Gasflowing 8v Head.

Discussion in 'Engines' started by JONNY-ROTTEN., Aug 18, 2006.

  1. JONNY-ROTTEN. Forum Member

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    Hi all. have read through all posts with respect to 2litre 8v, and bigger exhaust valves with great interest, and last night thought bugger it, and stripped the spare 8v head i have in my garage. i've become too lazy and spent far too much time going out and enjoyin myself, but have become bored with the power of the car now. forgot how relaxing a couple of cans, and being locked away from the world in the garage was!!!!!
    i have had a good look at the head stripped, and have a new die grinder to play with:)
    does anybody have any sound advice i can follow as i plan to go to 35mm ex valves, but also gas flow the head. The exhaust side seems easy as removing the ex manifold, there are black deposits on the head where the exhaust is bigger than the head, but not to the edge of the gasket. Do i grind out where the carbon is, or go further and the full size of the gasket, and match the manifold to suit???? or is the exhaust already ok, and just the ports on the head need to be enlarged. Also i have seen grinding stone kits in the local motor factors, but don't know if they are the correct set i need.
    i have read a couple of guides on it, but weren't exactly in depth. on advise from retro mag's guide, i intend to put alignment dowels in the manifolds to help me, any idea where i can obtain them, or can you knock them up diy??? i also read you can get less resrictive valve guides, worth it????. i also intend to use a tdi inlet manifold gasket, i've got the advice on here about that i think, but have lost the part no doh:thumbd: :thumbd:
    i've heard people talk about three angle valve seats, worth it also???? all information gratefully received:) :) gonna see if i can borrow a digi camera to log my progress
     
  2. domma Forum Member

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    Hello Mate,

    You will more often than not get a flood of messages telling you to leave it up to the experts with a post like that.

    As it is you sound very much like myself, rather have a go myself on a spare head and if i find out after all my hard work that its worse than before then at worst i take it off and then consider paying somebody else. At least you learn along the way having a go and getting stuck in. Personally i get no satisfaction from paying somebody to do the work on my cars, i understand guys that do and i don't knock them for it.
    Realistically though, if its out of my ability theni'll pay for expert services!! But i do believe that a diy port job is possible, especially if you listen to good advise gained on here.
    www.sa-motorsports.com/diyport.shtm has some good info but the equipment is geared at cast iron heads. Good pictures though.

    You should be able to get all the general advise on not going mad withthe grinder! Smoothing and not opening up the inlet and exhaust ports on the head to much, this can aparently make things worse for air flow. matching the manifold and getting a balance on the volumes on all four ports is advisable.

    As for dowls you can just double drill a couple of holes and use two drills to align them on assembly later. You don't really need to have the dowls perminantly in place, all the manifolds i've put on have been pretty tight anyway, trying to aligh another two dowled pins maybe more of a pain.

    As for larger exhaust valves, i'm still undersided as you can see from the post you mentioned.

    Just do your research mate and get yourself stuck in that garage!!

    Cheers Domma..........
     
  3. JONNY-ROTTEN. Forum Member

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    Yeah i am allergic to paying money out to people myself;) ;) . must say i have only ever learned by havin a go, so if i do bugger it, how hard is it to get another head!!! not very. The only time i have paid for people to work on my car is for a mot, thats it, plus if i learn enough,who says i can't help others, or possibly do a guide!!!
    i am not a trained technician, but am a workshop manager/ service advisor so i have access to everything i need, and have been inspired by others on the forum.
    i don't intend to go mad but do want to open the ports out a bit, and just wondered if anyone else has had a go with good results.
    i have rebuilt engines before, just not done this. gonna have to find that guide in retro magazine i read tho, was quite good.
    plus we have ties with the states at work , so you can guess where most of my stuff is coming from, can't see me paying 90 odd quid for 4 bl**dy valves, then 70 odd for the seats!!!! appreicaite the answer tho domma, thanks
     
    Last edited: Aug 18, 2006
  4. Bundles Forum Junkie

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    I've read evey book i can find on gas flowing, go to your local library, mine had about 4 different books on gas flowing, one of them being david vizards "tuning BL's A series engine" which has a HUGE section in it on gas flowing. I read them all and practised on a few scrap heads i got from the scrappies. The first road going head i did was a Mk1 golf 1.1, i spent three days doing the head and manifolds, fitted a webber carb and it went like stink, destroying Nova Sr/SRi's all over scotland and reving to 7500rpm in the process.

    From that i got people wanting me to do heads for thier motors, mostly novas sadley (which is a VERY easy head to flow tbh, really short ports.

    As a VERY rough guide, on an 8v engine you should be aiming at being able to fit a disk about 80% the size of the valve head right down through the port (without a valve guide in) any moe than 80% will not give you anything more. One of the main areas is around the valve guide/bend in the port, this is usualy CRAP!, so opening up around there can yield great results, the bend should be as constant and as smoot as possible.
    Also DO NOT polish the ports, this causes fuel droplets to form, the walls of the ports should be smooth but not shiney, I finish mine with 400 grit emery paper.

    Once I've done the head i do the manifolds by placing a VERY small amount of ink/paint around the ports on the head, then bolt the manifold up to it, this way you can see where the ports and manifold line up (you'd be surprised how off centre they can be!) and you can match the manifold to the ports as best you can, i always make the manifold SLIGHTLY smaller than the ports, it's better to have a step UP in diametre than a step DOWN like if you opened the manifold up to much.

    You can measure if you have increased flow at all with something as simple as a hoover, some hoovers have a vaccum gauge on them, which is just a simple slidey red bar. Plug the valve guide with a piece of cloth (if you have removed the valves. Place the hoovers hose over the port and turn on the hoover, the bar should show quite a lot of vaccum as the hoover struggles to pull air through the port, mark the gauge then flow your head. Once it's done retest with the hoover, if the gauge is showing less vaccum then you have more airflow. It's as simple as that.

    Hope this help you/anyone in some way, shape or form.

    :)
     
  5. JONNY-ROTTEN. Forum Member

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    Thanks for the info bundles, i read about not polishing the ports too much, but i must have a look at these books. understand what you say about making the bend constant, but i heard somewhere on the inlet the idea is to introduce swirl, and not to smooth the bend out to much. if you are at harewood this weekend, i owe you a pint, same also goes for you as well domma!!! (i will be bringing a crate btw) but i may have the head with me if any pointers could be demonstrated. really want to give the local boys a fright round here, by sticking a flowed head and a 2ltr bottom end and a cam at once;) ;) wtf!!!!!
     
  6. Bundles Forum Junkie

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    The swirl idea is kind of hit and miss, imo the air flowing around the bend and passing the valve guide and valve head will induce enough swirl.

    I'll take a rain check on that pint, not going to be anywhere this weekend because i'm flat broke, lol.

    Another one of those books is called "Practical gas flow" but i can't remember the author.
     
  7. domma Forum Member

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    I'll be decorating and taking my shift in changing nappies all weekend mate so a rain check also!!

    Good book that Bundles mentioned, i cut my teeth on Minin's and "Visard" was always the man that was listened too like a God. There will be plenty of info their about the three angled valves also Jon. Might need sombody with a cylindrical grinder to do you a favour on that one though.
    I remember some of Visard's Mini valves looking like big thin disks resting on a pin shank. Dont think i will be going that far.

    Valve guides can be shortened to Jon to gain better flow but expect a shorter life out of them. My Mk1 head has three oversized guides from the factory, look about 14mm so they are getting shortened for starters.

    Good luck mate and let us see some pics as you go!!

    Cheers Domma.........
     
  8. Bundles Forum Junkie

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    I'm going to do a head for my golf once i source a cheap(ish) head to overhaul. Might just do a photo diary of it too :)
     
  9. Barkstar Forum Member

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    Despite my Yorkshire roots unless I can get some good before and after pics of a well flowed head I'll be passing the job on to someone who knows what they are doing. I'm happy to do a clean up but porting is one of the last black arts. No two tuners will do the exact same thing and still get similar results, but combining their ideas and you'll ruin the head. If you've got a spare head then by all means give it a go but the only way to check results accurately is on a flow meter or do a RR run with no other mods at all. And cfm isn't everything, tuning is like an orchestra it all needs to work together, opening up the head without the right fuelling, cam and valves will just end up with the fuel falling out of the mixture as it looses speed entering the ports.
    Be interesting to see the results.
    Barkstar [:*:]
     
  10. mark25 Forum Junkie

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    The converse is also true for the exhast manifold.

    Have a look in the combustion chamber with the valve 1mm open, you'll see where the gains are comming from there. Although the german heads are usually a lot better than the mexican ones to start with in this respect. Whatever material you remove from here will cost you in compression tho!

    If you're opening up the hardend valve seats to match a bigger port, clarke do sets of 1/8 and 1/4" rotary carbide burrs, 30 and 60 sheets respectively, which will speed things up a bit...
     
  11. wildwilliebaret Forum Member

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    im really watching this one, have taken my head of my spare dx to do this over the winter, all my questions are as above!
    good tip about the carbide burrs, cheers,
    just asked for a dremel for christmas, with the flexi extenxion should be able to get those harder to reach places!

    does anyone know what the compression ratio would be with a 2l bottom?
     
  12. mr hillclimber Club GTI Supporter and Sponsor

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    I "think" it's John Dalton.
     
  13. mark25 Forum Junkie

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    when working on the exhaust port ,do all the machining with an eye on reducing the 90 degree bend in it, you can't really reduce it, but you can remove the material in a manner that tries to straighten it, rather than tighten it...
     
  14. Bundles Forum Junkie

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    Same for both ports tbh :)
     
  15. mr hillclimber Club GTI Supporter and Sponsor

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    Just use a couple of steel roll pins to locate the manifolds.

    Good luck with the project. If yr sensible, good results can be achieved.

    If yr using the head on a 2ltr, consider larger inlets as well.
     
  16. mark25 Forum Junkie

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    Very true, but the exhast has a tighter bend (90 deg as opposed to IIRC 70 deg) and is more restrictive. Not entirely sure the inlet port wants to be any bigger tbh[:s] (on road engines)
     
  17. Bundles Forum Junkie

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    About 80% of the valve head all the way through the port makes for a good road engine, imporiving flow and keeping a decent air speed.
     
  18. wildwilliebaret Forum Member

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    am planning on audi 80 bottom end with a mildish (272?) cam, audi 100 throttle body and wur, im planning to match the exhaust manifold to it and use an earlier one cos the reportedly flow better,
    ive heard about uprating kjet fuelling by using a saab fuel pump and faster /bigger injectores
    tis an 87 mk1 cab (pre clipperkit lol) so not really for track or owt, how does the bigger valve thing work then, would you reccomend doing that along with the other mods as above??
    sorry to sound stoopid, the rest ive got me head round.
     
  19. Tristan

    Tristan Paid Member Paid Member

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    From asking experts(!) over here , its a good idea to leave the inlets slightly "rough" as posted above , but only from the fuel injector area inwards , as there shouldn't be fuel upwind of that..... and to really polish smooth the exhaust ports , to prevent carbon build up , and help the waste gases get out of the chamber.
     
  20. mr hillclimber Club GTI Supporter and Sponsor

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    If yr just after some extra fast road power consider sticking with the standard valves. Bigger valves will give extra power but will cost around 12-14 quid each, plus extra cost for the bigger valve seats needed. I "think" the standard valve seats will accept 0.5mm bigger valves, but not really worth the effort and expense for road use.
     

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