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

[andrewzuku]

Hmmm... the main thing I see we have in common is the head has been off recently.

Is it possible we're both 1 tooth out?

[ian]

its hard to say , the only other thing that i can think about is i had the carbs off to clean them , maybe having them upside down has upset something ,jets are clear float levels are ok ,and no leaks that i know off

[S. Lowlux]

Hmmm... the main thing I see we have in common is the head has been off recently.

Is it also possible that you have bent a valve while the head was off. Just sitting the head down on the open valve will bend it. You must be carefull & sit it up on blocks.
The other Owen.

[andrewzuku]

Bent Valve?
Would a bent valve show up in the compression test? I'm getting about 130 dry and 170 wet across all cylinders.

We were always very careful with the head, and like you said, only ever sat it on blocks (with the valves clear).

Playing with Cam Timing
This afternoon I pulled the cam cover off to see if there were any markings on the cams. I wanted to see if maybe the intake and exhaust cam were mixed up (if they were even different).

I noticed some tiny marks that aren't in the green bible. They must have been made by whoever ground the cams.



With the crank at TDC, usually I align the center of the slits straight up (with the little cast arrows).

This time I set it like you see in the photos - aligning the edges of the slits with each of the tiny marks. It ran a lot smoother and quieter at idle, but under load at about 2000RPM it leaned right out to about 20 on my wideband sensor and just doesn't go any further. I feels like I've taken the main jets completely out!

Since they're regrinds, I'm sure these marks are a clue to how the cams should be set. I just don't know exactly what to line them up to. It's too late tonight to try more combinations (there's 4 positions on each cam gear), but I've drawn myself a 4x4 grid and am writing down what happens with each.

[andrewzuku]

I checked the valve clearance according to the procedure in the 18R-G manual, and discovered that I can't get them to protrude the same amount with any of the 4 cam gear pin positions.

As far as I understand, at TDC:

• Exhaust value lifters No. 2 and No.4 should protrude the same amount (approx. 2mm), and
• Intake valve lifters No. 3 and No.4 should protrude the same amount (approx. 2mm).

Am I understanding that correctly?

So here's where things sit for me at the moment...



Does this mean I may be a tooth out on my intake cam? Or are these regrinds just that far out?

[EDIT]
More photos - This is how my cams sit when I rotate them to where the valve lifters protrude the same amount.

[/EDIT]

[Willofan]

OK Andrew, it appears you have had the cams reground from standard hoping to gain more power. Did you get a specification and set up sheet for them? There should be a profile number, this sheet will also tell you valve lift at a predetermined degree.

In this thread somewhere I posted up degreeing an 18RG using a degree wheel and dial guage. Reason being the standard notch and timing marks become irelevant once you have gone wider durations 272 or 288 cams. I use 304s in my race motor and once set up correctly, the notch is about 5 degrees advanced from standard.

Post up the cam spec sheet if you have one.

[andrewzuku]

Hey Willowfan,

I bought the engine with these cams already in place.

A few of the Melbourne members may know the car. It's a red RA28 formerly owned by Alison, and I think used in a few 6-day endurance events.

I've never been able to find out any history or specs on the cams.

I'll have to get a hold of a dial gauge and find out what I've actually got

[Willofan]

I found the post I did on 18rg cam timing on page 165 in this thread.

Looking back at your images, the bucket height check is done when the head is off and no cam gears on. It can be done as you have indicated, but the base check of cam setting is done with the SST then resetting all your sprockets, chains and the little pins after.

The cams you have will have some numbers on them some where, usually on the end or up near the sprocket face. See if you can see them and let us know. Camtech and Wades have all the grind numbers and can usually work out what cams you have.

[andrewzuku]

Aha!! I just had a look under the cam gears. Both inlet and exhaust have 273A stamped in them.

A quick Google search brings up a post on the old toymods forum from 2004:

Clive Cams Grind No 273A with specs of:
Exhaust open 78, close 30, duration 288
Inlet open 30, close 78
Lobe lift In=0.405" Ex=0.405"

So where does this leave me? How do I set these?

On a side-note: Is there any point in 288 duration cams with 8.7 CR pistons?

[Willofan]

Well there you have it!!

288 cams are not designed to give much power under 4,800rpm and will work well peaking at about 7,800rpm and will keep it going to about 8,400rpm. That is of course the compression is above 10.5:1 on hi octane fuel and engine is breathing well. You have 45mm DCOE's and based on your previous comments the carbs are set up for road use on what was a fairly standard set up. What do the ports look like in the head and size of the valves?

Therefore your side-note is the big cams and low comps are a big contributing factor to your performance woes.

My race engine comps using big cams are always above 180psi.

[andrewzuku]

A big thank-you to everyone for all the help!

I'm waiting to hear back about a set of standard cams in the for sale section.

I'll post again on this thread when I get them

[EDIT]I forgot to mention, the ports and valves all look standard.[/EDIT]

Here's a close-up of the valves, and you can sort of see the exhaust ports in the next photo:

[mattysshop]

i have serached through filtering 'cams' found some info, but then not alot...

i have 2 questions -
some background....
basically we have a 270 head, (with 270 cams) and also have a mate who has some 251 cams that have TRD on them (although i'm sure there just an OEM part)

unsure about the bottom end, but i would say it is complete ordinary 18RGEU (was from a member's RA40) now wearing 20V BT ITB's..
the most i was able to find was lobe centres on all the OEM cams. not much about lift and duration specs, plenty on the best 'OEM' Combo... but not much unless ive missed it on the 251's in a 270 head

* Are the 251 cams bigger/better than the 270 cams (ie should i bother?)

and the injectors we have - are 195500-0285 not 0282 - i know it has been covered about what the 18RGEU uses and some mazda cross references etc.. these are blue also.. unsure if factory fitted but they appear to be.
maybe there was 2 different injectors put into the GEU? 282 and 285?

* Does anyone know anything about the 285 injectors?

[RA35GT]

Camshafts

88210 and 88231 camshafts take three-bolt, non-adjustable sprockets
88250, 88251 and 88270 camshafts take four hole, centre-bolt, adjustable sprockets.

Intake Cams:
cam type - lift (mm) - [email protected]", [email protected]", [email protected]"

88210 - 10.47 - 220.2^ - 580.2^ - 360.0^
88231 - 10.34 - 220.0^ - 581.6^ - 361.6^
88250 - 10.35 - 219.0^ - 584.0^ - 365.0^
88251 - 9.82 - 212.6^ - 572.8^ - 360.2^
88270 - 9.84 - 212.2^ - 580.8^ - 368.6^

Exhaust Cams:
cam type - lift (mm) - [email protected]", [email protected]", [email protected]"

88210 - 10.33 - 220.4^ - 361.0^ - 140.6^
88231 - 10.35 - 220.4^ - 362.4^ - 142.0^
88250 - 10.35 - 219.6^ - 360.8^ - 141.2^
88251 - 9.88 - 214.0^ - 364.0^ - 150.0^
88270 - 9.89 - 213.4^ - 358.0^ - 144.6^

Note:
^ indicates crankshaft degrees (divide by 2 for camshaft degrees)

All cam figures listed above are as we measured them from the cam, i.e 0.00mm valve clearance.

I intentionally haven't posted the total durations of any of these cams, as at 0.03mm valve clearance, the 88210 intake cam is actually a 300.4 degree cam.
I don't really think the world needs people boasting about stock 18RG cams being of 300degrees duration. That measurement just means that they have a lot of ramping and most likely don't idle as well as they could, or pass emission tests as easily as shorter duration cams.

Got this from the forums at some point. Can't recall who though, may have been Steve M

Not sure about the injectors. A change in the final number of a part number usually just denotes newer versions of that part number.

[mattysshop]

Cheers for that!

[andrewzuku]

Yep, it was Steve M:
http://www.toymods.org.au/forums/sho...l=1#post158856

I've been doing a lot reading about cams lately too, and came across it just now