1.6 Twincam, 4 x 4 Conversion

Oi!! Plaigarists! This stuff is copyright!
Not that it'll stop you ripping it off.

It's probably better to split this in two.

4 x 4 Conversion

1.6 Twincam

This isn't anywhere as complicated as people make out. Once you cut through the bullshit,  it's actually just a bolt on.

N.B. I have not done this conversion other than as a mock up. After chopping up and comparing the internals of the G16 SOHC and  G13 DOHC heads, I will NOT be completing this conversion. Since I am boring out to 1720cc, (78mm bore), I have taken the decision to stick with the 1.6 head, as I believe, for me personally, that it's the easiest  route to what I want. That is not to say this is not a worthwhile conversion ( Oh, I feel a flame war coming on! ), There are enough happy people running converted Swifts to prove it works.
It's just not for me.

1. Please don't ask me what power output a Twincam conversion will give, as I simply don't know.
2. Please don't ask me what is the best chip to get, as again, I don't know.

Myth 1. You need a Vitara gasket to lower the compression.

Yes, you need to use a 1.6 gasket, not to lower the compression but because the bore of the 1.6 is larger. If you used the 1.3 gasket, the fire rings, (the metal ring that seals the bore), would not seal on the top of the block and the gasket would blow  soon after you started it up. There is no difference between the Vitara/Swift 1.6 gaskets. If you want to lower the compression, you modify the head, which you really want to do anyway, to reduce the masking round the valves and, make best use of the increased bore.

Myth 2. You must increase the oil pressure of the 1.6.

So why are the pressure spec's for the two engines the same then ? Sure, the running pressure for the 1.6 is listed as fractionally lower, but it's marginal. It's up to you whether you increase it or not. (Really all you are increasing is the mid to high rev pressure, you won't do a damn thing to the pressure at idle. Adding a washer to the pressure relief valve, or a stiffer spring is all it takes ).

Myth 3. The 1.6 is not reliable.

So why are there loads of high mileage Swift 1.6's running around then ? It's true the engine has it's problems ( which won't be gone into here ), but it doesn't tend to eat cambelts and hence the valves, to the extent that the G13 goes. The main thing is that the crank has hollows at the journals, which makes it lighter and not as strong as the 1.3 item. (If you want to get technical, the 1.6 crank is a steel casting, the 1.3 is a steel forging). Hence the 6500 rpm limit of the 1.6, stick to that and there shouldn't be any problems. My normal starting procedure at Hillclimbs, involves revving the engine to 6000 rpm and simply dumping the clutch. Haven't broken one yet. Now 350 + "dumps" and counting.

Myth 4. The 1.6 is considerable heavier.

Whoever came up with that one has obviously never picked them up and carried them around. ;-)

There's not much in it, remember the G16 crank is considerably lighter, the head has only a single bank and one cam. It will mean that the head is carried higher, which will affect the CoG slightly.

Myth 5. You have to change the lower timing wheel. Oh really? so, why are the 1.6/1.3 items identical then ?  Again, I think this comes about from confusion. The MK1 timing wheels are not as wide as Mk2 and 1.6 wheels, which may explain why the MK1 eats belts, so as long as you don't use a MK1 head (or if you do you change the cam wheels for Mk2 or 2 1.6 items) you should be all right. You need to use a G13 tensioner wheel though. see below.

Myth 6. You can overbore and use 1.6 internals in a 1.3 block.

Sure can.

If you like an engine that does half a revolution between rebuilds. The 1.6 stroke is larger, the rods longer. put those in a G13 block and the piston will smack into the head long before TDC. That is if you could get the 1.6 crank to fit in the 1.3 block in the first place. Which you can't, for the simple reason the main bearings are different sizes...Doh..


Surely there can't be?
The Twincam head is far superior in every way to the SOHC. Which everyone knows is a pile of shite.
Well, "everyone" is wrong. 

Though I doubt you'll find another person on the planet who agrees with me!! So, obviously, these are my own personal opinions.

The exhaust valve in the DOHC, is 1mm smaller in diameter, the throat smaller still, below the throat at the valve boss, the port area is only approx two thirds of the valve area. The whole middle section of the port is similarly choked.
The port walls, both intake and exhaust are approx 4 - 4.5 mm thick, so not much scope for increasing them to 1.6 dimensions.

In contrast, the 1.6 SOHC head doesn't have anything like the restriction in the exhaust port. Also, the roof of the intake port is just over 6mm thick, which gives scope to change the intake angle and give a straighter port.  There will eventually be links and pics when I get round to taking them.

The fuel injection system of the DOHC is restrictive and antiquated.
Sorry, but it is. It'll still work well enough, if you're doing the conversion on a Twincam, but it would be a lot of work, to fit what is obsolete junk, to a 1.6 saloon.

Judging by past experience, I'm pretty  sure some sad bastard, will mail bomb me for uttering such blasphemy. Let me just say you are wasting your time. Yahoo's anti-spam software is pretty good, from past experience 90% of it goes straight in the bin, and I've gotten pretty adept at winkling out the other 10%. Still, it's your time, and it gives me a good laugh!!.


You can use 1.6 pistons in a G13 block, but it will result in lower compression, (see below for details), perfect for a turbo application. Or, you can skim the block and head and use vernier wheels to reset the timing (or not). There are other piston permutations, best to visit the Delphi forum. I have no experience of reboring a 1.3 block in this way, or other piston permutations. You can bore a 1.6 block out to 1720cc with 78mm pistons. This does however require a copper head gasket. This is the route I'm taking.

You may have read the above and thought "this guy's a prat, there are folk running 1.6 pistons in 1.3 blocks, and, they have no problems  with blowing G13 head gaskets".
I'll further confuse you, by agreeing with you !

The bore of the 1.3 is 74 mm, the bore of the gasket, if you measure it is 75mm. The bore of the 1.6 is 75mm, the bore of it's gasket, 76mm.
So, why do I say the 75 mm 1.3 gasket will overhang the 1.6 block, if the bore of the cylinder is the same as the bore of the gasket ?  The answer is simple. If you look at the top of the bore you'll see that there is a small chamfer, approximately 0.5mm deep by 0.5mm wide, taking the bore at the very top of the cylinder to 76mm. The chamfer is there to allow easier fitting of the piston rings. (which explains why "Mr Doofus" breaks his piston rings on a big overbore). The more astute of the doubters, will now realise, that when boring the cylinders and skimming the deck of a block to fit the 1.6, 75mm pistons, the chamfer is completely removed, so a 1.3 gasket (75mm bore remember) will seal successfully. Not so on a 1.6 block, which obviously has a bore at the deck, of 76mm. Pretty obvious then, that a 1.6 gasket must be used, I really don't know where the, "use it to reduce the compression ", guff came from. More than likely the old 2 + 2 = 5 scenario. Or, if you are really cynical like me, deliberate disinformation.

I can't really make the above any clearer than that, if you still can't figure out what head gasket to use, then may I suggest this conversion is not for you?

Further Piston Info.
type compression height  pin diameter  piston height
G13b  29.1 mm 19 mm  58.2 mm
G16b  28.5 mm 19 mm  56.0 mm

If it were me, I'd overbore to the max size available cheaply, i.e., 1mm oversize on 1.6 pistons. But, as someone pointed out recently, "what the F*** do you know anyway! You're just an un-educated, dumb-f***, Wally maker!"
I think my old schoolteachers and college lecturers would dispute the un-educated bit though.
And, I make crowns and bridges, not Wallies (dentures), not that it makes a difference.
The cheapest pistons are available from Asian auto parts or, Rocky Road Off-road in the States, both also sell high compression items. I have no details of the comp. height of the latter..
I'd also reduce the height of the 1.6 pistons.


This is the bit where it can all go tits up !.
Stick on the head, no problems, fit the belt. Now try to fit the tensioner wheel. Ooops!. Yep, there's not enough adjustment. So, fit the smaller diameter GTi wheel. Still not enough adjustment.

   Depending on which tensioner pulley you wish to use, you'll have to source a belt in the region of 126 - 130 teeth. If I ever get the time, I'll eventually figure out the fitments.



Fitting the Twincam head isn't the most complicated part of the process.
That, is deciding on the induction/fueling system choice;

It's certainly where the main expense is, and, where the greatest power improvement can be made. Whichever system you decide on, best of luck !

1. Fitting the GTi system in full, including ECU. This then needs to be reprogrammed (chipped) with a custom written chip. This is only really cost effective if you do any other modifications at the same time. If you add any other goodies, i.e., exhaust/filters/, then you are liable to put the fueling out , necessitating yet another chip.
Of course you could use one of the cheater interfaces ( Interceptor, etc., ), but, these don't modify the timing curve, which should really be optimised for the 1.6.

2. Fitting the carb and manifold from the 1.6, not as difficult as it sounds, a little redrilling and spacing using the flange from a GTi manifold, some grinding to match the ports to the runners and you're away. But, and it's a big but, then it needs to be set up on the dyno. Not sure if any parts are available. So, fit a twinchoke downdraught Weber, for which parts are available. Then you need a filter and housing.  Not to mention at least one dyno session. Back to escalating expense again.
You could fit the TBi injection system if that's what your 1.6 came with but then we're back to the dyno and subsequent re-chipping. Still leaves the same scenario as above though, any extra modifications and it's back to square one, to set up the carb/injection/timing to get the best from what you've done.

1 and 2 are definitely the cheapest routes though, if you really have to get rid of the SOHC for reliability reasons. Stick on a cheater box to fool the ECU and maybe a distributor from the MK1, or the internals from the SOHC, to get some vacuum and centrifugal advance. It won't be the optimum, but it should work.

All of the above have the drawback that you are trying to draw the air through a small restrictive opening. Quite a few people have gone down the road of boring out the standard GTi throttle body, or fitting a larger one from another car..
Myself, I can't see the point of any of the above unless, as I say, you simply want to get rid of the SOHC head for reliablity reasons. Then, you simply want to take the cheapest option that's available to you .

If it's best possible power that you seek then there is only one option.

3. Programmable ECU.

Now, I've had this argument countless times "Oh but that's going to cost an absolute fortune" Then, they start quoting me huge amounts for some exotic ECU.

Utter bollocks.

There are systems available to control fuel AND ignition from £450 GBP, less if you are in the USA or Australia. Most will allow you to do away completely with the Mass Air Flow meter, a major restriction point. Most are user programmable, allowing you to get some/most/all of the setup done before you visit the Dyno, so the dyno session should cost you, at most,the same as a re-chip (if you have to have a session at all, depends on what equipment you have access to in the first place, or how patient you are).
A custom ECU usually also allows the option of going to multi throttle bodies. Again, there is the argument that these are a fortune. And, once again, that argument doesn't hold water. The Twincam head has the holes for the injectors cast into it, so, you don't require injector-in-body units. Use an old set of Weber/De'llorto carbs. Been done countless times in the UK. You can pick them up for buttons, as long as the spindles don't leak, that's all you need. It's what mine are made from. You could also use a set from a bike. The kawasaki GPz 1100 had TBi injection and the spacing is almost the same as the Twincam. 42mm Gixer (GSXR..bike) bodies are often available on e-bay, I picked up a set for £60.
Future upgrades can easily be accomodated.
Ok, you're not going to get an all singing and dancing, sequential, multi-coil system, but what do you want for £450 ? Even at that, the Emerald system I'm going for has;

soft and hard cut rev limiter
nitrous control
multi batch capability (it'll run 8 injectors in 2 banks)
and a host of other things I don't pretend to understand.

 Compare to fitting a set of Weber twinchoke carbs.

You need a manifold (if you can't make one) £250,
You need an ignition controller £350
trigger for above £90 (and don't mail telling me you can use the Swift distributor as the trigger, it's a reluctor system, which gives an unstable signal for triggering purposes)
New fuel pump if you're changing from an injection system.
Fuel pressure regulator £50

Without even adding the cost of the carbs, you're already well above the cost of a throttle body system, which will be far more fuel efficient and give better bottom end power. Set up properly, it'll give more top end power too, (you can use the whole 40mm cross section rather than choke it down, after all, you don't need a venturi to draw fuel). Better mid-range and part throttle response due to more efficient vapourisation/dispersion from the injected fuel. Thats before you consider that recent experiments in the UK, suggest that at high revs, switching to 8 injectors gives more power. Most systems on the market can handle this task seamlessly, you just decide on the switchover point. The system will run on 4 injectors below this point then switch to 8 above it.

Still think it's the most expensive option ?


I'll state right now, I have absolutely no idea, how an exhaust will fit for the 2wd cars. I don't intend to fit this to either a 1.3 or 1.6 2wd gearbox, so I have no idea if the downpipe has to be extended or if any aftermarket manifolds will pass under the motor, without modification.
I only intend using the 4wd gearbox, the size and positioning of which necessitates a different  exhaust route, (not to mention the prop, rear diff and carrier).
I'm simply going to make up something from stainless, alloy and carbon components that meets the UK Motor Sports Authority noise regulations.

4 x 4 Conversion

I've twice been told by Suzuki dealers (Not Walter, I hasten to add), that it's simply a matter of bolting everything into place after chopping out the rear suspension mounts under the floor.

I'm ashamed to say I've actually repeated this crap without checking it.

It becomes glaringly obvious as soon as you strip out the full interior that this isn't the case. The spare wheel well is where the diff goes. So, angle grinder time.
As soon as I get the cage in I'm going to make an external frame that bolts to it and allows me to roll the car on it's side. I've retained part of the floor and the tunnnel from the saloon, so I can measure up and post pics of every difference. 

This is not at all  very easy conversion, a large part of the rear floorpan needs to be chopped out, and the floor of a 4wd welded in, to carry the subframe for the rear suspension . The front rack is set slightly higher on the 4wd's to accomodate the transfer box. Not quite sure yet how I'm going to get round that one!

I have been trying for ages, without success, to obtain  permission from  Suzuki GB to post an outline drawing of the 4wd system from the workshop manual. Anyone know  any bigwigs at Suzuki GB, or, Suzuki Japan??

Iain Paterson reserves the right to be identified as the author of this article. It is free to be downloaded for personal use only. It may be reproduced, in part or whole, in print or electronically, for information only and, ONLY with express permission of Iain Paterson. Permisssion will not be unreasonably withheld, provided I am identified as the author/source, but, I want to be asked first!! Reproduction, in whole or in part, in print or electronically, for any commercial purpose, or, in ANY connection with any commercial purpose, is EXPRESSLY FORBIDDEN!! patersoniain@yahoo.com Copyright Iain Paterson Feb 2002.