes no mention of differences when timing or spark plugs for the head. My book shows BPR6EA OR BPR6EY as the specified plug. YOU ARE ALREADY RUNNING A HOTTER PLUG WITH A #5 HEAT RANGE.

I'm a bit confused with correctly timing this engine as well. I'll present what I think is the correct method, and I'm hoping an experienced member will confirm or supply the correct method.

1) My Green Book states to time at 12 degree hot.

A very simple statement, with no mention as to if the vacuum line is on or off and plugged as most engines of my experience.

2) Reading more closely I noted that it states to time at 20 degree if the coolant temp is less than 60C.

3) My engine has a thermal sensor with vacuum line fittings attached to the thermostat. They are closed all the time (hot or cold), so I figure this valve is defective. Somewhere long ago, I recall reading somewhere that the valve is supposed to allow vacuum when cold to allow a better idle. This makes sense with the book directive to time at 20 degree when cold. I only noticed this tonight when I was doing additional research.

4) Can someone confirm that there is vacuum applied when cold and not when hot, and the correct timing procedure is 12 degree hot (no vacuum).

I hope this clarification may help your situation.

[73GTV]

The advantages on this engine is that the timing for the specific production differed from the green book in that individual timing labels were issued with that specific car as well as the specific spark plugs ranges. Either hunt up the correct owners manual which may state the differences in timing. That is my suggestion based on a lot of reading. Early engines had timing marks from 5 degree to 20 degrees on the 2TG as an example.

[73GTV]

Here are a few examples of the timing and spark plugs used on original engines from the early 1970 and 1980. I forget which pages from which manuals I gathered this information from but still good info for the possible timing needed.