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

[tricky]

What you are touching on here is an area which seems to be fairly shrouded in grey. I'll add what I think I know, and what I understand of the topic...

The motivation for tuning this aspect of the intake system is to control the manner in which the mixture enters the cylinder, and until recently, as far as I can tell, all work on this area has been entirely empirical. My understanding, in an empirical sense is that you would want the taper to start early and end in a length which allows a gentle change in radius, ie no sharp angles. This means that the flow has the most possible room to stabilise (in terms of bulk average velocity, and flow characteristics), much in the same way you place throttles as far from the port as practically possible (Yes, a different kind of restriction, but both represent a destabilisation of the flow). This scenario would seemingly flow more air, but we all know that volume is only part of the story...

There has been some proper research into whether a tumble flow (rolling into the port, kind of like an ocean wave) or an inclined tumble flow (aka swirl flow, aka vortex) will create better combustion. This seems to be where the trade off part is... Flow volume or complete burn. It seems that research (I'd cite, but I'm too knackered) indicates that the more turbulent tumble regime, potentially created by a late taper, promotes better combustion, and allows much leaner mixtures to be run. However, this only seems to apply to lower gas velocities (so cruising speed in the family car), so I'd say the early swirl inducing taper would possibly win out in top end power, as Owen mentioned.

If it were me, I'd taper early. In fact, when I match port my manifold later this week, it's what I'll be doing. Not only is it proven, but also easier. When it comes to the crunch, I don't think it will make a big difference on an 18RG. I think carefully tuning this aspect of the intake would be more fruitful on a multivalve head with better squish characteristics.

Now I'm thinking what playing with diffusers in the manifold would do... Maybe I'll sleep on it instead.

[floppy]

Hey guys,

Just a quick add on,

I am only getting around 100psi on all 4 cylinders so I think my valve clearances are the first thing to look at.

So apart from forgetting a bolt in the timing cover (oil leak), bolt with a buggered thread in the head inspection plate (oil leak), alternator mount bolt coming out on my test drive and the other one only finger tight........

Still have a leak at the front timing cover and I think its because I didnt use any liquid sealer where the timing cover and block meet before putting the head gasket on.

Oh the joys, think I will need to lift the head and apply some sealer, hope it doesnt destroy my head gasket ( on that note can a 18R head gasket be used, parts shop in their catalogue it states not suitable for yamaha head)

Dave

[o_man_ra23]

Yes, it can be used, you just dont get the bolt holes where the timing cover bolts upward to the head.

[Steve M]

You will most likely have to replace the head gasket if you do lift the head.

Can you seal those leaks from the outside?
Say, for instance with some kind of oil friendly silicone, squish it into the area?
Those aren't pressure leaks, just splashing around and capillary effect.

[leso]

" I am only getting around 100psi on all 4 cylinders so I think my valve clearances are the first thing to look at"

Dave if you have NO valve clearance it could give you readings like that...are you sure your valve timing is ok ???

[o_man_ra23]

Dave, if you have lots of overlap (as Leso stated as valve timing) then you will get lower pressures.

Steve, I have tried and failed many times to seal timing cover leaks from the outside Unfortunately removing the head is about the only way you will ever seal it... I have tried other ways many times.

[maurice c]

I had a leak form the bolt that holds the timing cover directly under the inspection cover. I tread locked the bolt and siliconed it and now theres no leak, try this first. The bolt hole is a natural pool for oil in the head.

[floppy]

Hey guys,

Ok just a few more notes based on the replies you guys have given:

Pretty sure the cam timing is correct, we followed the guidelines in the green book and set to TDC then made sure the cams had the notch vertical and then set the gears to the closest dowel hole that kept the cams on that notch.
the cams:
http://picasaweb.google.com/floppydj...51008404322738

and the gears:
http://picasaweb.google.com/floppydj...51034174126530


I am going to try changing the intake gear to another dowel hole as when we put it so that the mark lined up with the cam marker, with the hole we used the intake cam mark didnt line up anymore. (its so hard to word this stuff without repeating!!!)
Regarding the leak it seems to be coming from just above the bolt shown in the picture following. I have removed it and put the brown aviation liquid sealer in. But its hard to tell where it is leaking from exactly. Oil appears on top of the bolt bulge.
http://picasaweb.google.com/floppydj...50918210009506

I will remove the bolt again and use a different sealer first I think. I want to try and avoid taking the head off again solely because I am running out of holiday time and am a little knackered!

Does everyone else put sealer on the block where the timing cover meets the block? Ie where the manual says to put it?

Dave

[o_man_ra23]

Yes... if the manual says to do it, it works. Also dont forget that your still running it in, so air will be leaking past your piston rings like a mofo even when warm, which will give you a low compression reading. You wont get a proper reading until the motor is completely run in.

[tricky]

From memory, last time I put an 18RG together I didn't put the sealant on, and there was no leak (from there... Elsewhere was a different story ), but I would've definitely used the sealant if I hadn't conveniently run out... Just got a bit impatient.

On the HG front... I have acquired me a genuine toyota Head Gasket- Cheaper than ACL, $55 from Mr. Toyota spare parts department. But only because I knew the part existed and I was persistent enough to nag the parts dude into trying different car catalogues until he found the part number (catalogues didn't go back to RA23, so I got him to look through coronas until he found an RG... Nice bloke, better than the blunt dicks who are normally there ). So anyway, to save everyone else the heartache of either being told "fuck off", or spending half an hour waiting for old mate to sift through the parts catalogues, here is the part number:

18RG Head Gasket 11115-88231 $55+GST

Also got an exhaust manifold gasket:

18RG Exh Gasket 17173-88250 $22.25+GST

I hope that helps someone!

[The Witzl]

Thanks for that Tricky... i know they are available (i've bought two before), but never noted down the part number.

Good old James at Castle Hill Toyota - he knows all.

[Sagluren]

does anyone know where i could find a water pump backing plate thingo (where the pump bolts to then connects to the block) i can not find one in SA genuine or otherwise. cant find a aftermarket supplier either.
really quite annoying, one of the only things i need to put one of my rg's back together. im sick of the rc with 66% leakage...

[Steve M]

Sam,
Do you mean the pump housing? That's the bit that all the hoses go onto and the pump centre goes into.

Other than that, I'm not sure what you mean.

[Sagluren]

yeah that what i mean, sorry my descriptive ability is crappy

[o_man_ra23]

As I mentioned before Sam, the 18RC one is identical other than the bypass hose pipe diameter. Its a relatively simple job to remove the existing one and either braze in a larger item, or cover the hole and use a T piece from the heater outlet to do the job. 18RC one should be available from Toyota new.