18RC MAXIMUM PERFORMANCE!!

Discussion in 'Engine/Drivetrain' started by Bottle, Dec 12, 2017.

  1. Bottle

    Bottle Member

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    Hey guys, so I both wanted to post what i have found both on other forums and here as well as making phone calls to shops and asking friends performance wise for the 18RC as well as you guys what else you know of that could help these old misunderstood motors make power. I do not claim to have discovered all this myself and some information may be wrong. I would cite where and who i got info from regarding forums, but i really don't remember, i just wanted all the info in one place. Anything helps! Attached are some pictures of my current mods that i did recently.

    Head:
    So obviously you can port and polish the heads and manifolds, there seems to be a lot to gain here as they aren't the greatest castings and the runner designs seem to be crap, in the exhaust side there is a bit of a large dent in the roof of the runner that could be filled in. There is a sharp 90 degree turn in the bowl in each runner that could be smoothed out by raising the roof. The runners are also extremely rough from the casting and also have a decent amount of material that can be removed to match the manifold gasket (Factory intake and exhaust manifolds are more or less the same in this regard. I myself have have smoothed out and opened the runners of all 3 to match my gasket, but in the rebuild, i found that my new metal gasket (which came in an old, original 1971 complete gasket kit ordered of rockauto labeled for an 8RC) had smaller port openings than the one that i removed by a large amount. furthermore, they were made of a different material, at least they seemed that way. Possibly a difference between the 8RC and 18RC gaskets. Also, the head can be decked by quite a bit to bump up the compression ratio, but i have not done this yet as i don't have a way to correct the cam timing yet. The combustion chamber is football shaped on the 18RC head and seems to have room between the valves on the opposite side of the spark plug to weld in more material and further bump the compression ratio up. I have heard the 8RC is a direct bolt on and has a higher compression ratio due to combustion chamber design as well as non hardened valve seats, but i do not have one so cannot confirm any differences.

    Camshaft and Valvetrain:
    I have found a couple sites that offer camshafts and regrinds

    http://www.webcamshafts.com/
    Located in Riverside, CA, (30 mins away from me) Web Cam has 2 regrind options if you call in for the 18RC, one mild and one more aggressive, both will run you in the 140 dollar price range. They also do hard welding and with that, can maintain your base circle while providing any lift and duration you want, but will run you in the 500 dollar price range. The lady here also seems very knowledgeable about cam profiles.

    http://www.iskycams.com/cart/?main_...sort=20a&categoryId=14&categoryName=CAMSHAFTS
    Located in Gardena, CA (also close to home), is Iskys. They offer 3 different cams for the 18RC from mild to aggressive, and are all new cams with factory diameter base circles (i plan on getting the most aggressive one) each one for 250 dollars Also, after calling in, i was told they also offer inner springs that can run 8000 rpm reliably with their cams for around 140 dollars. (i plan on getting these as well as my goal is to run 8k reliably)

    I do not know of any aftermarket adjustable cam gears, but from looking at the factory one, it looks like slotting all the holes at a machine shop would be easy work. Ill have to do this if i plan on decking my head anymore to correct the timing. I can't find any aftermarket tappets either which is a shame because i'm sure they would increase the rpm limit a bit if they were aluminum. Hopefully someone knows someone that could rig something custom up. I don't know if you could do bigger valves on the 18RC, the valves seem really close to each other in the chamber.

    Intake and Carb:

    I'm sure everyone know how crappy the stock carbs on these are. I currently have a 32/36 down draft weber and adapter which i think i got from here: http://www.jameng.com/products/1971%2d1981-Toyota-Weber-32{47}36-Elec-choke-Conversion-Kit-8RC-and-18RC.html but they are all over online with various different weber carbs, and use existing linkage and manifold, so its easy to bolt on. They also run great out the box with minimal tuning (probably your best bang for your buck). Also i have the Cannon (happens to also be my last name, ha) manifold for dual weber side drafts or mikunis, but i dont have the carbs yet. I don't know where or if you can find that online new, i got lucky and a canadian sent me one for free for the cost of shipping (cool guy). Also, there is a single weber side draft kit you can get new here http://www.jameng.com/products/1971%2d1981-Toyota-Weber-40-DCOE-Kit-for-8RC-and-18RC.html and somewhere i have also seen a similar single manifold with the carb offset to the front (not sure on any performance difference). Also, a friend of mine and i have been designing a filter tube/adapter to mount on the 32/36 carb to increase intake velocity and run whatever intake tubing or cone filter you want, he has a 3d printer and is making proto types as well as other parts for various toyota motors.

    Exhaust:

    The factory header looks like it was designed by a shoe and is very restrictive as well as heats the factory intake manifold for some dumb reason, but headers seemed hard to find, but I see plenty available in Australia due to the motor being more common there (around 260 usd not shipped), and after messaging a few on ebay, they offered to ship to California for an extra cost. I think this was the guy https://www.ebay.com/itm/TOYOTA-CEL...RC-HURRICANE-HEADERS-EXTRACTORS-/262724291225 But before i baught them i heard on some forum that Kirks Racing makes some but i have to call in. Sure enough they charge 250 for the 'longtube?' header designed for a celica before shipping but they are made to order and were backed up for a month. I ordered one and it should be here any day now and then ill post some pics. Hopefully they fit!

    Block:

    Here, i don't really know much of whats available other than the standard machine shop expensive hi-comp pistons with gas-vents and loose piston rings, windage tray, and lightening and knife-edging the crankshaft, as well as lightening the fly wheel. Anyone know if there are aftermarket rods, or if another bottom end bolts up? What about a stroker crank and rods? Is the 18rg bottom end swappable, and are there benefits? Are there aftermarket flywheels? Can be over bore the cylinders?

    Ignition:

    I have heard that the distributor could be upgrades to magnetic points? I think with parts from a 3TC distributor and coil, but I'm not sure exactly.

    Transmission:

    I don't know about you, but i have that crappy 4 speed transmission and desperately want a 5 speed. Does any 5speed directly bolt on?

    Well that's about all i got at the moment, sorry its not the most organized, ha. I hope someone has something to add, i'm excited to see what kinda power we can get from these even if its not crazy.

    *side note, anyone know where to get camshaft bearings? cant find em anywhere, rock auto shows they have some, but the part number is different so i'm scared to order them, already bought some off ebay, but what showed up wasn't them, lol.
     

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    Last edited: Dec 13, 2017
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  2. Bottle

    Bottle Member

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    Update* Just got a message that a large package just arrived, most likely the headers. Ill find out tomorrow night and post pics if it is.
     
  3. Bottle

    Bottle Member

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    Learned how to resized pictures so here's one of the Cannon manifold. I can post more pics if requested.
     

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  4. Jesseh

    Jesseh Newbie

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    I’m stoked to find out about this thread. I just picked up an extra 18rc motor locally just for the intake and header that it had (man alive that Australian shipping cost!) and now I have an idea of what to do with the rest of a 18rc.
    Thanks!
     
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  5. Bottle

    Bottle Member

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    Here is the header from kirks racing. While it was cheap, it kinda shows. 4 into 1 design. Had to grind away a bit on the flange so it would fit with the intake, probly will have to take it off later to grind some more. 3 inch collector. Its made for celicas l, so it hits our frame rails, i had to pay a hefty price for it to be fitted. Asked the shop for 2 inch pipe with a mandrel bend and a magnaflow and i got 3 inch, lol and they didn't go to the point i asked. Oh well, glad it was finished in a day and it sounds amazing! Havent tuned it yet, but there is definitly more low end torque, i can burnout for quite a bit now. Dont notice much on the high end, but i havent been able to rev past 6k due to my distributor not upgraded yet. Cant wait to tune it and see what i really have.
     

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  6. Brennan

    Brennan Newbie

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    Hi I’ve got some Weber carburetor questions I can’t figure out how to make my own post
     
  7. Brennan

    Brennan Newbie

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    Specifically some linkage questions I have a Weber kit that’s missing linkage
     
  8. Bottle

    Bottle Member

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  9. Ross McCredy

    Ross McCredy Newbie

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    HI! This is great info, I'm currently trying to replace my Aisan carb on my 18-rc engine, but am not sure which Weber Carb to get that will fit, is it the model K744? Is there an adapter? The links you sent don't work anymore. ANy info would be awesome!
     
  10. Liquidhandwash

    Liquidhandwash Enthusiast

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  11. fred heath

    fred heath Veteran

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    Check with “Weber carbs direct”. They sell carbs with necessary mounting plates.
     
  12. sirdeuce

    sirdeuce Member

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    Headers. Heat and bend, done that before. Go to the muffler shop and have them use the bibbest rosebud they have and heat all the tubes in a strategic area and then gently bend the headers to clear.

    Head porting? the biggest restriction really is the manifold, but if you can afford to send it to Extrudehone to open it up. I've not seen an aftermarket manifold for an 18RC. Then, for the head, light smooth the port floor and raise the roof. Going carby needs a little roughness on the floor to keep the fuel from adhering. Raising the roof will allow a better mass flow. then do the typical pocket work and valve grind. Valve size can be increased, but anything more than a mm over is overkill with a single downdraft carb. Open the exhaust to the diameter of the header primary pipes and taper that to the valves. Unshroud the valves and poish the combustion chambers to a mirror finish, don't ceramic coat the head.

    Carb.
    I found the Aisin from a 20R with mods did as well as a Weber 32/36 with a few mods, but you gotta know what you're doing there. If you are staying with the single carb a Weber 38/38DGES does better than the 32/36. If you have the funds go side draft carbs and do more work on the head. Put an insulating plate and fabric under the air filter assy. to keep the exhaust heat from the intake, duct cool air to the filter.

    Cam.
    I had a cam from a place called "The Toy Store" that went belly up decades ago that had a 280 duration and I think a 410 lift that was more streetable than it might sound. It had mild ramps so it could run with just about any spring. Best cam I ran was a split 272/268 grind with .380 lift, lift at .05" was not listed on the specs. It did real good with a single carb. For adjusting the cam timing can be accomplished with offset dowels, unless you really want to make an adjustable set like you mentioned.

    Use a basalt sheet between the exhaus mani and intake mani to attemp reducing the intake mani temp. Try ducting air for cooling as well. Use an insulating fabric on the fuel line to keep the fuel from boilng. One of the secrets to getting anything out of this engine is cooling the intake as much as possible.

    Compression ratio.
    Keep it low, max 9.5 to 1. Keep your quench tight. At 9.5 comp and a tight , .032" you can get by with low octane fuel with a good timing curve and fuel mix.

    Pistons.
    Use a good hyperutectic piston and ceramic coat the head. Forged pistons are a bit of overkill. The hyper pistons will have a tighter clearance which will help with what you can get from this build. Total seal rings will reduce the blow-by.

    Get a light weight flywheel.

    Get a good machine shop and balance everthing.

    Do all that and you can expect 145-155 HP with a single carb. Or you can slap in an 18RG for about the same cost and have about the same. A 20R head on a 22R block build can get about the same and still be a bolt in. A 5/7MGE can be a little challenge but still fits easily enough while still having aftermarket carbs available. Then there's my fave, 4/7AGE. Those are the easy swaps that stay Toyota.

    Try looking at "Toyhead Auto", they have some parts for the 18RC. Toysport, if they are still there, has a bit as well.
     

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