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View Full Version : *HOW TO* Fit a 1.6 engine and twin 40's



Ste L
16-02-08, 02:32 PM
WARNING.
Before you do anything make sure that you are fully aware of the legal and safety implications of any non like-for-like engine transplants. Consult the forums where there are knowledgeable people who have first hand experience or ring known GM tuning experts advertised in the Magazines. Remember that the braking, steering and general running gear for a small car may perform inadequately or fail if subjected to a lot of extra power and weight.

THE CAR.
The Project vehicle is '91 Nova 1.4SR with a Blydenstein modified head, Piper fast road Cam and Jetex exhaust system. It has been lowered & fitted with 2nd hand Calibra disc brakes on the front and (we think) Astra discs on the rear. It is running on 16" Mille Miglia Spiders.

THE TUNING CHOICE.
The original idea was to bore out the 1.4 block, however we were advised to install a 1.6 which is better and cheaper. (The 1.6 is basically the same block bored out by over 1mm & stroked out by over 8 mm anyway.)

A few calls around the local breakers resulted in the discovery of a 1.6 GSi engine & transmission.

To get round the problem of having to install an ECU etc. for the injected engine we opted to install Twin 40 DCOE carburettors especially since we were going to be able to get some dirt cheap. (Twin 40's are the ones to get for 1.4 or 1.6 engines)

Additionally it was decided that although standard valves would be retained, the inlet and outlet ports and valve throats would be opened up by around 1mm all round. The valve stems were waisted and the undersides of the valves ground back to aid flow.

The Piper fast road cam from the 1.4 was added since it was unworn and the 1.6 one was fairly knackered.

HOW MUCH?
A straight engine swap can cost as little as ?2 -300. If you swap the transmission and do some work on the engine costs can easily rise to ?500. If you install twin 40 DCOE's you will need to add anything from ?300 (if you're lucky) up to ?7 -800 if you are forced into buying new stuff. (Very approx. costs for us - 2nd hand carbs ?35!!!! New inlet manifold ?150ish (includes alternator bracket). New throttle linkage and gasket kit ?60 -70. PiperX air filter kit ?75.)

HOW LONG?
Engine & transmission out and new one stripped down clean - a weekend.
Engine reconditioned & back in including the transmission - weekend
Twin 40's on and engine running - about a day.

WHAT YOU WILL NEED (main items)
A well stocked toolkit (metric) including clamps etc.
Haynes manual.
Lift/hoist and suitable chains or sturdy ropes.
Car ramps, axles stands & blocks or planks of wood
Large screw driver or drift to pop the driveshafts out.
A bar to lever the engine around.
Gasket and seal sets for head and sump etc. (if overhauling implant engine)
New oil, filters, cam belt, antifreeze and liquid gasket etc.
Handy mates
Paraffin and cleaning tools plus airline to blow down with

TOP TIPS BEFORE YOU START.
It is quite possible for relative novices with the right equipment to do most of the work to get the engine out and back in but an experienced mechanic is recommended for key periods such as lining up shafts and jiggling engines back into place into the transmission. In any event it is not a one-man job so get help.

Make sure that you install the 1.6 transmission since the 1.6 engine has a bigger flywheel and therefore needs a larger bell housing than on the 1.4 gearbox

Read the Haynes manual thoroughly to make sure you are familiar with not only engine removal (section 1.46) but also the transmission (section 6. as well. You also need to be aware about the differences between the injected and carburettor engines (section 13).
Otherwise basically the two engines and transmissions are identical as regards mounting points and shared components, so it is a fairly straightforward procedure. NB. It will not be necessary to seam weld or make any modifications to the bulkhead as with the 2.0l implant. There is no appreciable increase in weight either.

When buying a 2nd hand engine take a plug spanner, some basic tools, the Haynes Manual and a torch (a knowledgeable mate would be handy as this part of the process is critical.) Check the dipstick - make sure it's got oil and that it's not muddy or grey coloured. Take each spark plug out and compare it to the plugs shown on the back page of the manual - this will tell you a lot about how the engine's been running. Look inside the oil filler cap with a torch at the cam lobes - if you can see a clear worn ridge on the sides of any of the lobes, the cam will need changing. Look out for hot water rusty coloured deposits that may have been running down the outside of the block from around the head or head gasket area. Other signs of overheating may also show up as an area cleared of oil and gunge that has gone recently rusty or where paint etc has been burnt off. Check that if it's out of a crashed vehicle there isn't any physical damage.

BEWARE OF STEAM CLEANED ENGINES - the breaker might be trying to hide obvious problems and make sure that the head hasn't been frost damaged. Try to look at other examples & always ascertain the engines age, mileage, donor vehicle and why it's being broken.

NOTE: If you are buying a GSi or any injected engine and are intending to retain it so, you must make sure that you have all the ancilliary pipework and wiring to fit, & in particular the ECU along with its wiring loom and engine sensors. In this circumstance it is preferable that you get advice and ideally remove the whole lot out of the donor vehicle yourself with someone who knows what they're doing with ECU's.This is the reason why we opted for adding carbs - they make the transplant simpler (I think!)


STEP 1.
Note. You will need a torque wrench & a valve spring compressor if you complete this section.

Get your 1.6 engine and associated parts (carbs, inlet manifold and throttle linkage). Personally I would recommend cleaning & stripping the engine down so it can be checked over. It is likely to have done significant mileage and would benefit from some attention. At the very least you should consider taking the head off so that you can change the valve stem oil seals. The procedure to do this is covered in the manual (section 1.24 also section 13). I would also recommend that you thoroughly clean the sump and in particular the gauze in the oil pick up pipe as this can be badly clogged. Check that the water pump moves freely when its retaining screws are loosened to make the cam belt adjustment easier. Note that you will need a new head gasket kit and new head bolts to overhaul the seals. De-coke and re-seat the valves at the same time. Check that the bores are OK (if the plugs were healthy i.e. not oily and black, then the bores won't be badly worn) and make sure you keep them scrupulously clean and covered.
Next you will need to do some work to "match" the inlet manifold to the head if you are going to fit twin 40's. This is best done by carefully grinding out where the ports and the manifold meet with a "Burr" that can be obtained from a tool wholesaler. A small electric drill will be all that is necessary to drive it and, to stop it clogging up with the soft aluminium, periodically apply a little oil. Get the area as smooth and even as possible for the air flow over the joints but make sure to leave a co**** rough filed finish to prevent the fuel dropping out of suspension.

STEP 2.
Remove the bonnet and then, following the manual carefully, start to strip the engine down making sure that all components, pipes and attachments etc. are carefully marked, cleaned and stored to facilitate easy re-assembly. The more careful, systematic and conscientious you are at this stage, the easier it will all go back together again.
NB. During this stage make sure that the car is safely supported and fully chocked as you will be
working below as well as above the car. Try to remember how everything comes out and in what relation it is to other components.
TOP TIPS. It sometimes helps to ease something complicated only partially apart and then temporarily re-assemble it before finally taking it apart. This will show you how it all goes back together. Draw diagrams of wiring or component positioning as it is very easy to forget things.

STEP 3.
When the engine has been successfully removed follow a similar procedure and remove the drive
shafts and then the transmission.

STEP 4.
With the engine and gearbox out, take stock of the situation. Check the engine mount bushes and
any other parts that may need to be replaced now that they've come to light. Compare the 2 engines and gearboxes in case there are any major differences. If everything appears to be in order you can start to install the new gearbox and then the engine. This is basically the reverse of the removal procedure. NB If adding twin 40's I would recommend leaving the head off whilst the engine is being replaced making sure that the bores are sealed over.

Ste L
16-02-08, 02:33 PM
STEP 5. (Adding Weber twin 40DCOE's)
General description
The two Weber 40 DCOE carburettors that we fitted are the usual side-draught dual barrel types
with each barrel containing 2 venturis (as shown above). The effect of fitting this type is to give each cylinder its own individual inlet tract and carburettor although all are synchronised together via the throttle spindles and associated synchronising linkage. You will see from the diagrams that there are individual idle, main and air correction jets for each barrel.

The advantages of this type of carburettor are:
Gas flow is individualised for each cylinder & is much better than through a standard
carburettor fitted by the manufacturer.
The twin venturi system is more efficient and a lot more fuel can be delivered effectively.
When fitted to modified engines they can be easily tuned to deliver the greater amount of air
and fuel necessary & hence give more power.
Sound like they mean business.

The disadvantages are:
Petrol consumption is increased. (late teens to late twenties)
Emissions are higher.
It can be a fiddle to get them synchronised and jetted properly. The main power jetting and choke selection is fairly straight forward. The easiest way to do this is on a rolling road which can be expensive. However once this is done the fuelling for full power is set and shouldn't need altering. Getting them to idle evenly in all conditions quite often isn't so easy- there are definite differences between winter and summer idle settings.
Ideally get someone who is experienced with them to go through the procedures for sorting this and then its just a matter of listening to them and making small adjustments with a screwdriver. An airflow meter that you place in the trumpets is an invaluable bit of kit for helping to make setting it up easier.

Fitting
As mentioned previously the throttle plates, mounted on a central spindle, are linked to each other by a synchronising linkage. This ensures that each one opens exactly the same amount, which is important because the inlet tracts are not interconnected. Therefore the correct synchronising linkage must be fitted to make the spindles move as one when the accelerator is pressed or released. There is an adjuster in this linkage to allow the movement to be fine tuned. Although it sounds complicated it's quite straightforward & it's just a question of placing the carbs on and off the manifold and fiddling around with the different bits until it works. We found the whole set up worked best if the throttle cable bracket was mounted on the top of the right carb (nearest the gearbox.) This then allowed the cable linkages to be easily linked to the throttle spindle in the middle between the 2 carbs. Once you have got this part sorted clean everything thoroughly and blow it all down. Next the inlet manifold & its gasket can be bolted onto the head. Then after this the carbs can be bolted onto the inlet manifold. Take care to correctly install the rubberised "O" ring gasket kit, which act as seals and vibration dampers between the carbs and the manifold. The reason for this is to stop vibration from the engine causing fuel frothing problems in the carbs. DO NOT USE THE PLASTIC SPACER AND DOUBLE O RING TYPE OF CARB GASKET - ITS CRAP. Use the steel ones with an integral bonded rubber O ring and secure with nyloc nuts- its a fit and forget solution. Whilst the inlet manifold is off install the various pipe unions into as there is little room under the carbs once on the car.

THROTTLE CABLE INSTALLATION
You can use a single or double throttle cable kit - we chose the double one for extra durability.
You should have with it all the necessary adjusters and springs to tension it up correctly with the kit. Included there should also be a small steel block with holes in it for the wires and adjusting Allen set screws. This needs to be added to the accelerator pedal. I did this by removing the old accelerator cable completely, taking the pedal out and sawing the top off. It needs to be straightened a bit as it is canted over to one side. I then bored out the block, slid it onto the pedal and locked it in place. Next I removed the rubber grommet in the bulkhead where the old accelerator cable had been and cut out a piece of tin to cover the hole. In this I drilled 2 holes to take the cable ends and then tech screwed it onto the bulkhead over the exposed hole. The cables could then be threaded into the tin and lock-nutted in place leaving the wires sticking out into the car near the pedal ready to be fed into the block on the accelerator. Finally I threaded the wires into the block and secured them in place with the Allen set screws. Fine adjustments to tension can be made in the same way as brake cables can be adjusted on bikes. We didn't find it necessary to connect up a choke system as a couple of pumps on the accelerator before starting seems to do the trick even on the coldest days.

STEP 6.
Add the exhaust manifold, put the alternator back onto the block and then everything is ready for
the head to go back on.

TOP TIPS.
When you get the inlet manifold you must make sure that you also get the modified alternator bracket that goes onto the block otherwise the alternator will foul the manifold (this comes as a kit with a new manifold). You will need to manufacture or acquire a new alternator sliding adjuster arm. This is longer and kinked over to meet up with the new alternator position.

I had to get a slightly larger belt to fit the alternator in its new position. Even then I have
to take the bottom pulley off to get it on. This is one of the most difficult bits to sort and you may need some specialist help if you aren't much good at fettling things.

Make sure you have got the appropriate unions (from the breakers) to plumb the heater hose and brake servo vacuum pipe into the manifold. Note that some more fettling and cutting of rubber pipes will be needed to fit these into their new positions. You need to make sure that when you plumb in the heater hose that comes out of the manifold that it doesn't foul the back of the alternator otherwise it will chafe through.

You will find that the crankcase breather manifold pipe work has nowhere to plumb into although strictly speaking these gases should vent into the carb filters for emission reasons. (It didn't cause me a problem in the MOT tho')

I found that the new inlet manifold fouled a bit sticking out from the camshaft housing casting about half way along where it mates up with the head. Check this before permanently attaching the inlet manifold as we needed to file ours down a bit.


STEP 7.
Finish re-assembling the engine, connect up the throttle mechanisms and go through the timing procedure. Add all necessary oils and water and connect up the fuel system using new pipes and connectors as the old ones won't fit. Note that it is advisable to plumb in a return fuel line. Once the engine is ready to start you may have to turn the engine over a fair bit to get the fuel system fully primed. Eventually there will be some chuffing and back-firing with smoke and fumes coming out in an alarming manner from the carbs. Don't worry about this - blow back is
part of life if you have twin 40's - and if it doesn't start up apply choke by manually pulling the 2 starting control levers over momentarily and this should do the trick and get it all going. It will probably run very rough with lots of coughing and back-firing but this should slowly disappear.

TOP TIPS
Before starting make sure that the throttle cabling is adjusted to allow the throttle plates to be fully closed and that the throttle stop adjusters are synchronised.

Screw the volume control screws in (fully shut) and then open each a half turn

Let the engine get properly warm before attempting to further alter settings to the carburettors.

Normal timing adjustment markings may be out so loosen the distributor clamp and twist it slightly one way or another (advancing or retarding) to get the engine to run smoother. NB we found that if we loosened the distributor bracket too much the engine misfired and ran badly.

STEP 8.
Setting and trouble-shooting the carbs.
To adjust the idling, fully slacken the carburettor stop screw in the left carb. Then using a
piece of flexible tubing placed in one of the trumpets of the carb with the engine running,
listen to the volume of the hiss and compare it to that in one of the trumpets in the other carb.
Adjust the central throttle spindle synchronising screw and the carburettor stop screw in the right carb to match the sounds. Note that you will only need to listen to one barrel in each carb. Once this is set you can adjust the four volume control screws an eighth of a turn at a time, allowing the engine to settle in between turns, until the engine runs evenly. Ideally the screws should be all set the same but it is permissable to have a difference no greater than a quarter of a turn between any of them.

Ste L
16-02-08, 02:33 PM
Jetting.
It will be almost inevitable that some re-jetting will need to be done. However since twin 40's are designed for engines around 1.6 l, it should be adequate enough to get the engine to run OK especially at higher revs when the main venturis come into full operation.
At the rolling road we had to concentrate mostly on the idle jets and slower speed settings to get it through the emissions test at the MOT.

Remember that a new/recently overhauled engine won't run smoothly for sometime until the engine settles down. More radically altered engines will need greater alterations to the jetting in the carbs.

If the engine doesn't run right check other component first before fiddling around with the carbs.

Cold start difficulties - check the carburettor needle valves operate freely. Hook up the chokes and use them

Warm start difficulties - check air filter. Make sure the chokes aren't sticking on. Check the float chambers aren't over filling. To do this remove the top covers which come away with the floats and valve mechanism intact on them. Hold them on their ends so that the floats are free to hang down and can swing to either open or close the needle valves. The correct adjustments are 15 mm from float to cover when fully open and 8.5 mm from float to cover when fully closed. If not bend the little metal tab by the float hinge to pitch the mechanism higher or lower.

Slow starting and irregular slow running - check for air leaks around the gaskets. Adjust the volume control screws. Check jetting.

Poor acceleration - check filters and fuel supply. Check the jetting of the main venturis.

Excessive fuel consumption - check filters. Check for fuel leaks. Check float level. Check jetting.

STEP 9.
Air filters.
Once the carbs are on there is not much room for filters. I eventually ended up with a PiperX manifolded filter rather than trumpet socks. Trumpet socks can be have disasterous effects on air flow around the trumpet intake and hence power - be very wary about using them. I had to have a slimmed down version from the standard (the supplier should be able to tell you what to use). Even then I had to shorten the trumpets to get it to fit and its not very satisfactory because of the lack of space and will have effected performance. What many people do to avoid this is to modify or remove the baulkhead panel behind the trumpets to give more space


RESULTS
We had the car rolling roaded straight away after installing the engine as it failed the MOT test on emissions and needed re-jetting. The results were a reasonable 116.3 bhp at 5633rpm (flywheel reading) and 125.5 lbft torque at 3626rpm. This compares to 100bhp for the standard engine so we achieved a modest 14% gain. It is usual, after head work, that about another 2bhp will be found after a few thousand miles due to coking which aids efficiency.

CONCLUSIONS
We were a bit disappointed with the horsepower figures, although very pleased with how it drives. It goes to show how easy it is to get carried away with totting up all the possible gains that the various components are supposed to give. The skill comes in knowing how components interact when on and running and this can only be found with experience and trial and error. If you make fairly large alterations to an engine and expect it to all gel straight away you are probably deluding yourself.
Overall, however, I have found myself wondering whether this is the right path to take. Would it be simpler and cheaper to just buy a 1.6 GSi or GTE injection, mod the head and ECU, add a good exhaust and induction kit and leave it at that? I know of examples like this that give 100bhp at the wheels (120bhp at the flywheel) with fuel consumption around 35mpg. Twin 40's can deliver a big gain in power, but it's not guaranteed. One thing is for sure though, they are to a large extent wasted on cars that haven't had at the very least their heads modified and free flow exhaust systems added.


l.-----------------------------
Written By: CP

Mk1'SR'Dan
17-03-10, 11:02 PM
hey, not sure if ill get an answer here or ill have to ask it one of the other forums, but ive recently got my 1400 built up and im running 40s on a mechancal pump (nova sports didnt have a problem before you tell me io need an electric pump) and im not sure how to go about plumbing in a return pipe, seems simple in concept but im sure you must have to throttle it down to stop all the fuel just p*ssing down the return...? please help!!!

Stuart
17-03-10, 11:09 PM
just put an adjustable pressure reg infront of the carbs and you will be fine.

Mk1'SR'Dan
17-03-10, 11:14 PM
is there a pressure regulator built into the 1.4 MPi system? it certainly looks like one, and if it'd do for the time being it'd be good because i have one, cos this 'little project' is skinting me...