18RGU Carby and Cam Questions (long winded and a few pics)

[floppy]

hey guys,

I'm hoping some of you knowledgable guys who are into 18RG's can help me out a bit here.

This is my first twin cam motor and a lot of stuff I am completely unfamiliar with. **Not that I am even that good on singles either!!!!

So please bear with me and my probably vague understanding on how some of these things work.

NOTE: Compression test gave all cylinders around 150-155. I think I read somewhere they should be around 170 or so.

Carby problems:

Ok here we go, the problems I have with the carbies when I bought it was that it was running as rough as heck.

After rebulding the rear carby it was running smoother but I was getting backfiring through mainly the front carby. Rebuilt it and am now getting a lot more backfiring through both, even under idle.

The back carby had the tip of an idle screw lodged in the passage which we carefully removed (gently tapping). Polished the venturi's, housing etc with a 600 grade paper to make it all nice and smooth. All new gaskets and o-rings as well as idle screws were used. Thorough cleaning of the body and passage ways with compressed air. A friend of mine who has rebuilt many webbers etc gave me a hand to do this checking that all the passages weren't blocked etc. Float level has been set on both so that when the top housing is upside down the float were level.

Now I am not sure whether the vacuum lines are hooked up correctly as its an 18RGU the pollution gear has been removed and hoses blocked off etc. In the following images I have drawn in red along side the hoses to hopefully get some clarifcation on if they are connected correctly. Yellow is the one that is connected to the dizzy?

Rear Carby

I don't think this vacuum hose is correct. its just going between the 2 barrels of the one carby. If my thinking is correct on the front carby picture below, the vacuum line from the dizzy goes to a diaphragm under the cover to the right. it seems strange that the vacuum advance from the dizzy goes into the front carby but there doesnt seem to be any way for this to linked to the rear carby. Is this making sense?

Front Carby:

Ok the yellow line indicates that this hose is coming from the dizzy. Is this even correct? should it be coming from one of the inlet vacuum lines?

The longer hose that just seems to be looping on the inlet and there is a smaller one looping as well.

The big thick red hose with the socket stuck in it as well. And to the right of it there is a hint of a smaller red hose next to the yellow throttle linkage. not sure exactly what this does as what its hooked up to isnt connected to anything.

Any clarification on these things would be much appreciated. The manual I have doesnt have any diagrams for vacuum hoses on the 18rg/u


Cam Timing:
This is the area I am the least familiar with.

My more mechanically minded friend wanted me to find out about the cam timing because he thought that it might be that they are out. ie the intake is open when it should be closed, hence allowing the backfire out through the carby.

I have the 18R/18RG toyota manual on the engine and am trying to work out a few things that aren't matching up with the pictures in the book. I am wondering if this is because maybe the cam grind is not standard or just been put together wrong. But most likely because I don't quite understand everything yet.

Here are the pics of the cam gear pin positions and there alignment marker from the top when set at Top Dead Centre.

Pic of cam gears on from front @ TDC.

Note: an 88253 head.

Left Cam Gear showing pin position:

Left Cam Gear showing marker from top in TDC:


Right Cam Gear showing pin position:

Righ Cam Gear showing marker from top in TDC:

Not exactly lined up compared to the left cam slit.

On Pages5-27 it says when installing the cam shaft to make sure the slit in the front is pointing upwards. This seems to correlate with my pics.

But then on page 5-29 image 5-93 it talks about aligning the pin hole. This is where my main question is. How do I tell if the pin is in the correct hole based on the position of the slit position at TDC?

I'm also trying to understand why on page 5-30 through 5-33 there is options to advance or retard the timing with these gears compared to adjusting the timing with the distributor. If these cogs/pins are advanced or retarded and I am setting my timing with the distrbutor to 12degrees, is this causing some of the bad popping and backfiring as well?

Hopefully I have made some sense with my questions as I am not that familiar with the terminolgy and my mechanically minded friend isnt here tonight to help me word everything.

Thanks
Dave

[floppy]

Me again,

I wanted publicly thank Rodger for all his help in getting the gasket kits for these Type-T Solex's and for all the questions I've asked as well.

Dave

[blue22]

Hey floppy!
The compressions of 150 - 155 should be ok provided that they're within 5-10 of each other, when they were new I believe they were around 175 but that depends on the head. The 253 number visible in one pic is the giveaway, I heard somewhere that this was the lowest compression of all the 18rg*s. Some say that the 253 head is best 'cause they have the most meat in the ports...so can be machined further than other heads. the compression also tells us that the correct pistons are fitted, with 18rc pistons you'll only have around 110-115 psi.
I had a similar problem to yours with the carbs on my 18rgu, the problem was that the floats were set too high, check your plugs if they're black as black she's running too rich. The manual describes how to set float level with some special tool, but it's easy to make one, I can send you a pic of the one I made for mine if you want. I also had a small problem with a vacuum leak between the manifold and head. Another possible cause is simply the state of tune, following the instructions in the manual should sort that out.
As far as the vacuum lines go...I plugged ALL the lines in mine ( my vacuum advance unit was stuffed so no pont in connecting it!!) and have no probs now.
Cam timing and ignition timing are completly diferent animals. Valve timing shouldn't be played with till you know what youre doing. it is said that valve timing and ignition timing have oposite effects....so that advancing valve timing has a similar effect to retarding ignition timing....and vise versa............The slots for both cams must point straight up, I think ...from memory ('cause I don't have the manual handy) there was another "special tool" that locks the two slots a certain distance apart, then you simply line up which ever pins fit the closest....a bit fiddly but doable.
I hope this helps . I can prolly send you some links to usefull 18rg* stuff on the web if you like.
No doubt there are others on the forum that can help. Cheers Phil.(the old fart)

[Rodger]

Thank you Dave,

All the plumbing really needs to do is block off any access for a vacuum leak. It appears correct and you have checked all pipes.

The pipe across the rear carby can be removed and the lower back pipe fitting can be crimped over to block it. The vertical pipe on the rear carby just needs a dab of silicone to block this one.

The vacuum advance only needs to run off the front carby as you have it. You could run without it, blocking it off, if the dizzy gets regraphed to run without vacuum.

I am sorting out the exact same running problem with Damo's RA28/18R-G here in Canberra.

First thing to check is the balance between the two. Without the engine running; set the balance screw so that both carbies reach the full open stops together. This will be close enough. Then back off the front idle speed screw until you can feel the throttle plates close fully, then use the screw to open up, about three full turns from contact with the throttle arm. This will be a high idle speed to start with but gets reset as the mixtures are sorted out and the balance is adjusted when the motor starts to finally idle.

Can you tell me what sized pilot jet you have?

The poping and back firing and inability to idle is due in part to it running quiet lean on the idle/pilot system. It improves as the idle screws are turned out to a point and at the four turn mark they no longer effect the mixture so no change is noticed with the running.

I found on Damo's we were out to about 4 turns on the idle mixture screws to improve it but still lean just off idle.

Damo's set has #60 Pilot. I will be trying a #63.8 and then #65. He and I wont get back to it until mid next week with results due to conflicting work and travel.

But I have seen this problem several times before.

So try scewing out the idle screws to four turns and see if the idle improves each turn. It may still not idle but put a bigger pilot jet in and the idle screws can be brought back to the 1-2 turn range to start the process again.

If you already have a #65 pilot then we will explore futher.

Cam timing has to be a long way out before problems occur and then the problems will be a lot worse and more mechanical conflict than running issues.

Plug leads in correct order?

Regards

Rodger

[floppy]

Hey guys,

Ok... when i pulled the plugs out to take the cover off, then were very clean(running lean), but i hadnt had it running for that long. When i put the new idle mixture screws in i did then 1 turn only so will look at adjusting them a bit further when i get home tonight. I'll also look at the balancing.

When I had them apart I wrote the jet #'s down but misplaced it last night when I originally typed the message. I think the main jet had 140 on it from memory. Will investigate this.

Regards to the cam timing, we just wanted to make sure that things that were supposed to line up were. I don;t intend to change anything here, although while I have the cover off i am gonig to check clearances.

Thanks for the quick responses guys.

Rodger, hopefully that spring arrives today or tomorrow and I'll pop it in so its back to what it was.

I'll be back with more questions most likely

Dave

[floppy]

Hey guys,

Havent had a lot of time to get into checking everything out you guys have suggested. (Don't want to annoy my neighbors at night time)

Some specs I gathered while the Top Cover is off.

Cam Numbers:

Intake: NPR 1 351 -88251
Exhaust: NPR 1 351 - 88251

Carby Jets: 140 and 63.8

I havent got the number of the starter jet. I will do that when I get some daylight time to play with it.

Intake Valve Lifter Heights: as per shown on page 5-24 image 5-74 of the green 18RG manual.

No3: 5mm
No4: 5mm

Exhaust Valve Lifter Heights: as per shown on page 5-23 image 5-72 of the green 18RG manual.

No2: 5mm
No4: 5mm

If the head has been faced, could that account for the extra few mm I am getting over the manuals suggested 2mm?

Are shims still available ?

Valve Clearances

Exhaust:
No1: 0.30mm
No2: 0.35mm
No3: 0.31mm
No4: 0.35mm

The manual says the exhaust clearances are between 0.31mm-0.37mm which these are.

Intake:
No1: 0.18mm
No2: 0.17mm
No3: 0.15mm
No4: 0.13mm

Tha manual says for the intake the clearance should be between 0.26mm and 0.32mm.
Are these lower values acceptable?

I have gathered all of this info just so I can get some confirmation from you guys who have been playing with these motors for years.

I have another question about the dizzy too, when its on TDC should the lobe be just about to open on or be opened?

Ok thats all for tonights questions I will hopefully get to the carbys saturday afternoon after helping my sister shift house....

Dave

[Rodger]

Ok,

For the carbies. #63.8 pilot should be close. Try screwing the idle screws out another one and a half turns (total 2.5). Then if you get to that four turn mark, a #65 pilot will be needed.

Don't bother checking the starter jet. Up there in the north you do not need to be using the choke and it has no effect on the whole fuel system when the chokes are off anyway.

However it maybe a convenient way to add a bit of fuel at idle to determine if you do need to go up a pilot jet size. Open the chokes a little as it idles and see if it improves the running.

The fact that the compression has been raised by shaving the head indicates to me that you probably will end up with a #65 pilot.

I run tighter valve clearances in my 2T, it gains just that bit more duration and lift.

Shims could be hard to get. Calculate the numbers for the thickness needed, then try Toyota first and then go to someone like Performace Springs in Brisbane(?) to make some to your numbers.

Your exhaust numbers are good and you could try getting all down to the lower value but it takes time. One of the things that get done when chasing that last little horse.

The inlets need opening up and aim again for the lower number and then you could use 0.24mm.

If you know the thickness of all eight shims you may find you could swap some around.

The dizzy points should just be opening at the first mark on the crank pully, ie the timing mark. If they are just opening at TDC then the static timing is at zero degrees. I have never noticed if at TDC the points are on top of the lobe.

I set the intial static timing with #1 compression on the timing mark, as usual. Then with the ignition turned on I listen for the click of electric current as the points open as I turn the dizzy back and forward. setting the dizzy as it turns forward and just clicks.

Regards

Rodger

[floppy]

Hey guys,

Well I got a bit of time on saturday to try and make the beast hum nicely.

I succeeded reasonably well.

I'm still getting some hesitation down load and under load doing around 60 in 3rd or 4th. (mostly 4th)

Ok what I did.

After measuring the clearances etc during the week i put the cover back on!

Removed the distributor cap to see where the rotor was pointing in relation to TDC. To my surprise it was a fair way out! (I hadnt actually checked this at all since purchasing the car). This would most likely explain the flame backfires I was getting from the carbs

Sorted this out and while I was at it changed over the coil just in case ) points, leads etc were all replaced before roadworthy.

Then added the spring to the diaphragm I lost. (Thanks rodger). Replaced all the idle screws with new ones (hanks again rodger . And initially set all of them to 2 turns from closed.

Timing is currently set just a bit further than factory 12degrees and there is still some popping and backfiring through the carbies.

I have noted one anomally though, the throat for cyclinder 4's idle mixture doesnt seem to affect it at all. This was the throat where the old idle screws tip had broken off and lodged in the hole.

We removed this by slight tapping of it and it came out very easily so it wasnt very tight. The passage is clear (used a single strand of thin soft guage were to poke through as well as testing with compressed air.) I am wondering if the overtightening of the original screw has opened the passage further hence the new screw not working well at all ?

So getting there and I can drive it around pretty much now although its a bit chuggy and the backfiring through carby is annoying.

I am going to recheck float levels and check the plugs for colour as time allows this week and work from there.

Dave

[RT104GT]

Did anyone tell you that the timing of the valves looks out by one tooth on your inlet? But I guess it depends on the dowell position.
using that timing template I posted with the tool in the notch the markers should be vertica and yours are in place. There is a link on that chain makers page that shows all the timing marks and even a high lift advanced cam wont be one tooth out. There is also a section about cam timing and how critical it is and it goes through all the dowell offset rationale.

[RT104GT]

PS I have a fully factory set up carbie system so I will take a photo and show you the vacuum connections if you like? SOme of the hoses are wrong.

re pressure I have an 88253 head on an early block with 9.7 pistons and have 155's.
The old P210 head on 9.7's gave 175's OK?

.

[RT104GT]

Carby Jets: 140 and 63.8

Could be 135-145 so thaere are ok.



Intake Valve Lifter Heights: as per shown on page 5-24 image 5-74 of the green 18RG manual.

No3: 5mm
No4: 5mm

Exhaust Valve Lifter Heights: as per shown on page 5-23 image 5-72 of the green 18RG manual.

No2: 5mm
No4: 5mm

If the head has been faced, could that account for the extra few mm I am getting over the manuals suggested 2mm?

Are shims still available ?


YES a whole range between 0.050mm in 50 steps worth hundreds so get local made ones.

I GAVE SHAUN MALONEY A COMPLETE SET OF 4 OF EACH.


Valve Clearances

Exhaust:
No1: 0.30mm
No2: 0.35mm
No3: 0.31mm
No4: 0.35mm

The manual says the exhaust clearances are between 0.31mm-0.37mm which these

EXHAUST ARE FINE
are.

Intake:
No1: 0.18mm
No2: 0.17mm
No3: 0.15mm
No4: 0.13mm

Tha manual says for the intake the clearance should be between 0.26mm and 0.32mm.
Are these lower values acceptable?

THEY WILL BE QUIET BUT A BIT TIGHT WHEN HOT es the 13mm one


I have gathered all of this info just so I can get some confirmation from you guys who have been playing with these motors for years.

YEAH 33 LAST COUNT

I have another question about the dizzy too, when its on TDC should the lobe be just about to open on or be opened?

OVER THE TOP OF THE LOBE AND DESCENDING BY THE DEGREES ADVANCE >>10-18

SET THE GAP AND THEN SET IT USING YOUR DWELL METER.


Ok thats all for tonights questions I will hopefully get to the carbys saturday afternoon after helping my sister shift house....

Dave[/QUOTE]

[RT104GT]

http://www.romac.com.au/


Degreeing camshaft timing etc etc follow the links

[floppy]

Hey RT,

Thanks for the info.

[QUOTE]Did anyone tell you that the timing of the valves looks out by one tooth on your inlet? But I guess it depends on the dowell position.[QUOTE][QUOTE]

Yeah we think there might be something up with the intake still. I am going to make up the tool so that when I remove the intake cam to get the measurements I need for the shims. we can try and set it as factory as possible.

The backfiring I am getting still seems strange as it seems we can set the timing, go for a drive and come back and its different. (maybe the chain and guides need looking at as well. I can hear timing chain noise when I am driving it around, at idle it isnt so obvious)

The distributor on this 18RGU is branded an 18-rc one which I am guessing is fine? There wasnt a specific 18RGU one?

[QUOTE]THEY WILL BE QUIET BUT A BIT TIGHT WHEN HOT es the 13mm one[QUOTE][QUOTE]

By being tight when hot, how does that affect the running. I am not sure of this kind of thing and am trying to understand it a bit more.

One thing I'd like to note is that before I took the cover off I thought it was tappet noise I was hearing, but realising there were not tappets to set as such, I am wondering what the noise would be? Floating lifters? The chain?

And I'd love some good pics of a factory setup version of these babies? Are yours the Type-T solex's as well?

Thanks for the info on that site too. I have forwarded it to my friend and unfortunately won't get to play again until saturday.

Dave

[RT104GT]

OK LAST FIRST.

If the hot engine closes up the clearance then the valve will stay open especially at revs. So it is best to use or try to get a half way decent set of clearances.

re the tool I can accurately trace out on a piece of cardboard the cam timing tool or I can send you the photo/scan providing you accurately print it out on A3.

But your cam keyways look fine they are straight up and if the TDC on the crankshaft is on the numbers you have TDC and the back of the number 1 inlet and ex cams should be facing the valve pad.

I have a twin cam m here i just opened up so i will take some photos today OK


OK ON THE DIZZY This is a real worry.


MY 18RG DIZZY has no tongue at bottom, it doesn't need one to drive the oil pump.

All I have seen on thes epages are what i think are 18R dizzy's used aftre the high cr 210 engine.

So maybe it doesnt matter but when i was taught engine tuning (1969) and rallied 1600 S coronas we always used 1600s dizzy not 2R.

REASON: Counter weight throw out and dwell and advance characteristics of a performance dizzy are beter than domestic model.

SO you need to go through the tech specs and see what is specified for each 18RG the G the GR the GRUY the GEU.

They are all different, based on CAM TIMIN, CAM LOBE LIFT, and CR.

At a pinch any 18R dizzy will work but for real grunt you use the real one..
E.G. THE REAL 18RG first series engine would pull from 3000 to RTED LINE 7000 in every gear including 4th. and 6500 in 5th.

I now run 88235 head still have 9.7 pistons but have lost 15 BHP and the engine struggles to 6500 rpm.

REASON? TIMING of 235 head and CAMS are totally different.


SO you have to wrok on the head and get thoses cams timed to perfection.

See this link.. Its called camshaft degreeing and it spells it all out.....

http://www.romac.com.au/pdf/Cam%20De...Rollmaster.pdf

[Steve M]

1. Check that all short circuited vacuum lines are connected to the same side of the butterfly.
2. Connect the vacuum advance to the balance tube (vac points right next to the head). This really helps with tuning. Engine runs so much better.
3. Check all points for vacuum leaks (especially the balance, there are two points under it).

4. Fix those intake valve clearances before you bother tuning it.
It will run crap if the clearances are too tight. Just get your existing shims reground to the correct thickness. This should cost about $5 each.

5. That cam timing shouldn't make too much difference, fix it if you want, but not critical.

6. 18R dizzy? eh, that;s a common one, disregard it if you've got no other easy option, it makes bugger all difference anyway.
Check the points as said above.

The toyota book says have your idle screws 1 1/2 turns from contact to start tuning.

Balance it first, then play with the idle screws one at a time and with 1/4 turn intervals.
Set each cylinder individually as old engines and old carbies are not uniform anymore.
Just listen to it and you'll figure it out soon enough.

have fun with it, you'll have tuning down in no time.