Rebuild 18R cylinder head *with pics*

[mike1980ra40]

i wasn't far off

[thechuckster]

I would still run a straight edge along the "new" head to check if it is true, and if not get it skimmed, is cheap and saves you having to do it all again.

Being a steel head it's not going to warp without a serious attempt at overheating the engine ... but a good clean and a check with metal ruler for straightness is good workshop practice.

chers,
Charles.

[timbosaurus]

Thanks guys!

I had a closer look last night, and it is just carbon buildup on the piston... good to know!

There hasn't been any overheating at all, so i'm not expecting a warped head. But it would be good practice to check with a straight edge.... thanks for the suggestions.

My CR is 8.5:1??? why oh why do people make such low compression N/A engines

I didn't notice anything around no. 4 cylinder on the manifold gasket, but i didn't get a chance to have a good look. I do remember seeing plenty of carbon between cyl 2 & 3 when i first took it off, so that would explain the crappy noise!

I'll check the manifold for cracks/leaks too. Luckily enough ALL the pollution gear went bye byes when the weber was put on, so it's a pretty simple manifold to debug!

*Edit* Seems that all the guys helping me out here have helped me out before recently! I've gotta spread the love a bit more before i can rep you guys again

[Ben Wilson]

My CR is 8.5:1??? why oh why do people make such low compression N/A engines

My Navara is 8.3:1, I thought it was a misprint at first.....

[Screamn_Sleeka]

My CR is 8.5:1??? why oh why do people make such low compression N/A engines

Thats y the enigne is still going! from 76-82 (or when ever toyota used the 18R's), aus ron was somthing like 85, if they had some a decent compression ratio, 9.5 or somthing, then there wouldnt be an 18RC alive today

When you removed all ur polution gear, did u get rid of that smog pump thing? (the belt driven one above the alternator).

[timbosaurus]

then there wouldnt be an 18RC alive today

and that's a bad thing why?

When you removed all ur polution gear, did u get rid of that smog pump thing? (the belt driven one above the alternator).

I have only recently seen a complete original 18R and was amazed at how much CRAP there actually was on them!!! I'm sure it's not completely legal as it is, but the rego guy didn't seem to mind.

I didn't remove all the pollution gear on mine personally... the carby/manifold came from a different engine and whoever fitted it must have removed all the pollution gear at the same time. We just took the best bits (carby and extractors basically) from the 18R's i had at the time and screwed them together. Also replaced plugs/leads/points/hoses and had to get a new fuel and water pump as they both failed not long after it was on the road (prolly been sitting for too long) and the distributor still has a bit of slop in it's bearing which i need to replace. but once that is done, there is not much left on it that isn't new! If only it wasn't for the minor piston slap. That's why i want to fix this engine... i know it will last the 6 months before the conversion with no trouble at all!!

The vacum pump has gone... all of the manifold heating stuff is gone (the extractors made that possible)... all of the air-injection stuff is gone... and the charcoal canister isn't even hooked up

I dont think any of it actually contributes to the engine running any better, just makes it run cleaner and provides opportunity for a lot more vacuum leaks! Feel free to correct me if i'm wrong though...

[Screamn_Sleeka]

and that's a bad thing why?

Its old crap like 18R-C's that keep some of us going

As for the smog gear, it is legal to remove some of it, as it affectivly creates more CO2, which is now seen worse than smog. Really all thats smog stuff on 18R-C's is so califonia could get a slightly transparent atmosphere

I was just interested to know if any of that stuff was connected to critial running stuff, like maybe some smog pump created a vacuum that was necessary, although if uve got a weber, it wont need anything.

What weber do u have on it btw, and what jet size?

[timbosaurus]

Haha... myself, i haven't been priviledged enough yet to have anything more powerful in my celica than an 18R-C! So i shouldn't bag them yet either

It has a 32/36 downdraught weber, but i am unsure of the jet size. If i take out the jets, is there an easy way of telling? is it stamped on them? I'll take some pics of what is (or more correctly ISN'T) connected on the engine tonight hopefully and you'll be able to see from the photos.

Pretty much everything is disconnected. the only vacuum lines (AFAICR) are the brake booster hose which plugs directly into the manifold and the PCV valve hose which goes into the air cleaner. Oh... and the vacuum advance line, which i think is plugged onto the bottom of the carby, not the manifold.

That's all the hoses it seems to need

[Screamn_Sleeka]

ull need to put the carby apart to see the jets, and ull have to measure them, so its not really worth it, i jsut wanted to see what jets ppl are running on 18r's.
Most 32/36 came on engines like 2.3ltr and above, so they need smaller jets, but i suppose it doesnt really matter.

Id like so see some pics though, even of the whole engine bay, so i can see whats happn with all the pipes that arnt connected.

[mike1980ra40]

Hi tosco, about the smog gear .... when I bought my celica it was totally standard.
problem I had was the emmission recirc valve in the exhaust manifold had seized wide
open so it was sucking in pure exhaust all the time while the choke was closed and engine was cold it was i bitch to get going.

since it was impossible to replace that long silver snorkel thingy (EGR valve), i ditched the whole manifold and put in extractors but still left half of the smog gear on. ie the air pump,
MC valve the only bits i got rid of were the bits that recirculated exhaust gas because
theres no lead in petrol anymore.

another thing is the air pump was put on there to recombust unburnt hydrocarbons
that are recirculated thru the carb from the exhaust. thats why there is i big hose going to the inlet.

I have found through experimenting with current setup, that taking of the air pump decreases fuel economy. with the airpump on i'm getting 10.5Km per liter @ half a tank. when I took it of it dropped to 7.

at the moment my emssions are (running premium ) roughly 125 PPM HC (legal limit 250ppm) 0.8% CO or there abouts.

if your interested I'll post a picture of my setup.

when super was the norm, its ron was 97.

[Screamn_Sleeka]

Hey Mike,
thats very interesting, i dont understand some of it, like how the air pump is increasing fuel economy, as it bascially puts crap into ur carby. Its giving me more ideas for my 18R testing. Yea, i you could get a pic of how all ur pipes are running with extractors that would be great.
If ya recon this thread is dead, u can email them to me, [email protected]

[mike1980ra40]

no worries I'll get some photos up soon. heres a bit of info on some parts of emmisions
systems hopefully will explain things better

Charcoal canister

The function of the fuel evaporative control system is to trap and store
evaporative emissions from the fuel tank and carburetor. A charcoal canister
is used to trap the fuel vapors. The fuel vapors adhere to the charcoal,
until the engine is started, and engine vacuum is used to draw the
vapors into the engine, so they are burned along with the fuel/air mixture.

A purge valve is used to control the vapor flow into the engine. The purge
valve is operated by engine vacuum. One common problem with this system is
that the purge valve goes bad and engine vacuum draws fuel directly into
the intake system through the canister. This enriches the fuel mixture and
will foul the spark plugs. Most charcoal canisters have a filter that
should be replaced periodically. This system should be checked when fuel
economy drops.


EGR VALVE

The purpose of the exhaust gas recirculation valve (EGR) is to meter a small
amount of exhaust gas into the intake system, this dilutes the air/fuel mixture
ratio so it lowers the combustion chamber temperature. Excessive combustion chamber
temperature creates oxides of nitrogen, which is a major pollutant. While the EGR
valve is the most effective method of controlling oxides of nitrogen, in it's very
design it adversely affects engine performance. The engine was not designed to run
on exhaust gas. For this reason the amount of exhaust entering the intake system
has to be carefully monitored and controlled. This is accomplished through a series
of electrical and vacuum switches one of them the MC valve which is hooked up to the
air pump and the vehicle computer. (In RA40 celicas the emission computer is located
above and to the right of the heater blower relay behind the left kick panel.)

Since EGR action reduces performance by diluting the air /fuel mixture, the emission
system does not allow EGR action when the engine is cold or when the engine needs full
power. common problem with the EGR valve is it becomes carbonized, sometimes through
lack of keeping engine tuned and running rich when engine is running rich excese fuel
burned in the exhaust manifold will build up over time and clog up the egr valve,
if your really unlucky the valve will stick open causing major headaches starting the
engine cold.


air pump

Inside the original exhaust manifold there is sufficient heat to support combustion,
if air is injected into manifold any unburned fuel will ignite. This combustion
will not produce any power, but it will reduce excessive hydrocarbon emissions.
Unlike in the combustion chamber, this combustion is uncontrolled, so if the fuel
content of the exhaust is excessive, explosions, that sound like popping and backfiring,
will occur. There are times when under normal conditions, such as deceleration, when the fuel
content is excessive. Under these conditions we would want to shut off the air
injection system. This is accomplished through the use of a diverter valve, which
instead of shutting the air pump off, diverts the air away from the exhaust manifold.
Since all of this is done after the combustion process is complete, this is one emission
control that has no effect on engine performance. The only maintenance that is required
is a careful inspection of the air pump drive belt.

another way of checking good operation of the air pump with origianl manifolds on is
put your hand over the tail pipe and feel the pressure of the exhaust coming out, when
you take the drive belt of the pump you'll notice a huge drop in pressure.

[Screamn_Sleeka]

Thanks Mike, thats awesome.
Im still digesting most of it, but referring to the last sentence, is this drop in pressure when the air pump is removed a good thing? im assuming it is, although i have limited understanding of exhaust systems.

To update this emissions system, would i be correct in saying i could remove everything except the charcoal condenser, and put in place a cat converter? Which would deal with the N problems, and CO which this system wouldnt.

What would be the modern approach to fuel evaporated hydrocarbons from fuel tank (although i think they are very sealed now days) and crank case? - Ie, how is a charcoal condenser replaced?
-I would like to use the newest and most effective emmisions system for my 18R project.

I assume all this is what the "C" means in the latter part of toyota engine numbers, eg 18R-C, 4K-C, and that jap spec engines with out the C, have neither a charcoal condenser or egr/air pump? as they have a "U", eg 18R-GU.

[mike1980ra40]

cat converter, from a technical point of view one is required on all unleaded cars after 1985
or 6 to (off the top of my head) convert HC to H20. because an RA40 is pre 1985 one is not
needed, then again if you do an engine conversion to something like 1g-ge then one
is required because that motor is post '85, and then again now that leaded is phased out and cars running ULP one is needed. (so i was told by lots of people including engineers).

so yes chuck in a cat converter... thats the modern approach. i'm not running one yet, i've been really lucky having an 18R that burns as clean as a whistle.

that drop in pressure just lets you know that the air pump is doing is job, and removing it
I have found actually puts the emissions up, I've had my car analised several times in original configuration and watched levels go up and down when hoses are blocked off.

however, with my config at the moment, taking off the air pump makes the car use more
fuel because the secondary throttle is opening up more often. when air pump is on
secondary isn't opening up anywhere near as much. so far this week (on 20L of fuel) I have done 150K's and there is still enough in the tank to go another 75k's or so.

from what i've read up on, the C in 18R-C stands for "californian emissions system" there
is a webpage somewhere that lists the letters and what they mean, i'll post that if I can find
that.

modern approach to evap HC, not sure, next time i'm in the library I'll have a look, and or
have a look at my friends VY commy and see what the setup is on that.

[Screamn_Sleeka]

From what i understand, you are getting lower fuel economy when the air pump is disconnected because the carby is tuned and designed to need it? For a stock 18R-C with out an air pump hooked up, a 18R carby and probably manifolds should be used? (ie, basically converting it to a 18R).
Or as timbosaurus has done, a completely different carby, such as a weber 32/36.

I aslo intend to put a cat system on my ra40, even though the car and engine were produced way before 85/6, as i see the emission pros to greatly out weigh the power loss cons.

I know of a few sites that list all the toyota codes, and as ive read on them C does stand for Californian emission system, which i think is to lower coloured emission (and effectively lowering N and HC's), as calfornia has a pretty bad atmosphere haze.

Sounds like you are getting way better fuel economy than me, although i think mine is running rich as there is ocasionaly black smoke from the exhuast. And my rings must be pretty worn as she is a smoky ones when first started in the day. Although im building an 18RG that should be pretty close to facory condition, even with the standard bore. Unfortunaly it has been ported, by someone who must thing "bigger is better" and has left me with pretty much a race head, and i doubt i will get decent low end torque now, and the intake side is polished... ah... 2nd hand stuff sux.

Thanks for all ur help, egar to see those pics.