Head work --(Dustin)

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i have a TF Gemini and live in geelong. I have extractors webber hotcam remaped dizzy and a little bit shaved of the head (10tho)

whats the next best thing to do to give a bit more oomph
what should i do to the head
Big Vavles Porting ?????
any one have a head with these mods in the geelong area
and wish to sell ????
any help

[old forum]

I am after significant power gains
the cam is a crow stage 4 38/70
any other ideas
eletric water pump
would twin carbs be a better investment than the head ???
help

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Twin carbs would be sweet, but you are better off going for the head, both in terms of bang and bang for your buck if you are planning on buying say, for example twin 45DCOE webers. For a number of reasons, firstly, if you fit DCOEs or other sidedraft webers onto a gemini they don't fit without moving the brake booster and master cylinder, unless you use a comparatively ugly(looks and design) lynx manifold.

If you do re-engineer the brakes to fit em, lemme know how.


Ok, headjobs, well, firstly port and polish if you haven't done this already, get your self a pneumatic grinder, or abrasive grinding bit for your power drill, or a Dremel(TM) style grinder.

Firstly take off your head as per the workshop manual, carefully or you will warp the fuck out of it, I fucked two heads this way. Once you have it off, disassemble it, cleaning everything thoroughly and laying it out in order on a CLEAN and CLEAR work bench. Wash everything in petrol then thinners. Using a valve spring compressor take out the valves. Sandblast the head ports and combustion chamber spotlessly clean before giving the head a long soak in whatever cleaning solution your local head guy uses for ALLOY heads. Now that you have a spotless head, we can start doing the fun part.

Get your head and sit it somewhere solid, in a vice between some lumps of wood to prevent damaging it is my suggestion. Fit a new gasket, there should be a fairly substantial area of metal between the edges of the gasket and the edges of the ports, roughly 2-3mm.

Hold the gasket dead set in position and mark the area with a nicko. Remove the gasket, take your trusty metal removing tool and grind the port out until about 1mm of that nicko is left.

Refit the gasket, compare, hopefully there should be 1mm showing, but this is the safe way, if there wasn't then you are lucky you checked, if there is, no problem, finish up the grinding, regularly compare the gasket to what you have ground, smooth the port deeper into the head maintaining the new larger size. If necessary maybe even do some smoothing from the valve side of the port, but that is more porting than port-matching.

Once you have done this, do the same to the manifold, both sides of the engine. Once all this is done, leave a smooth surface on the inlet side but polish the fuck out of the exhaust side.

Afterwards wash the head under a high pressure hose with warm soapy water, if you leave ANY, and I mean ANY shavings in the head you can kiss your engine goodbye. Then rebuild the head, if you don't know how, ask me.

Ok, the next step is a porting, there is a black art to porting, based around years of practice, so instead we do the next best thing, have a go and hope for the best. Do what you did above but grind all the way up to the valve, not quite to the seat, that would be BAD, making sure you get a constant cross-sectional area of the port and trying to maintain a smooth path for the gas flow, the best way to do this is to grab 5 head for about $50 from a wreckers or the trading post (the better option) and to take them to a head shop with a flow bench, but this costs the dollars I just don't have.

So instead you have to think like a gas and imagine what you would like to flow through. Making sure to leave enough support for the valve seats and stem and try to avoid breaking through into the water galleries, that would be bad.

Again, leave a smooth finish on the inlet side and polish the exhaust port until it looks like a mirror.

The last option is a full headjob, including bigger valves, er, I haven't done this one, so I am passing on inaccurate hearsay and 324th hand advice, er, go bigger valves, I think the inlet on the 2litre is a few mm bigger about 44. This would be nice. While you are at it pay someone to do a good three angle valve seat job. I really don't know what valves to use, just ask someone at your local headshop they will probably be more than willing to give you some advice, particularly if you come bearing a carton.

With any of these, it is MORE than worthwhile to do a good job when you put the head back on, you might want to consider having the head shaved to up the compression, if you haven't already that is. I would suggest 9.5:1 for normal road use. Get new valve springs, probably have to redo the valve guides with a set of K-Line(tm) sleeves, new headgasket, tappet cover gasket, inlet and exhaust gaskets, um, high quality high concentration coolant, preferably premixed or made with genuine demineralised water. Bad coolant will root the fuck out of alloy much faster than your block.

Um, that is about it, what else, careful retorqueing the head, don't warp your beautiful piece of work, re-set your tappets and check them regularly for a while afterwards. um, it might be worthwhile taking your car in to have the dizzy regraphed and the carby re-jetted to suit if you do any wild mods

Any more questions, I check the forum at least once a week

[old forum]

thanks adam
just got hold of twin 40mm down draft webbers the same as the guy with his 202 gemini has got on his 1.8lt

how much should i take of the head to get the comp up
i have a 75 model head on it
will the porting give a notacible differance ???
thanks again

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p.s Just how would i go about rebuilding the head
ive been told i wont beable to do it u need speactial tools

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1. A 12mm spanner to undo the air cleaner bolts
2. A pair of pliers to undo the air cleaner hose clips, or just maul your fingers but don't say I did warn you
3. A 10mm spanner to undo the tappet cover bolts, careful not to lose the rubber half moons or the tappet cover bolt rubber seals.
4. Whatever size (12-14mm I think) spanner to remove the inlet and exhaust manifolds.
5. A 12? to undo the bolts recessed into the timing chain recess, DON'T DROP THEM, I MEAN NO, NO NO, if you drop them, take out the engine, take of the sump and find them, YOU CANNOT leave them there OK, my suggestion is to stuff the recess with a rag so you can't drop them.
6. A spanner to undo the Camshaft pulley bolt, be careful not to let the chain lose tension or it can either skip teeth or just fall off the crankshaft pulley gear.
7. You know you could read most of this in the workshop manual, try your local library, or just shell out and buy one.
8. A 10mm allen key to unbolt the head bolts, IF YOU DON'T GET THE ORDER RIGHT YOU ARE FUCKED, THE HEAD WILL BE BENT TO BUGGERY OK.
9. that is it, your head should be off now
10. To remove the timing gear follow the workshop manual it is pretty darn straight forward, just a few spanners we have already decided we need. Only other tool is a valve spring compressor to get the valves out, I would suggest buying one if it isn't too expensive, otherwise beg, cheat, borrow or steal one.



So far the only wierd tool is the 10mm allen key but they aren't to hard to find, I REPEAT be stupidly careful removing the head bolts.

To port it you just need one of the grinder things I listed in my original post, plus a few grades of wet & dry for polishing the ports, a gasket, and, and, and a nicko, there I thought of something.

As far as bigger valves etc. to do valve work you need special machinery, if you wanna buy it just for your gemini can I move into your house with you? You will have to pay to have the seats reground to suit and to have the each valve ground to each seat. And also make sure they check that the valve spring seat pressure is right.


You will need to go to a headshop for that sort of thing, have the valve runout and alignment thoroughly checked, not just a quick job, if they don't have the tools then leave and go somewhere else.

As for the re-assembly, that valve spring compressor will come in handy, you will NEED a torque wrench and a 10mm allen key fitting for it. Other than that, er, new gaskets, some gasket goo, some some some elbow grease and knuckle skin will be required, but usually us gemmy owners have lots of that.


As I keep reiterating WORKSHOP MANUAL.

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Can't say, sorry, compression ratio is pretty easy to check, if your Gem displaces the standard volume and has a zero deck height. Then you either pay someone to CC the head or just get yourself a syringe and do it yourself, if you can't figure out how, guess, then ask me.

20-40 thou is typical I THINK, but I while my head was getting decked I was up at the shop buying the guys from the workshop lunch, You will have to be at a machine shop to get the head decked/shaved anyway so they should know, just get the combustion chamber CCed to give the correct compression ratio for whatever fuel you plan on running, for my leaded gemini we aimed for 9.5:1.

The porting will make a noticeable difference, although I can pick the difference in my gemini between when I set the tappet clearance normally or 5 thou too small.....

What manifold are you using for the carbies? IDF webers??

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not sure on the manifold havent got posetion of them yet
and i a m 99% sure there 40 IDF webers
is $400 a good price for these ???

thanx

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can't say for certain, never priced a set of IDFS but I know they don't come cheap and $400 sounds about on the money, I know of a gemini with a hot G200 and twin IDFS which used to lap lackside in the super sedan class in 1minute 8seconds. which is quick, DAMN quick, what I am saying is with that set of IDFs properly set up they will be MORE than capable of fuelling your 1600 donk