OK, the toothpaste colour car is owned by a chap outa Scotland, and I'm buggered if I can remember his name now which is really really embarrassing because I have had some great chats with him at Billing over the years... That car features a 2.4 Vauxh/Opel CIH 4 pot out of a Frontera with Carlton sump and gearbox to make it fit the RWD application here. It also had some tweaks and he was talking about a turbo conversion last I spoke to him but that must be 3 years ago now. Maybe 4. The solenoid doors are particularly clever, the button is hidden behind the B pillar trim finisher which is colour coded on that car for extra smooth points. The wheels are Compomotive MLs finished in black with flake and a lot of clear. They were custom PCD and offset ordered to be the biggest you can get under a stock FD arch. The engine bay on that car is super smooth and very very clean. I have some photos somewhere.
The yellow car is his mates, and might be the one which used to run a Senator engine but not sure if it still does. It used to run a Ventora grill and TSW Hokenheims back in the 90s. Very nicely built car. Or it could be a completely different one as a DVLA check shows it as a 1975cc slant 4... Mind you my Cortina is still reg'd as a 1600...
There are two basic variants of the 1975 (2 litre) slant 4, there are also 2 variants of the 2.3 SOHC slant 4 as well as the DOHC 2.3.
Early 1975 is designed with a 4-1 exhaust, Zenith carb, log type inlet, fixed fan, and IIRC this is the narrow dowel head. As of 1969 (the 1970 model year cars from chassis number 0V250000 or so) the 1975 gets a 4-2-1 exhaust, Stromberg CD175 carb, an improved runner design intake, viscous fan and broad dowel head.
The cylinder head from the 1968-1969 model will not fit the 1970-1972 model engine. I believe that they do not fit the other way around either but I have not tried that. Head based hardware like the cam carrier does interchange though. You may be able to machine an early had to fit a late block etc.
The early 2.3 SOHC uses the same head pattern as the later 1975 lump. It also uses the same manifolds, carb, etc. as the 1975. These were introduced in Feb 1972. By 1975 the head was revised again, and I am told that the early and late heads do not interchange on the 2.3 so a late 2.3 head will not fit a 1975cc engine. All external doo-dahs are the same.
2.3 DOHC is a more exotic beast and I know little about it.
email me so I remember to forward you all the contacts I have at home.
stuff like the cam is the same for all models, gaskets, oil pumps, etc all the same. usually the same rebuold its work across the ranges except that I believe the main bearing size is different on the 1599cc / 1800cc version because I had a set of Vandervels which specifically stated they were for the 1599c c slant 4....
Yor VX 4/90 should have twin CD175 carbs, these are exactly the same as the 2300 ones even down to the jetting. And yeah, the choke is supposed only to work on one carb. When set up well they are good so don;t change them just for the sake of it.
Blydenstein used to do a 2.6 stroker kit for the slant 4, chances of getting one now though... Hmmm... I may have the article with the feature in them somewhere.
As for specialists, well, there aren't really any. Carpenters in Boston (number in previous poist about them) and Onthecut on eBay are about the only two places who do stuff for Vauxhalls this old. Other than that its eBay or people who have stuff hoarded. Parts are REALLY hard work to get for these cars. Vauxhall land filled all their obsolete stock 10 years ago and nobody does remanufacture as the number of cars left is too small to warrant it. They were not sold in any great numbers in any export market so thats your lot really.
You can try Vauxhall Herritage but I have found them to be a complete waste of time.
www.vauxhallheritage.com/Best bet used to be a chap who worked for Vauxhall who did dealer inventory searches to find obsolete stuff on shelves out there which had escaped the skip, but I heard he sadly passed on a while ago.
eBay, autojumble, clubs, wanted ads in classic mags, eBay, any forums you can find, etc.
You are on your own though really with these.
Its one reason I own a Cortina now rather than sticking with the Vauxhalls.
Gorgeous cars. I love them really. But...