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

[o_man_ra23]

Owen, the 9 in your last sentence seemed to have been turned upside down

I can't remember if my latest set of valve springs are duals, I don't think they are, but would have to check. Pretty sure the Precision springs were though.

[S. Lowlux]

O.K. here we go. I just spoke to Allen from Performance Springs, who's actual phone number is 07 55491055 (sorry wrong number RA35GT ) he is supplying me with a set of valve springs. These springs are a higher pressure than standard & he assures me they are the go.
He also said that the old valves were flogged due to VALVE FLOAT, a condition whereby the valve bounces or flutters against the seat. This is caused by not enough spring preassure.
Keep asking experts till you have 52 answers, shuffle & pick a card.
I pick what Allen said as this is his speciallity & he makes the damn springs.
Owen.

[o_man_ra23]

Hmm... can you post a high res pic of the offending valve's damage?? I should be able to tell you if the wear was from hitting hard or otherwise. Your description sounds like the valve had ground itself on the seat, which would be from rotating against the seat, not hitting the seat too hard.

[RA35GT]

O.K. here we go. I just spoke to Allen from Performance Springs, who's actual phone number is 07 55491055 (sorry wrong number RA35GT ) he is supplying me with a set of valve springs. These springs are a higher pressure than standard & he assures me they are the go.
He also said that the old valves were flogged due to VALVE FLOAT, a condition whereby the valve bounces or flutters against the seat. This is caused by not enough spring preassure.
Keep asking experts till you have 52 answers, shuffle & pick a card.
I pick what Allen said as this is his speciallity & he makes the damn springs.
Owen.

Sorry dood, I just copied that from the sponsors page LOL

[S. Lowlux]

Nah, don't be sorry RA you were the one who put me on the right track.
Owen, I will try for a photo of a valve.
Owen.

[S. Lowlux]

Valve photo's 18 RG. What would cause this wear shape ?
I'zz behive myself .
Owen.

[o_man_ra23]

The even wear around the head indicates that the valve was rotating on the seat. I would imagine the seat would have an even wear pattern similar. The surface finish looks to me like what you would find off a lathe, not a hammer, which would have a shinier surface. This is consistent with Allen from Performance Spring's theorum of valve float from not enough seat pressure.

I would suggest that if the valve has been worn like that, the guides would be in terrible shape as would be the seats. Not a cheap repair, but not the end of the world either.

[ian]

i am looking for some help i searched the thread but the diagrams dont show it
does the 18rg head have seperate cam bearings
as a friend of mine has had the head rebuilt twice and it keeps grabbing the cam
he is currently pulling it down again to see what damage has been done
any suggestions to a likely cause ?
this time it happened just above idle running only for a couple of minutes
with 60lb oil pressure
ian

[o_man_ra23]

No cam bearings on the 18RG.

My thought on grabbing a cam might be that somebody has swapped a cam cap out from another motor. If this occurs, then that cam tunnel needs to be line bored true or the swapped out cap will grab.

[Omegaman]

i would agree with o_man, but would add, maybe the lob is not getting oil and maybe the cap is scratched inside. just a thought...

[Steve M]

Ian,

I can think of a few reasons why this might happen.

1. Incorrect cam cap (either put in the wrong location or from a different head, as per O man's post). You should be able to feel if the caps don't align with the head. If you can feel any diffference between their surfaces where they meet, then it is the wrong cap. Measuring left to right diameter and top-bottom diameter could also reveal a problem.

2. Blockage within the camshaft oil supply gallery.
It could be in the oilfeed to the head / #1 camshaft journal, limiting flow to all journals on that cam.
It could be in the camshaft itsself. If a foreign body (eg. separated sealant bead) gets into the camshaft it doesn't come out unless you pull out the welsh plug from the end or back flush it from cylinder 4 cam oil hole through the inlet hole.

3. Camshaft is bent, causing more friction. Straighten or replace camshaft.

4. Cam or journal has a foreign inclusion/burr that is hooking the two together or causing a tighter clearance. Remove foreign inclusion or burr.

5. Head is warped, causing more friction on the journals through misalignment. Line bore may fix. Straighten head may fix.


The journal sizes are the same for all 18R-G engines. We've tried all cams from 88210 - 88270 and they've been fine in an 88270 head. 88210 cams had a little more clearance because they're older and been used more.

[jwebb2876]

http://www.youtube.com/watch?v=jndRx...embedded#at=16
Footage of the Williamson RA40 at about 28min, they show a laps worth of in-car with a bit of external stuff

[TRD184]

hello 18RG guru's, i come to you yet again for help.
my RA23 (stock 18RGU) has a problem, after a long drive, if i turn my car off, a few seconds later it emits an almighty POP! and a little orange flame from my exhaust. interestingly, if i let the car idle for say 30 seconds, then turn it off, it wont happen, my thoughts are, the car is running rich, and the flame and pop is just it lighting up on the hot exhaust, explaining why it wouldnt do it on very short drives, and after being let idle for a bit. except im not sure why it takes so long for it to happen, 3-6 seconds. i thought id ask if someone has experienced something similer?
i think im pointing the finger at the culprit (rich mixture) thanks for any advise anyone can offer, hope to meet alot of you at CCD!

[o_man_ra23]

You are correct with it being a rich mixture. What you don't seem to have a grasp on is stoichiometry. Basically there isn't enough oxygen in your exhaust system to ignite the fuel, as there are too many other gasses (carbon dioxide etc) which prevent fire. What happens when you stop is that the leftover gasses in your exhaust escape and are replaced with the oxygen rich atmospheric gas mixture we call air.

When the fuel to oxygen ratio gets to a nice mix, you get combustion, with the hot exhaust providing the ignition. This makes for a nice bang as the gas expands rapidly.

To cure this, fix your mix and make sure you are getting good ignition (plugs, leads, cap, rotor, condenser, coil and points need to be good). The end result, as I learned about 11 years ago from witnessing this happen to a flatmate's sigma, is that your rear muffler decides enough is enough, and it basically peels open like a christmas present.

[TRD184]

oh wait, i see, that why it takes so long for it to light because theres no oxygen until the very end of the tailpipe.. kinda seems obvious now... sorry to ask a no0b question its been a long day. im actually getting my light vehicle mechanics certificate on monday, i should think of these things.
i did indeedy check the ignition system (most of which is new) im getting good spark. the mixture is rich on the back 2 cylinders though.
thanks heaps for the help, someone else needs to help me so i can spread the rep around! my thanks will have to suffice

id like to witness a muffler peeling open though