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Thread: Flat pistons in EK engine?

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    LX User 1GCustomAccord's Avatar
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    Flat pistons in EK engine?

    After 15 years gathering new and used parts i am restarting my restoration projects, the first one is my 79 Accord, and now i added a 80 Accord that i bought few weeks ago ( As a donor car but i had to rethink about dismantling it after opening the door ashtray and discovering the the tray lamps still work, if the ashtray lamps work the car is worth restoring! Oh, also everything else in the car works...) and a 79 Prelude. I have en EL1 engine for the 80 Accord (Or Lude maybe, must decide) and i want to raise the engine outpud a lil bit. The engine is technically a EL block and head BUT with factory 1751cc crank, con rods and pistons ( And is non CVCC). I was thinking in using the flat pistons from the 1.6 but not sure if the compression rise will be a little too much, still didnt make calculations.
    What do you think guys?
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  2. #2
    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Made some calculations and flat pistons should rise compression to 9.75:1, not much but enough for me. I have to take in count that the hear may be already rectified end that may further rise compression.

    To make calculations i used this measures, hope they are accurate:

    Original piston dish volume: -5cc
    Combustion chamber volume: 47cc
    Bore: 77mm
    Stroke: 94mm
    Gasket thickness: 0.40mm (Compressed)

    Resulting compression ratio:

    With dished pistons: 8.45:1
    With flat pistons: 9.75:1

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    LXi User 79cord's Avatar
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    Re: Flat pistons in EK engine?

    '82-3 EL 1.6 had a slightly higher compression ratio 8.8:1 vs 8.4:1 (EL), via domed pistons that apparently fitted the older (1.6) EL if they were worth seeking out.
    I remember 2nd gen guy's EK rebuild pictures of pistons protruding above the engine block though!

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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Wow didnt know about that! That would rise compression a lot in an EK.
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    Re: Flat pistons in EK engine?

    Hmm was that my car? My car has dished pistons. Maybe you were thinking of Kurt's car, he has the EL/EK hybrid engine. Maybe the EL pistons are flat and stick slightly above the deck?


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    LX User redr2's Avatar
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    Re: Flat pistons in EK engine?

    Yes, my dished pistons in my 81 EK came up very high.

    Technically the EL and EK blocks are the same - the extra displacement of the EK (1751) over the EL's 1600 is from Honda basically stroking the EL motor to give it a longer stroke. Looks like they used dished pistons to drive the compression down to the 8.8:1. My 81 EL has the flat pistons and I recall exploring this as an option too. I do not have the numbers handy but the flat pistons in an EK would drive the compression very, very high. I also wonder about some issues with valve clearance with my larger valves.

    I should add though that my head had some work done that would have risen compression anyway, so it may not apply. I am running about 10.6:1 and that may have just been raised now that the machine shop had to plane my head down a bit after blowing the head gasket.

    PS - John, got the studs in and torqued down today

    - Kurt

    http://www.roadsailing.com/images/40Over_1.JPG
    Last edited by redr2; 06-26-2013 at 02:11 AM.

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    Re: Flat pistons in EK engine?

    DO love me some build thread

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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Quote Originally Posted by redr2 View Post
    Yes, my dished pistons in my 81 EK came up very high.

    Technically the EL and EK blocks are the same - the extra displacement of the EK (1751) over the EL's 1600 is from Honda basically stroking the EL motor to give it a longer stroke. Looks like they used dished pistons to drive the compression down to the 8.8:1. My 81 EL has the flat pistons and I recall exploring this as an option too. I do not have the numbers handy but the flat pistons in an EK would drive the compression very, very high. I also wonder about some issues with valve clearance with my larger valves.

    I should add though that my head had some work done that would have risen compression anyway, so it may not apply. I am running about 10.6:1 and that may have just been raised now that the machine shop had to plane my head down a bit after blowing the head gasket.

    PS - John, got the studs in and torqued down today

    - Kurt

    http://www.roadsailing.com/images/40Over_1.JPG
    Cool. I remember the job done on your heads, they were heart shaped to improve swirl as they did in the old times when racing with those engines. I comtemplated that option with dished pistons or the flat pistons without the head mod. I wonder wich one will get better results (Heart shaped improving swirl and rising compression vs flat pistons improving compression with unmodded head).
    I also will use the bigger valves as the head is 83, but i dont think there's clareance issues, since the EL engine with those bigger valves uses flat pistons and in both cases (EL vs EK) the pistons should not protrude over the deck, even with the longer EK stroke as the con rods are shorter. in that engine.
    I also have to take in count heating problems due of higher compression, even with the external (factory) oil cooler i will use. Did you have any heating problems yet?
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    LX User redr2's Avatar
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    Re: Flat pistons in EK engine?

    I must admit for the cost and all the work the gains were not as much as I had hoped. Maybe on a dyno, but real world driving and the "seat of the pants dyno" did not yield great results....at least to me. The flat pistons would be much cheaper then all the head work too My best gains yet were with the dual carbs. I have had 2 different style headers on there and no noticeable difference either. The Colt cam really changed the power curve and when set up with the adjustable cam gear it will pull right up past 7000 rpm and still climb...but their is a noticeable loss in torque down low.

    As for over heating, I did yes. Not in every day driving but those times when stuck in traffic or long lineups (drive thru's!!). BUT -my motor is in a first gen Civic 1200 body with a small 2 core rad. I have since swapped in an aluminum rad of the same size. The Accord had much, much bigger rads so you should be good.

    Oh and I should mention - I just blew the head gasket with about 12,000 or so kms on the motor......so use some ARP studs for some insurance...I was running the Honda bolts


    Here are the photos of the head work : Untitled

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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Great info!
    Well i guess i will just use the flat pistons and larger valves, not modded, i am using the 83 heads as they have bigger valves already installed compared with the stock EK head in this engine, but they are not so big as the ones you used, i will also use the 83 block as it has the oil cooler outlets and is the only block i have available with the EL head bolt pattern, and with the bigger stroke of the EK.
    Do you have an estimate on how many HP your engine has now?
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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Btw, i saw in your page info that the EK was only available in North America, but it came to Paraguay in Non CVCC form, just an EK block with EL heads. A real odd ball.
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    LX User redr2's Avatar
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    Re: Flat pistons in EK engine?

    Quote Originally Posted by 1GCustomAccord View Post
    Btw, i saw in your page info that the EK was only available in North America, but it came to Paraguay in Non CVCC form, just an EK block with EL heads. A real odd ball.
    Wow thats pretty cool. Seems Honda new of the little secret too!! Any idea what the published numbers of the set up was for HP?

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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Quote Originally Posted by redr2 View Post
    Wow thats pretty cool. Seems Honda new of the little secret too!! Any idea what the published numbers of the set up was for HP?
    82 HP for the non CVCC 1751, i wonder how much it increases with mods like yours.
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    2.0Si User Hazwan's Avatar
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    Re: Flat pistons in EK engine?

    How much does a stock EL makes? I've seen 69 and sometimes 79 and even 80 does anybody know for sure?

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    LX User PDXAccord79's Avatar
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    Re: Flat pistons in EK engine?

    So could I fit a later model head on my 79 CVCC Accord 1.8? I'd love to get rid of the CVCC crap and get 4 exhaust ports instead of 2.

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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Quote Originally Posted by Hazwan View Post
    How much does a stock EL makes? I've seen 69 and sometimes 79 and even 80 does anybody know for sure?
    Yeah, i could'nt find an exact figure also. Geez we need to get it dynoed.
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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Quote Originally Posted by PDXAccord79 View Post
    So could I fit a later model head on my 79 CVCC Accord 1.8? I'd love to get rid of the CVCC crap and get 4 exhaust ports instead of 2.
    You can use an EL head from 76 to 81, but from 82 onwards it changed the head to block bolt pattern slightly, is very subtle but the difference is there. Or you may use a head-block combo from an 82/3.
    Kurt, correct me if i am wrong!
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    LX User redr2's Avatar
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    Re: Flat pistons in EK engine?

    Quote Originally Posted by 1GCustomAccord View Post
    You can use an EL head from 76 to 81, but from 82 onwards it changed the head to block bolt pattern slightly, is very subtle but the difference is there. Or you may use a head-block combo from an 82/3.
    Kurt, correct me if i am wrong!

    Ya, you can swap on any EL head from 79-81. The 82-83's were different but they also can have the 82-83 head mounted. Maybe best to source the intake too. The EL intake ports are slightly larger and of course do not have the CVCC auxillary ports in the head.

    I need to get mine on a dyno but would estimate around 100 to 110....no more than that though.

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    2.0Si User Hazwan's Avatar
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    Re: Flat pistons in EK engine?

    I just found the stock specification for an EL in the 79 sales bulletin.

    Max power: 59 kW at 5300 rpm
    Max torque: 126.5 Nm at 3500 rpm

    Converted to hp and lb/ft

    79 hp and 93.27 lb/ft

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    Re: Flat pistons in EK engine?

    I'm sure anywhere from 75-85 is going to be accurate. It's going to depend on the day, the temperature, humidity, gas, proper tune on the carb, the way the particular head was cast, the way each valve seats perfectly... There will never really be an "exact" horsepower.

    That's why you can buy a Spec Miata engine for like $20,000. That's a STOCK engine by the way. But the racers want every last horsepower, so they flow bench like 30 heads and test every single part for the one that is 1-2% better than the rest, and do the same for every part in the engine. So they wind up with like 10hp more than everybody else.

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    LX User 1GCustomAccord's Avatar
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    Re: Flat pistons in EK engine?

    Thats very interesting data guys, is true that it depends on some factors. i've been told that a brand new car will have much more power than other brand new car of the very same model and specs due to slight differences in casting and parts firtting carb, etc.
    Its interesting to note that there was a turbo kit for the EK that rised output to 126HP, pretty soft gains for a turbo setup, but i guess was intended as a daily driver system.
    I pretend some 100/105 HP for my 1751, with the mods i am going to perform, including head porting/polish, con rods lightening, crankshaft lightening and polishing, bigger valves, exhaust 4X2 end to end, 4 bike carbs setup, camshaft lift and duration mod, lightened flywheel and high compression pistons. I already did this mod (except the high comp pintons & camshaft mod) to my last EL (that i sold and is still running strong after 10 years) and the power gain was awesome. Going at 160 Km/h it still pushed very well with 1/4 throttle remaining, never tried to go faster than that. Also my o/100 time was 8.8 seconds driving alone, with a passenger it was considerably slower.
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