Nobody wants to make a project car budget because budgets are rude. They take the beautiful idea in your head and ask why you have priced the turbo but not the clutch, tyres, mapping, insurance, fluids or recovery truck.
Make one anyway.
1. The car itself
Start with the car. Purchase price, transport, initial inspection, registration, tax, MOT and insurance. Do not hide these numbers somewhere else because they are not exciting. They are part of the build.
Include the pre-purchase costs too: a history check, fuel to go and look at it, maybe an inspection. Money spent deciding not to buy a car is still money well spent.
2. The maintenance baseline
Next, create a maintenance baseline category. Tyres, brakes, fluids, belts, hoses, battery, bushes, bearings, filters, plugs, leaks, wheel alignment and anything needed to make the car safe and honest. This category should come before performance parts. A project car with fresh maintenance is a platform. A neglected one is a trap.
If you do not know when the timing belt was last changed, it goes on the list. Assume anything undocumented is due.
3. Modifications, by system
Then list required modifications by system. Drivetrain, suspension, brakes, wheels and tyres, cooling, fuel, wiring, interior, bodywork, safety, mapping and fabrication.
Grouping by system does two jobs. It shows where the money is going, and it exposes the gaps. A drivetrain section full of parts and a cooling section that is empty is a warning, not a tidy spreadsheet.
4. Supporting parts
For each part, include the support parts. A gearbox is not just a gearbox. It may need a bellhousing, clutch, flywheel, mount, prop, shifter, hydraulics, speed sensor work, tunnel clearance and fluid. Write all of that down before declaring it a bargain.
Put supporting parts on their own lines, not bundled into the headline part. That is how you see that the £800 gearbox is actually a £2,000 gearbox conversion.
5. Labour
Add labour separately. Even if you plan to do most of the work, some jobs may need specialists. Alignment, mapping, welding, cage work, diff setup, machining, exhaust fabrication, electrical diagnosis and paint can all land outside the home-garage comfort zone. A budget that assumes free labour for everything is usually fiction.
Price your own time too, even if you never pay it. Not in money. In weekends. A job that needs eight weekends and you have four free a month is a two-month job, and the car is off the road for all of it.
6. Consumables
Include consumables. Fasteners, clips, heat sleeve, cable, terminals, hose, clamps, sealant, gaskets, fluids, welding gas, cutting discs, drill bits and paint. These are the small charges that turn into an ugly number because you buy them one emergency trip at a time.
7. Tools
Tools get their own line. Some you will already own. Some you will need once. Buy, borrow or hire, but decide on purpose rather than at 9pm in a panic.
8. Legal and insurance
Registration changes, inspections, engineer reports where your local rules need them, and the insurance cost of the modified car. Get an insurance quote for the finished spec before you build it, not after. Rules vary a lot between countries and insurers, so check the current guidance where you live. This line is a planning prompt, not legal advice.
9. Contingency
Now add contingency. Ten percent is optimistic. Twenty percent is sensible. More if the car is rusty, incomplete, previously modified or bought from someone who says “just needs wiring” without blinking.
Contingency is not a treat fund. It is the money that pays for the snapped bolt, the seized caliper and the part that turned out to be a different revision.
An illustrative example
On paper, it looks something like this. The numbers are made up to show the shape, not a price guide for any particular car.
| Category | Planned |
|---|---|
| Car, transport, checks | £3,000 |
| Maintenance baseline | £900 |
| Modifications | £2,500 |
| Supporting parts | £700 |
| Labour (specialist jobs) | £600 |
| Consumables and tools | £300 |
| Legal and insurance changes | £250 |
| Subtotal | £8,250 |
| Contingency at 20% | £1,650 |
| Total | £9,900 |
Look where the headline “£2,500 of mods” ended up. The car you are building costs nearly four times that. That is normal. It is only a shock if the spreadsheet did not exist.
Track spend as you go
Finally, track spend as you go. Not to punish yourself, but to make better decisions. If the budget shows that the cheap engine swap is becoming expensive, you can stop early instead of finding out after the money is gone. If the gearing plan needs a different diff, you can compare the cost now, not after fitting the wrong box.
Two columns do the job: planned and actual. When actual starts running ahead of planned in one category, stop and look before you buy the next part.
The structure is simple: car, baseline, modifications, support parts, labour, consumables, tools, legal and contingency. The budget is not there to kill the build. It is there to stop the build killing your bank account by pretending every missing part is “only another fifty quid”.