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Thread: No power after rebuilding 18RG engine

  1. #1
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    Question No power after rebuilding 18RG engine

    Hi guys, Im newby and not a mechanic, also i can not do necessary repairs or measurements my self too. The only thing I have is a love for my 76 Celica RA28 :-)

    Originally I had a 18R engine in the car, but let it swap to an 18RG which was available in the guy who sold it also rebuilds it for me and installed it as well.
    Unfortunately, I feel that the car does not have the expected power/torque and really does not pull. It has poor power all over rev, 1 st and 2nd gear rpm goes up fluently, engine screams but no pull really. in 3rd and 4 th gear low end is good, but when flooring it has power gap around 3000rpm till 4500. The guy is located in Germany and i live to far away to bring the car to him again for checking. Also i do not have that much trust in the guy meanwhile.

    The oem 40 Mikuni Carbs are serviced with a complete overhaul set. Im wondering whether probably the jetting can be the issue?!

    The jetting is as follows:
    Main Jet 145,
    Main Air 170,
    Pilot Jet 60,
    Pilot Air 180,
    Outter Venturi 34,
    inner Venturi 10,
    Pump Jet 50

    Igniton Timing: 10 degrees Btdc.

    Only external upgrade is a 4-2-1 header with a Sebring rear muffler from a professional header mechanic.

    Should I experiment with different Jets first to overcome the power issue? Your replies and suggestions are very much appreciated.

    Regards, Sergi
    Last edited by OSS117; 18-07-2021 at 05:17 AM.

  2. #2
    Junior Member Automotive Encyclopaedia
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    Default Re: No power after rebuilding 18RG engine

    What's the compression, what do the plugs look like?
    How do you know it's 10 degrees?
    Is idling horribly, missing, surging, no load RPM increase have big gaps & jumps & not progressive/smooth, exhaust smell worse then sticking your nose into the tank's filler, blowing black smoke: Don't F with jetting?

    Cam and/or ignition timing.
    Good luck.
    'I've scrapped better.' John stated when asked about the car by the guy with the silver tipped cowboy boots!

  3. #3
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    Default Re: No power after rebuilding 18RG engine

    Hi,
    Did not check the compression so far, car runs rich as well, I know because i let the emissions check by and independent touring club.
    The CO value is 5.8%, should be around 2-3% I read and the HC measured too and that showed around 700. I therefore do not think that the plugs will show more then dark black signs, but will pull them out soon. They also measured ignition timing there. It showed 10deg with vac at 980-990 rpm and 10.7 without vac. I saw different manuals where in one says 5 degrees in another around 12 for the 18RG.

    Idling is lil to high as mentioned, but no jumps. When driving with constant mileage in 3rd gear you can feel slight surgings. No black or white smoke, but exhaust smells as described by you.

    i also suspect the clutch slave cylinder playing a part within. I changed it a little while ago after i saw it dropping, but it was not oem Toyota part and the mechs said the day had to adapt the guide pin to fit, since then, also effected my 18R back in days, the clutch pedal never felt like before. Its quite hard to press the pedal, it goes to early and from 1 to 2nd gear the release feels strange, not slipping but strange. I already ordered a new one, which should be available the next days.

    I finally talked to the guy who made the swap today and he was asking me whether i switched to electronic ignition module, which you fit into the existing dizzy. I said no, i thought thats a goodie for future tuning if necessary. Now i found out the the cap, rotor and contact points are not new as supposed to. So i do that first, but im still not sure how much degrees needed btdc, 5 or 12? After that im going to adjust the carbs again and check compression and plugs.

    Sergi

  4. #4
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    Default Re: No power after rebuilding 18RG engine

    Hi guys, picked up my RA28 today and pulls quite good now! Carbs synced, new jets main air 180, main jet bored a little idle jet 65. No stumbling at all, pull from 2500 quite good, after 3300 rpm quite fast and strong, also ignition timing adjusted to 5 deg with electronic ignition module change to http://e-spark.eu/en/. Looks like that new 421 handmade extractor takes a little from down low my mech said. that can be regulated by new cams he adviced with minor bypass drills at the carbs he suggested. But thats the winter project. Im wondering to what specs I need to regrind my cams to gain more torque down low, or can I buy some directly? Looking forward to your replies. Thanks for your help so far and many greetings from Vienna.

    Sergi

  5. #5
    Junior Member Backyard Mechanic
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    Default Re: No power after rebuilding 18RG engine

    Quote Originally Posted by OSS117 View Post
    . Im wondering to what specs I need to regrind my cams to gain more torque down low, or can I buy some directly? Looking forward to your replies. Thanks for your help so far and many greetings from Vienna. Sergi


    For reference Only: This was an advertisement for the cam degrees once offered by HKS back in the day. Left side mild grind - Right side race grinds once offered.

  6. #6
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    Default Re: No power after rebuilding 18RG engine

    Generally manufacturers make a car with max torque low down to make it easy for town driving. Grinding more duration into the cams gives more power at higher rpm, but at the expense of low-end power. So adding more duration will give you better power at 6000rpm, but less under 3000. Keep it under 270deg.

    You could cut more lift into the cams, but you will need to check carefully that you retain piston to valve clearance. The killer is having the piston hit the inlet valve as it opens on the start of the inlet stroke. Grinding the base off the cam will also make tappet gaps difficult, so you have plenty of research to do.

  7. #7
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    Default Re: No power after rebuilding 18RG engine

    I see, thank you for the details and the HKS cam sheet. I read in different posts in this forum, that the 304/288 cams offered in TRD catalogue, should increase power strong from 2500 to 6500 and are highly recommended. These are what my engine engineer recommended too. He also talked about adapting valves, pistons and adjustable timing chain. He builds racing engines for Motorsport purposes. Its hard for me to follow his explanations, because im not expert at all. Im not sure, whether the expenses are worth it really. 1200 the cams, 6-7 hundred the Webers, and so on, this can reach approx to 5-6k Euros I think. Thanks for sharing your experiences with this or similar set up in advance.
    Last edited by OSS117; 01-08-2021 at 10:33 PM.

  8. #8
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    Default Re: No power after rebuilding 18RG engine

    https://buyee.jp/item/search/query/18rg?searchHis=1
    http://www.kameariengineworks.co.jp/

    Look at another source for these parts available. Straight from the source, You can see the prices, if you can find the pages.

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    Thumbs up Re: No power after rebuilding 18RG engine

    Quote Originally Posted by 73GTV View Post
    https://buyee.jp/item/search/query/18rg?searchHis=1
    http://www.kameariengineworks.co.jp/

    Look at another source for these parts available. Straight from the source, You can see the prices, if you can find the pages.
    Thank you for the links! Could not find them so far unfortunately, but I wrote an Email request. Somehow or other the engine work allone will be expensive I think. Not and easy swap, plug and play thing as you already mentioned above. My engineer suggested to dyno the car next Friday on the street first of all. He needs to check the actual outputs first to be able to calculate the possible power outputs and and all work what needs to be done he said. The portable Dyno will be mounted directly on the rear wheel. Like this https://www.youtube.com/watch?v=fBBP...nel=WSTRgarage
    I will post current power and torque graphs next weekend.

  10. #10
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    Default Re: No power after rebuilding 18RG engine

    Quote Originally Posted by OSS117 View Post
    Thank you for the links! Could not find them so far unfortunately,[/url]
    http://www.kameariengineworks.co.jp/CONTENTS-2.html
    Pages 45 and 46

    The index is in both Japanese and English, don't people read anymore!

  11. #11
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    Default Re: No power after rebuilding 18RG engine

    Quote Originally Posted by 73GTV View Post
    http://www.kameariengineworks.co.jp/CONTENTS-2.html
    Pages 45 and 46

    The index is in both Japanese and English, don't people read anymore!
    Yes, yes thanks I found that 2 pages already, but cams are not listed as far as i see, valves, springs, chainset, overhaulkit yes, but cams?

  12. #12
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    Default Re: No power after rebuilding 18RG engine

    https://www.kelfordcams.com/global/camshafts/toyota
    http://toyheadauto.com/PerformancePages/18RG_Parts.html

    They once offered cams or will be worth an inquiry. I gave you Yahoo Japan so you could search for out of production items like the rest of us do. This is a hunt and here are the hunting grounds worthy of only those motivated to find those lost gems. These are the places that I found mine! Can you now find your own?

    Yahoo japan where you can find used cams that can be used for regrinds cams. Since they are not making any more new cams for this engine, picking up a few pair of stock cams and contacting Kelford would be the direction that I would have gone... (Or a Cam grinding service near you) (Just realized that you are not local) Hint Hint!!

    https://buyee.jp/item/yahoo/auction/...search_suggest
    Last edited by 73GTV; 05-08-2021 at 04:27 AM.

  13. #13
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    Default Re: No power after rebuilding 18RG engine

    Thank you for the sources really. Will get in touch with Kelford. Toyhead do not have cams available at the moment, i was in touch with Rick as well. Im going to ask where my mech got those he already offered me.

  14. #14
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    Default Re: No power after rebuilding 18RG engine

    Quote Originally Posted by 73GTV View Post
    https://www.kelfordcams.com/global/camshafts/toyota
    http://toyheadauto.com/PerformancePages/18RG_Parts.html

    They once offered cams or will be worth an inquiry. I gave you Yahoo Japan so you could search for out of production items like the rest of us do. This is a hunt and here are the hunting grounds worthy of only those motivated to find those lost gems. These are the places that I found mine! Can you now find your own?

    Yahoo japan where you can find used cams that can be used for regrinds cams. Since they are not making any more new cams for this engine, picking up a few pair of stock cams and contacting Kelford would be the direction that I would have gone... (Or a Cam grinding service near you) (Just realized that you are not local) Hint Hint!!

    https://buyee.jp/item/yahoo/auction/...search_suggest
    These cams just appeared and there are 6 days left in this auction.

    Inquire with Buyee about lifting the restriction since the current price is less than $50.00 US on this item.

  15. #15
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    Default Re: No power after rebuilding 18RG engine

    oh thanks for the info, but they seem to be the least aggressive i suppose, although I really do not know what duration lift they have. Somebody knows? http://www.retrojdm.com/Files/18R-G_Cheat_Sheet.pdf

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