18RG Tuning help required

[fletty999]

Hello Toymods,

Long time reader, first time poster. I have a ra28 celica with an 18RG with the following specs that Im having a couple of issues tuning:

18RGU

- 88250 Head with stock Cams and Valves
- Refurbished block with possibly the last set of stock pistons on the planet
- standard bore, top of pistons milled down slightly to give around 9.7 compression ratio
- standard intake, cast exhaust manifold
- Mikuni Solex Carbies with:
- 140 air
- 135 mains
- 63.8 pilot
- 32 venturi
- 35 pump
- 1 hole from bottom on pump stroke

- MSD 6AL2 programmable ignition mapped at 12deg up to 1500rpm with straight line to 37deg at 7000rpm
- vacuum advance connected


First issue is that I am reading the green Toyota 18rg book and it says that I should be getting 330mm/hg vacuum at idle from each of the two manifold connections, but I'm only getting about 150mmish.

Second issue is that the engine bogs down when coming off idle slightly, and it bogs hard when you jump on the accelerator like its flooding. I have changed the holes on the pump stroke on both the carbies which helps but it is still doing it.

Third issue is that I have kind of taken an educated guess with the MSD timing map, as I just took the 12deg idle timing from the manual, and then added the 25degrees that were stamped on the dizzy weights, but the dizzy was converted to electronic, so the weights may not be from this motor.

Fourth issue is that the car chews through petrol like crazy!


Can anyone help with some advice here?


Thanks,
Fletty999

[Rens]

Have you balanced the carbies and checked that the venturies aren't wiggling loose?

Mine need checking every 6 months or so

[Celica RA45]

std 18rg had 170 airs and 145 mains with 34mm chokes from memory with 57.5 pumps or 60 pumps .yours sounds out of wack

[fletty999]

std 18rg had 170 airs and 145 mains with 34mm chokes from memory with 57.5 pumps or 60 pumps .yours sounds out of wack

I checked this website:

http://www.rmcarburetors.net/Tuning%20Tips.htm

and the table for the type T seems pretty similar to what I have. Where did you find that jetting for a standard 18rg Celica RA45?

I will double check the numbers on the venturis to see if that is the cause of the low vacuum.

[73GTV]

Rebuild your carbs, the metering block is what is a major problem with these carbs since they are the lowest point within the fuel system. Dirt and crap fill the tiny passages.

[fletty999]

Carbies have been rebuilt, I had an issue with the non return valve (little ball getting stuck) in the pump circuit in the parts you have pictured but that's all fixed now.

How do you check the float level with these carbs? In the manual theres a special tube tool that you stick down the jet block hole while the car is running, but theres no chance of finding one of those tools anymore.

Has anyone made one?

[73GTV]

Carbies have been rebuilt, I had an issue with the non return valve (little ball getting stuck) in the pump circuit in the parts you have pictured but that's all fixed now.

How do you check the float level with these carbs? In the manual theres a special tube tool that you stick down the jet block hole while the car is running, but theres no chance of finding one of those tools anymore.

Has anyone made one?

here is the part number:

[fletty999]

here is the part number:

Thanks 73GTV do you own that tool? I know the part number from the 18r manual, but it doesn't really help unless you know where I can buy one!

If you own it, could you take some measurements from it so I can make one?

[73GTV]

Thanks 73GTV do you own that tool? I know the part number from the 18r manual, but it doesn't really help unless you know where I can buy one!

If you own it, could you take some measurements from it so I can make one?

you could make this with a straw a large o-ring and a magic marker, it is just used to reference your fuel level height which you can check between each carburetor. The O-ring adjusts the depth and you can mark the level. Too easy, what you really needed while rebuilding was this setup.

[fletty999]

73GTV does the metal ring on the outside of thee tube move?

If not could you please give me the length of the tube and the distance from one end to the metal ring? and the thickness and diameter of the ring?

You not only use it to check the float levels between the carbs, but you use it to check the distance between top of the main jet hole in the carb body and the fuel level in the bowl, which should match the distance in the 18r book.

[73GTV]

73GTV does the metal ring on the outside of thee tube move?

If not could you please give me the length of the tube and the distance from one end to the metal ring? and the thickness and diameter of the ring?

You not only use it to check the float levels between the carbs, but you use it to check the distance between top of the main jet hole in the carb body and the fuel level in the bowl, which should match the distance in the 18r book.

No the ring was glued in place and this tool is packed away, the photos are from a while ago when a friend asked the same questions about OEM tools, I have a travel job and I'm away from my stuff, will get back to you when I return back there. That is why I suggested the straw and o-ring, figuring that you would try it, mark your results and check the second carb to compare the fuel level. This would have allowed me some time to return home, dig thru my tools and post the size. Heck, I purchased these tools back in 1983 so...

Hey, it is only a thin glass tube with a thick metal washer glued to the tube with two small marks less than ten mm from the end of the tube if memory serves me correctly and each mark was an estimated 3 mm apart. best that I can do from here, Good Luck.

[fletty999]

Hey 73GTV have you managed to measure the length to the o ring on that tool?

Any help would be greatly appreciated!

[73GTV]

Hey 73GTV have you managed to measure the length to the o ring on that tool?

Any help would be greatly appreciated!

Sorry but I am currently on the road miles away from my stuff, so No! Kind of working up until Xmas eve before I get back to my area. You have to have fixed this problem by now, what is your delay other than trying what I originally suggested? In 30 years I have used this once because after I saw what it was used for, I adjusted my floats and went on my way...OEM tools are great as a reference, however the average mechanic always find the proper work around...