What to Ask a Machine Shop Before an Engine Rebuild
Updated: Oct 19
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You've pulled the engine, or at least the heads, and now you have to hand some of the most important parts of your project to a stranger. You're not even sure what to ask for. "Uh, can you… machine it?"
Everyone feels that way the first time. A good machine shop is one of the best partners a DIYer can have, and walking in prepared makes the whole thing smoother, cheaper and less stressful. I'm budgeting machine work for the V6 swap in my 1989 Toyota Pickup, so this is the list I'm working from.
What does a machine shop do (and not do)?
An engine machine shop cleans, inspects, measures and machines engine parts so they're back within spec. Think cylinder heads, blocks, crankshafts and connecting rods.
What a shop usually doesn't do, unless you ask and pay for it:
Diagnose why the engine failed. They'll tell you what they find, but they weren't there when it happened.
Assemble the whole engine. Many shops offer assembly, but it's a separate service.
Supply every part. Some shops source gaskets, bearings and valve parts. Others want you to bring your own. Ask.
Knowing the line between "machine work" and "everything else" keeps your quote from surprising you.
How do you choose a shop? Questions to ask on the phone
Call two or three shops before you load anything into the truck. These questions tell you a lot fast.
Do you work on my engine? Some shops specialize in certain engines or in performance or diesel work.
What's your turnaround right now? Busy shops can be backed up for weeks. Plan your project around it.
Do you quote before starting work? You want a written quote, and a call before anything extra gets done.
Do you provide a spec sheet? A good shop can give you the measurements they took and what they machined to.
Do you supply parts, or do I? And if they supply them, can you see what's being used?
How do you handle surprises? If they find a crack, what happens next, and who decides?
Is there a warranty on the machine work? Get the answer in writing.
Also ask other builders. Local car clubs and owner forums for your engine are the best way to find a shop with a good reputation.
How should you prep parts before drop-off?
A little prep saves the shop time, which saves you money, and it protects you if there's ever a question about what you dropped off.
Clean off the worst of it
You don't need to make parts spotless. The shop will clean them properly. But knocking off the heavy grease and dirt makes inspection easier and shows you care.
Label and bag everything
Put small parts in bags and label them by part, location and quantity. I use write-on resealable parts bags in a few sizes so the label goes right on the bag. Tip: save the resealable bags that come with online orders and reuse them. "Left head, intake side, 4 bolts" is far more useful than "bolts." Keep valve train parts in order if the shop asks you to.
Photograph everything
Shoot each part from a few angles before it leaves your workspace. Include close-ups of any damage you already know about. Those photos are your record of what went in.
Bring the specs and history
The engine code and any casting numbers
Your factory service manual specs, or a copy of the relevant pages
What happened to the engine (overheated, spun a bearing, just high mileage)
What you want from it: stock rebuild or something more
Don't forget a thing: Our Machine Shop Drop-Off Checklist ($3) is a printable checklist for exactly this: prep, labeling, the questions to ask, and what to check at pickup. Print it and take it with you.
What do common machine shop services mean?
Here's a beginner's translation of the words you'll see on a quote. Exactly what's included varies by shop, so ask.
Cleaning
Removing oil, carbon and scale so the parts can be inspected and measured accurately. Shops use different methods depending on the material.
Crack testing
Checking for cracks you can't see with the naked eye. The method depends on the material, and it's one of the most important services, because there's no point machining a cracked part.
Pressure testing
For cylinder heads, the coolant passages are sealed and pressurized to find leaks or cracks. It's common after an overheat.
Resurfacing
Machining a flat, smooth surface on a head or block deck so the head gasket seals. Warped heads from overheating usually need it.
Valve job
Work on the valves, valve seats and guides so the valves seal properly. A "valve job" can mean different things at different shops, so ask exactly which steps are included.
Block work
Depending on what they find, the block may need the cylinders bored and honed, along with other machining. This is where measurements decide everything, and where quotes can change once the parts are inspected.
How do you read the quote?
A clear quote should answer three things.
What's included vs extra?
Look for each service listed separately with a price. Watch for words like "if needed" or "as required," and ask what would trigger those charges.
Who's supplying the parts?
If the shop supplies gaskets, bearings, valves or seals, they should be on the quote. If you're supplying them, confirm what they need from you and when.
What happens if they find a problem?
Ask them to call before doing anything that isn't on the quote. Write "call before additional work" on the work order yourself if you have to.
For reference, I've budgeted $3,000 for machine work on my Pickup's V6 swap. That's my budget, not a quote, and your number will depend on the engine, its condition and your local shop. See how it fits into the whole build in what a 1989 Toyota Pickup project really costs.
What should you check on pickup day?
Compare the parts to your photos. Everything you dropped off should come back.
Ask for the spec sheet and the final measurements.
Get the invoice itemized to match the quote.
Ask how parts should be stored until assembly. Bare machined surfaces can rust quickly.
Keep every piece of paper. The work order, the invoice and the spec sheet belong in your build records.
When it's time to reassemble, you'll be working to your factory service manual's torque specs, often in a specific sequence. If you've never used one, our guide on how to use a torque wrench is the place to start. And a clean, organized bench makes assembly much easier. Here's how to set up a DIY car workspace in any space.
FAQ
What does a valve job include?
It varies by shop. It generally covers the valves, seats and guides so the valves seal, but ask exactly which steps are included before you approve it.
Should my cylinder head be crack-tested and pressure-tested?
It's worth asking about, especially if the engine overheated. There's no point paying to machine a part that turns out to be cracked.
When does a head need resurfacing?
When it isn't flat enough to seal the gasket, which is common after overheating. The shop measures it and compares it to the spec in the factory service manual.
What should be in the quote?
Each service with a price, who supplies the parts, the turnaround time, and what happens if they find something extra.
The Bottom Line
You don't have to be an engine builder to work well with a machine shop. Call ahead with good questions, prep and label your parts, understand the quote, and keep every piece of paperwork.
Walk in prepared: Get the Machine Shop Drop-Off Checklist for $3 and bring it with you. To keep the work order, spec sheet and receipts together, the Project Build Binder gives every page a home. Building out your bench? Start with what tools you need to work on your own car, and subscribe to ProjectDaily on YouTube to follow my V6 swap.
Build your dream daily.
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