Between the MB, the BMW and the Jag V-12's, what are some of the positive/negative qualities of each, e.g. cost of parts, complexity, weight, etc.? We don't need itemized lists of reasons, just bench racing fodder. :)
Between the MB, the BMW and the Jag V-12's, what are some of the positive/negative qualities of each, e.g. cost of parts, complexity, weight, etc.? We don't need itemized lists of reasons, just bench racing fodder. :)
Don't forget the Aston Martin. For many of them, they are far more pedestrian than their Ferrari counterparts.
alfadriver said:Don't forget the Aston Martin. For many of them, they are far more pedestrian than their Ferrari counterparts.
I doubt you can pick up an Aston engine for Challenge-ish money, but your point is taken that others may have interests different than mine. 
In reply to stroker :
Ah, didn't know that was the standard. I've been pretty surprised that a MB V12 can be gotten for challenge=ish money, but it's happened. I knew that you could get the BMW back in the day for challenge $$.
One advantage to the BMW is its compact length, due in large part to its 14mm smaller bore spacing (x6) than the Jaguar.
My old PnP yard did flat rate pricing on engines at $300. I saw an S600 in there with rear end damage. Stock it's mated to a 722.6 which is a very stout transmission. They're just so smooth, torquey and sound amazing.
Per our French fry, the Jag V12 uses a GM BOP transmission bellhousing and was in production for quite awhile. It's bore and stroke are close enough to the chevy tree-fiddy that it's pistons can be used, but I think that requires new rods. Heads exist for both injection and carburetion, but I think both stock parts are pretty poor. Engine is heavier than the weight of my sins; so I'd say, easy mode is the Jag.
Love to hear more on the other two, the Mercedes V12 is one I rarely see in yards. I do remember the BMW V12 is a problem only because it needed 2 ECUs running in tandem because computers at the time couldn't handle that much.
In reply to LopRacer :
With fewer than 300 ever making it to North America it's a rare entry. Figure that number again of the Audi A8 of the time. Still not many to grace our shores.
I'm curious as to engine management with all these engines. The Jag engines seem old enough to be fairly simple. Not sure if the BMW, Merc or VW engines can run standalone on the OE ECU?
In reply to WillG80 :
VW, would take some finagling, as they were new enough that they were probably ME7/ME9 and had all the immobilizer fun stuff.
BMW, at least the older ones, were actually controlled by two inline six computers, each bank had its own distributor and airflow sensor and throttle body.
Mercedes... some were pre-network, some not, who knows what it takes to make them happy.
Pete. (l33t FS) said:In reply to WillG80 :
VW, would take some finagling, as they were new enough that they were probably ME7/ME9 and had all the immobilizer fun stuff.
BMW, at least the older ones, were actually controlled by two inline six computers, each bank had its own distributor and airflow sensor and throttle body.
Mercedes... some were pre-network, some not, who knows what it takes to make them happy.
But if we're bench racing just the engine, then we're just going to slap a megasquirt in there, right?
Then I suppose it becomes a question of which one has the easiest sensor suite.
Before the mid 2000's, computers were not fast enough to handle over ~5000 rpm with 12 cylinders and operate well enough.... We did the same thing for Aston that Merc and others did. Had to coordinate the two computers, though- one was the master over the other- otherwise, the system would fight each other.
In reply to alfadriver :
How would they be fighting each other? I'm really curious.
I can see how idle air control should be left to only one computer, at least.
In reply to Pete. (l33t FS) :
Kinda curious about this as well. If the CPUs of the time couldn't handle the additional cylinders I assume the ECU's had to split duties for ignition and injection events (i.e. the things that are happening 2x as often as in a 6 cylinder). So that stuff would have to run in parallel.
Dunno why they couldn't handle the rest of the stuff that way as well.
GIRTHQUAKE said:Per our French fry, the Jag V12 uses a GM BOP transmission bellhousing and was in production for quite awhile. It's bore and stroke are close enough to the chevy tree-fiddy that it's pistons can be used, but I think that requires new rods. Heads exist for both injection and carburetion, but I think both stock parts are pretty poor. Engine is heavier than the weight of my sins; so I'd say, easy mode is the Jag.
Love to hear more on the other two, the Mercedes V12 is one I rarely see in yards. I do remember the BMW V12 is a problem only because it needed 2 ECUs running in tandem because computers at the time couldn't handle that much.
Please let me correct some of your statements. First the transmission on 1978 -1997 use a common GM locating dowel. But the bolt pattern is different. GM transmissions though. Prior to that 1971-1977 everything is different. The transmission is either a 4 speed Jaguar or a Borg Warner automatic.
The heads from 1971-1980 are the Good Hi flow heads. With only 7.8-1 compression the power is the same as the HE with 11.5-1 compression.
All V12 camshafts are the same just different ways of measuring them. Regrinding the camshafts easily add at least 80 net horsepower and can be done in less than 1/2 the time swapping cams in a domestic V8.The factory tested the stock engine up to 8300 rpm before valve float.
The official weight of a Jaguar V12 is 680 pounds.
The stock bore of a 5.3 is 3.50" and stroke is 2.75 The V12 can easily go out to 8 liters without expensive parts.
Power wise they made 831 hp without Turbo's running on French pump gasoline (85 octane) for the 24 hour races back in the 1980's
In reply to WillG80 :
The Jaguar system is horrible. Prior to Ford's purchase they were analog. Without any Prom chip to modify. You have to get in the mother board and start soldering and unsoldering. Sometime around 1992 that changed. The distributor went away and digital happened still without an EPROM.
According to internet myths some have been successful swapping to Megasquirt.
I would use GM sensors before I attempt that.
Pete. (l33t FS) said:In reply to alfadriver :
How would they be fighting each other? I'm really curious.
I can see how idle air control should be left to only one computer, at least.
It was all about idle. One would go into idle, the other would continue in decel mode, and the engine would stall. Drove us nuts until we saw the data that one needed to run the show.
The simple solution is carbs. From 1971-74 they were stock and only cost 18 horsepower over the fuel injection.
If you eliminate the dog leg used to keep the carbs before the XKE hood you actually gain 40 horsepower.
Another possibility is there are manifolds made for 2 Holley 4 barrels. Or cut the front of the fuel injection manifold off and put 3 SU carbs ( from an MGB ) per side. That will actually net 72 horsepower over the stock manifold, according to my computer.
Cost wise I used to get most of my V12's free but now the market price is around $500.
out of the 50 I kept only two had any damage. One from a loose oil filter that was driven home. And the other from leaves and trash between the Radiator and A/C that caused overheating.
They are the strongest engine you will ever see. Massively over built. Usually let down by the EFI. You can take a junkyard one and be reasonably confident it is in good usable condition . No rebuilding required.
They adapt to Chevy manual transmissions easily. At least 1978 Jaguar V12 and newer.
Before you Poo Poo 262 horsepower realize that is still 32 more than a Chevy 454. ( except the rare LS6 Stampie would like me to say. I don't know how much net horsepower that one has so you'll have to take his word for that. Or I saw one sell for only $15,000 on bring a trailer so you could put it on a dyno and find out ).
Power wise I'm taking a mainly stock 5.3 V12 and will be making about 400 horsepower(chassis Dyno) for a cost of only $300 beyond stock. They same mods done to a 6.0 should get to 475
Carbs might be "simple" but six Weber DCOEs is going to cost more than the engine, even before you have to buy twelve of any tuning supplies needed.
In reply to Pete. (l33t FS) :
Weber's actually will make less power than SU's. The reason is IDA's are too tall and even short IDF's need the hood modified to fit. At that the length of the intake is way to short.
If you fabricate an intake manifold that goes over the cams and use DCOE's now you can start making power. But plan on spending a fortune tuning them.
The cheap and simple way is to buy 3 set's of good MGB SU CARBS. (HS4's) And weld a plate on the cut off EFI manifold to hold 3 per side. (6 total).
The stock ES needles should even be a good starting point.
I will just leave this here for you.
702 CID GMC V12 After market support, zero. Weight, the crankshaft alone is 180 lbs. Horsepower, 250 to 275 at 2,400 RPM. Torque 585 to 630 lb-ft at 1600 RPM.*
Specs procured from Chevy Hardcore GMC 702
There's no way in heck that the Aston V12 could have made 400hp with SU's.
And simple is relative.
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