User Tag List

+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 40 of 51

Thread: lotus/ford twin cam

  1. #1
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    lotus/ford twin cam

    A bit of a departure from the norm for me. i started out building a x/flow, then a flat top piston-ed x/flow, now its morphed into a twin cam, but its anything other than straight forward, its got to be road legal in another country so as soon as the decision to use a twin cam head was made the x/flow block couldnt be used, instead the owner sourced a 1500 pre/xflow bottom end with a "L" casting block, so effectively we are building a twin cam which never existed from bits only, although we are retaining the x/flow crank, so we are going to end up with a pretty non standard twin cam.



    a big wing sump was sourced, but that had three problems, 1 it had a fair few dents, 2 it didnt come with an oil pick up and a standard pickup doesn't fit, and 3rdly, it was very dirty internally in the wings, try as i might, i couldnt get it clean, so end up cutting holes in it to clean it properly, that did give an added bonus in that it made it easy to make a standard escort pick up pipe fit


    once i was sure it was a clean as possible to get i plated over the holes, for this i bolted it to the block and brazed plates over the holes, braze is excellent for this as it flows nicely, its basically high temperature soldering so water tight



    Last edited by Graham; 10-03-2019 at 23:54.

  2. The Following User Says Thank You to Graham For This Useful Post:


  3. #2
    Racer Decade Plus User

    Join Date
    Jan 2008
    Location
    Up the garage
    Age
    43
    Posts
    2,775
    Thanks
    218
    Thanked 179 Times in 172 Posts

    Re: lotus/ford twin cam

    Interesting to know what you'll do with pistons for it as even if you use Lotus rods and pistons with a 1600 crank you'll still have pistons poking out slightly. You could marginally shorten some of the late type large cut-out pistons if not going too wild on cams.
    The block will probably need careful relieving around the con rod clearance pockets in the block - these can and do go through here! It's more the con rods that catch but also the TDC indicator (for re-grinding purposes) on a 1600 (I think it's on the 2nd big end journal) will also catch the STD bore bottom.

    I have a genuine pickup pipe for the big-wing sump - it's amazing how many are for sale with the incorrect pick-up pipe - I have a feeling that's why the sumps change hands regularly!

  4. #3
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    we have a set of domed low compression height pistons, for use with long rods, and some not quite "long" rods, which in a trail build nearly worked, it left the pistons a bit down the bore, so we have now moved onto a set of custom made rods, well we will when they turn up.

    despite what two twin cam experts told me, when i did the first trial build the block didnt need any clearancing at all, i just had to grind that TDC indicator off the crank. that may of been down to the steel rods that were used
    Last edited by Graham; 11-03-2019 at 08:28.

  5. The Following 2 Users Say Thank You to Graham For This Useful Post:


  6. #4
    Racer Decade Plus User

    Join Date
    Jan 2008
    Location
    Up the garage
    Age
    43
    Posts
    2,775
    Thanks
    218
    Thanked 179 Times in 172 Posts

    Re: lotus/ford twin cam

    Should make for a nice engine if you've got slightly longer rods than the xflow length rod. Steel rods do tend to have a lower profile on them just above the con rod bolt hole so that's a nice way to go that you don't need to modify the block.

    Has the owner decided on spec for the head and cams?

  7. #5
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    yes he bought the head in already modified/ported by nick stag and fitted with QED 420 cams

  8. #6
    Racer Decade Plus User

    Join Date
    Jan 2008
    Location
    Up the garage
    Age
    43
    Posts
    2,775
    Thanks
    218
    Thanked 179 Times in 172 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by Graham View Post
    yes he bought the head in already modified/ported by nick stag and fitted with QED 420 cams
    Can't go wrong with Nick Stagg stuff! Should be an interesting engine when done!

  9. #7
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    thanks Graham for taking the time to show your work.

    Please keep up showing all your great work if time allowed.

  10. #8
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by HonkyWhiteTrash View Post
    Can't go wrong with Nick Stagg stuff! Should be an interesting engine when done!
    It took a while, but head turned up to be work of art.

    Purchase head from a member in here and sent it to Nick Stagg for full rebuild

    Head spec:

    1) Full set of valve seats
    2) Bronze guides
    3) Cam bearings and the required studs and nuts
    4) QED 420 cams
    5) Cam followers
    6) Full spring pack that will include collets,platforms and retainers
    7) Competition valve set. 1.625/1.400

    fully port and gasflow, hardened valve seats, bronze valve guides , shim cams, new studs and paint

  11. #9
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    a few pictures of head
    Attached Thumbnails Attached Thumbnails LOTUS_HEAD.jpg‎  

    LOTUS_HEAD1.jpg‎  

    LOTUS_HEAD2.jpg‎  

    LOTUS_HEAD3.jpg‎  


  12. The Following User Says Thank You to chrisis For This Useful Post:


  13. #10
    Racer Decade Plus User

    Join Date
    Jan 2008
    Location
    Up the garage
    Age
    43
    Posts
    2,775
    Thanks
    218
    Thanked 179 Times in 172 Posts

    Re: lotus/ford twin cam

    Lovely, doesn't come any better!

  14. #11
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by HonkyWhiteTrash View Post
    Lovely, doesn't come any better!
    I agree, but the most important is to find someone to build it right.

    Even sourcing many parts from twin cam experts, Graham spotted numerous issues with parts and the build.

    Graham also sourced the correct parts for me offering improvements for both reliability and to be able to extract the most out of this engine.

  15. #12
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    its been a while, but i finally been able to get the pistons back in the block on the new custom rods, i was a bit nervous when it came to doing the trial build, id measured carefully, but since i had worked out that the Williams rods were not going to work, we also had a change of crank to a steel one, a few thou out and the squish would be still too big or perhaps worse too small, as it was we finished up with the pistons 8 thou down the bores, not too big not too small, but it still leaves me room to take a fraction more off the top of the block if needs be,

    next stage was to drop the piston down the bore 5mm and work out what effect the intruder was having on the compression



    the answer was lots! CR is 12:1, great for full race cams, but we dont have full race cams! Nick stagg told me the 420 cams dont need much over 10;1 although other twin cam builders have suggested i should be more like 11.1!!!!! reading between the lines i think nick stagg likes to be a little conservative and would rather not push the compression to the edge if the engine isnt a full on race unit where every single bhp counts.



    either way the pistons have now been in my mill and had a haircut! nice thing is with my jig i can set one up and with a slow feed mill the piston in one single cut, then do all the rest exactly the same without touching the mill settings

    Last edited by Graham; 24-08-2019 at 22:36.

  16. The Following 3 Users Say Thank You to Graham For This Useful Post:


  17. #13
    Spanner Monkey Tony B.'s Avatar

    Join Date
    Mar 2007
    Location
    Nr Chichester, West Sussex
    Age
    74
    Posts
    331
    Thanks
    23
    Thanked 41 Times in 39 Posts

    Re: lotus/ford twin cam

    Graham, from your first photo, it doesn't look like the block has been drilled for the big wing dipstick ?. I am sure you know, but the depth the insert is pressed into the block is critical to getting the oil level correct as the dipstick has a bottom collar that sits on the top of the insert.
    Last edited by Tony B.; 25-08-2019 at 11:47.

  18. #14
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam


    thought i would post a few comparison pics between the forged and std pistons and long rodas against standard rods, because i dont have any 125e rods the ones in the pic are actually 1500 116e




    it then occurred to me there was quite a weight difference some 770grams, thats massive, infact im certain a 116 rod is lighter than a 125 rod we have a huge weight saving over the standard set up, this twin cam might not have full race cams but it sure will want to rev




    the crank is back in the block again, its been in and out like a yoyo, as to have the rods and pistons, but for the first time the big ends are tightened by the stretch method



    cam follower holes! the eagle eyed of you may notice the engine block only has half of a camshaft, or more correctly called a jack shaft. a bit ott for this engine perhaps but on engines where every last scrap of power is needed doing away with the actually redundant rear end of the shaft saves a minuscule spot of power, i suspect it also helps reduced the amount of oil being flung up at the breather


    the rear cam bearing has been removed and turned round to block the oil supply to the non existent bearing, which should have the bonus of a slight oil pressure gain.



    one now 2mm shorter piston, showing a nice small squish gap, the intruder is still bigger than the standard twink one so its still got plenty of compression @ 10.6 just slightly up on the 10.5 suggested by QED.
    Last edited by Graham; 26-09-2019 at 06:23.

  19. #15
    Racer Decade Plus User rallyrob's Avatar

    Join Date
    Apr 2010
    Location
    Middlesex
    Age
    55
    Posts
    2,656
    Thanks
    267
    Thanked 221 Times in 208 Posts

    Re: lotus/ford twin cam

    My knowledge of crossflow/twinks is very limited, but bloody hell that looks lovely Graham.

    What's the idea behind stretch bolts for the big ends then, any advantages or disadvantages?
    That piston and rod weight combo should certainly make it rev well.

    And I like your ARP dial gauge

  20. #16
    Racer Decade Plus User

    Join Date
    May 2012
    Location
    Camberley, Surrey
    Posts
    3,237
    Thanks
    5
    Thanked 353 Times in 339 Posts

    Re: lotus/ford twin cam

    That's the first time i've ever seen a rod stretch gauge actually being used - neat little device. Is this the sort of build you enjoy doing the most - bit out of the ordinary, one that makes the 'little grey cell' work? It's very nice BTW!

  21. #17
    Racer Decade Plus User rallyrob's Avatar

    Join Date
    Apr 2010
    Location
    Middlesex
    Age
    55
    Posts
    2,656
    Thanks
    267
    Thanked 221 Times in 208 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by katana View Post
    That's the first time i've ever seen a rod stretch gauge actually being used - neat little device.
    Oh is that what it's called..


    So as that bolt stretches will the values on the dial gauge go up or down? I'm think down.
    Last edited by rallyrob; 26-09-2019 at 09:56.

  22. #18
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by rallyrob View Post

    What's the idea behind stretch bolts for the big ends then, any advantages or disadvantages?
    )
    the main advantage of the stretch method is you are always tightening the bolt by a known amount, friction on the threads or under bolt heads makes no difference to how much clamp load you are putting on the rod.

    you can also use the gauge to keep a check on bolt lengths. so if you remove them you can see if they have stretched from new. i personally dont bother with that, i will use a an ARP rod bolt a maximum of twice, then throw it away.

  23. The Following User Says Thank You to Graham For This Useful Post:


  24. #19
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by rallyrob View Post


    So as that bolt stretches will the values on the dial gauge go up or down? I'm think down.
    incase you had not spotted the tool has a pointed end, which sits in a dimple in the threaded end of the rod bolt so as you tighten the bolt it gets longer.

  25. The Following User Says Thank You to Graham For This Useful Post:


  26. #20
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by katana View Post
    That's the first time i've ever seen a rod stretch gauge actually being used - neat little device. Is this the sort of build you enjoy doing the most - bit out of the ordinary, one that makes the 'little grey cell' work? It's very nice BTW!
    i get bored doing the same thing over and again, so different is good. unfortunately 98% of my time is taken up with running an garage and mot station, so i dont do as much engine work as i would like

  27. #21
    Racer Decade Plus User rallyrob's Avatar

    Join Date
    Apr 2010
    Location
    Middlesex
    Age
    55
    Posts
    2,656
    Thanks
    267
    Thanked 221 Times in 208 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by Graham View Post
    incase you had not spotted the tool has a pointed end, which sits in a dimple in the threaded end of the rod bolt so as you tighten the bolt it gets longer.
    Quote Originally Posted by Graham View Post
    the main advantage of the stretch method is you are always tightening the bolt by a known amount, friction on the threads or under bolt heads makes no difference to how much clamp load you are putting on the rod.

    you can also use the gauge to keep a check on bolt lengths. so if you remove them you can see if they have stretched from new. i personally dont bother with that, i will use a an ARP rod bolt a maximum of twice, then throw it away.
    No I can't say I had noticed that bit of the gauge, top end of the rod then.


    Okay yea I understand that too then, more acurate than a normal torque wrench then.

  28. #22
    Racer Decade Plus User Willid1's Avatar

    Join Date
    Dec 2001
    Location
    Hertfordshire
    Age
    61
    Posts
    2,139
    Thanks
    3
    Thanked 21 Times in 20 Posts

    Re: lotus/ford twin cam

    Evening Graham

    Very interested in this build thread, excellent photos as well.

    I'm wondering which type of water pump you are going to be using as my twin cam is in need of a new pump (mechanical that is - not going remote electric) and looking for a bit of insight/recommendation before I spend money and time on the rebuild.

    David

  29. #23
    Racer Decade Plus User Forest_rallying's Avatar

    Join Date
    Feb 2013
    Location
    Derbyshire
    Posts
    2,438
    Thanks
    92
    Thanked 393 Times in 348 Posts

    Re: lotus/ford twin cam

    I can't remember but years ago someone like Vegantune or QED did a front cover with a removable water pump, whether these are still available I am not sure.

  30. #24
    Racer Decade Plus User Forest_rallying's Avatar

    Join Date
    Feb 2013
    Location
    Derbyshire
    Posts
    2,438
    Thanks
    92
    Thanked 393 Times in 348 Posts

    Re: lotus/ford twin cam

    Further to the above I have just looked on Burton's site and they do a removable water pump front cover and they are a very expensive. It's probably easier and cheaper to buy a repair kit for your excisting water pump.

    Wilcox might be a good choice to try for your needs, they are very helpful unlike the name mentioned above.

  31. #25
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    im going into work later i wil try and get some more pics, but this will have a modified front cover with a removable modular pump. i dont know where the kit came from(engines owner sourced it) but it was somewhere in America IIRC. the pump itself is clearly off something else modified for this application, i have a suspicion the pump is actually bmw m40/m42/m34/m44

  32. #26
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by Willid1 View Post
    Evening Graham

    Very interested in this build thread, excellent photos as well.

    I'm wondering which type of water pump you are going to be using as my twin cam is in need of a new pump (mechanical that is - not going remote electric) and looking for a bit of insight/recommendation before I spend money and time on the rebuild.

    David
    David after searching for a good water pump kit i decided to use a modular water pump as i don't want to remove engine/head if i have a water leak.

    It is expensive as the kit includes:

    - Timing case front cover
    - Timing case rear casting
    - Modular pump housing
    - Water pump repair kit

    I then had the choice between burton and dave bean engineering one. I choose the second as it is race proven by the lotus guys in US.


    It was expensive (880 USD) for the kit.

    If you don't race or putting 10000 km per year on the escort i cannot justify the cost of this conversion.
    The engine will probably be ready for another overhaul at that point anyway.

    In my case the convenience of being able to replace it at the side of the road
    should be worth that.

  33. #27
    Racer Decade Plus User wildo105e's Avatar

    My 1st Project
    My 2nd Project
    Join Date
    Oct 2006
    Location
    Manchester
    Age
    53
    Posts
    3,150
    Thanks
    131
    Thanked 237 Times in 230 Posts

    lotus/ford twin cam

    They do seem expensive but so are replacement standard covers. Even second hand ones without damage command a nice price. They are so easy to break off lugs etc.


    Sent from my iPhone using Tapatalk

  34. #28
    Racer Decade Plus User Forest_rallying's Avatar

    Join Date
    Feb 2013
    Location
    Derbyshire
    Posts
    2,438
    Thanks
    92
    Thanked 393 Times in 348 Posts

    Re: lotus/ford twin cam

    QED do a water pump kit for the std front cover for £35.00. That's got to be a decent price.

    Back in the day when we ran Lotus Twinks we never had a problem with the std water pumps and I think they would be the original pumps that were manufactured in the 60's.

  35. #29
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by Forest_rallying View Post
    QED do a water pump kit for the std front cover for £35.00. That's got to be a decent price.

    Back in the day when we ran Lotus Twinks we never had a problem with the std water pumps and I think they would be the original pumps that were manufactured in the 60's.

    Back in the day most twin cams were fairly new, but those days were gone so most of them are corroded.

    Main contributor for pump failures are:

    1) over tightening the fan belt
    2) Not running the engine in many
    years (usually seal failure).
    3) Not usage of proper coolant.

    I'm pretty sure under regular use and proper belt tension,the pump seal and bearing should last 20 - 30 k miles, but as most of them are old and corroded the price to get new covers are expensive either way.

    If you count the cost to "proper" build/rebuild a twin cam i don't think the price for a removable modular pump is that expensive.

  36. #30
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam









    a few front cover/pump pictures.

    when it came to bolting the covers on for alignment purposes i did it with the water pump installed, having previously greased the seals on the pump to stop any sealant gluing it in

  37. #31
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam



  38. #32
    Racer Decade Plus User Forest_rallying's Avatar

    Join Date
    Feb 2013
    Location
    Derbyshire
    Posts
    2,438
    Thanks
    92
    Thanked 393 Times in 348 Posts

    Re: lotus/ford twin cam

    A very interesting thread Graham, it takes my memory back to well over 40 years when we had Twinks.

    Out of interest what overlap are on the cams @ tdc?

  39. #33
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by Forest_rallying View Post
    A very interesting thread Graham, it takes my memory back to well over 40 years when we had Twinks.

    Out of interest what overlap are on the cams @ tdc?
    dont know, i didnt spec the cams, i was told where to degree them in to, so will measure tdc lift once they are dialed in

  40. The Following User Says Thank You to Graham For This Useful Post:


  41. #34
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    nick Stagg was very specific to degree the cams in at 100 and 106 degrees respectively so that was what i set out to do.

    i had dialed the inlet cam in ok, but found the exhaust a mare to get right, i ended up at the end of the vernier slots i tried to rejig it and ended up miles wrong on both cams! despite being early saturday afternoon i realised i was really tired and went home! so sunday lunch time i came in to have another go!

    now having said i didnt know the lift at TDC figure, ive since found a QED data sheet for the 420 cams, inlet 0.155 ex 0.122 with timing figures as specified by Nick.

    armed with a data sheet i took a different direction, set the cams to the TDC lift figure with toothed sprockets unbolted from the vernier middles, put the crank back to TDC and refitted the sprockets with the vernier slots in the middle of the adjustment. rechecking the timing using the degree method, the inlet was bang on, exhaust was a couple of degrees out, then 4 degrees out, yes i went the wrong way again exhaust cams on twin cams always throw me at first





  42. #35
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    Graham out of curiosity why it is so difficult to set the exhaust cam?

    It is something that happens in this type of engines when you have to set up both cams and crank from zero?

  43. #36
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    there nothing particularly difficult about the exhaust cam when dialing it in by degrees, it just goes against what you are used to doing ie BTDC rather than ATDC and the lobe the other side of the follower compared to the inlet, so when you want to change the timing a fraction you go the opposite way to what would you do on the inlet.

    30 something years ago when i first started learning about building performance engines i work with two engine builders both had been doing it for donkey's years, they always ended up with the same dilemma with twin cams ( lift at TDC method was un heard of then) when over 99% of performance engines you dial in are single cam and so you never even look at exhaust timing, you get so you can do inlets with your eyes shut, exhausts confuse the brain!
    Last edited by Graham; 04-11-2019 at 09:07.

  44. #37
    Spanner Monkey Turbosport Subscriber chrisis's Avatar

    Join Date
    Apr 2011
    Location
    cyprus
    Age
    41
    Posts
    200
    Thanks
    11
    Thanked 12 Times in 10 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by Graham View Post
    there nothing particularly difficult about the exhaust cam when dialing it in by degrees, it just goes against what you are used to doing ie BTDC rather than ATDC and the lobe the other side of the follower compared to the inlet, so when you want to change the timing a fraction you go the opposite way to what would you do on the inlet.

    30 something years ago when i first started learning about building performance engines i work with two engine builders both had been doing it for donkey's years, they always ended up with the same dilemma with twin cams ( lift at TDC method was un heard of then) when over 99% of performance engines you dial in are single cam and so you never even look at exhaust timing, you get so you can do inlets with your eyes shut, exhausts confuse the brain!
    Got it

    Thanks Graham.

  45. #38
    Racer Decade Plus User rallyrob's Avatar

    Join Date
    Apr 2010
    Location
    Middlesex
    Age
    55
    Posts
    2,656
    Thanks
    267
    Thanked 221 Times in 208 Posts

    Re: lotus/ford twin cam

    Quote Originally Posted by Graham View Post
    there nothing particularly difficult about the exhaust cam when dialing it in by degrees, it just goes against what you are used to doing ie BTDC rather than ATDC and the lobe the other side of the follower compared to the inlet, so when you want to change the timing a fraction you go the opposite way to what would you do on the inlet.

    30 something years ago when i first started learning about building performance engines i work with two engine builders both had been doing it for donkey's years, they always ended up with the same dilemma with twin cams ( lift at TDC method was un heard of then) when over 99% of performance engines you dial in are single cam and so you never even look at exhaust timing, you get so you can do inlets with your eyes shut, exhausts confuse the brain!
    The whole lot confuses my brain anyway, regardless of single cam or twin cam engines.
    I just can't get my head round what makes a lairy cam or a mild cam. I know it all works around 360degrees an atdc or btdc, but other than that I just don't get it.. Not doing it for a living makes it difficult too, as if you do something enough you get it eventually, mostly anyway..

    Ask me to blind side an artic on a loading bay door an I get that...
    Last edited by rallyrob; 04-11-2019 at 12:58.

  46. #39
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    dont seem to of updated thread for a while, but there been progress, its been on an engine dyno, run in and set up Craig who dyno'd it recons his dyno is conservative but that doesnt really matter. Craig builds twin cams for a living so he knows what to expect and said its very strong and has good torque and given 420 cams and 40's revs on pretty well.


    he said we would probably seen 160bhp on 45's but that would of completely rubbished the bottom end. with the lightweight internals, long rods and short pistons and flat torque it should be a hoot to drive on the road
    Last edited by Graham; 05-03-2020 at 21:23.

  47. The Following User Says Thank You to Graham For This Useful Post:


  48. #40
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: lotus/ford twin cam

    the more i look at the graph the more impressed i am with it, 154bhp from an X/flow usually needs a 254 cam, which gives zero bottom end power, just shows how right the lotus head is

+ Reply to Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts