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Hi Folks I've been given a what I believe to be a 4.2 motor that was a spare for a 1985 XJ6 Sovereign
I'm considering putting it in a Sprintcar frame. Class rules dictate that I must run carburetors. So 3x Webers it will be. But unfortunately due to the frame design sidedraft Webers won't fit. Has anybody seen a Downdraft manifold for triple Webers
Must also run on methanol. Or will this project be to big & expensive
Will also be looking for high compression pistons & performance cams etc
As far as I know there have only been 2 downdraft manifolds for the XK engine. One was for the original 2.4 and Mark 2 2.4 engine, but that won't fit the XJ6 cylinder head. The other was a manifold for a Solex carb that was used in the Scorpion light tank for the British Army. There have been donwdraft manifolds for the V12, but that won't work for the 6 cylinder.
Why Webers? The SU carbs are generally more flexible and give just as much (or more) power than a 3x Weber DCOE45. I have a friend who was into vintage racing and dyno tested both the trip SU and Weber carbs on his race prepared E type engine and he was able to get more power from the SU and as a benefit the engine used less fuel. He described the SU as the logical choice.
Try <www.weberperformance,com.au> in Chelsea Heights, Victoria. Their kit price for triple 45DCOE on manifold for 3.8L / 4.2L XK engine is AU$3,990. I see you have fitment issues in Sprint Car frame, but I'm sure they will try to help.
In my day (yes, kids, cars had been invented!), I began my part-time engineering around Lynx Engineering on Paramatta Road near Burwood. On land, it was short lived (marriage, kids, career). On water, it saw a brief reprise. I don't think Lynx had any connection with UK replica specialists of same name. John and Leon have gone now, but their website <www.lynxauto,com,au> contains a link to the Victorian firm above. I note the latter is replete with RAMFLOW air filters, manifolds etc . . . all developed by Lynx in Sydney, as was an innovative fuel injection system,
If the Vic firm can't help, why not fab your own as Lynx designed for our hill-climb special some 55 years ago. Standard inlet manifolds will give you the plates bolted to head . . . 6x U-shaped pipes bend over the inlet camshaft . . . 3x 45DCOE between cams. I can't recall whether the paired inlet pipes splayed in or out slightly because the carb and inlet spacings are different. I do recall we had to fit a balance tube that linked into each inlet pipe above the bend, and separate outfeed from the inlet plates for coolant. Another issue was placement of the Weber inlet horns over the hot exhaust area . . . not an issue once our 250bhp glorified go-kart was unleashed, but it did not like standing at its idle of 1,500 rpm.
This was for our 40 Bends hill-climbing years at Lithgow NSW, with a much modded 2.9L (ex 2.4L) Jaguar XK engined special. That engine had sleeved block, ground crank and new machined con-rods and pistons courtesy of Lithgow Small Arms Factory. Later. they played a pivotal part in our record breaking hydroplane, "Jagged" which was based on a vee-drive 6.0L (ex 5,3L) V12 Jag engine sporting twin Supra turbos, methanol injection, dry sump, Hall Effect dizzy, and tuned extractors into long, big bore, chromed water injected megaphone exhausts that fair bellowed at any thing more than idle,
However, that's irrelevant to your quest. I do encourage you to push ahead. Aussies have a rich heritage in race engineering, punching well above our weight. I think there is a specific sub-forum here for such topics and I do trust that you keep us informed of progress.
As yet I'm rather undecided as to which way to jump. The Sprintcar frames I have will be both "raced" [ Spirited Demonstraion ] in the vintage class. Up to 1990 or there abouts. Both frames are high bars
1. Drake - genuine wingless car fro California ( CRA car )
2. Foster #1 ~1986
Trying to do every thing on a very tight budget. $0.00 Both cars would have been Small Block Chev powered back in the day. Don't need 800 Hp to demonstraight
Neither Chassis is here at the moment. So both are long term projects
Just push hard. Back your intuition and don't give up.
Do what Brabham dared to do . . . and his partner Ron Touranac who went on beyond the BT years (Brabham Tauranac) to design and build RALT racing cars. As I have shown, my knowledge of sprint cars is insignificant but I'm sure that your $0 budget will be challenging.
What I do know is Jaguar engines of the 50s to the Ford years. That 2.9L XK I6 engine could red-line at 7,500rpm, perhaps further, and it produced higher output than its longer stroke 3.8L cousin.
What I do know is Jaguar engines of the 50s to the Ford years. That 2.9L XK I6 engine could red-line at 7,500rpm, perhaps further, and it produced higher output than its longer stroke 3.8L cousin.
Cheers and best wishes,
Wow! I learned something today. I figured the smaller displacement xk's were completely anemic.
Wow! I learned something today. I figured the smaller displacement xk's were completely anemic.
And you're quite right . . . about as exciting as watching grass grow in factory delivered "single downdraft strangleberg" form . . . but they had one enormous advantage. The much shorter stroke (76mm) compared to the "grown up" 3.4 or 3.8L (105mm) produced two great benefits . . .
.
shorter "throw" reduced con-rod rotational forces, so con-rods were shorter and thus, the engine block was significantly lower (about 3" IIRC);
being significantly "over square" with bigger pistons, and with big induction and exhaust mods, these engines still had that great bottom-end foundation of well supported crankshaft and would happily rev well beyond the 6,000 to 6,500 rev limit of the taller engines.
Upstairs, the gold top head with bigger valves, re-profiled D-Type cams, triple SUs or triple DCOEs, custom extractors and free flow exhaust, 10:1 CR and methanol fuel . . . all made for a potent race platform, but weight (not power) was our biggest limitation.
This is a photo of one of my chassis' ( Foster #1 )
Not the one I was toying with the idea of putting the Jag 4.2 in
In a previous life I raced a Mk3 Zephyr (155 cu in ) against Holden 192's and did ok . Not as must top end horse power but could out grunt them coming off the corners . Torque baby torque. Hoping for soming simular with the Jag 4.2 . Not that I need bulk HP these days as it is only for a demonstration hahaha.
Thank you all for your great comments. They have been very helpful. This is a long term project. Should really get the yellow car done first. Or I might be in trouble with a number of my mates especially as the #6 chassis has been gifted to me
If you're looking at manifolds, be aware there have been 2 different bolt and port patterns and they are not interchangeable. The earlier is the B type head pattern, used from the beginning of the XK engine, and on saloons up to the end of S Type/ Mark 2 in 1967-68. The other is the straight port, used on E Types and all XJ6.
The straight port became the standard after about 1968, but was used on various cars earlier. The exhaust manifolds all had the same bolt patterns, so any can be interchanged, but the intakes were different.
Webers to 1985 XJ6
Both cars would have been Small Block Chev powered back in the day. Don't need 800 Hp to demonstraight 
Wow! I learned something today. I figured the smaller displacement xk's were completely anemic. 
