Thread: Improving performance?

My 2a lwb, which has the same engine, easily, if somewhat noisily, will maintain 100kph on the level and will do better than 80 up most main road hills.

From that, I would say you must have one or more definite problems. Things to look for:-

Dragging brakes go for a run and check all four drums and handbrake - none should be uncomfortable to put your hand on. Similarly with wheel bearings.

Tyres - right size, right pressure. Too large diameter or too low pressure will sap performance.

Ignition timing - retarded spark will leave you with an engine that runs well but does not produce full power.

Ignition problems - poor running can result from many ignition faults, although most will also cause rough running.

Carburettor giving poor mixture, if it is a Zenith likely from a warped top cover.

Low compression, due to worn rings. Do a compression check.

Camshaft timing a tooth out.

Once you have everything working properly, there are a variety of engine improvements that can be made. The simplest is to skim the head to increase the compression ratio. Yours is probably 7:1 (most were) and the head can be skimmed to raise it to 8:1 without any real down sides (early heads cannot be skimmed). Even higher is practical if you don't mind being confined to premium unleaded.

An improved exhaust manifold is another option, as is fitting a SU carburettor, and I have heard of a few being fitted with a belt driven supercharger.

John

Our SIII 1976 LWB also manages 90-105 kph on flat ground and in still air, although this is with the overdrive engaged. Without the overdrive, 95 on the flat is still achievable (both with earmuffs on ).
I have a Zenith carby, and when I overhauled it I was surprised at how much re-facing was needed on the top and bottom faces of the housing, and also on the mating face of the centre block. I used wet and dry (used it dry) taped to the surface of an old mirror. I took pictures after first giving the face a quick rub to identify where the high points were, and the next showing the completed job on each piece.
The warping was clearly robbing me of considerable power, and the vehicle now starts much more easily too.
First two images are the top cover:
Carby1.jpg Carby2.jpg

Next two the mating face on the body:
Carby3.jpg Carby4.jpg

Finally, there is a large O-ring in the centre of the carby which was somewhat second-hand on my machine. The image shows it just after I've removed it from its location around the circular part to its right.
Carby5.jpg

I used all the components in the overhaul kit apart from the new throttle spindle and butterfly because the new spindle was even looser than the old one .
Hope that helps
Cheers

Coop

Thanks John and Coop, I will go through the list provided and see what I can find and also check the carby. I have a solex and have no idea whether it works properly or not. I will let you know how I go.

I agree with John and Coop, to check the basics first.

A reasonably cheap modification for about $500, is to replace the distributor with Megajolt ignition, for a spark guaranteed to arrive at the right time, always.

If that seems too expensive, consider the wasted fuel and it doesn't take long to realise that there will be a financial gain eventually depending on how much motoring you do.

In any case, buying Magnecore high-tension leads and NGK Iridium spark plugs, is a good start for any engine, even if it does have a crappy old distributor

Cheers Charlie

I replaced the carby on my 2.3 1976 swb with one off a holden 161 with an adjustable main jet. Everything else was standard. Fuel consumption was lineball with my 300tdi defender & when I tested its get up & go I got up to 130kmh & then backed off with it still accelerating cos it started feeling a bit unstable

Sent from my GT-I9505 using AULRO mobile app

Will look at the leads and plugs and depending on the Mrs a distributor. At the moment the performance is a turn off to use it as a daily driver as I need to use some 80-90kmh roads and the build up of traffic behind me isn't worth the stress.

If i am looking at my Solex Carby, am I better off to buy a new one at a couple of hundred bucks or just get a refurb kit at $70 odd. That said I have no idea how efficient or not my carby is at the moment. How can I test it?

I have found that electronic ignition is a big plus. Allows you to really get the most of advanced timing and much better pick up.
Tappet settings are important as well.
If you want to spend some money go for a higher compression head (8:1 or 9:1) with new valve seats. You can then take advantage of higher octane petrol and even further advanced timing. Extractors also make a big difference but they are pointless if you dont do the ignition and head first. A matching exhaust also works to go with the extractors. Just depend how much you want to spend.
At the end of the day though the 2.25 will NEVER be high performance, but you can unleash at bit more potential.
Phil.

Originally Posted by Jondavball

Will look at the leads and plugs and depending on the Mrs a distributor. At the moment the performance is a turn off to use it as a daily driver as I need to use some 80-90kmh roads and the build up of traffic behind me isn't worth the stress.

If i am looking at my Solex Carby, am I better off to buy a new one at a couple of hundred bucks or just get a refurb kit at $70 odd. That said I have no idea how efficient or not my carby is at the moment. How can I test it?

There is no real easy test, but one thing I would do is check that the throttle is opening completely. If the engine is running smoothly, without flat spots, and the only problem is that it seems down on power, it is unlikely that there is much wrong with the carburettor. I would still disassemble it end ensure it is clean and no obvious problems. Putting a kit in it is probably worthwhile. Also, ensure the filter on the petrol input union is clean. When reassembling it, ensure that the accelerator pump diaphragm is not going to be overstretched or torn because you tightened it with it flat not stretched.

JOhn