For the love of a tractor engine: The life and times of the 18R-G

[o_man_ra23]

As Steve said... zero clearance will give you an inaccurate shim reading.

Also, re-check the intake 4... 3mm is a MASSIVE clearance (and frankly I have never seen anything close to it before). It would be really noticeable by eye.

[Omegaman]

I've taken all the shims out now. I'm rechecking them and may even take out the valves to check the length and grind these if required. my shims seem to be 2.0mm -2.3mm max.
So it leads me to believe that the valve length may have a problem. As I said two were replaced but the head never used since then.

I am wandering why the cam gears are not the same. As in the pic above, it shows the intake not to be inline as the exhaust gear

[o_man_ra23]

The cams need to be in (whole thing re-assembled) to re-check it. You had 2 replaced, and 3 fairly wild measurements (1mm is wild)... Something seems fishy.

[bnicho]

Okay, I'm starting to get pissed off with my 18RGU now. It's been in it's stylish JDM home for months now and is still not running properly. I thought it would be greatful to be mounted in such a sexy car, but oh no!

On Saturday I fitted a pair of recently reco'd Mikunis with K&N filters, new NGK leads, new Bosch dizzy cap and rotor. Plugs are NGK BP6ES and are only a few months old. Ignitor is the BIM 024 that came with the donor car. Dizzy is stock 18RGU electronic. Coil is still the original 1975 edition that came with the RT112. Fuel pump is a three month old Fedpro (Facet copy) 4.5psi mounted below the parcel shelf in the boot. Fuel Filter is mounted in the bay, is only 1000km old and does not look dirty.

It starts easily and idles beautifully once warm. But when i try and drive it, it just backfires and hesitates at anything over about 1500rpm.

When I last drove it with the old carbs and leads it backfired occasionaly but it was driveable. Now I struggle to get around the block.

Advancing or retarding the timing makes no difference.

I definitely have not messed up the firing order.

The carbs were used on another engine before I bought them, so I don't think they are the problem. I reckon it's ignition related.

My thoughts:
- Coil: Maybe the electronic ignition does not like the old Nippon Coil. Would this cause these symptoms? I previoulsy used the same coil with a Crane Cams ignition on the old 16R engine without issues. I have a non-ballasted Electronic Ignition type coil from the donor car. If I use this, how do I wire it up without the ballast resistor?

- Ignitor: Could I have fried it somehow, perhaps by using the wrong coil above? Should I just grab a coil and ignitor from an RT142 or similar?

- Plugs: Are BP6ES the right plugs? Is it possible I have a duff plug?

- Fuel: It's got 3/4 of a tank of Ultimate, about 8-10 weeks old. I expect it's gone a bit off, but I don't think it would cause it to run that badly alone.

Grateful for any advice received.

Thanks,

[Omegaman]

[QUOTE=
- Plugs: Are BP6ES the right plugs? Is it possible I have a duff plug?

-
Thanks,[/QUOTE]

Even though I can't get mine going, I did change the plugs to BPR'sand it started. sounded shit, but kicked over. Whether the heat range plays a part at those rev's unsure.
But i'm EFI so carbs out of my league.

[o_man_ra23]

R is for Resistive. You must use Resistive plugs. BPR6ES or BPR5ES are fairly normal. (or it might be EY... can't remember fully off the top of my head)

[bnicho]

Damn, I checked and I have BP6ES. I bought the wrong plugs. (Slaps forehead) I'll get the correct plugs tomorrow.

Cheers,

[o_man_ra23]

Just check the NGK catalogue. You can vary the heat range if needed (the number) depending on how your engine is burning, but you need to get the rest right. Also, set your plug gaps right, if you have points, .8mm is your friend, if you have decent electronic ignition, then 1.1mm will give you a better burn.

[bnicho]

Thanks for the advice (again).

Thee NGK website recommends BPR5EY-11 for 78-81 Celica import with 18RG. (I know the "11" refers to the 1.1mm gap.) I'll grab a set and try them.

The engine is running the factory electronic ignition and is stock (AFAIK) except for filters, extractors and exhaust. So I don' think I need to vary the heat range. Which way do the NGK plugs run anyway. Does a higher number (eg: BPR6EY) indicate a hotter plug or a colder one?

[o_man_ra23]

Can't remember, they run opposite to Bosch though. The factory standard was indeed 1.1mm gap. Changing plug heat ranges can have a lot to do with tune, wear and atmospheric conditions. Even my DR-Z400E handbook (brand new bike) suggests checking the plugs and changing heat ranges if necessary, and that is without ANY mods to the engine etc. I will dig that section out and type it onto here, as it mentions which way the heat ranges go too and how to determine if you need a hotter or colder plug.

[The Witzl]

if you are running the 9.7:1 pistons... i would use the BPR6EY, but if you are on the lower comp 8.7:1 or 8.3:1 pistons, then the BPR5EY might be a good option.

Personally, i would test out using a STOCK ignitor from a 21R-C or 22R-E instead of the Bosch BIM024. The bosch unit is designed for the ford/GM reluctors, which dont have quite as high an output as the toyota VR sensors.

I had much similar problems to you here when using a GM Delco ignitor ony my 18RGE with megasquirt. The Delco ignitor did the VR signal conditioning... and when the revs went up above 2000-3000rpm, i would get misses and backfires.. BADLY.
When i ditched the Delco ignitor and did the VR signal conditioning inside the megasquirt, the problem went away.

Ditch the Bosch ignitor i rekon. A 21R-C or 22R-E ignitor is easy to find at your local wreckers, and is perfectly pocket sized

[o_man_ra23]

Or... PM me your address, I am sure I have a surplus one in the shed...

[airfireman1]

One thing to check is make sure the wiring to the dizzy is not near the coil lead, even though it is shielded it can pick up the spark from the coil and cause the ignitor to work out of sequence, I had this problem with mine. It would start idle and run well but continually had a misfire. I moved the coil lead away from the wires that go from the ignitor to the dizzy and the problem was solved.

[o_man_ra23]

Shielded?? I have never seen an electro-magnetically shielded one... only ever with a heat resistant sleeve. And the electromagnetic radiation from a coil lead is massive... it can give you all sorts of grief if you have the dizzy wiring near it.

[The Witzl]

he meant that the VR sensor wires are shielded.