Engine and Gearbox change
Discussion
I'm currently looking into Kitcar models, as a lead up to deciding whether something like an Ultima GTR is for me.
On the flip side, I'm also looking around at costs/potential to strip out an exisiting 'sportscar': lighten, strengthen and upgrade. (for information, I'm thinking of the potential of stripping an old Jag XKR, into something akin of their new GT3 racer)
In general terms, would should be considered when changing out an existing engine/gearbox configuration in any vehicle?
On the flip side, I'm also looking around at costs/potential to strip out an exisiting 'sportscar': lighten, strengthen and upgrade. (for information, I'm thinking of the potential of stripping an old Jag XKR, into something akin of their new GT3 racer)
In general terms, would should be considered when changing out an existing engine/gearbox configuration in any vehicle?
I can have a go at answering this one for you. I built a TVR Sagaris race car using a Tuscan Challenge chassis and running gear and a heavily modified Sagaris body shell. Initially I used the engine and transmission for which the chassis was designed. I then changed the 4.5 litre TVR AJP V8 for a Chevy LS engine.
Factors to consider:
Will the new engine fit? To answer this question you need to couple the intended engine with its intended gearbox and bellhousing and offer it into the hole. In my case, although I was replacing one V8 with another, I ended up have just a millimetre or two in all three planes of movement to play with. Any lower and the oil pump hit a chassis tube, higher and the starter motor fouled. Further back - starter motor again, further forward, fouled the steering column. As you can see, you also want to fit the ancillaries to the engine too, as it will be those that cause you most issues. I also had to strip and rebuild an oil pump to have the outlet point the opoosite way. I was fortunate that this was possible.
Engine and gearbox mounts: it is easier to fabricate and affix revised mounts to a car with a spaceframe steel chassis than a steel monocoque. Mounts will probbaly be bespoke
Similarly, if you find a bit of bulkhead in the way, GRP is easier to cut and reshape than a steel bulkhead.
Gearbox - can you keep the existing one or, like me, will you have to change for something that will cope with increased power and torque?
Does the final drive ratio need to change? In my case I went to a lower revving engine so had to change the diff ratio to retain an acceptable top speed.
Prop shaft - new one needed as different length required
ECU and wiring - will your existing ECU and wiring run the new engine. I rewired the entire car and went for a programmeable/mappeable ECU. You can spend a small fortune just on electrical connectors
Exhaust system - you will most likely need a bespoke set of manifolds as a minimum, and possibly the rest of the system
Cooling system - will the existing rad cope or is an upgrade required? Similarly wil the oiling system cope if it is dry sump.
Air inlet - you will probably have to make something bespoke to get air to the engine - including filtration.
In my case I found the engine itself was the cheap bit - it was all the rest of the bits and pieces which made it expensive.Â
It was a very satisfying project - though I'm not sure I'd do it again!
Factors to consider:
Will the new engine fit? To answer this question you need to couple the intended engine with its intended gearbox and bellhousing and offer it into the hole. In my case, although I was replacing one V8 with another, I ended up have just a millimetre or two in all three planes of movement to play with. Any lower and the oil pump hit a chassis tube, higher and the starter motor fouled. Further back - starter motor again, further forward, fouled the steering column. As you can see, you also want to fit the ancillaries to the engine too, as it will be those that cause you most issues. I also had to strip and rebuild an oil pump to have the outlet point the opoosite way. I was fortunate that this was possible.
Engine and gearbox mounts: it is easier to fabricate and affix revised mounts to a car with a spaceframe steel chassis than a steel monocoque. Mounts will probbaly be bespoke
Similarly, if you find a bit of bulkhead in the way, GRP is easier to cut and reshape than a steel bulkhead.
Gearbox - can you keep the existing one or, like me, will you have to change for something that will cope with increased power and torque?
Does the final drive ratio need to change? In my case I went to a lower revving engine so had to change the diff ratio to retain an acceptable top speed.
Prop shaft - new one needed as different length required
ECU and wiring - will your existing ECU and wiring run the new engine. I rewired the entire car and went for a programmeable/mappeable ECU. You can spend a small fortune just on electrical connectors
Exhaust system - you will most likely need a bespoke set of manifolds as a minimum, and possibly the rest of the system
Cooling system - will the existing rad cope or is an upgrade required? Similarly wil the oiling system cope if it is dry sump.
Air inlet - you will probably have to make something bespoke to get air to the engine - including filtration.
In my case I found the engine itself was the cheap bit - it was all the rest of the bits and pieces which made it expensive.Â
It was a very satisfying project - though I'm not sure I'd do it again!
mk2 24v said:
if the other option is to strip out a jag xkr, just go with that 
what kind of kit car are you going to be looking at, and what do you need it to do?
the xkr strip does appeal - but reckon i would want to change out the engine/box for something more powerful (as I believe the xkr is heavy in standard guise) but being a 'Ford' product, was hoping swopping out for something else would be easier?what kind of kit car are you going to be looking at, and what do you need it to do?
kitcar was going to be something along the lines of the ultima concept
Burba said:
the xkr strip does appeal - but reckon i would want to change out the engine/box for something more powerful (as I believe th]e xkr is heavy in standard guise) but being a 'Ford' product, was hoping swopping out for something else would be easier?
It's all jag underneath. 
Moving up from the XKR the only direct fit will be out of an Aston Martin Vantage V8, or from the current model year Jags, neither of which will be cheap. So as Mr. Chapman said, "add lightness".
Edited by davepoth on Friday 10th September 11:38
davepoth said:
It's all jag underneath.
Moving up from the XKR the only direct fit will be out of an Aston Martin Vantage V8, or from the current model year Jags, neither of which will be cheap. So as Mr. Chapman said, "add lightness".
Of course, the XKR was based on the XJS platform, with subtle changes! Good point. Moving up from the XKR the only direct fit will be out of an Aston Martin Vantage V8, or from the current model year Jags, neither of which will be cheap. So as Mr. Chapman said, "add lightness".
I was hoping as there is enough room in there for a 4.0 V8, getting a SBC in there (or similar) might not be 'too' difficult?
mk2 24v said:
whats wrong with the supercharged jag v8? 
surely be easier and cheaper to tune that to 500(ish) bhp than fit a chevy v8 and gearbox in there
My only reservation would be with the slush-box and how it would react to a 'track' environnment and similar demands of it?surely be easier and cheaper to tune that to 500(ish) bhp than fit a chevy v8 and gearbox in there
Is there a box you can mate to it?
you could always look to the states for auto upgrades if you want to keep the slush box
my mk2 granada has had 2 thrashings round Brands with the standard for autobox without any troubles so far. think you just need to make sure the autobox fluid is kept ffrom getting too hot
otherwise, i have heard rumours the Jag v8 uses a ford bellhousing pattern, so it may just be a case of getting a t5 box from a stang
sure someone will correct me if im wrong tho
my mk2 granada has had 2 thrashings round Brands with the standard for autobox without any troubles so far. think you just need to make sure the autobox fluid is kept ffrom getting too hot
otherwise, i have heard rumours the Jag v8 uses a ford bellhousing pattern, so it may just be a case of getting a t5 box from a stang
sure someone will correct me if im wrong tho
mk2 24v said:
you could always look to the states for auto upgrades if you want to keep the slush box
my mk2 granada has had 2 thrashings round Brands with the standard for autobox without any troubles so far. think you just need to make sure the autobox fluid is kept ffrom getting too hot
otherwise, i have heard rumours the Jag v8 uses a ford bellhousing pattern, so it may just be a case of getting a t5 box from a stang
sure someone will correct me if im wrong tho
very good info mate! my mk2 granada has had 2 thrashings round Brands with the standard for autobox without any troubles so far. think you just need to make sure the autobox fluid is kept ffrom getting too hot
otherwise, i have heard rumours the Jag v8 uses a ford bellhousing pattern, so it may just be a case of getting a t5 box from a stang
sure someone will correct me if im wrong tho
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