Theoretically there will come a speed at which the pump will turn faster than what the water can physically be pumped through the water system. At this point it will start to cavitate, meaning that it will spin so fast that water will enter and exit the housing in short bursts, moving much slower and not at the same speed as per normal.

The solution was usually to fit a slightly larger water pump pulley, or smaller crank pulley, so that the water pump would turn slower at high engine speeds. Unfortunately this also had the undesired effect of slowing the flow down to much at idling, so that the engine might overheat when doing so.

6000 sounds very low, taking into consideration that an A12 GX motor would happily rev past this in standard form, and I wouldn't start to worry until past 8000 if I were you.

My bro-inlaw says he saw 2 x 4 door 1200's standing at some scrapyard. I was looking for a fuel tank... Will try to find out where, and send you the number...

1200gxman did say that he aims to achieve that if;

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Yes that'll be ok, as the collector has already brought the size down to this, and you wouldnt gain much by going bigger.

We made our own collectors from 80mm pipe, and thus used a 80mm "tailpiece"

Clive, I suggest you go buy the CAR magazine, and read the top of the left most column on page 122, and continue to read about how great the engine is that he built for that car(It's a V6 Ford Essex for a Cortina Perana replica that is run in a historic racing series, for those of you unable to buy said magazine). The guy known as "Lammies" is the owner of Lamco Developments. He's been doing camshafts since before Camshaft Dynamics even thought of setting up shop, and have been around the bush many times. I know, we quoted Camshaft Dynamics on their grinder when they wanted to set up shop... If you have to, at least point people to Richie Jute, they also have a wealth of knowledge when it comes to this subject, that dates back many decades.

It is a mistake is to even think of grinding a decent cam from a secondhand donor cam. The best cams are ground from billets, that way the cam can be ground so that the lifters, cam followers and rockers operate in their normal positions where they were designed to work. Otherwise you end up with premature failure on said parts.

The mistake was probably not to install the cam according to their instructions. They normally give instructions on valve clearances and suggestions on ignition timing with every cam they put out. If these weren't followed you would most probably have problems.

I would put any cam they ground into any of my cars, any day.

A well designed set of extractors, have already done their job when all it's runners have joined into one, that's what they are there for. Anything after that would make absolutely no difference in performance other than to restrict flow. The main reason people have any exhausts/ silencers on their racing cars these days is mostly because of noise.

For our hotrod, we used to take a piece of pipe about 80mm ID and about 2m long, enough to stick out the side of the car just behind the front wheel. It was polished up to a shine in the lathe, with some very fine sand paper and some brasso. We then either spot welded it to the collector or tied it with some wire, but tried to make it air tight.

The car was started, and the throttle was gunned up to high revs in short bursts, until a blue ring formed around the polished pipe somewhere in it's length. The pipe was then cut diagonally across this ring at a shallow angle, as this was where a high pressure zone was formed. When cut across this zone, you ruled out most if not all back pressure, but pressure was also high enough that cold air wouldn't find it's way up the exhaust and onto your exhaust valves.

Many guys still runs their rods this way, if it's not to loud, and I would suggest you try this if the car is only going to be used on the track.

EDIT: This procedure was repeated when any internal changes was made to the engine or extractors, as the pressure zone would shift when changes was made.

Get the A15, and throw it in. With the money you have left over, I could probably get you a decent performance camshaft from Lamco...

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Unless you already have the sidedraughts, why don't you rather look for a set of Toyota 20V throttles, and fit those, along with management.

Never any worries about adjustments going out anymore, and full control over fuel delivery.

Heck, a complete Toyota 20V engine costs less than one 40 sidedraught Weber, might as well buy the engine, take the throttles of and chuck the engine. Or sell it and make back some money... Like that you even get a set of injectors with...

The benefit would be that the BMW valve might have a different seat angle as well, which is better for higher flow. I also know that BMW valves are a good deal lighter then the Datsun ones, so that's less weight to stop with your valve springs, hence higher RPM's.

Also the way BMW valves are manufactured, they use a different material for the actual head of the valve than for the stem. The two are friction fused together. I've never seen any of them break. The reason for the different materials are, that different heat dissipation abilities are needed for the head and stem, and the wear characteristics for both are different. Thus using two different materials more suited to the jobs at hand, gives you a better valve all round.

If he can do the job properly, and it sounds like he can, I would say go for the BMW valves, you wouldn't be disappointed.

Mmmmm, let me see... I once worked as a rep selling/servicing/installing automotive machinery, like re borers, crankshaft grinder and surface grinders etc. We were selling newly imported AZ(Alvise Zanrosso) machines.

This one particular VB150 boring machine had one boring bar that would shudder when boring, and as a result screw up the bore so much that you had to bore it to the next size up. Well after an inordinate amount of time trying to adjust it, and having given every one in the shop a go, I completely lost it after trying again, and threw it across the workshop floor. It skid out the door onto the side walk.

The shop went quiet, and every one was waiting for my boss to fire me. Luckily my boss was Italian, and completely understood my anger... He actually laughed his ass off.

So after standing around a while I went and picked it up, and fitted it to the machine again. Lo and behold, it didn't shudder anymore, with no extra adjustment. To this day it still works like a charm. Now explain that to me...

EDIT: TYhis is the particular machine I'm talking about, VB150