The Complete Guide to Dual-Carb Engine Access — Big Washburn Windows (BY01)
Big Washburn Windows
The complete install guide for our 11″×7.75″ laser-cut carb access panels — open up your Beetle's rear inner fenders and reach your dual carbs, linkage, and valve covers without ever pulling the engine again.
Reach the whole top end without dropping the motor
The stock Beetle engine bay was drawn up around a single center carb and a modest amount of tin. It was never meant to swallow a pair of 44mm IDF or HPMX carbs, tall stacks, and the linkage that ties them together. Bolt that onto a stroker or big-bore motor and the rear inner fenders end up standing right between your hand and the parts you need to touch.
The Big Washburn Windows fix that for good. You cut a clean opening in each inner fender, weld in a laser-cut mounting ring so it looks factory, and cap it with a screw-on cover you can pop off in seconds — turning carb sync, valve lash, and linkage work from an engine-out ordeal into a five-minute job.
The full install, start to finish
Follow along as we locate the ring, cut the opening, weld it in, fold the lip, and mount the cover. The written steps below mirror every move in the video.
Pick the size that matches your build
| Build | Panel | Opening | Notes |
|---|---|---|---|
| Beetle · dual carb / big engine | Large #BY01 | 11″×7.75″ | This guide — twin carbs, linkage, outer valve covers |
| Beetle · single carb | Standard #BY02 | 7.5″×6.5″ | Smaller opening for a single-carb build |
| Show finish | #BY01-CFKit | 11″×7.75″ | Large windows with carbon fiber covers |
Tools you'll need
This is a metalwork job. You'll be cutting, welding, and folding steel, so the list leans toward fab tools.
How to install the Big Washburn Windows
Read all the way through once before you pick up a tool — this is metal you can't un-cut. These 20 steps mirror the video above, grouped into five phases. Repeat the whole process on the second fender.
Locate & mark the ring
Level the car first — you can check the measurement on the edge of the engine seal tray. A level starting point keeps both windows square and matched.
The mounting ring does not weld to the engine compartment — at this stage it's only used to locate a few holes. Slide its vertical edge as far forward as it'll go and find the ring's “zero-degree” level position.
Add a few clamps so the ring can't move while you work the next steps.
Drill three 1/8″ holes in each section of the ring and set Clecos to hold it. 1/8″ holes · 3 per section
Move the ring to the outside of the fenderwell and set Clecos there too, so it's held on both sides.
Use a spring-loaded auto-center punch to mark every threaded hole location — you'll want to steer clear of drilling into those.
Scribe all the way around the inside of the ring, then use a caliper to scribe a second, even 1/4″ line inside the first. That inner line is your cut guide — the 1/4″ band becomes a lip you'll fold over later. Keep the 1/4″ lip
With the ring removed, drill several 1/4″ holes about 3/8″ outside the ring line (away from the punch marks), positioned to land squarely on the backside of the ring. These become your rosette (plug) welds. 1/4″ holes · 3/8″ outside
Cut the opening
Make the initial straight-line cuts along the inner scribe line with a 3/32″ cut-off wheel, cutting the corners at an angle so the panel drops right out. 3/32″ cut-off wheel
Grind the corners round with a small abrasive disc to match the ring's radius, then clean up with a fine file — but don't over-file: you need that 1/4″ lip intact.
Inside the engine bay, grind the area around each rosette hole down to clean bright metal, and sand the whole ring-contact surface to bare steel so your welds and primer bite. Bare metal for welding
Weld the ring in
Give the body side of the mounting ring — and the matching fenderwell surface — a heavy coat of weld-through primer so the hidden seam won't rust. Weld-through primer
Cleco the ring back into place and clamp it down with long vise grips. The entire ring must sit dead flat against the body with no gaps.
Rosette-weld it home: pressing against the backside of the ring, weld shut each 1/4″ hole and each Cleco hole from the engine-bay side. The welds bond the fenderwell and the ring into one piece. Rosette / plug welds
Grind all of the welds smooth. Weld the Cleco holes shut on the outer side too, and grind that side flush as well.
Fold the lip & finish
That 1/4″ lip from Step 7 now folds over onto the edge of the ring. Make thin relief cuts at each corner so the lip can wrap without buckling.
Start the fold with a body hammer, then flatten it tight — a wide flat punch (a spare King Pin works perfectly) gets into the tight spots. Folded down, the edge wraps cleanly onto the ring. Body hammer + flat punch
Tack-weld the corner relief cuts, grind those tacks smooth, and dress the whole edge with a fine file. Prime the finished ring — from the inside, the folded edge now looks factory-rolled.
Mount the cover
Because the cover is curved, start it on the flattest edge and work toward the short end. Leave the screws a little loose while you walk it into place — it seats far easier that way, then snug everything down. Flattest edge first
Repeat the entire process on the opposite fender. Then pull a cover and enjoy it: carbs, linkage, and outer valve covers, right there in the open — a decklid and a couple of screws away for the life of the car.
The windows, in the metal
Real panels and real installs — the laser-cut edges, the hardware kit, and the finished look in the engine bay.
Specs at a glance
Install & fitment FAQ
Do the windows bolt on, or do they weld in?
How do I make sure I cut the opening in the right place?
What's the 1/4-inch lip for?
Will cutting the inner fenders weaken the car?
Which size do I need — Large or Standard?
Can I get the finished carbon-fiber look?
What pairs with the Big Windows
You've got the bay open and accessible — here's what rounds out the dual-carb setup, and when you'd want each.
Single-carb build? Start smaller
“Not running twin carbs? Don't cut the big hole. The Standard window opens just enough for a single-carb build and keeps more of your fender intact.”
The show finish — carbon fiber covers
“Show car, or you just want the bay to look as good as it works? Get the Large windows with matched carbon fiber covers.”
The whole dual-carb setup
“Haven't bought your carbs yet? Do it as one move — the bundle pairs a 44mm HPMX dual-carb kit with the Big Windows.”
While you're doing bodywork
“Tools are already out and you're welding metal. If the forward tunnel cover is rusty or missing, button it up now.”
Big Washburn Windows — Large
Cut the openings once and reach your dual carbs, linkage, and outer valve covers for the life of the car. Ships as the laser-cut window pair with a stainless button-head hardware kit.