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

[bmxer54]

i also found ngk RC-TX99A, apparently off "Toyota Cressida RX60 2.0L I6 Cyl, DOHC, Carb, 8V, 0 21R 1981 - 1985" sounds like an rg to me. hope that helps

Cheers, Peter.

[bmxer54]

Whoops sorry bout the double post missed the "Toyota Cressida RX60 2.0L I6 Cyl, DOHC, Carb, 8V, 0 21R 1981 - 1985" looks like RC-TE94 is the one to use.

Cheers, Peter.

[andrewzuku]

Rebuilding my 18R-GU, I have a question about valve timing. But first, here's some background...

The car will be used now and then as a daily (I work from home) and the occassional country-drive.

It's got:

• standard pistons ("ART" 88251, 8.7:1)
• I'm told "freshly reground" cams (standard "NPR" 1351-88250)
• Weber 45DCOE's with 34mm chokes
• Pacemaker 4-2-1 extractors
• Electronic Ignition (Crane Cams – Fireball XR700)
• It looks like the rods have been balanced

Valve timing is retarded on both the intake and exhaust cams.

Can anyone tell me why this might have been done? Should I change it back to the standard cam timing?

[Omegaman]

then cams normally are in the standard, straight up position.
Or the exhaust cam slightly advanced one notch for more torque (or retarded) one or the other.
There is explanations for this somewhere. Sorry i dont have them handy. Others will know.

[andrewzuku]

After a little bit of Googling, I found this simplified set of rules:

To increase overlap, you have to RETARD the EXHAUST, and/or ADVANCE the INTAKE.
To reduce overlap, you have to ADVANCE the EXHAUST, and/or RETARD the INTAKE.

Simple cam tuning rules for NATURALLY ASPIRATED engines:
Advancing both cams => more low-RPM power, less high-RPM power
Retarding both cams => more high-RPM power, less low-RPM power
Less overlap => more low-RPM power, less high-RPM power
More overlap => more high-RPM power, less low-RPM power

Source


I think I'll put it in the standard position then.

I feel silly for not Googling first. I just wanted to double-check if there was some well-known 18R-G quirk/trick. Also, I'm excited to be this close to actually driving the damn thing

[o_man_ra23]

If they are reground, then they may have been offset by the grinder, however this is quite unlikely as the usual reason for regrinding is to reduce the size of the base circle thus providing more lift. To minimise the amount of grinding, the timing of the cams would not change. If the purpose of the regrind was to change the ramp up and ramp down profiles separately, then the lobes may end up offset, however this is a very unusual grind, and would generally only be looked at for pure race engines, in which case they would be ground from new blanks anyway.

In all, I would start at the standard position, and if interested, play from there with back to back comparisons and minor changes.

[andrewzuku]

Thanks Omegaman and o_man_ra23.

So to be sure, are my labels correct in the image below?



Also, measuring with a vernier, the cam circle on both cams is 32mm and the lobe is 42mm. So lift is 10mm. Are those numbers standard?
Andrew

[lilcrash]

Edit. Sorry. Just realized I read it wrong.

[o_man_ra23]

Incorrect on the cam hole assessment. The holes are there to adjust for manufacturing tolerances, so to coin the old phrase, any hole's a goal! There are notches on both cams. These should both be vertical at no. 1 TDC.

[lilcrash]

As I edited out. Both those cams appear 12atdc. Just for informations sake.

Also if you did set the cams at that angle you will bend 6 of your 8 valves.

[Omegaman]

guys.
My 18rgeu, has a new issue. It starts idles nicely, but when i open the throttle it dies out. there is fuel at 45psi on the regulator.
could it be a timing issue, its at 12deg tdc or there abouts. pleanty of air to be had from the Afm and pod.
I'm thinking TPS adjustment or timing, that is my dizzy is not set right.
i'll upload a vid tomoz to show what i mean. But any advise would be great.

edit. i was reading another thread. My exhaust cat converter is cactus. all particals inside are broken.
As this would be a flow restriction, would that cause an instant shut down, on acceleration?
i wouldn't think so. it still flows through, just wouldn't be effective.

[lilcrash]

Just remove your cat, you don't need one afaik. A collapsed cat can cause issues similar to you described but I don't think it explains your problem. I would be thinking lack of fuel so faulty tps or injectors not getting signal, are they all firing? Could be idleing on the cold start injector.

[Willofan]

Building up two 18rg's for racing at the moment and putting the heads together with the cams as per the spec sheets

my 180hp build: cams are 292 in a 253 head std valves and 10.5:1 forgies, 48mm side draught webers, dry sumped (using a 152e 3 stage pump), knife edge crank, lightened flywheel and 7.25 twin plate clutch. Should be very reliable



the other 210hp+ is somewhat of a hand granade: 310 cams, larger valves in a 253 head, 38mm ports match to 50mm quad throttles. 12.1:1 92mm TRD slugs and Argo rods hanging onto a knife edged peened and chrio'd crank, lighented and pinned flywheel (clutch?) and managed by Motec. Not legal for historics, but will be fun in some sprints

[Willofan]

Double post, sorry

[Omegaman]

Just remove your cat, you don't need one afaik. A collapsed cat can cause issues similar to you described but I don't think it explains your problem. I would be thinking lack of fuel so faulty tps or injectors not getting signal, are they all firing? Could be idleing on the cold start injector.

i cant remove the cat, as i need a blue slip. I can remove the insides to free it up. tps seems to be ok, it shows the volts in open and closed throttle as 0-5.
injectors are the 210cc which are old, so i'll change them to 240cc again tomorrow and give it a go.