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My Chevy's... Lol, I own an L92 Powered Escalade and LS2 powered GTO. Both very capable cars with vastly different purposes. No big block powered bricks under my care at the moment.
Actually AJ6 engeneering does sell intake items... (See here) So they have a financial incentive to suggest there are gains to be had. On an otherwise stock engine, the gains are there but very minimal. I evaluated some upgrades for a customer. I found no meaningful real-world intake restrictions on a 6.0. I never did test the 5.3 air boxes.... they do have a rather thin trumpet opening and I can imagine bigger gains can be had by lopping off the trumpets and extending the intakes with some larger tubing flexible tubing. Someone need to test that. Wont be me as I don't go near 5.3's. With the 3 speed, tight converter, propensity to drop valves.... they are just cruisers.
School is in session.... Tri-Y is a Ford / Chevy V8 thing / 4 cylinder import thing. The term TRI-Y comes from a type of header that is popular with some Fords and import 4's that makes 3 Y's. Never a term used for I6 or V12. This type of header is more popular on Fords than Chevy's becasue the ford firing order favors the design. For use on a Chevy one of the primary have to be crossed over to prevent 5 and 7 firing adjacency...so then packaging in a chassis very difficult. IF you use a 4/7 swap cam on a SBC then no cross over is needed and fabricating headers is much easier to package in a chassis since 5 and 7 no longer fire back to back. I know nothing about the 4 banger import uses but I suspect the same issues apply.
All in-line 6 and by extension V12's can benefit from 3-2-1 headers. As show below. From road car to race car. 3-2-1's work becasue of pulse tuning. The fact is that on a I6 or V12 you get a pulse every 60 degrees so separating them is even more importance than on a v8 which has more time between pulses at any given RPM.
please take a moment to look in the XJS and B12 Sedan’s engine compartment. Do you really see enough room to put that collection of tubing in there?
I'm just trying to learn how to help my XJS work well. The HE had a purpose, no surprise it's not "optimal" for a build. I'm so confused. It doesn't help that the above seems to be comparing a 326 cubic inch engine with a 454 cubic inch engine. And it's not like a Chevy Big Block doesn't get hot. Any '67 Vette driver can tell you that! I guess I'm not understanding the discussion here.
There is a large variety of people responding here each with their own perspective and background. If you’re a hot rodder you can make decent power with that HE. No it’s not optimal. Yes it requires more creativity and out of the box thinking. But it can be done. Don’t go for some magic number, improve what you have on a budget you can afford. Just clean and polish that engine and it can be pretty eye popping stock.
My background is that of a Racer. Not a collector or someone who has a mechanic do the work. Since my income is only slightly above average. I’ve had to figure out cheap ways to go fast. To most people speed costs money, how fast do you want to go?
Me? I make homemade jigs to mill valve reliefs in pistons using my drill press and a fly cutter. I balance pistons with a simple knife edge balance beam. I’ve been building race cars on a tiny budget since 1962. I adapt, make do, and do without. Yet there I am successfully racing with some pretty impressive names. Right now I’m getting my XJS race ready with a $2000 budget. ( including the purchase price)
You don’t have to do all that though. You’re not going to spend weekends with your foot flat to the floor. Leave it reasonably close to stock. If you want the EFI be prepared to learn how to work on it. Real experts are few and far between but there are enough U Tube videos on it and Kirby’s free down load so you should do OK. Yes there are aftermarket ECM’s you can use. Some can actually be an improvement. If you don’t mind being the only person who can work on it.
I like the simplicity of carbs. Those SU’s/ Strombergs are lawn mower simple. Easy to modify.
Let’s be honest. Carbs cost you 17 horsepower over EFI. Plus fuel mileage will take a hit. Using the magic Corn Juice (E85) requires a lot more than some math and a drill bit.
But if you can weld or have someone who can weld for you, you can gain back not only the 17 horsepower but another 20+ besides. Then the 10%+ real horsepower gain is just a matter of figuring out how to flow 20% more fuel.
I just put a Tremec TKX in a XJ coupe, There's more room than I expected. The TKX is very compact and the Hydraulic TOB yields back a lot of space. It would very practical in this case and this is what I intend to do on my next coupe project. 6.0 V12, headers, TKX amd Isky cams. In any case the v12 E-type guys already run and fit this type of header but in their case the secondary's are too short.
I've already done Long tubes on BOTH sides of a SBC conversion with a T56 with the older type of lever clutch slave in the way. It was very tight but survived the only 2 track days it ever ran. They were in the car that Ran down a Super Charged C5 Corvette. That video his here
This type of header already exists for the E-type but secondary's are too short. All the space offered up but a TXK would allow the secondary's to run side by side and thus could be much longer as they should be.
secondary's are too short.
Last edited by icsamerica; 08-29-2021 at 11:57 PM.
I just put a Tremec TKX in a XJ coupe, There's more room than I expected. The TKX is very compact and the Hydraulic TOB yields back a lot of space. It would very practical in this case and this is what I intend to do on my next coupe project. 6.0 V12, headers, TKX amd Isky cams. In any case the v12 E-type guys already run and fit this type of header but in their case the secondary's are too short.
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Oh this is nice. Glad to see one in car. I've been wondering about the TKX fitment since it came out and I've been suggesting it as possibly an option to ask about for those thinking of doing a 5speed conversion. I'm assuming that bellhousing isn't the one you'd get through the Driven Man if buying a kit? Don't they use a brand who's company color is blue? Quartermaster maybe? Anyway. Nice.
I wouldn't say the HE wasn't optimal, for it's time it was a very powerful engine, and like most engines it has things it does well and some not so well.
A major difference is that Jaguar has already unlocked most of the potential, so there is not much left that can be done. I am assuming a street engine in a road driven XJS, all out race engines are entirely different design goals and compromises.
“Unlocked most of its potential” ? Only if you consider fuel mileage. There were major trade offs to gain slight improvements in fuel mileage at the time.
Introduced slightly before the Suez Canal problem, followed by the first Fuel Crisis. And Later the second one. An 8 MPG car ( if driven Briskly ) was not in demand. That and new Smog regulations coming from America where over 50% of Jaguars sales came from meant Jaguar had to focus on improving fuel mileage instead of power if it was to survive.
The delay in introduction of their EFI caused by their suppliers failure put them behind and had them scrambling.
But as bad has the New HE head was it. It’s a Golden opportunity combined with E85. Corn Juice is a power adder. A cheap and simple power adder. Look at the timing of the pre HE engine. 38 degrees BTDC and with only 7.8-1 compression it makes the same power as the HE does with 11.5-1 Now look at the HE’s timing. Only 17degrees BTDC
What happens if you advance the timing to 38 degrees? With no other changes PING, ping , ping until failure. Now switch to E85 (Which is $1.50 /gal cheaper than premium). No ping! More power!!! A lot more power you’ll go from 262 to 300 hp
One change. Granted few of you can figure out what to do to modify your V12 to take E85.
But that is one simple change. There are many such changes available. Yes more power requires more fuel. You can’t have everything.
No! an engine conceived in 1954 designed in the 1960’s and produced in the 1970’s won’t get the fuel mileage and clean air of modern engines. But it’s one beautiful thing under all that hoses and band aids.
Oh this is nice. Glad to see one in car. I've been wondering about the TKX fitment since it came out and I've been suggesting it as possibly an option to ask about for those thinking of doing a 5speed conversion. I'm assuming that bellhousing isn't the one you'd get through the Driven Man if buying a kit? Don't they use a brand who's company color is blue? Quartermaster maybe? Anyway. Nice.
~Paul K
the Bell housing can be a Chevy bell housing. It’s a simple conversion. If you can drill holes in Aluminum and cut that aluminum. In a couple of hours you come up with this That will take a couple of easy hours. Alignment is done by the two alignment pins that both Jaguar and Chevy share. ( due to use of the GM Turbo 400 transmission).
that’s about $40 worth of surplus aluminum.
to late already done that on many type engines , including my V12 XJS,, 24yrs ago!
still got the car HOW about you MG?
like i said MG can go on forever, credit his mastery of arguments!
to late already done that on many type engines , including my V12 XJS,, 24yrs ago!
still got the car HOW about you MG?
like i said MG can go on forever, credit his mastery of arguments!
could you clarify what are you asking about? Are you saying you already use E85? F so good for you. I like how you lightened your car up. I wish that was allowed in Vintage racing.
Thanks, I've actually already worked up a CAD pattern for it helping work up a file for/with Robert Knodt (who you know of course)...so tucked away for future use. I was just looking at the TXK install (which - would usually be a The Driven Man kit - given the American Powertrain Association.) Just didn't look like 100% their stuff from the kit I've seen - wondered about the possible variation.
08-29-2021, 10:24 PM
