return to a naturally aspirated 4Y

[Tim Neary]

some month ago we purchased a low milaege (135 000km and 3 family member owners) double cab and the licence papers say 1984. She arrived with a turbocharged 4Y............great Jhb to Moz in an hour and the fuel consumption of a jetline onroad and of a tank off-road.

"Lets get it back to standard" i decided....a quick weekend job..........and so the fun started. Everything done by the engineering works including bostick contact on th gaskets was undone and redone!!!

With the great help of members of this forum we obtained advise and manual extracts. After much muttering we went with the Golf carb conversion...........adapter plate was obtained from a local engineer and we decided in despiration to go with the pirate "german" 1,8 carb.

We have added the golf "surge pot" which allowed for a fuel return to tank, have used a standard golf airfilter system and built an exhaust which must do until pennies allow a new manifold and exhaust..........she has twin tanks and thus the exhaust is a plumbers nightmare.

On starting the beast purred and during initial tests the carb earth broke somewhere which resulted in a lot of frustration. As usual the fear of the unknown rules and circumstances forced us to use her for this past trip of around 2000 km..........about 1400 on road and 600 on the reserves we were working on.

We still need to locate a good cowl and move the radiator back to its original position which hopefully will mean a more consistant temperature.

With all the kit we are not light in the least and this trip returned a fuel consumption between 12 and 14 lt/100km. Low down is great but we need a dyno to set the upper limits but for the present we are happy at an easy 110km/hr cruise

With workingon reserves simplicity is the ruling factor!!!

Many thanks for the advise and assistance

Cheers

Tim

[Family_Dog]

Tim,

Sounds intriguing! Do you have any photos of the "re-conversion" back to standard? Will make for interesting viewing!


-F_D

[Dadz Toy BFI]

Glad the Manual stuff I sent you helped; it's from a really nice Workshop Manual that Uncle Eric put me on to.

Looking forward to seeing some photos Tim

Isn't it rewarding when you do your own work hey

Rich

[Tim Neary]

will get out the camera in the next day or so and challenge the brain and get the pics up for you. must admit i am enjoying the tinkering with the old lass.......this is one of those "shoe string" projects which makes it even more fun

[BenHur]

Tim

Do not expect to get much more at the top then what you currently get. With the one we did we saw that going above that speed the fluctuation of vacuum in the manifold v.s. horse power meant that trying to use last 15-20% of the throttle was more wasting fuel then anything else. On the one we did we decided not to increase the jet sizing on the second barrel as the gain in power vs. air fuel ratio did not make sence if you want an economical vehicle. We felt the loss of 1-2 HP on top vs a posible horrible consuption there was not worth while. Problem is the second venturie is maybe very slightly too small for running optimally here at the Highveld.

With no head wind running at about 100-110 she will give you the most economical performance. Try fitting a vacuum gauge and note when the second barrel opens up. If you can drive her without using the second barrel your consumption will increase.

[Family_Dog]

With no head wind running at about 100-110 she will give you the most economical performance. Try fitting a vacuum gauge and note when the second barrel opens up. If you can drive her without using the second barrel your consumption will increase.

You mean decrease, Bennie?


-F_D

[Tim Neary]

Hi Bennie

Many thanks for that advice.I did notice that trying to use that last bit of throttle made no difference at all and your advice makes good sense. fortunately we are not concerned with a power race and both of us are just as happy to take an extra hour or more on the journey......Claire reads or snoozes while i drive. We are always very heavily loaded with kit and generally 10days food etc at a time...........around 4 small and 8 large ammo boxes plus plus! I was very impressed with the low down performance. I also am a firm believer in less is more and that running her as she is now will result in many years of service

[Hoppy]

Your biggest problem is that the conrods on the 4y turbos were shortened by 2mm to lower the compression ratio and an extra mild cam was fitted.
You have to replace the rods and cam to get the performance and consumption back on spec.

[BenHur]

What I saw on the one I did for Dawie is that the smaller venturies caused more torque at low RPM then normal. My neighbour explained it has something to do with wind moving faster throuh the smaller holes causing more torque or something to that effect. It is the same principle as the cars with the 16 valve heads as two smaller holes produce better torque then on larger hole even though the total diameter may be the same.

Alan how much lower is the compression, is it really cost effective doing such a change or will it be a lot of money spent for very little gain. Maybe just a different cam may make sense?

[King Rat]

Bennie, your neigbour is correct. A longer intake also improves torque. But because of this a 16 valve head may have the same torque as 8 valve, the torque lower down in the rev range will be significantly less for the 16 valve head because it cause less restriction (wind speed) than the 8 valve.
How much can the heads be skimmed to try and get some of the 2mm back Alan? But then again, it will have to be matched to the pistons etc.

[Tim Neary]

Hi All

When we stripped we checked all specs and found that the pistons had been machined and this was confirmed by the fellows at Alpine Developements, so we were fortunate that the con-rods were still standard

[freeflyd]

Tim,
Bennie did the conversion for me. My truck has a permanent roof rack and Ironman suspension (Lifted about 5cm).

Ihave only been driving it around town since the conversion and get 13.2l/100km instead of the 19.4 I used to get.....

[BenHur]

Dawie

Long time no see. You must please make a turn here by me when you are in the area again.

[Tim Neary]

Hi all, hope these pics work. The adapter was roughly milled and then a few hours with a dremil to flow the beast..........Cheers Tim

[BenHur]

Tim

That 8V/12V coil with the coil resistor is a big no no. Rather get yourself a decent coil that works on 12V all the time or better still a Toyota integrated electronic Dizzy

[Tim Neary]

Hi Bennie

Many thanks, i have just tossed out the pints system and fitted the electronic conversion from Petronix. can we start with a simple coil from Autozone or such like?

[BenHur]

Yes but just make sure its not a cheap chinese one.

The wire that is now connected directly to the + on the coil gets blanked off and the one that was connected to the far side of the resistor goes to the new coil's + The one you blank off is actually connected together with the starter so that it bypassed the resistor and raise the voltage on the coil from 8v to 12 v when you were cranking the engine.

[Tim Neary]

many thanks Bennie...............this sort of info is hell of a helpfull