In reply to fortee9er: Don't forget to offset grind the crankshaft.. Stock rod journals are 2.30 inches.. use Chevy rods and bearings (you'll have to narrow them a bit) and you can go to 2.10 which gains you almost .40 in stroke. Or use the small journal Chevy Rods and gain .600 stroke. The NASCAR boys go all the way down to Honda journal sizes (I think 1.94?) and still rev their engines over 9000 RPM. That combined with 96mm bore will get you up to 445 cu.in./7.3 liters or so (with a 6.0 crank)..
Don't face the throttle bodies forward.. Aston Martin, Ferrari, etc. don't.
As far as modifying the intake plenum Look at what AJ6 engineering is doing for their race manifolds..
Isky and Crower here in the states will regrind the stock camshafts but the end result won't be as good as the Kent cams. Use the oversize lifters available from Rob Beere Racing but you'll need to go a long way to find better valve springs than those Isky sells..
Headers, Don't buy any.. I have yet to see a set of headers that really offer power gains.. If the individual pipes aren't all the same length those are tubular manifolds not headers.. and the length is determined by the camshaft specifications.. Mine call for 27 inch long primary pipes (1&3/8ths) and 22 inch long collectors.. (3&7/8ths)
In reply to frenchyd:
To behonest, I don't really get your reply to my post. I'm not trying to convince you of anything. So, what are you trying to convince me?
Depends on my goals for that particular build. And what v12 (jag,bmw,benz). If I'm using an already FI engine then I'll try to run on stock ecu (ecu's) before anything.
I don't think there is one right way to do it. I think there's many ways to go about it to suit whoever and whatever budget.
In reply to yupididit: I believe this is where we agree,
Any V12 will be more interesting than the normal V8/4/6 cylinder, There are affordable BMW, Mercedes Benz and Jaguar. Each has their strength and weaknesses. The goal of the build determines the approach not that there is any one correct way to build..
Where we differ is in the need of a computer.
The early (1971-1975) V12 Jags didn't use a computer.. So it would be possible to retro the last V12 to run computer less. A simple approach would be to cut off the face of the injection manifold weld a plate that is set up for 3 carbs(per side) and run the distributor as a stand alone device. What carbs offer is ease to convert to alcohol.. either ethanol or methanol. Just drill out the jets and the potential is there for 20% more power.. Unlike gasoline alcohol carries some of the oxygen needed to burn thus it's sort of like a mini supercharger.. It runs cooler and has a higher octane rating.. (106 compare to 87 or 92 for gasoline)
In short a 6.0 V12 Jag makes 318 horsepower.. going retro can kick that same engine up over 450 without big expense.. basically gaskets and a reground cam. Around here the dirt track guys buy alcohol for a little over $3 a gallon.. ..
I have no problem with the carb route. I think we completely agree just in a different way.
I have a question for you though,
There's an 84 v12 with a th400 for stupid cheap about 30min from me. Can that be converted to carb? If so, how. And can an GM t56 be adapted to it? LT1 t56?
frenchyd wrote:
In reply to rcutclif: If BMW has the weight of their V12 down to 435 pounds, then their six cylinder must weigh 240 pounds? A V12 has two times nearly everything.. 2 heads, 2 6cylinder blocks, 2 times as many pistons, connecting rods, crankshaft throws, intake manifolds, exhaust manifolds, etc..
An inline X cylinder and a vee 2X cylinder aren't all that different in weight. Most of the hard mass is in the main journals/bulkheads. The cylinder walls and cooling jackets are surprisingly thin in a modern casting, and the decks may be relatively thick but there's not much actual deck surface, it's all holes.
60 degree V12 cranks don't need split pins like a 90 or 60 degree V6, so they look exactly like I6 cranks but with slightly wider journals. (Vee engines usually have narrower big ends than inlines)
In reply to yupididit: Yes it can be converted to carbs.. Not probably street legal but depending on where you live it may not be a problem.. Depending on your budget and ability to weld and scrounge you might not spend very much doing it.. Bunch of questions depending on your goal, race car, hobby car, or daily driver?
The 1984 has the HE engine.. If significant power increase is your goal you'll want to find the heads from an earlier engine.. (1971-1980) Oh and while you are grabbing the heads take the distributor it has a better advance curve than the H.E. otherwise the 11.5-1 compression will offset some of the problems caused by the recessed exhaust valve of the H.E..
The engine in the Jaguar looks like a nightmare with tubes and junk hanging all over it.. Look past that. what's underneath is fantastic..
To use a manual transmission instead of the Turbo hydro 400 isn't that hard but will require some cost.. A flywheel, pressure plate, and clutch for a start.. No a Chevy Flywheel won't adapt to a Jaguar.. I'm not sure the bell housing can be adapted.. maybe, maybe not but if not I'm sure there are aftermarket scatter shields that can be made to work. Oh and forget metric wrenches..
In reply to Knurled: Jaguar doesn't have any block deck surface.. But there are 12 conrods, 12 wrist pins, 12 pistons, 2 cylinder heads two intake manifolds two sets of exhaust manifolds. The crank rod journals are 2.30 and the mains over 3 inches. I'll bet the crank alone approaches 100 pounds.(I really should go down and weigh one..... Oh and it's big, some are taken out as large as 445 cu.in. or 7.3 liters. But Jaguars V12 is right about twice as heavy as their six cylinder (the newest 4 valve per cylinder all aluminum one) {about 30 pounds lighter than their old Cast Iron block one}
I think we've established that the Jag V12 is cheap to buy and can be modified to produce more power. So what is the story on the BMW and Mercedes V12s?
I guess for comparison purposes we should look at the earlier versions such as BMW's M70/S70 and Mercedes' M120. What about the cost and availability of hi-po parts? What are the power goals?
They dont really have an aftermarket. Theres a Japanese company that makes headers for the m120 that makes it sound like a f1 car.
https://m.facebook.com/tgsasaki?refsrc=http%3A%2F%2Fcarbuying.jalopnik.com%2Fhow-to-make-a-used-mercedes-sound-like-a-pagani-zonda-1611782156&_rdr
I think if you're not looking for '500hp' and you're okay with the stock horsepower then you'll be fine.
Like I said in an earlier post. Pagani used a stock untuned m120 in their c12.
In reply to fortee9er: I'm sorry I haven't had anything other than a casual interest in BMW or Mercedes Benz V12's. I have heard that like the later Jaguar HE the earliest BMW & Benz V12's used a version of the Chevy six Fireball head of the 1940's and 50's in order to reduce thirst and run cleaner emissions. Thus ultimate power potential is decidedly lacking.
My assumption is that since they were only used in their biggest and heaviest cars They too were designed to make power at low RPM which would indicate relatively small ports and valve sizes.
I know Mercedes Benz is pretty jealous of others cutting into it's parts business and to limit that they tend to make slight changes on frequent intervals. Thus to get parts you usually need to use the cars serial number to ensure they fit correctly.. (it's also a good antitheft technique)
I haven't seen either BMW or Mercedes Benz race their V12's unlike Jaguar who has been racing theirs since the early 1970's. Jaguar not only sponsored Teams like Group 44, Huffacker racing, Walkinshaw , Broadspeed, Forward engineering and others but provided guidance to hobbyests. S.C.C.A. LeMans, Daytona and most of the major race tracks in Europe were venues for Jaguar's V12. In addition to Pro racing like IMSA, and European touring car etc.. There is amateur class racing in England for V12 and six cylinder Jaguars. There are at least two V12 drag race cars and that doesn't even include autocrossing or Vintage racing..
Well, BMW didn't have a V12 to go racing with in the '70s, so you have to content yourself with what BMW motorsport did in later years.
As for the weight, BMW V12s are barely bigger than their 6 cyl, so no, they aren't twice as heavy as the 6 cyl, but they are quite light.
As was said, mostly holes:
In reply to frenchyd:
Mercedes m120 powered race car.
And the BMW V12 in a Starion engine bay. Not that big of an engine at all.
BMW inline 6 in the same Starion. See the difference in size between the inline6 vs the v12?
In reply to Chris_V: That's a very nice looking engine.. I see what you mean about being light.. No cast Iron Liners like Jaguar has. On the other hand it does have a block deck which adds a few pounds back on.. Just eyeballin' the thickness of it's strengthening ribs and bell housing mounts etc.. It doesn't look that much thinner than a Jaguar block. On the other hand it sure is compact..
Since you can bore a Jaguar out to 96mm and offset grind the crank out to 84mm (7.3 L/445 cu. in.)I suspect that is bigger than the BMW will go and that is where some weight is.. There is a Jaguar V12 that has been taken out to 110mm stroke and a 98.5mm bore (600 cu.in/10 L) for airplane use. So obviously it's a lot bigger than the BMW
On the other hand I do see 2 cylinder heads and while a Jaguar V12 head is pretty light with only a single overhead cam and no rocker arms there are two of them and 2 intake manifolds . Sure, they are aluminum but twice as many as a six. Two times as many connecting rods, two times wrist pins, 2 times pistons etc.. It does add up. I'll bet the BMW crankshaft while not twice as heavy does weigh a significant amount more than the 6 cylinder crank. and of course with two times the friction surface as a 6 the oil pump must be significantly bigger etc.. Bigger water pump etc..
Just because I had easy access to a cast Iron exhaust manifold I weighed it. 4 pounds was all it weighs.. Yes there are 4 of them but I suspect that is about what a BMW manifold weighs as well.
The fit and finish of those race cars is really high, of course I doubt you could expect much less from Mercedes Benz.. The details between a designed in the 1960's engine and a designed in the 1980's engine is significant.. Not to mention that in those years Jaguar's income was tiny compared to Mercedes Benz income in the 1980's.
Spending 1.5 million dollars for the development and purchase of equipment to build that V12 is why William Lyons sold out to British Leyland.. It's a very good thing he did since shortly after it's introduction in 1971 the OPEC oil embargo killed the market for fuel thirsty engines. With sales some years barely exceeding 1000 units the profit wouldn't even pay the interest on the loans.
As to size, yes a V12 will fit almost anyplace an inline 6 once sat without a lot of effort.. Notably more narrow than a V8 it's added length is it's only handicap.. While not longer than a 6 cylinder it can be a few inches longer than a V8. A Jaguar is 32 inches from bell housing to fan belt..
V12 in a Starion is beyond bizarre lol
So how about some off the wall ideas?
I was just day dreaming of V12 power the other day...and all the stuff is expensive or not around me (that I've seen in junkyards often)
But what about combining two v6s? Like the VG30DE- its 222bhp stock and something around 180whp, so about 30-40hp lost through a typical drive train. Add a second engine in front of it, with the original engine just retaining its water pump, oil pump and cam drives. Do typical bolt on mods and you have no less than 450bhp before serious mods, or roughly 400whp.
Thats two $100-500 engines and stock ecus to control them.....Not the same as a single V12 engine but I've seen some home built dual engine cars......
In reply to Rustspecs13: There are simply too many V12's available for cheap money. I've paid as little as $50 when a hot rodder who wanted a Chevy V8 instead of the V12 in his Jaguar. That engine was so sweet I put it in a XJS as I bought it and had it running within a day..
Sometimes you can pick a rusty car up and it will have a solid low mileage motor in it..
Craigslist, Car parts.com or your local import wrecking yard. $300-500 is the real world selling price for a solid engine/sometimes with transmission tossed in free..
Wasn't it last month That Grassroots motorsports had the article about buying from a junkyard? one of the places Copart last I looked had 324 Jaguars and while only about 20 were V12's some of those would have sold for scrap iron money. Don't forget the sedan had V12 option as recently as 1997 so from 1971 to 1997 is quite a spread. BMW seem to be more expensive as do Mercedes Benz but with a $500-1000 budget I'm certain you can wind up with several options.. Some of them might even run and drive! Imagine the Adventure of driving some dented Jag home from a junkyard..
Once you get to be known as a collector of Jaguars you'll be surprised at how many cars come your way for modest or no money..
Do the BMW engine. I'll help with parts sourcing, in exchange for the knowledge gained.
A V12 e28 M5 clone would be fantastic.
Rustspecs13 wrote:
So how about some off the wall ideas?
I was just day dreaming of V12 power the other day...and all the stuff is expensive or not around me (that I've seen in junkyards often)
But what about combining two v6s? Like the VG30DE- its 222bhp stock and something around 180whp, so about 30-40hp lost through a typical drive train. Add a second engine in front of it, with the original engine just retaining its water pump, oil pump and cam drives. Do typical bolt on mods and you have no less than 450bhp before serious mods, or roughly 400whp.
Thats two $100-500 engines and stock ecus to control them.....Not the same as a single V12 engine but I've seen some home built dual engine cars......
ive always though about doing this with some SBC's in a tube frame basically like this:
^this one, if i remember right, makes around 1000 hp, and look at those headers! 
there are probably already couplers available for small blocks in the tractor pulling community. And its pretty easy to make a reliable 350 hp small block, with 2 of them you would have a reliable 600 hp v16 with parts available at any parts store 
In reply to edizzle89: It's difficult to discuss any of these ideas.. We all come with our own interests and bias. One person may be building a budget race car that's different while another seeks a streetable cruiser. Budgets enter the conversation and things get really complex.. The budget I had in my youth is long gone but others my age may have more money than time..
Then comes things like talent, skill, and experience.. Not to mention equipment, training, and knowledge..
The cool thing about this site is the ideas everyone is bouncing around.. Maybe they won't fit exactly what others had in mind but at least they aren't boring..
In reply to frenchyd: I'm new to this forum but I have been following this thread. I'm starting a rebuild of my 5.3L v12 and wanted to share what I'm doing and get some feedback. Overall goal- 7L engine making over 400hp. Heads: - mild porting, not enlarging anything, just smoothing out the transitions and cleaning up the valve pockets. I am going to oversize valves, 45mm on the Intake and 37mm for the exhaust.Guides replaced with bronze, stainless steel valves and seats.
Block: installing 96mm liners. Pistons are from Ross and are dished with a CR of 10:1 would like to go higher but I don't think its possible with 93 octane gas. Will be using SBC 6" rods with 2.1" BE. The crank is being offset ground to increase the stroke to 80mm. That will yield just under 7L. to maintain the "in the hole" piston depth of .160, the pins in the piston are being moved up. .160" + .040" for the head gasket will keep the deck at .200". The CAM is being upgraded to an ISKY XM3 grind with .424 valve lift. with the deck height of .200 there is no problem with piston to valve clearance. I'm keeping the exhaust headers but having them ceramic coated. The rest of the exhaust will be a Hayward big bore mating to the headers. The carbs are 6 - 40IDF webers.
Any thoughts or suggestions will be greatly appreciated. thanks Ken
In reply to Flyingprince: That sounds interesting.. What is your goal? What sort of budget? What car will the engine be used in? How much will it weigh? Is it a all out race car or street cruiser? What transmission and final drive ratio? It's an odd mixture of parts plus which heads will you be working with? The early flatheads or the later H.E.? Cheapest and ultimate power gains will come from the early Flatheads (1971-1980) There isn't any big power increase in the port work you are discussing. Plus it's a lot easier to lose power with port work than to gain it.. I couldn't do port work that yielded any real gains until built my own flow bench and combined that with the ability to exactly measure volume and flow changes on each port.. To expect to do repeatable port work, (critical for real power gain) plan on using a vertical mill to do your base line work and then hand blend measuring volume and flow numbers several times on each port.. Don't fixate on any one compression rather use the compression in conjunction with timing to optimize power.. The later H.E. engine runs just fine with 11.5 compression and pump premium. The trick is ignition advance and which fuel.. For example gas with a higher alcohol content will accept more advance and greater compression.. (which will in turn yield more power) One trick in common use around here is buying non-oxygenated 92 octane gas and adding E85 to it to bring it's octane rating up over 96-98
Off the top I'm questioning your use of ISKY XM3 and Webers.. First most Weber intake tracts are way too short. Second tuning Webers requires a whole bunch of parts and dyno time.. Third the ISKY cam while a good offering for the cost isn't up to what the Kent cam will make.. Power comes from making components work together and while I haven't run that particular combination on the computer yet I doubt the pieces will combine well. If you can give me flow numbers plus size and length's (primary and collector) of your headers I'll re-fire up my analyzer and give you numbers within 2-3% of actual final output.. one final note, as the size of the engine increases the engine starts to be rougher and less turbine like.. and weight of pistons and rods start to become critical.. Oh and don't forget to increase oil volume with stroke increase.. The stock oil pump has limits at higher RPM and increasing the stroke will increase the needed oil flow.
In reply to frenchyd: Thanks for the info. The car is a 1974 XKE so it has the flat heads which have the potential for more power. Just looking for a fast street car with over 400HP. As far as porting, the heads flow well stock, but i'm just going to smooth out the transitions and imperfections but not increase any of the dimensions. Your point with the webers is well taken as the velocity stacks will only be about 5/8" to fit under the bonnet. I can probably use more cam than the isky xm3 without it getting to lopey. The new pistons and rods will take almost 10 LBS out of the rotational mass which will help greatly. Good point on the oil pump i will have to look into that. The HE engine can use the higher compression because of the EFI and the ability to adjust the timing on the fly. I could most likely push it to 10.5:1 but that might be the limit. As far as the lengths on the exhaust, I can't find that info on the Hayward / Smith website, but they can't be much different than the stock headers since they fit in the same space. Thats one of the reasons I'm sticking with the stock headers.
In reply to Flyingprince: I would be inclined to start out with a 6 liter engine.. It has a bigger oil pump to start with and the oil path works better. Then I'd put your flatheads on for greater power potential than the H.E. heads the 6.0 liter has.. The downside is Flatheads aren't as fuel efficient at partial throttle (cruising) Since you intend to bore the engine out you'll need custom made pistons anyway. Don't even think of using the H.E. pistons on a early flathead.. you'll wind up with something like 18-1 compression ratio. For the street I'd be inclined to use the fuel injection manifold. Fuel injection can be used up through about 450 horsepower if properly modified.
Don't worry about a V12 getting lopey with a wild camshaft.. I had the biggest one Kent makes and it sat there and idled at 600 rpm nice and pleasant.. Don't use a big camshaft for street use.. (You actually lose power at the lower RPM you drive around the street at) in order to gain it at high RPM.. You don't run around on the street at 6500+ RPM where a big power increasing camshaft makes it's power. Read what AJ6 engineering has to say about camshafts..
Actually the H.E. doesn't have as much advance in the distributor as your flathead does.. Only the much later computers in Jaguar were able to adjust timing on the fly based on feedback. Frankly for the money I'd buy a used or wrecked 6.0 sedan from 1993-94 (the early 6.0 engines had forged cranks rather than the sintered iron of the last ones) and take the whole engine, computer, fuel system, etc.. I've seen wrecked ones sell for as little as $500 plus buyers commission. Take the parts you want and resell the remains to any junkyard bidding for it at the auction. You start out at 318 horsepower rather than your 242. AJ6 engineering sells a bigger intake. Plus they have a how to for 20 pounds. Even buying everything from AJ6 you will still spend a whole lot less than going Webers. I can see you getting real close to your goal with a relatively stock 6.0 Plus better than 2 times the fuel mileage..
As for headers.. If each pipe isn't the same length as every other pipe you don't have headers you just have tubular manifolds. (and you haven't gained any horsepower) I don't see any equal length headers being sold commercially.
Headers must be equal length, the right length (based on the camshaft used) and the right collector length.. On my Race only XK-E I had 27inch primaries 1&5/8th with I think 22 inch collectors.. That's 588 inches (49 feet) of tubing uner the hood.. A camshaft closer to stock will need longer tubes to gain power. It takes a real artist to get that to fit in an XK-E.
I think headers were probably are heavier than the stock 4 pound manifolds.. Unlike a V8 headers on a V12 really only help marginally.. Adjacent cylinders on a V8 may fire from 90 to 270 degrees so those pulses interfere with each other.. The even 60 degree firing of a V12 doesn't have that issue. That's why they feel so smooth
