DDK - Die Deutschen Klassiker

Hi all, I am having to rebuild my engine so thought why not take the chance to update some of it like the cam etc and the fuel pump.

But im not sure which one is the preferred choice.

I want something new tech so the old pump is out.

I have a mainly custom block off plate so far.

Also looking for a pull switch as used on the carrera or s90GT.

I have considered a facet pump with moroso filter but not sure which model I need or where to get it wit hall the connectors needed.

I want to do it once and right.

Dave Ren
rusty B t-5

I think from looking at Andy's race cars. I don't think he uses Fuel pumps. Could be wrong.. worth asking him why he doesn't

how does the fuel get `pumped` to the carbs then ?

think he means no aftermarket electric pumps, instead just the standard mechanical one, so long you're not running big ass carbs i would've thought the standard one should provide enough fuel if in good shape.

in that case it will depend on what carbs your running

Reply from Andy Prill:

Dave
The Precision matters full flow is a very well designed and executed. It works well because it maintains the original oil systems bypass valve which diverts oil to main bearings at start up. For some reason Mobil do not import the filter that it uses. We have however sold enough of them to have a stock at all times. The price is £485 + VAT.

I do regularly use electric fuel pumps but almost always in competition cars where a higher fuel flow is necessary to cope with the engines increased demand for fuel. If you fit an electric pump you need to pressure regulate it as well. A lot of people confuse flow and pressure and if you have too much pressure the needle valves in the carbs will not be able to hold the fuel back leading to very poor running at tickover and low RPM and in extreme cases a flooded engine.

In 99% of cases road cars do not need an electric pump. The Porsche mechanical fuel pump is very good indeed. Both the early type and the late type have in built fuel pressure regulators so the carbs receive the correct amount and pressure of fuel at all times. In practice the earlier pump is harder to set up because you have to ensure that the stroke is within specified limits by removing or fitting extra gaskets when you fit it. We regularly see cars that owners tell us have carburettor problems that actually have too much fuel pressure that the carbs can't cope with due to the pump being fitted incorrectly. The later pump is designed in a way that allows you to simply fit and forget it. In my experience a rebuilt Porsche fuel pump will give many years of trouble free service.

Electric pumps do have a distinct advantage if a car is not used regularly as they will fill the carbs and allow the engine to start quickly unlike the mechanical pump that will need the engine to be turned over for some time before it can re-fill the fuel system. We have in the past fitted a small electric lift pump that is switched off again when the fuel system is primed.

As you are probably aware I don't actively participate in the DDK forum. I do look (I like the enthusiasm) of course but it would not be professional to contribute to technical debates on the web not least because I do not have the time. I am happy for you to quote the above and give everyone at DDK my regards and best wishes for Christmas.

Regards

Andy

485+vat for the precision matters full flow filter kit seems alot of dosh. if you want a full flow oil system why don't you use a pump take off plate like the one from csp that cost about £65, drill and tap the the front part of the case for the return and mount the filter away from the engine. There is, or at least there used to be a full flow filter kit similar to the precision matters kit for the vw engine. a lot of vw engine builders did not use it as they felt that it put the filter close to the exhaust heat. I don't see why this should be any different for the porsche engine. check out this page on the 356 registry for details on full flow
http://www.356registry.org/tech/full_fl ... stems.html