rmarkc
Reader
5/23/12 5:44 p.m.
My SBC swapped 82 Jag XJS is quickly going down hill. It never really lived up to the OMG SBC Jag reputation. Performance was "meh" at best.
The engine swap was a good 12 years old when I got it and it overheated on me in a spectacular fashion on Monday. The overflow tank was spewing like a tea kettle and eventually blew the top. The top flew 8 feet and was followed by an explosion of rusty water.
In the English fashion, it kept a stiff-upper-lip and got me home before the collapse though.
While I don't doubt that I could refill the rad and drive it some more, I think it is time for a new heart. I've been itching to do a GM LS swap and this gives me a chance.
From my research (Internet and Desktop Dyno 2003), I think an LM7 with a couple tweaks will put the Jag at about 100 HP and 150 TQ over stock. It still won't be OMG fast but should make for a nice cruiser. It is still a 4000lb car.
The plan, so far, is:
- stock LM7
- SBC to LS mount adapters
- Edelbrock dual-plane carb intake
- 600cfm Edelbrock carb (the Jag was already carb'd and I already have the 600)
- Edelbrock 2215 cam maybe with LS2 springs
- whatever stock exhaust manifolds will fit
- higher stall torque converter for the existing 700R4 trans with GMPP flex plate adapter
I'll use whichever MSD box is right for the engine I get to control spark.
I've already ordered a GMPP muscle car LS oil pan but I don't know if I'll use it for this. The existing Jag to SBC mounts are pretty tall so another pan may fit and I can save the muscle car pan for my El Camino.
I appeal to your collective wisdom. Do you see any problems or oversights? Will a 2800 or 3000 stall work well with the Jag's 2.88 rear end?
Sounds like fun, assuming your chosen engine doesn't surprise you by being drive-by-wire. (The all-knowing internets are telling me that can happen with 04-up.)
^^ So what? Then you just run a wire between the pedal and the throttle body instead of a cable, DUUUUHHHHHHHH! 
He's running a CARB-u-RETT-or (/hillbillyaccent) fellas.
rmarkc
Reader
5/23/12 7:56 p.m.
Numbers revision...
www.automobile-catalog.com says the 82 XJS had 262hp @5000 / 290 ft-lb @3000, weighs 3979 and does 0-60 in 7.8 with a 2.88 rear gear and a TH400 trans.
DD 2003 says an LM7 w/2215 cam puts out 306hp @5000 / 362ft-lb @3500
...so only 44hp / 72ft-lb over stock
A 2004 2WD Suburban w/ LM7 is rated 295hp @ 5200 / 330ft-lb @4000, weighs 4947lbs and does 0-60 in 8.3 with a 3.43 rear gear and a 4L60E trans.
How conservative is Desktop Dyno? Please tell me that my planned engine will out perform a Suburban in a noticeable fashion.
Cutting 1000 pounds in weight results in a very large increase in acceleration. I promise.
rmarkc
Reader
6/15/12 8:28 p.m.
One step forward and 2 steps back...
Three weeks ago, I took my El Camino on a 30 mile round trip to look at a "Low miles" LM7. Apparently, this particular yard regards 160k as "low miles." Along the way, the elky managed to drop 2 quarts of oil and probably killed thousands of mosquitoes along the route.
So, the plan changed to swapping the El Camino. I found a 60k LM7, started the tear down and clean up. I ordered parts, parts and more parts. I think I have 6 Jegs hats just from this project. I was waiting for my cam to arrive when a demon, let;s call it Craig, tempted me. I picked up an LQ4 short block last week.
Now the plan is:
- LQ4 6.0l stock bottom end
- ProComp ebay heads w/ 2.02" intake valves and 62cc combustion chamber and .577 max lift springs
- Edelbrock Performer dual plane LS1 intake
- MSD 6010 ignition controller
- Edelbrock 2215 cam
- JBA shorty 2010 Camaro headers
- 600cfm Summit carb (gotta bring something from the old motor forward)
The heads on the LQ4 give a 10.5:1 compression ratio. Desktop Dyno says the combo is good for 418HP @ 5500 and 465lb-ft @ 4000.
The El Camino should give me some good practice with the LS engines and I still have most everything I planned for the Jaguar when it's time comes...
rmarkc
Reader
6/15/12 8:40 p.m.
In reply to rmarkc:
Those numbers seem very appealing to me.
If you can, would you please give me a rough estimate on what it costs to get 418HP @ 5500 and 465lb-ft @ 4000?
rmarkc
Reader
6/15/12 10:49 p.m.
418/465 is purely speculative thanks to my educated guesstimate on the heads' flow rates and whatever voodoo Desktop Dyno uses to calculate power and torque.
LQ4 shortblock w/ unknown mileage from CL - $400
Edelbrock 7118X intake manifold from Jegs - $255.75 price matched
MSD 6010 LS1 ignition controller from Jegs - $263.36 price matched
Edelbrock 2215 cam from Jegs- $310 price matched
eBay heads - $499 + $40 s/h (I made an offer and got them for less)
flexplate adapter and bolts from Jegs - about $60
2010 Camaro titanium coated headers were an eBay find for $250
Summit has a 750cfm carb I'd probably get if I didn't use my old 600cfm: $249.95
Dirty Dingo adjustable LSx swap engine mounts - about $120
GM performance LS1 muscle car oil pan kit from eBay - $129
ARP LS1 04+ head bolts from eBay - $110 Rockauto has stock-ish replacements for $56
misc bolts and gaskets - ? I haven't added those up yet
Completeness of your donor engine, your ability to weld/fabricate and your comfort level with reusing existing parts can swing these numbers.
Supposedly, Edelbrock made over 400 HP and torque with just the cam, intake and a 800cfm carb on an LS1 so the new heads aren't really needed. You could take off around $660 for heads, head gaskets and head bolts.
