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

[andrewzuku]

Hello,

My car has never run right. I suspect it was just slapped together with whatever jets were laying around when I bought it.

After my engine rebuild I thought I'd see how the jetting recommended for "2ltr 18rg on twin 45s" went:
http://www.toymods.org.au/forums/tec...jets-18rg.html

With those settings (specifically, 45F11 idle jets) I get such a bad flat spot at 2000rpm that the engine stalls. I put 55F17 idle jets back to make it semi-drivable.

Is there anything I'm obviously doing wrong?

Here's what I've got at the moment:

Head	11111-88253 (18R-GU)
Camshafts	"NPR" 1351-88250 (apparently reground. I've measured 10mm lift, unknown duration)
Cam Timing	Slots straight up at TDC
Pistons	Standard "ART" 88251 (8.7:1)
Exhaust	Pacemaker 4-2-1 (2" system. 2 mufflers.)
Ignition	Crane Cams – Fireball XR700
Initial Advance	15° BTDC @ 1000 RPM
Mechanical Advance	23° Crank (11.5° at the Distributor)
Total Advance	38°
Vacuum Advance	Removed
Coil	Bosch GT40
Leads	NGK RC-TE94
Plugs	NGK BPR5ES
Fuel Pump	Jidosha Kiki - Solid State Electric Pump
Fuel Pressure	Regulated at 3psi using a Holley #12-804
Carburetors	Twin Weber 45 DCOE (13)
Chokes	36mm
Auxilary Venturis	4.5mm
Air Correctors	170
Main Jets	140
Emulsion Tubes	F16
Idle Mixture Screws	2 turns out
Idle Jets	55F17 (45F11 gives me an undrivable flat spot at 2000rpm)
Pump Jets	40
Needle Valves	200
Float Open	8.5mm
Float Closed	15mm

Any suggestions are welcome. I've just ordered a wideband O² sensor/controller/gauge. Hopefully that will tell me a clearer picture when it arrives.

[Javal]

Well the wideband will certainly help to clarify whether your issue is fuel related. I am kinda scratching my head over the deletion of the vacuum advance though.

That said if you're having improvements with changing the idle jets, i'd definitely be keen to see what the wideband says. I don't know shit about jetting webbers but you'd want to get some actual AFR's before jumping to change out those jets again, it could well be that the jetting is masking another issue or another issue is fucking with your jet selection.

[iTz InSaNiTy]

I'm only a n00b, but I'm sure when we set our webers up that our float closed was 11mm, whereas yours is 15mm. Give that a spin. I'm sure most weber set-up guides say to use 8mm and 11mm. Cheers.

[Willofan]

Hey Andrewzuku,

Can you give more information on what you mean by 'My car has never run right'?

My first thoughts are based on a standard engine configuration you have described, the chokes are too big, the mains are too lean for the chokes and the air correctors are too small for the mains. But depending on what the engine is doing - hesitation, surging, running lean low, running lean high etc will depend on what you need to change.

Base set up for a roady 18RG with std cams and 8.7 CR is 34 chokes, 140 mains and 190 air correctors, F16 emulsions, 45F9 idle jets and 40 pump jets. Idle jets might not be right either, but without checking my charts they could be OK.

Other things to consider are; throttle shaft balanced, mixture screws worn (stepped tips), worn dizzy/cap/rotor and manifold air leaks.

[andrewzuku]

Thanks everyone for taking the time to look into this for me.

Javal:
I've removed the vacuum advance because webers don't generate the correct vacuum signal (ported vs manifold... I forget which).

iTz InSaNiTy:
I'll try that and report back here tomorrow.

Willowfan:
I should have mentioned, by "never run right" I meant that it always lacked power to the point where it's embarressing in traffic - overtaken by trucks etc. It doesn't seem to mind higher revs, but it takes a while to get up there. The flat spot has always been there too. more of a stumble with the 34mm chokes, and definately a lot worse when the engine is cold.

I actually changed FROM exactly the setup you just suggested, except I had the 55F17 idle jets. I'll change it back this weekend and do a compression-test to double-check.

• I have a synchrometer and the carbs are balanced.
• I'm not sure how to check if the throttle shaft itself is bent though.
• The mixture screws are new from a rebuild kit.
• The dizzy/cap/rotor is new too.
• I couldn't find any manifold leaks when spraying a little "Start-ya-bastard" around the place.

I'll be able to paint a more complete picture when my AFR gauge arrives.

[lilcrash]

Thanks everyone for taking the time to look into this for me.

Javal:
I've removed the vacuum advance because webers don't generate the correct vacuum signal (ported vs manifold... I forget which).
.

they have webers stock, how can that be true?

[Javal]

they have webers stock, how can that be true?

They're Solex's standard? I know they share the same bolt spacing at least.
(I can't remember whether I read something about the Solex 40's being made under license? That might have been the Mikuni-Solex's?)

At any rate, if the solex's have a vacuum port to suit 'ported vacuum advance' and the webers do not, the you won't be able to use vac advance with the webers. You could just use a dual diaphragm type from a later car though so you can use both ported and manifold vac advance.

[andrewzuku]

I put the 45's back together with willowfan's recommendations for 34mm chokes (except with my 55F17 idle jets) and it seems a little better than the last time I had that exact setup... maybe. It could be a placebo.

I've also just removed my charcoal cannister that I'd plumbed into a t-piece off the balance tube (between the carbs on the mannifold). So now the little ports where there would be a balance tube are blocked with rubber caps. Could that have been causing a weird vacuum leak into the charcoal cannister? Is it a good idea to remove the balance tube completely?

I still haven't tried playing with the float levels yet.

P.S. I did a little run without the air box, and wow does it make all the right noises! I can't wait 'til it's running right.

[andrewzuku]

Here's a little video demonstrating the flat spot, and generally just showing how it drives.



And hey, who doesn't like listening to 18R-G's?


P.S. I did a compression test, and this is what I measured:

Cylinder:	1	2	3	4
Dry (psi):	135	130	130	133
Wet (psi):	170	168	168	173

The green bible says STD pressure is 184.6psi. Limit is 142psi, and the difference between can be no more than 14.2psi. So I'm happy with my results for old 8.7CR pistons, and new rings.

Out of curiosity, Are the figures in the green bible for the 9.7CR pistons?


[EDIT]
I looked into it, and the float levels I'm running are correct.



I think the level iTz InSaNiTy quoted is for the newer Nitrophyl (Spansil) floats in the 45DCOE 152. 12mm and 26mm.

See the full PDF here:
Weber-DCOE-Carburetor-Service-Manual.pdf
[/EDIT]

[Steve M]

Specs for the 8.7:1 engine:
Ignition timing: 12 degrees btdc (vacuum advance disconnected)
Vacuum advance should be connected on the engine side of the butterfly valve (Standard Mikuni/Solex carbs have a vacuum point at base of carb near firewall) Connecting this makes your engine idle better and makes it easier to adjust idle fuel mixtures.
Compression: 170psi STD, 142psi Limit, difference limit 14psi

It sounds to me like your "idle jet" (referred to as "slow jet" for Mikuni carbs) is cutting out before your main jets kick in.

Idle jet could be too small or running to lean.
Mechanical advance in dizzy could be kicking in too late.

Do you know the specs of your cam regrind? Without those specs, your cam timing could be a long way out of place, which could cause the problem.
Different camshaft grinds require different timing. I've got a set of regrinds here where the grinder has ground the inlet cam 10 degrees too advanced for their own spec sheet.
I measured up the timing events and lift of a whole bunch of camshafts and have found the information very useful.

[andrewzuku]

Cam Profile
I'll see if I can borrow a dial-gauge and measure my cam profile.

Ignition timing
I'll play with this, and see if advancing further than 38degrees total helps.

Air Fuel Ratio gauge kit
I finally got my Innovate Wideband AFR kit and wired it all up. Put some new plugs in, rechecked the carbs were synch'd, and did a few test-drives.

Now the flat spot is almost completely gone (maybe the new plugs and re-sync helped?). Overall, it looks like I'm running too rich.

Observed AFR:
12 @ idle (1000 RPM)
20 @ 2000ish when the flat spot was there. It seems to have gone away now though.
12~13 @ 3000 RPM cruising
10~11 under hard acceleration above 3000 RPM

Check plugs vs Colortune
I checked the plugs. 1 and 4 were too rich (black), while 2 and 3 were a little lean (tan to white).
What's the best way to ensure all cylinders are the same mixture? Make adjustments and check plugs, or what about using a colortune?

Thermos = Bigger Alternator?
I forgot to mention that I'm running two 10" thermo's. When they switch on, the idle drops from 1000 RPM down to about 700 RPM. Does this mean I need a bigger alternator?

[Steve M]

You don't need a bigger alternator, you need to install an idle-up system to deal with that problem.
The bigger alternator allows you to attach more electronic stuff and still charge to battery.

Idle-up system is basically a switch that receives a signal and allows more air to flow into the engine by opening the throttle more.
My suzuki sierra does this when the blower-fan or lights go on. It's been really useful for bumping the idle speed up as it idles on about two cylinders (500rpm) when it's warm.

I don't have any suggestions for how to connect one of these systems to your R-G carbies.

[blanky]

Just a quick question

Does the plate that holds the oil pump/dizzy shaft go on with the raised ridge facing out or I. Towards the seal?

[Steve M]

My memory is a little foggy, but I reckon it has the ridge facing out. If you put in backwards it will either bend the plate or it will have a whole lot of thrust movement on the shaft.
The green book picture looks like it has it facing out as well.

[Pagie84a]

Hey guys thinkin of puttin a 1uz in my 28 so unfortunately I have to abandon my freshly rebuilt rg to do it can sum1 give me a ballpark on what its worth. It a stock eu with solex 40s and has efi manifold etc to go with + the elec dizzy conversion