Modified 8v project head

Discussion in '8-valve' started by mr hillclimber, Nov 5, 2007.

  1. R.b!n_16v Forum Member

    Joined:
    Nov 3, 2010
    Likes Received:
    1
    ok i started, but i read on the first page the same but you opend the port there till 33mm ? i did that now im almost done with the inlet ports. I think i screwed it up now? i want to juse schrick 288 degrees.My father removed the guides is went pretty easy i think it last 30 seconds hihi. the valve seat is still in but there is a pretty big edge from the port till the seat grind it away and smooth it. I hope you understand the last part from the valve seat i couldent found the right words for it.
     
    Last edited: Dec 1, 2010
  2. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    131
    Location:
    Southwest
    Blimmey... was it that big! :lol:... no wonder that engine goes so well!

    I've since found that decent flow can be had without such a big port (I did'nt have the flowbench when I did the 1st head), and, on some castings, opening to 33mm will break into the head bolt holes.

    Now this is'nt a problem as long as the shoulder of the head bolt seals at the top, and the gasket seals off the bottom, but for road type applications I dont feel the need to go so big... the race engines are different tho.

    I'm just in the middle of a road head on std 40mm inlets with a 31mm port... I'll have it on the flowbench in the next day or 2 so hold on till then for the results. If you have already opened to 33mm its not a problem.

    I'm also trying a different throat size to taper from the bottom of the seat, tho the venturi is still 34-35mm.

    To use a 288 cam you will need good c.r... around 11.5:1... which is on the high side for std type cast pistons. Is it for an 1800 or 2ltr?
     
  3. R.b!n_16v Forum Member

    Joined:
    Nov 3, 2010
    Likes Received:
    1
    yeah i just finish the inlet ports yesterday haha came out pretty well for the first time i ques.. Now im sarting with the exhaust ports any changes there? Its for a 1800cc pf
     
  4. caistor_bmx Forum Member

    Joined:
    Nov 7, 2009
    Likes Received:
    0
    If you are a complete novice like myself here are a couple of simple diagrams which will aid reading the initial artical with a little more fluidity (if thats even a word?)

    [​IMG]

    well... there was meant to be a couple but i have lost the important one haha, will try to track it down.. watch this space
     
  5. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    131
    Location:
    Southwest
    Throat, guide boss & Venturi need adding/marking up.... good call tho.

    I cant believe this has reached of 30K hits!.... I hope there's plenty of ported heads out there!

    A few details have changed since I wrote the original... the basic's are the same, but since having the flowbench running (it was built after I did this head to test the theory and carry out further development) I've found how much work is or is'nt needed for positive results on both road and race heads... what valve size's give what flow, and how they relate to power from genuine dyno testing.

    When time permits (!) I'll update some of this... but for now, this guide still works very well, and will give positive results for anyone who put's in the effort.

    If anyone is uncertain of any aspect of it just ask.
     
  6. walkinginperu Forum Member

    Joined:
    Nov 15, 2010
    Likes Received:
    0
    Location:
    Leamington Spa
    As one of the 30,000 who is now having a go at my own head, i think i'm nearly finished on the inlets. Being a novice there are a few area that are still a bit rough where either the burr ran away from me and took a tiny chunk out, or where i haven't been able to get into a corner of the port to clear away casting imperfections. My question is, how good does the finish have to be? I'm not after the ultimate performance, just a bit of an improvement. Cheers, and thanks for the fantastic guide, easy to follow and really useful :thumbup:
     
  7. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    131
    Location:
    Southwest
    Yr more than welcome.

    If you have any pics put them up and I'll take a look..or pm them to me.

    As long as the basic shape and sizing is right then you'll be 90% there.

    I see in another post your modding a 1600 head?...still on std valve sizes.. 38/32?
     
  8. walkinginperu Forum Member

    Joined:
    Nov 15, 2010
    Likes Received:
    0
    Location:
    Leamington Spa
    Yeah its the 1600 carb head on std valves so 38/32. I've back-cut the valves, bullet nosed the new valve guides and i've made up a little grinding thingy to sort the seats out. My intention was to reface the seat face and then put in a 60 degree cut down into the throat. I'll sort some pictures tomorrow and post them up here if i can figure out how :thumbup:
    Thanks yet again for the help, i love this forum.
     
  9. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    131
    Location:
    Southwest
    Well done.

    I'd open the inlet throat/venturi at the lower edge of the 60 degree cut (more or less where the seat insert joints the alloy of the head casting) to 32-33mm, the throat/bowl itself to 35-36mm, and the port runner to 30-31mm. Use the current lower section of the port runner as the base and take the extra from the roof and sides the best you can. Try not to dig into the bend around the port roof/down the bowl sides.

    For the exhaust open the throat/venturi to 27-27.5mm, the throat/bowl to 29-30mm, and the port runner to a bit bigger, say 30mm wide by 31-32mm tall... non off the floor.. take it off the roof.
     
  10. walkinginperu Forum Member

    Joined:
    Nov 15, 2010
    Likes Received:
    0
    Location:
    Leamington Spa
    my shoddy efforts

    As promised here are some shots of my poor efforts at recreating the skill of mr. hillclimber.
    These are inlets, i haven't bothered too much with the exhaust because i didn't think it would affect flow too much.

    http://www.flickr.com/photos/58732530@N04/5693473632/in/photostream

    http://www.flickr.com/photos/58732530@N04/5692904853/in/photostream
    Is this surface too rough and uneven?

    http://www.flickr.com/photos/58732530@N04/5693473312/in/photostream

    Throat is 34mm, area just underneath goes out to 36-38mm, then the runners are 31mm measured across, but i think bigger, maybe 34mm vertically, I think that's because i was a touch over-enthusiastic with the flap wheel trying to get further into the runners.
    Any thoughts much appreciated!
     
  11. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    131
    Location:
    Southwest
    You've got the right idea, and while the finish has the... "worked" look, it's less important than the shape & size. Dont go any bigger on size in general, but after the guides are fitted and the seat's cut, you need to blend them into the intsert. You "could" widen the cheek just where the short side comes around to join the walls, but it's not mega important in this case.

    To get in around the "corners" as such where the bigger diameter of the flap wheel wont fit, use a split rod with some emery paper. You can run this at a normal drill speed and not a high speed like in a die grinder. Just wind a small amount around the split rod so you can get in the awkward area's, and a larger amount so work a little around the short side turn.

    Dont forget the valves need back cutting when you have the seats cut. And make sure the stems are in good condition or fit new... the machine shop should measure this.

    Hope thats a help.

    Well done for having a go.
     
  12. milesmk2 Forum Member

    Joined:
    Oct 22, 2010
    Likes Received:
    3
    Fantastic guide this!!!

    Im keen to do this to a 16v head, and i have one stripped down and ready but i am unsure as where to start and what to cut out. I know this guide is for an 8v head but im hoping you can point me in the right direction for a valver head :)
     
  13. Jon Olds Forum Junkie

    Joined:
    Jan 28, 2004
    Likes Received:
    371
    Location:
    United Kingdom
    agree. great to see so many involved.
     
  14. milesmk2 Forum Member

    Joined:
    Oct 22, 2010
    Likes Received:
    3
    I have been having a go with a spare 8v gti head i have.

    So far ive cut away and smoothed the edges under the valve seats, ground down most of the valve guide boss and started gasket porting the inlet ports.

    Got afew photos, just wanna see if im doing this right.

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    Unfortunatly rain stopped me as i dont have enough room in my shed to do this so have to do it all out in the back garden.

    Also i was wondering where you get your flap wheels from? The only place i seem to be able to find them is Homebase and they are not cheap!
     
  15. Jon Olds Forum Junkie

    Joined:
    Jan 28, 2004
    Likes Received:
    371
    Location:
    United Kingdom
    Cromwell tools. Look out for the offers magazine.
     
  16. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    131
    Location:
    Southwest
    Going in the right direction. . Don't go over the top with the main port or you'll find the head bolt holes! Stick to 30-31mm on std size valves and it wont be lacking.

    Don't go too far into the seats. .Follow the guide for that.

    Flap wheels are available from loads of places...most of the tool supplys do them..do a google. .J&L, RS, etc.
     
  17. milesmk2 Forum Member

    Joined:
    Oct 22, 2010
    Likes Received:
    3
    Yeah I'm going steady with it, just doing bits at a time, just need to get hold of an old valve. As for the seats I only skimmed the area under them so i could see everything in there when it comes to polishing.

    Homebase do flap wheels but they don't seem to last 5 minutes.

    I gasket matched the inlet manifold too, but didn't go over the top with it.
     
  18. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    131
    Location:
    Southwest
    Get yrself a pair of internal calipers to do some measuring up. Dont waste time on polishing... it does nothing for flow.
     
  19. milesmk2 Forum Member

    Joined:
    Oct 22, 2010
    Likes Received:
    3
    Okey doke
     
  20. milesmk2 Forum Member

    Joined:
    Oct 22, 2010
    Likes Received:
    3
    I managed to get hold a 33mm valve and have got as far as just before the throat using it as you described.

    Just wondering which burr you used to cut out the valve guide boss? Was it a long shank cylinder burr?
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice