Big Uno's R26 Project / Engine Build

Discussion in 'Megane Projects' started by Big Uno, Oct 28, 2017.

  1. Big Uno

    Big Uno RSM Trader

    Hi All, I am new here and starting this thread following my latest project.

    To cut a long story short I have decided to buy another R26 in the near future, however ended up pre-buying a 225 engine to rebuild prior to buying the car it will power.

    Long term I am looking to build the car for weekend road use and hopefully track. As for power figures I have no real goal but am definitely aiming well above the 300hp mark.

    I will be doing as much of the work as possible myself, as this is something I have been meaning to do for a while now.
    Any constructive critisism, input or general interest is welcomed, would love to hear what people think.
    Will try to keep posting with progress, can take photos or add more info for anyone.

    Started with stripping the engine down, made use of some good weather and decided to work outside while using degreaser. The cylinder head and block turned out to be in great order with no scoring or detonation damage. Sent the block to be bored and washed, and also to remove and check the oil squirters during boring. Boring oversize and check clearence for 83mm Wossner forged pistons.


    Crank showed some very minor surface markings, so sent for polish not needing regrind.

    Will now begin headwork while waiting for block and crank to come back so more to follow.
    matt e likes this.
  2. Big Uno

    Big Uno RSM Trader

    Started removing casting marks from the pots, the stock head is quite rough and took me ALOT of time to get all four roughed out.


    Following roughing I decided to get them semi-polished, ready for a cc check which I will need to do later.


    All four part finished!


    Next I started removing the step left from machining the intake side from the factory, its hard to get a photo of but at the top of the port in the photo below is a angle. Ground these back to create a smooth radius. Left port stock, right port roughed out.



    Next I removed the steps again left from machinimg the ports on the radius into the cylinder head. Left is semi poliished right is roughed out.


    Next to bring the inlet splits to a knife edge, again they are pretty rough and round from the factory, alot of time taken to get all 4 straight and even.

    Here is the rough cuts done.


    More to follow once I get the polishing complete.
    ianplymouth likes this.
  3. ianplymouth

    ianplymouth RSM Club Member

    Great going there mate, going to sort my head out when i get it back from being repaired, dropping a valve at about 6200 rpm doesn't leave the head in a good shape

    Also now going down the forged route and i am upgrading the valves and springs as apparently it's a problem with them breaking.
    Big Uno likes this.
  4. Big Uno

    Big Uno RSM Trader

    Yikes thats the exact reason I am going with single piece valves, not too sure about what the stock springs are rated to? In theory unless your lifting the rev range or valve lift standard springs should do fine?

    As bad as it looks that head is probably savable! Let me know if you need any help with it in any way!
    What is it from the N/A F4R??
  5. ianplymouth

    ianplymouth RSM Club Member

    I have ordered a set of Supertec valves, looking for some uprated springs to go with them, as from what i have been told the springs aren't really man enough for the job, they recon the valves have been bouncing and touching at high revs, not totally convinced on that though, but changing just in case.
    what valves are you going to use ?????

    The head is in Cornwall at the moment being repaired, the guy took one look at it and said no problem :sunglasses:

    This is a f4r 874 engine, from a 250 mk3 Megane, yes i thought it was going to be stronger than the 225 it replaced :openmouth:
  6. Big Uno

    Big Uno RSM Trader

    Im going for supertech also, inconel exhaust, not sure about sizes yet as I cannot find any info on the benefits of oversized valves with this engine and forced induction??

    Pretty sure supertech do make various springs, single and double I believe? Cant be a bad thing changing them but what type for depends what your plan is with the engine :smilingimp: I have no plans to lift my rev range above stock but it can be done.

    I guess any engine is only as strong as its weakest point, are the 250 valves also 2 piece? Never seen the internals so cannot comment on them. Have you looked at rebuilding the bottom end yet? How bas was the piston and bottom end in yours?
  7. ianplymouth

    ianplymouth RSM Club Member

    I have ordered the bigger ones, the guy is also going to polish and port the head for me while he has it, i will only be going for stronger single springs £500 + for double valve springs is a bit strong, not sure on changing the cams yet cant find any info on the possible gains and at nearly £1k i would prefer to put that to a hybrid turbo.
    I think the standard 250 valves are 2 piece.

    I think i can polish up the piston :laughing: IMG_20171019_153108_zpsbgx39och.jpg

    So i will also be going forged, need to go oversized as it has damaged the cylinder wall slightly.

    I really only use the car for track days, but i do drive it there and hopefully home as well not happened the last two times :openmouth:
  8. Big Uno

    Big Uno RSM Trader

    Will be interesting to see what power you get, I really need to look into the valve sizes and lift also, again like you I am not certain the gain from cams is worth the money or losing bottom end power either although for track use thats not really an issue.

    Reckon you could use a balance too with the polish

    I still have a lot to think about and research to do, mainly the turbo as I want bigger than a hybrid but it will likely bring other problems such as fuel pump, feed, and also injector sizes along with everything else. My priority for now is to get the engine built and ready, then get the car. Luckily I have no timescale
  9. ianplymouth

    ianplymouth RSM Club Member

    I am not going for an all out power engine i am to old for that :laughing: the set up i had before was great, a great spread of torque from about 2.5 k rpm right through to the limiter, running 320 hp and 340 lbs torque, standard 250 engine and turbo with decat and 630cc injectors, i was happy with that setup till it dropped the valve, so now will get the bits in and then see what it will give me.
    I thought about balancing the crank but for me there isn't anyone close, so i would have to send it away to someone i don't know.
    I think i might have the turbo sorted just need to speak again with the person responsible.
    I have already uprated the fuel pump but still running the same pressure as standard, so i have that to play with if needed.
    I am not on a time scale either, well not until February time for the start of the track day season :laughing:
  10. Big Uno

    Big Uno RSM Trader

    I think the valve is probably just back luck, although it could have been getting hotter than it should with the extra power you are running which may have contributed to it failing? The supertech ones should stop it happening again anyway!

    Would be interested to see your head when its back and the work thats done. I dont have much experience with these heads and would love to see results from other people with headwork done and their opinion. Im quite reluctant to go overboard on the inlet side until I have more facts, worried boring out may do more harm than good slowing the flow rate, thats why I have left it to standard size, although with a larger turbo it may help.

    Is anyone on here running unequal headers? Have had a look but couldnt find any info, would be interested to know if anyone has tried and how they got on!
  11. Big Uno

    Big Uno RSM Trader

    Got the headwork nearly finished up, inlets cut and semi polished, couple of marks to get rid of so might go over again. Bored exhaust ports out by 0.5mm on each face, and got rid of the same step on the inside of the bend as on the inlet side. If anybody is interested in this kind of work doing drop me a PM. Heads nearly ready for skimming and valve seat cut and a clean!



  12. Similar to what I did, I left the exhaust ports untouched though, as I was under the impression if you make them bigger you lose velocity etc which is more important. I made the inlets as big as the gasket on both the head and manifold
    I also cut the valve guides back in the inlet side so.they were flush, left the exhaust ones though t dissipate the heat

    Sent from my FRD-L09 using Tapatalk
    Big Uno likes this.
  13. Also I left the inlets fairly rough to help with atomisation of the fuel but polished the exhaust to prevent carbon build up

    Sent from my FRD-L09 using Tapatalk
    Big Uno likes this.
  14. Big Uno

    Big Uno RSM Trader

    Did you notice any difference after yours was fitted? Or make any more power, better throttle response etc?

    I have left my valve guides alone, just for a bit of extra stability for the valves. Guessing you havnt had a problem with them short?

    I think there are arguements for any porting, in my opinion with a engine running a turbo it is better to remove anything that looses pressure between the ports and turbo, NA / supercharged back pressure is not needed as it is created by the turbo anyway, as any loss of pressure could of been used more efficiently at the turbo. Again would love to hear anyone elses opinions.

    Inlet side I think is less important with a Turbo, as the air is being forced in the only thing you really have to lose is pressure in bends etc, as for fuel mixing I guess the only way to prove right and wrong is with a flow bench rigged with injectors.
  15. Havent fitted it yet its my old spare engine that bent a con rod, been sitting in my garage for a while now(too long!) Havent had the time to find a clio to put it in.

    I will disagree with the exhaust ports as you want them fairly smallish on a turbo car to keep the velocity of the gasses up to help the turbo spool.quicker, larger ports = slower gas. If you look at na cars they have bigger exhaust ports than a turbo with less than half the power. You want less pressure after the turbo not before IMO.

    I dont see how a flow bench would help with seeing fuel atomisation as its nit about the flow its about the fuel splitting into very small parts to aid the combustion. If you spray fuel at high pressure on a polished surface some of it will "stick" and run down the polished surface instead of bouncing off the rough surface and forming smaller droplets.

    All IMO of course!

    Its good to see someone else tinkering!

    Sent from my FRD-L09 using Tapatalk
  16. What tools are you using to do the work, would be interesting to see!
  17. Mine was just a dremmel with a few attachments! Mainly small sanding wheels/ grinding stones

    Sent from my FRD-L09 using Tapatalk
  18. Big Uno

    Big Uno RSM Trader

    Same here pretty much, deburr tools, sand paper different grades, vernier and of course the dremmel doing most of the work, I started with grinding wheels to take the most off, sanding to get surfaces flat, wire-wheel to get it semi polished along with sand papers and oil, then rubber for final polishing, its serioisly time consumimg! :laughing:
  19. Big Uno

    Big Uno RSM Trader

    I agree with you about total port volume, and volume between cylinder and turbo (think I misread what your first post said) although I wouldnt say I have taken much meat off more smoothed the casting marks away and tried to help the flow.

    And I can also see your point in fuel hanging up on a polished surface (again wouldnt say my inlets are mirror more 300grit ish)
    Would be interesting to see the inlets in slow mo though!

    Any more plans for the spare engine? Ill look forward to your results when you put it in (hopefully not at the running engines expense lol)
  20. Ha ha tbh ive been at least half drunk for past two weeks on holiday so no doubt some of what im saying isnt 100% clear!

    300 grit is more than enough for proper atomization of the fuel, where you said polished I thought it was almost mirror smooth.

    The current engine is staying in the megane, bought a brand new old stock engine from fred at btm before he emigrated to OZ. eventually the rebuilt one will hopefully go in a clio. My heart is set on a mk2 but my brain says mk3 due to the ease.

    In all honesty with the increased boost that your probably going to be running I cant see it being detrimental maybe a 50 rpm lag on the turbo spooling (complete guess).

    When im back and not drunk I may try and wokout the velocity of the gasses with the different port sizes

    Sent from my FRD-L09 using Tapatalk
  21. It was a budget rebuild, got some cheapo.chinese forged con rods (after measuring weighing etc I was really surptised how good they seem tolerance wise). But bar that and the headwork it will just be getting a 250 turbo and injectors

    Sent from my FRD-L09 using Tapatalk
    Big Uno likes this.
  22. Big Uno

    Big Uno RSM Trader

    It looks much higher polished in the photos that it is close up by eye, definitely dont want a mirror shine on the inlet!
    Still got another polish to do inside the pots as they can be.

    Out of interest you mentioned you had polished your exhaust side, have you had much experience taking a head off after running an engine for a while with polished exhaust? I have never taken one apart thats polished already so cant say on the improvement, my stock head was pretty coked up, thick layers behind the valves that took a beating from a wire dremmel brush to shift lol.
    If you think it could help stop the build up I can give that a go sure it cant hurt.

    Agreed the headwork wont make a huge difference, but its something I wanted to do while it is off and to be honest fairly low cost.

    Do you know anybody who makes up decent tubular manifolds or could reconmend any that are proven from a retailer, I have seen a few for sale but have no experience with them on this engine. Unfortunately I will probably be going V band turbo so will need to start looking into manifolds soon. I think you usually get what you pay for with exhausts.

    Enjoy the holiday!!!
  23. Great work mate :grinning:
    Big Uno likes this.
  24. Big Uno likes this.
  25. Big Uno

    Big Uno RSM Trader

    Thanks will get hold of them!
  26. Big Uno

    Big Uno RSM Trader

    Block and crank back, rebore to suit new pistons, honed and oil squirters removed and checked. Had the crank polished and checked against new bearings too.

    Also have most of the parts for the bottom end, wossner pistons, PEC I beam rods, ARP con rod bolts, king racing bottom end bearings and kolbenschmidt main bearings.
    Just waiting on ARP cap stud kit and gasket sealant and I will be ready to start building back up.

    Will be checking the block over today and tomorrow, cleaning it down and repainting it can post photos up if anybody wants to see that!?

    Can also post some close ups of the pistons and rods etc if anybody is thinking about buying them I can do a review and comparison too?

    Marvin, Korky, ianplymouth and 2 others like this.
  27. Post everything mate, we are all interested!
    Big Uno likes this.
  28. Big Uno

    Big Uno RSM Trader

    So been at it all day cleaning the engine down and painting, forgot to take photos from before but it was not in all that bad condition, rear facing side of the engine was almost mint but the front looked like its taken a beating from rain and salt from the road, so ill post some photos up when its finished and dry!

    Onto the pistons and rods, for anybody who has not seen different makes of uprated parts this should be interesting for you!
    So to the left there is obviously the OE parts, rods and pistons (yes I have been lazy and left them together) to the right Wossner forged piston with PEC con rod.
    Not sure of the upper capibility of the new parts, undoubtibly considerably higher than the OE and more than enough for the power I am seeking (for now anyway :tearsofjoy:) if anyone has more experience with them would love to know your opinions!
    What I do know is the OE rods are one of the first things to bend when running higher power, they might not be the highest spec parts on the market but they are a large improvement over the standard parts.




    So just waiting for cap studs, sealant and bottom end gaskets and ready to start putting the mess back together.

    Also have my head volume check plate nearly ready so will post up this when i do the checks and also see how good my headwork is (and hopefully not how much more work I have to get them even :sweatsmile:)
  29. Have you weighed the pistons, rods and pins?
  30. Big Uno

    Big Uno RSM Trader

    No not yet mate, dont have scales that are accurate enough until I go back to work next week, will put the results up though if you want to know!
  31. ianplymouth

    ianplymouth RSM Club Member

    Post up the results matey, will then see if mine need doing when they turn up :laughing::laughing::laughing:
    Big Uno likes this.
  32. Where did you get your rods & pistons from buddy??
    I'm seriously tempted on re-directing my engine build towards forged pistons & rods
    Only problem is ive had all the block work done, bought new rings, big end bearings etc, unless you can get them in standard size too?

    Keep up the good work by the way and post any pics up you have as we all like a good thread with pics :sunglasses:
  33. Yeah i was just curious.

    If you're going to all this effort on the engine then you may as well weigh them to make sure you get a balanced setup.
  34. Big Uno

    Big Uno RSM Trader

    PM sent Trophyboy about rods / pistons!

    To be honest I think it depends where you are now and what your planning to do to it later with the rods, the pistons do come in standard size (82.7) and the big end bearings are not expensive, thats all you really need. How many miles since it was rebuilt?
    Trophyboy likes this.
  35. Big Uno

    Big Uno RSM Trader

    Yes your right, and I will be, just dont have the tech to do it at home, have also been looking at getting the bottom end assembly balanced together too.
  36. Could be worth doing, but i bet it's quite costly to get that done?
  37. Big Uno

    Big Uno RSM Trader

    Not really sure not had to have it done before, need to start getting quotes!

    Got the block painted, not the best job in the world I know but still much better than rust :smile:
    Touched in the embossed numbers etc to make it look a little less boring, I think it looks alright anyway.



    Is there a way I can add *pic heavy* to the title this is heading that way now :tearsofjoy:
    Marvin and sen like this.
  38. Big Uno

    Big Uno RSM Trader

    Ran into a problem when checking the block over preparing the head surface, noticed a small ding on the top edge of a bore. So with two choices either attempt flatting it back by hand or send the block for a skim. see pic below.


    Fortunately the hand work has paid off, worst case is you end up making a low spot somewhere else trying to get it flat and have to get it skimmed anyway.

    Been left with a very small ding in the squish zone on the inside of the cylinder but that shouldnt be a problem.


    So here are two pics of the face half cleaned up to show the difference and the final, and looks like there is no need for a skim!


  39. Lucky!

    How much could you have skimmed off if needed and not affect cambelt tension too much?
  40. Big Uno

    Big Uno RSM Trader

    Guess that would depend on the tensioner and how much room you have to play with on that, although to be fair if you had to mill an excessive amount off the block or head you could use a thicker gasket to make it back up but its not really ideal. Would also be needed to bring your compression back down depending on how much you took off.

    I could take it to work and clock its flatness and or even CMM it but if I start going down that road I would want to skim the head and block myself.
    And as it would irritate me forever knowing something isnt square it is best the local motor engineer does it :tearsofjoy::tearsofjoy:
    JamesBryan likes this.

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