One thing I will add is that I did the Crane conversion awhile back for my distributor. It eliminated the stock distributor points set up. I had a MSD coil and the MSD ignition box. On the dyno, before my intake and cam mods, the dyno computer had a tough time picking up the ignition timing as the rpms got around 4500rpms. I found that the wet coil, even with the MSD box, could not keep the spark strong enough, which caused my power to start dropping. I recently added the MSD high voltage coil, the dry coil for high revs and track use. This allowed my rpms to keep going and not fade out. The stock 'single' MSD wet coil for the v12 engine can't recharge fast enough as the rpms get higher up. So this is a must. Unless you have the 2 coil set up (Marelli) or individual coil pack set up. Just think, spark wise, a single coil v12 at 4500rpm is equal to 6750rpm with a v8. That's a lot of quick sparks!

 

Good job on the intakes. they will make a difference especially if you add a programmable ECU.

 

You said you had it on the dyno before the cam and intake mod, what was it making then?

 

Ready for the disappointment...

I will have to say that the dyno that I was on is a true, accurate one. It takes the weight of the vehicle into consideration. The dyno adds resistance to the rollers so you will get a real life, driving result. Numbers are lower than a free revving dyno.

I will also say that these engines like a richer A/F mixture. 12 to 13's:1 ratio. As you can see on the paper with the dots.

This result is 10HP higher than my stock 5.3L (with 9:1 pistons) breathing through those little snorkels/silencers. It's actually 10HP and 8 ft-lbs of torque gain cutting those things off, but it was super loud afterwards. Through K&N air filters.

Also, you can see how the power was dropping off around 4500rpms. It was because of my coil. It could not keep up until I added the new MSD transformer type mentioned in my comment above. Now the rpms climb with no issues.

Going through a 700R4 automatic transmission.

 

wow , that dont seem right, must be the type of dyno, and how it calculates things!

sorry i dont have my dyno sheet (dynojet rollers),lost in moving and travelling FLA. =TX.

but the lowest i ever made when things were out of tune, was 275 rwhp.

HMM, food for thought?

 

way back when getting up and running, 1995 i do remember some ignition problems!
plus ECU tuning,(thats another story in its self) WHEW! have fun buliding you own MAP.

i was very lucky to have Crane factory 3 miles away, and became good friends with the chief electronics engineer.

i 1st set up with the Crane XR700 kit and there HIoutput coil. and the SDS ecu.

ran fair but some odd stuff, new to me breakups come and go!

talked with chief, he said try this new XR3000 box and improved coil, it ran terrible start hard and breakup bad above 4000rpm.

back at Crane we talked, he became interested good luck for me, he supplied me with what ever i needed,, said ALL crane stuff is engineered to V8 engines,thats the market!
not V12s.

he said try this box its a modified V6 circuit and chip, something about spilt the break period( i had NO idea what he was talking about, or ever will).

use only a standard coil with out a resistor (Advance auto). use a Mopar resistor at the box for running , and latest NGK Iridium plugs ,.025 gap. well that made all the difference been running now for 23years, without probs.

i do run a lot of spark lead ,25* btdc initial up to 1200rpm, then curve it all in at 45* btdc 3000rpm.
have had it at 50* , actually runs great but somtimes kicks back starting(bad).

also my engine has many small mods ,like oversize valves, slightly reshaped ports, thermal coated pistons, exhaust ports, and head deck surface ,dont need any famous V12 overheats(in FLA.-TX.) other things a cant think of!

actually engine is not as torqy as some believe , i make my torque thru gearing, 700R4, and 3.73 rear LSD. Jeep ring & pinion.

another , opening the main bores allows more crank movement , so the usual rope rear seal leaks get more annoying!

TWR finally had to major block mods using Neo seals.

 

Please excuse my interruption, but how did you get a 700r4 to mate up with a 5.3?

 

A whole lot of mods. This is my experience... Ronbros (Ron) might have a better experience.

I actually had a custom adapter plate made. But, if I am not mistaken, you should be able to put one on with only one hole not lining up. (I could be wrong) Do I recommend this mod? NOPE!

The 700r4 is longer. So, you will have to make a custom rear transmission holder.

The drive shaft will have to be shortened.

Physically, the 700r4 is larger, so, everything is super tight in the tunnel.

Your exhaust will need modification and will be super tight along the side of the transmission (heat) and nearly touching your fuel lines (heat). Wrap them.

If your starter has issues, you will need to drill a large hole in your floor to get at one of the mounting bolts. Almost impossible to get at.

Your shifter in the console, depending on year, is set up for your 3 speed. So, Drive, Reverse, Park, 1,2. Don't line up.

A modified linkage on the transmission will have to be made so at least the shifter will allow you to put it into park and drive and reverse. The rest do not line up.

You will have to wire in a relay to engage the lock up torque converter.

The RPM shifter weights pull out from the side of the transmission under a cap. You can remove the cap, but, there is not enough clearance to pull the weights out. So, you will have to pound a large bend in the tunnel to allow you to take it out to adjust for your rpm shift points.

Hmmm, what else... oh right, when the car travels at about 5 mph, it will shift into 2nd gear. So, if you want to accelerate quickly after that (say turning a corner then accelerating), it will not drop down into 1st gear after this. So, you will have a slow acceleration because the v12 doesn't have much torque like a v8 does. Now, if you make a complete stop, then floor the car, it will then stay in 1st until it reaches the higher rpms. The best I was able to adjust my rpms is 6200 1st, 5700 2nd, endless 3rd, 4th overdrive. The transmission will not go higher in 2nd unless you adjust 1st gear like around 7000 rpms! lol

Also, at wide open throttle, the transmission will not allow you to go into 4th (overdrive), it will stay in 3rd no matter the rpm of your engine. It will only allow you to shift into 4th when you lift off the accelerator pedal a bit. The 700r4 does not want you to drive hard in overdrive (4th).

Yup, that's it. For the money and I am still trying to adjust the shifter linkage, definitely not worth it. My exhaust still hits the bottom of the car under acceleration. I have a vibration under acceleration that vibrates into the car (I have no clue where to start looking) I would hands down buy a manual transmission and put a clutch pedal and slave cylinder in first. At least I could make the car stay in a better rpm range of the engine.

Now, I did see a company awhile back that made a gear housing that bolts directly behind the automatic that would cut the drive shaft speed by half then lock the gear speed up at every gear. So, the stock TH400 (3 speed) would turn into a 6 speed. You would have to just shorten the drive shaft accordingly.

I also know there is a lock up converter that also bolts behind the stock transmission that gives another 10% or so, to the final drive.

Just to mention, the stock TH400, Jaguar set up the shift points at very low rpms. The weights in those can be adjusted to allow the revs of the engine to go higher before the shift happens. A huge improvement.

 

G'day Jamey, haven't heard from you for ages. How's it going?

I have the electronic version 4L60e it's not a difficult swap, especially if you bought the John's car kits.

I made everything from scratch except the bellhouse adapter. So it took me a little longer.

One of the advantages of going electronic is the ability to program shift points, lockup and a host of other parameters. These days with the plethora of TCU's available it is not that expensive .

Here is my trans swap thread, The 700R4 is almost identical except it's not electronic.

https://www.jaguarforums.com/forum/x...e-swap-167463/

 

Sorry things didnt work out well but there is a lot of mis-understanding here that I can shed some light on.

Personally I'm a big fan of the 700R4. I got one tuned to perfection in my low 12 second coupe, that's always in the right gear. Took a lot of fiddling with the gov. The 700R4 is about 2 inches longer but it has lockup and an extra gear so that's to be expected.

As for the shifting issues sounds like you messed up the governor by using lighter springs and lighter weights. Too light of spring will make it shift too early on light throttle and too late a WOT. The good setup for a 700R4 is a "corvette " or "z28" governor, then trim just the weights conservatively until you get it were you need it to be. 1st gear on the 700R4 is very deep so they do overshoot RPM wise... this way when they hit 2nd gear you're back into the power band. That's valuable design characteristic if you work with it.

You will need to R&R the gov a few times to get it right. I used a 3 inch hole saw to make an access hole in the tunnel Then I used a 4 inch hole saw on a piece of scrap metal trimmed into an oval to make a cover panel held on with 4 screws. I used riv-nuts to make it clean and precise.

The 4th gear WOT issues and other shift issues are solved with a trans-go shift kit. Shift timing and quality at partial thottle can be customized but adjusting the pull on the TV cable but make sure it all the way at WOT.

Lockup can be controlled with a vacuum switch. So you only get lockup in high vacuum cruise conditions. To refine...You put a small tank and welding tip (.025) as restriction in the hose before the switch and tank. This offer a delay and buffer to prevent TCC hunting. The tank can be a metal fuel tank from an old RC air plain. You also have to wire up the trans to only lock up in 4th gear so when it down shifts to 3rd lockup comes out immediately.

The 3 speed shift-er can be made to align up right if you adjust the moment arm (lever length) on the transmission side. All gears will indicate correctly and you can get to 1st with out indication if you trim off the stop in-side the shift-er.

If I ever did another 4 speed conversion I'd use a 4l60E and a engine PCM from a TBI car. That PCM only needs an RPM signal and TPS sensor and it will shift the transmission where programmed. It doesn't care that the rest of the sensors are not there. Much easier than "in and out" with the gov.

As for the Intake. Larger plenums do nothing for performance if the engine size remains the same. Its fairly well understood that a larger plenum will deaden throttle response. Personally speaking, I recently switched out my intake for one with shorter runners and a much smaller plenum,the throttle response improvement was much more noticeable than I anticipated and I would characterize it as drastic.

I am surprised the longer runner didn't improve low end torque, this suggests the cam on the V12 is actually too big, probably necessary to crutch a poorly flowing head.

You were referring to a gear vendors overdrive unit. They are very expensive, add considerable length and weight yet no lockup. The are really for guys with, 600HP+, tall gears and need to drive their car to the track for some reason. For a road car a 700R4 is a better unit, lighter modern design and far less parasitic than a TH400. Lockup converters for the Th400 cost more than an entire rebuilt 700R4...and are for all out racing, not designed for the street.

In an case... keep at it. Car life offers lots to be learned and it helps to ask. Sometimes the knowledge is shared for free and sometimes it's not. Right now I'm planning another Jag coupe project...top secret at this point but I'm in the phase of "lots to learn." Everyday, I talk to someone who knows something that get me closer to my intended result. After awhile you learn from reaction or resistance whether or not you are on the right track.

 

I didn't do anything with the shifter, I used the shift arm off my TH400 and the gears line up perfectly, was I just lucky? 3 is D4 and 2 is D3, I do need to get another face plate made that says 4,3,2,1, I just haven't found anyone local that can do it.

I can get to first but I didn't trim the stop, didn't even think of it, maybe mine is worn. I do plan to make a lockout for 1st. My trans has a Sonax 2-3 shift valve giving engine braking in 1 2 and 3 with the lever in D3.

 

you guys got me thinkin, about something i did 23yrs ago. on my V12 1978 XJS.

OK my trans is one of the last yrs for mechanical TV cable, 1991 Chevy van 350 engine (important best of that model). before 4L60s.

Summit racing BOP to chevy V8 adaptor plate, along with pilot bush adaptor T400 trans. bolts to 1978 up V12 T400 blocks using grade 8 socket head COUNTER SINK bolts, and Chevy 700R4 bolts to plate.(got apic cant find it)

custom 400 convertor 10" dia. much lighter rotating weight ,NO lockup,dont need it! pix.

rear mount, aluminum driveshaft, GM HD joints, Jeep ring&pinion 3.73.

4th gear, final ratio gives 2.60 , better than 2.88.

i didnt know how to do all this stuff, back then not much info about it, so i just use my own logic!, today i got many new and improved ideas.

pic of TV cable on pedastal.

trans uses B&M shift kit and shift lever, can hold gears up or down, shifts 1st-2nd full throttle around 6K-6100rpm blows the tires off in 2nd 295/18s.

2-3rd ,3-4th little soft but holds it OK!, good front oil cooler,pic

 

Ron, what engine did you have back then? To smoke those tires? My 5.3 can barely break my tires loose with a brake stand!

 

With the 4L60e and 3.54 diff my stock 5.3L will break traction and kick sideways 1-2 shift, not as much as Ron's car though.

 

Oh man! What's up with my car! I do have either 3.54 or 3.73 gears in the diff... they were changed years ago. I know my altitude is higher here, but, this a huge difference between my car and yours. Torque converter, maybe? My tranny was done at a speed shop. Hmmm. I will have to figure things out.

 

In my (limited ownership), a properly sorted XJS V12 should chirp the tires from a standing start, and at full throttle from 1-2 upshift. Easily. Sometimes on 2-3! With the stock transmission. If it doesn't, you've lost power somewhere. Common misconception (from tired examples) that the stock XJS can't lay rubber.

 

As discussed previously I'm going down the efficiency route with my tired old 73 XJ12. I have new heads being made up by Bonner Engineering in the UK and AT Power are doing a throttle body set which will be run by a Motec. As my car currently has 4 Strombergs and makes about 180hp on a good day I was wondering whether anyone out there had an engine on a stand and could take some measurements for me. Otherwise it means pulling all of the plumbing off the block and the carbs and intake manifold. Its pretty awkward under all that plumbing with a vernier and straight edge. I have searched extensively online for tech drawings/blueprints for the V12 but cant seem to find anything with dimensions.

Attached is a drawing from ATPower with the missing dimensions that I need. Many thanks if you can help.

 

I have an HE engine on a stand. Please list exactly which dimensions you need. AFAICS all the dimensions are there on the diagram you posted.

 

Hi Greg

Thanks for replying. Dimensions that I need:
1 Distance between the Bore centre of cylinder head inlet from Bank A to the bore centre off inlet on Bank B.
2. Offset between Bank A and Bank B cylinder head inlet bore
3. Clearance between cylinder head/cam cover and throttle body at 59mm above cylinder head inlet gasket face.
4. Vertical distance between the valley plate and the height of the inlet face on either cylinder head.

Hope that makes sense.

 

Sorry, I cannot measure these things accurately. The heads are on the engine, and I am not sure what 1, 3 and 4 mean. Apologies, maybe another poster with an engine with the heads off can help.
Greg