The JDM collection grows... and Dixie has some competition for my time.

toopy

Club Member
It depends on the variant - 18RGs aren't homogenous as there are several versions as the applications and smog/emissions requirements evolved, and compression ratios were lowered with time. The early versions that are just called 18RG have 9.7:1 comp and run 140bhp on the Mikuni/Solex 40s. 18RGR - 9.2:1, 130bhp with air injection and EGR. 18RGRU and 18RGU, increasingly complex smog gear, non-rebuildable carbs, and power down to 125 and 120hp respectively. 18RGEU - 8.7:1, fuel injection, 120hp.

Basically, plan on rebuilding the engine and sprinkling fairy dust on it in the process! For example, my planned build will be:
Boring out to 2.2L, 92mm pistons (standards are 89)
High (11:1) comp pistons (RG heads can only be skimmed 1mm tops, so refacing is probably best and bump things with piston design and head gasket)
Rally cams, big valves, high rpm springs
Port job on the head (the one I've got is a Yamaha-made 18RGU head). The casting is really nice and will port very easily. The head has had new valve seats at some point which could be oversize as the ports at the seat end have been throat cut a few mil past the seats. This makes it perfect for blending the porting into those machined areas. There isn't much that can be done on the chambers as they are very smooth and bowl-like from the outset, just a bling polishing job.
Kameari valve guides to go with the port job and trimming to the guide bosses (similar to what I did to that Kameari SPL-style N42 head I'm making for Dixie).
44-45 carbs on Kameari/Harada intake with cable throttle.
Tubular manifold - I intend to have JP make one based on the TRD design for these cars; I have a copy of a TRD manifold for the 1600cc 2TG engine that can be used as a sample. It doesn't fit the 18RG, but the basic design is the same, so the aim will be something similar in appearance but with the right flange and bigger primary tubes.

In general, that and other related tweaks should get power up into the 160-180hp range. Which will be fine for what I want with the car, given it weighs 200kg less than a Z!

Of course, if you want 130-150ish, you don't need to go that far, just bigger carbs, maybe cams, etc.

I have to say Rich, the amount of research you put into these projects and the subsequent work that follows is pretty inspiring, i wish had the money, time and inclination to follow suit! :D
 

richiep

Club Member
I have to say Rich, the amount of research you put into these projects and the subsequent work that follows is pretty inspiring, i wish had the money, time and inclination to follow suit! :D
I like to know what I’m letting myself into! On the money front, I probably need to slow down. The credit card balance is now making me wince.
 

Col-b

Club Member
Hi Richie i just checked my engine although its a 1975 it the 18RGU so less power any tips on getting more power without changing cams etc would be appreciated :conf2:
 

richiep

Club Member
Hi Richie i just checked my engine although its a 1975 it the 18RGU so less power any tips on getting more power without changing cams etc would be appreciated :conf2:
Without opening the engine up, it's pretty much exhaust and carbs - a tubular manifold and suitable exhaust, and swap the Mikuni 40s that come as standard for 44s or similar (Dellorto/Weber/OER 45s, etc.). Also, you may have the non-rebuildable carbs, so tuning them for power is a no-go. You could track down some of the earlier ones if that's the case so that re-jetting, etc. can be done.

From what I can make out from my research so far, the pistons are the main tool for controlling compression and thus much of the power potential in these engines. The RG heads are not suitable for major skimming like L-series heads can be. 1mm is apparently the absolute max. I presume with the twin chain setup, things are much more sensitive in terms of chain tension, and messing with head thickness could be more risky. The higher compression piston options are domed beasts that come up into the chambers, with big valve reliefs. That's how you get into the 11:1s, etc.

The twin cam head I have for my build is a Yamaha RGU version. I think they may have a deeper chamber, which might contribute to the lower compression. It will be interesting to see what I can do with a bit of playing around with it. Bigger valves apparently make a big difference, and as mentioned before, it looks like its had new oversize seats put in, given the step in the "throat cut" in the top of the port below the seat.

Also, see what smog crap you have on the engine - recirc valves, carbon canister, etc. A lot of that could be done away with probably.
 

Col-b

Club Member
Cheers Rich i will do. I have Solex carbs can these be tuned and can i do away with the standard air filter by adding carb trumpets for more air ? and as you said there seems to be a lot of smog crap on the engine
 

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Col-b

Club Member
To be honest i would not know where to start and knowing what was smog control will check you tube etc
 

richiep

Club Member
Those are the non-rebuildable Mikuni-Solex carbs. Tops are different to the tuneable ones. The emissions stuff is that spaghetti of hoses and valves around the place. You’d need to do some research too with respect to what you can get away with removing. This is probably the advantage I’ve got - because I’m building an 18RG, it will be bare bones - nothing there that strictly doesn’t need to be. The RA25 is also a simpler car than the 28, so less ‘stuff’ in the bay overall! That might help you further down the line because then I’ll know what it will run with and what you don’t need!
 

richiep

Club Member
Little update on this non-Z topic - had a fun delivery today:
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You think 89mm L-series stroker pistons are big. Try these 92mm mothers!
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Kameari 2.2L big bore pistons, 11:1 compression.

Project Twin Cam continues to gain momentum, although the car is still stranded waiting for the DVLA to issue a reg after I forgot to put the cheque in when I sent the V55 off the first time...
 

Col-b

Club Member
Looking good Richie have you had any luck sourcing a full s/s exhaust yet i will have one too maybe we can get a deal on two.

thanks

Col
 

Col-b

Club Member
Hi Richie just a quick catch up i removed all the old smog stuff and had a new s/s exhaust and manifold fitted runs much better now ! Hows your Celica coming along ?

Colin
 

richiep

Club Member
All good with the Celica Colin. Mostly just been enjoying using it when I can:
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Fitted Hero Shuttle Racing wheels and replaced the original metal front valance with a FRP replica and added a chin spoiler to that. Painted them myself and they came out great. Had to have a custom Lechler colour match done though as the mint green shade of white that the car was resprayed to in Japan is a tinted mix based on the original 023 white rather than the factory shade.

Had a stainless exhaust system made and fitted by JP Exhausts in Congleton, Cheshire. Very pleased; plus they made it so that it can be easily adapted to fit the 18RG when the single cam comes out.

18RG still a project in waiting. I have a complete engine sitting in the garage awaiting tear-down. I have however got a second head that I’ve done the port and polish work on that is finished. A set of Cat Cams rally spec cams will be going in it.
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Hopefully will do some engine building during the winter, although I’m trying to get the Z project ready for final paint first.

I have also made a stainless steel custom linkage setup that fits onto the factory intake manifold (which I have port matched) that is based on the linkage style fitted to the Harada manifolds available. Like my Z, it will feature a cable throttle setup.
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Col-b

Club Member
All good with the Celica Colin. Mostly just been enjoying using it when I can:
View attachment 53703
Fitted Hero Shuttle Racing wheels and replaced the original metal front valance with a FRP replica and added a chin spoiler to that. Painted them myself and they came out great. Had to have a custom Lechler colour match done though as the mint green shade of white that the car was resprayed to in Japan is a tinted mix based on the original 023 white rather than the factory shade.

Had a stainless exhaust system made and fitted by JP Exhausts in Congleton, Cheshire. Very pleased; plus they made it so that it can be easily adapted to fit the 18RG when the single cam comes out.

18RG still a project in waiting. I have a complete engine sitting in the garage awaiting tear-down. I have however got a second head that I’ve done the port and polish work on that is finished. A set of Cat Cams rally spec cams will be going in it.
View attachment 53704
View attachment 53705
View attachment 53706
Hopefully will do some engine building during the winter, although I’m trying to get the Z project ready for final paint first.

I have also made a stainless steel custom linkage setup that fits onto the factory intake manifold (which I have port matched) that is based on the linkage style fitted to the Harada manifolds available. Like my Z, it will feature a cable throttle setup.
View attachment 53707View attachment 53708
Looking good Richie lots of work done !
 
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