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Made myself a small furnace to melt aluminium.



Here are some suitable candidates.



Need to get some greensand and do things properly but for now steel does the trick.



Many hours of machining.





End result is to adapt this throttle body to a square bore four barrel manifold.

Where is that Thumbs up button when you need one?

You don’t see that too often. Next level.

Nice work!

Making some more aluminium parts, had to weld this one together - I have carefully hidden most of the ugly welding from this photo but it's structurally sound at least.


Found the necessary 7mm machine screws hiding inside some old head bolts.


Add some threaded spacers and you get this.


Which will eventually fit here.

As with so many things on cars, the coil brackets needed to be done twice (one for each side). Got the remaining hardware turned and stitched together the second bracket, then fixed the colour.


Much better, doesn't stand out as much.


Since the air cleaner base will need re-doing anyway, it shouldn't hurt to add a half inch spacer for some added insulation. Ordered an open spacer, apparently there are none in the country... luckily its easier to make an open spacer out of the four-hole variant than the other way around.


I had wondered if the 82mm throttle body was going to be slightly on the small side given the massive sizes people are going for these days, but I don't think it will be an issue.

Depends on the target HP output of the engine. I found no calculators or guides on the net for common plenum single throttle body size vs hp requirements, only ITB calculators.

I do have a Helmholtz theory PDF with the relevant formulas that you can calc the size of the ram tube and in turn the TB. The other way is to sim a engine with a certain hp and play with the TB size until it starts to choke and then you know the min approx size. From memory, 60mm chokes at about 320hp and 70mm is good for about 400hp using Dynosim 5. That is for a 6 cyl though so the pulse frequency vs an 8 probably change it slightly.

Also a larger plenum also increases the efficiency of a smaller TB by smoothing out the intake pulses seen at the TB and henceforth decreasing the peak velocity so it doesn't exceed the magic speed limit (I can't recall what that was? speed of sound?) and avoiding an airflow stall if that the right term? This will get HP back from a restrictive TB, but a larger plenum makes an engine lazy and less responsive the larger the plenum.

82mm should be north of 500hp I'd imagine.

Going too big with the TB makes the all the power happen with less throttle % and over a certain % opening there is no additional flow or power as the engine just doesn't need it.

Some people like it touchy (I do), other's like a more progressive pedal where 100% is 100% and need more pedal at low speeds to get the car going.

Yeah I compared quoted values on other throttle bodies and tried some CFM calculations, they vary a lot. Decided to just suck it and see, if it can't make 100kpa at wide open throttle then I have an issue but I doubt it will be a problem.

vlad01 wrote:Going too big with the TB makes the all the power happen with less throttle % and over a certain % opening there is no additional flow or power as the engine just doesn't need it.

Some people like it touchy (I do), other's like a more progressive pedal where 100% is 100% and need more pedal at low speeds to get the car going.

Absolutely, I was very conscious about going too big also as I'm still looking for more progression than the current four barrel throttle body offers. It can be a bit tricky to drive smoothly sometimes. Hopefully the drive-by-wire will help here too as progression can be programmed to an extent.

The alternatives were the GM 87mm 'truck' and 93mm LS units, the Bosch is better laid out for this application and cheaper.

From my calculations 82mm throttle body should flow 805cfm@ 1.5" or 1139cfm @ 3".

Crank trigger wheel, this is basically just a piece of 1/4" mild steel with the requisite features to mount behind the pulley. Note the additional countersunk screw hole, this ensures exact placement.



Because the wheel mounts behind the pulley, the pulley needed to be altered. I carefully cut the back off the old steel pulley in the lathe and tig welded a new piece in - but must have got carried away with the heat as it pulled out of round in one spot. Found this in the spares pile which has plenty of material in the right places.



Looked up the specs for a K profile belt and ground a 40 degree tool out of an old broken end mill. The belt seems to fit well enough.



Will be interesting to see how it lasts as it obviously no longer has the anodizing, we'll see.