With advice from my mechanic, I just bought a Jaguar XJS that had been converted with a 86 350 TBI Corvette motor. The car has the 700R transmission. He will be taking the engine/transmission out to put in a Rolls Royce Silver Shadow II.
I really wanted a carburated 350, but he says I will be much happier with the TBI. I would appreciate any comments about the 350 TBI…both positive and negative. He also wants to put in a TH400 tranny (instead of 700). The RR came with a 400 (with different casing). Again, any feedback appreciated.
Not an expert on XJS but I do know about GM engines and transmissions. In general fuel injected engines are more even tempered than carbureted motors. TBI is like a little self contained fuel injection unit to perform the function of a carburetor. It will generally yield better cold starting, mileage and predictable performance. Less tuneable than carburetor, but usually doesn’t need tinkering anyway. 350 TBI is a proven GM setup, I would feel comfortable with it.
700R4 is an overdrive transmission, good for highway cruising and mileage. TH400 is GMs heavy duty automatic from the muscle car era. Robust, gear ratios and final drive is a little low . I would prefer the 700 unless I was racing.
700R is better choice… better first gear ratio to get the car moving and OD.
I just converted mine to a modern TBI fuel injection. No problems starting now with the
turn of the key… and it shuts off all the time without run on. Do not have enough miles
to know how much the mileage has improved.
Mine came with a “tablet” for tuning and it gives instant engine and accessory information
but it is a state of the art fuel injection conversion, not by GM…
Go with TPI if possible rather than single point injection.
R700/4 a great transmission as long as the set up is observed for the particular application. Skip that party, and it will be costly. Every failure of one of these I’ve seen, due to setup. John’s Cars has the best kit. Bow Tie Overdrives is where I bought my rebuilt core.
Richard,
What year is the Rolls? What’s your budget? Did you buy the XJS with the intent of using the drive train in the Rolls? The progression of advancement in fuel injection has been very good since the introduction of the throttle body injection (TBI) in the 1980’s. It was followed by the tuned port injection (TPI) which was a huge advancement and very popular for conversions. After the TPI, GM came out with the LT1 in the mid 1990’s along with an improved version of the 700R4 called the 4L60E transmission that is electronically controlled by the same computer (PCM) as the engine. In 1997, GM came out with an entirely new small block V8 known as the LS1 which has continued to evolve since it’s introduction. The prices for good used GM V8 engine & transmission is inverse to their age and mileage. The newer versions are more reliable and consistent throughout all operating ranges and temperatures, have far superior fuel mileage and are much more powerful. I recently helped a friend re-engine a 72 Chevy C20 pickup. I tried to get him to go with a modern V8 Vortec truck engine with a 4L80E transmission. Due to his fear of modern stuff, he went with an old school small block 350 V8 with a Holley carb and TH350 trans. He now regrets that decision. Good luck with your project and keep us posted.
There was a time, way back when the 700r had an issue or two. A plastic thing would fail. One of my son’s
pals had a pickup with it and as I vaguely recall an infamous computer controlled carb. Each raised a fuss. It’s SBC not all that healthy as well.
So, as my son had his machine shop in full bore, they attacked. Built an engine, a good one. Holly carb’d 350 trans. Troubles gone, not missed. Of gone, missed a bit. SMOG inspect? don’t ask…
Pal and son swapped something with Tom getting the truck. Served well, til a customer came up with too many $'s for it.
My Jaguar sure enjoys it’s LT1/4l60e swap. It just seems to belong in there…