1600vx 8v Classic - light tuning options

[acbluemarlin]

Having just spent a day at Harewood Hillclimb drivers school I would like to investigate gaining a little more power/torque for my 8v Classic.  I'd be happy with another 10 or 15bhp and a few more lbs/ft.  I don't want to break the bank or my Ital rear axle.

I want to stay below 1700cc for the engine in case I'm tempted to the odd Class 2a run, and at this stage I don't want to swap the car for a K-Series

Having searched Blatchat there is plenty of information about Kent AST15 cams and Blydenstein heads, but Bill Blydenstein is no longer an option and I believe CAT cams and Newman cams are possible options to Kent.  Has anyone tried a slightly wilder profile than the AST15 for example?  Is there anyone else who can do the cylinder head work?

The threads on 1600vx tuning seem to have died away recently, so does anyone have up to date guidance on the best options?

 

[Wrightpayne]

Have you searched the wider net? I would have thought there would be vauxhall forums with tuning info on this engine.

Ian

[acbluemarlin]

Thanks I've put some posts out there as well, but not much is coming back so far.

One useful snippet is that the C18NZ engine from 1.8litre Cavaliers seems to be the same block and has bigger valves as standard.  Same may also apply to the C20NE from the 2.0litre cars.  Not sure if they will bolt straight on though.

[Johnh]

I have the 1.8 8 valve and that gives out 120 bhp on paper but I've never  checked ..if your sure you want to keep the car?  try and source a complete 1.8 engine ..if it were me I'd upgrade the car for more power /suspension/axel and brakes in one hit if that's an option.

[acbluemarlin]

Thanks Johnh but I want to stay below 1700cc capacity

[Roger King]

I had almost nothing to do with the 1.6 Vauxhall, nor am I aware of what parts are available, so the following is largely a series of generalisations. From memory, I don't think that Vauxhall ever used this lump in any of their own vehicles (prepared to be corrected on this); the block is physically much larger than that of Vauxhall's production 1.6 engines, being more akin to a 2 litre block in size.

Firstly, as a general principle, I am not a fan of changing camshafts until the rest of the engine has been optimised to take advantage of it. In an extreme case, you fit a performance cam to an otherwise bog standard engine and you end up with a cam that only breathes well at high revs in an engine that can only breathe well at low revs; result - the engine is worse everywhere than it would be in standard tune.

It may not seem the most obvious place to start, but fitting a 3D mapped ignition system might be the best way to go. This will probably provide no more power, but it will fill in the torque curve and part throttle power and response to a dramatic degree, effectively making the engine feel larger. As a bonus, fuel economy will be drastically better if done properly. You need to speak to somebody who has added this type of system to their carburettored car - I guarantee they'll rave about the difference. Another advantage of this is that you don't have to dismantle the engine.

The next most obvious thing to do would be to increase capacity to nearer to 1700ccm. This might be done with a rebore or an increase in stroke, or both (see above about not knowing what is available for this engine). After this, improving the flow of the cylinder head and increasing the compression ratio would be possibilities. A mild camshaft upgrade may work with the above.

I'm assuming that you are running a pair of 40DCOE carburettors. On the face of it, this is fine, but you really need a nice straight passage through the inlet manifold from the carburettors to the cylinder head ports; unfortunately, to clear the chassis, the inlet manifold on this engine has an incredibly nasty "swan neck" internal profile that causes horrible restriction to the air flow and partially negates the advantages of the free flowing nature of the carburettors. This would be bad enough with fuel injection, but with carburettors the induction air whizzes round the corners inside the manifold, while the fuel droplets, being heavier, fail to get round the corners and simply splat into the wall of the manifold, thereby badly damaging fuel atomisation. With injection, you do at least have the option to squirt the fuel in after the corners and thus maintain decent atomisation (although this may not be the ideal position for the injectors for other reasons).

The real answer to the inlet manifold problem is to fit injection with an inlet manifold giving as straight a passage into the inlet ports as possible. Carburettors are forced to use the existing manifold design because they have to be mounted more or less level. Injectors don't care what angle they're mounted at so you have much greater freedom on manifold design.

Two final points.

1) Don't fit a 3D mapped ignition system and then try to fit injection; just about any aftermarket injection system will include the 3D ignition anyway.

2) Be aware that this engine enjoys a reputation for being one of the least tuneable units from the last few decades, so don't expect miracles.

[elie boone]

Not the easiest option for you but if Mantzel in Germany tunes theses they are a safe bet. http://www.mantzel.de/ Beware that you need to speak German