Building a 904

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Bill Sargent
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Re: Building a 904

#46 Post by Bill Sargent »

Hi Jacques,

Your question about needle bearings in place of flan blocks is beyond my knowledge. The 904 parts book only shows the flan blocks. I do not have a 906 parts book.

This is a question for Tidwell!
Last edited by Bill Sargent on Thu Mar 16, 2023 1:29 am, edited 1 time in total.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

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Bill Sargent
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Location: Seattle, Washington

Re: Building a 904

#47 Post by Bill Sargent »

The 904 used an oil filter cup that was 21.6mm taller than the oil filter cup on the 356 carrera. The same 904 oil filter cup and filter top was also used on the 911R (see 911R photo below).
904 type oil filter in a 911R
904 type oil filter in a 911R
As you might expect 904 oil filter cups are long NLA so I borrowed a 356 carrera oil filter cup and had a friend measure a 904 oil filter cup. And about 2 hours later I had a CAD model.
Oil filter cup CAD screen shot
Oil filter cup CAD screen shot
I plan to make a small run of both the 356 carrera and the 904 type oil filter cups and the special bolt that holds the cup to the filter top.

Many years ago Bob Garretson reproduced the 356 carrera/904/911R oil filter top. I purchased one from him many years ago for my 356 build and recently purchased his last one for my 904 build. Bob said the foundry that cast the filter tops had gone out of business and the pattern had been lost. So reproducing the filter top may be a future project.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

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Bill Sargent
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Location: Seattle, Washington

Re: Building a 904

#48 Post by Bill Sargent »

Work is progressing on the chassis/body in the UK. Barrie is currently fitting the doors and latch/lock mechanisms as well as the front suspension.

The driver’s seat modification was completed a while ago. The seat was lowered about 1 inch and moved back about 3.5 inches. It was then re-glassed into place. There is a 1/8’ thick sheet of aluminum between the seat bottom on the fiberglass belly pan to provide some level of safety from road debris penetrating the floor. Barrie made a new mold for the modified driver’s seat as there are two other tall owners in the queue behind me who will need the same modification. The interior will all get a textured coating and painted gray when the car is painted.
Modified Driver’s seat
Modified Driver’s seat
The rear view before it was glassed in gives a good feel of how much leg room was gained. It will look a little strange from the engine compartment side but there is plenty of room with the 4 cam motor.
Driver’s seat modification from engine compartment
Driver’s seat modification from engine compartment
Fitting the doors is a tedious process that requires the inner door skin to be fitted on hinges. Then the door latch mechanism is fitted. And lastly the outer door skin is glued on a section at a time to match the contours of the body. Porsche sourced the lock/latch mechanism from a Simca 1000.
Left side inner door skin mounted and internal latch mechanism fitted.
Left side inner door skin mounted and internal latch mechanism fitted.
Close up of internal latch mechanism
Close up of internal latch mechanism
External latch mechanism on door
External latch mechanism on door
Latch mechanism on car body.  The gap will be glassed in once the door fitting is complete
Latch mechanism on car body. The gap will be glassed in once the door fitting is complete
The front suspension is also going together. This will be the first car where Barrie has used the original style flan blocs (bushings) with the correct M14 bolts and original style ball joints. Things went together without problem. Note that the lower ball joint is a dummy for trial assembly. The lower ball joint will be pressed into the lower A arm during final assembly when the car is here in the US. The front hub is the same as a 356 C/SC or early 911. The lower front A arms have straight sides, but on the 906 (which used the same suspension) the sides are dished in to allow wider wheels to be run. I will be running 5” on the front and 6” on the rear. I went with the Group 4 aluminum wheel that looks like a steel wheel.
Front suspension - note forged Titanium front upright
Front suspension - note forged Titanium front upright
Front suspension
Front suspension
Front suspension
Front suspension
As you can see there is some additional fiberglass work needed to fill in areas around the suspension pick up points. Leaving it open like this makes trial fitting the suspension easier.

After the door fitting is complete the remaining areas around the front suspension and in the foot well area will be glassed in. The rear clamshell will then be fitted. The struts holding the rear clamshell up must be individually fitted to each car - no two are the same. After that the hood gets fitted and the car is ready for paint prep. The photo below show the strut arrangement that allows the rear clamshell to pivot open.
Rear clamshell struts.  Note that this is an early Thunder Ranch replica but the mechanism is the same.
Rear clamshell struts. Note that this is an early Thunder Ranch replica but the mechanism is the same.
Thanks for following along.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

Justin Rio
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Re: Building a 904

#49 Post by Justin Rio »

Hey Bill, This is really coming together for you. So impressed with all the effort to recreate every component of a 904 as accurately as possible. The control arms and uprights look fantastic. A great deal of time form fitting that cage but it too is turning out nicely. Life is all about timing and its too bad you hadn't started this about 7 years sooner. I had access to this genuine NOS seat insert I sold for my buddy:
1970.JPG

He had bought a 904 back in the late 80's and this insert with a few other parts from it stayed in his collection long after he sold the car.
1971.JPG
1973.JPG
He can't remember which car it was but it was the only one painted red from the factory according to him. You I'm sure would know more about that at this point. Anyway, He bought it as a quick cash sale as the feds were coming up the garden park to seize the previous owners assets. We sold this insert but he still has the original wood wheel and the Sebring exhaust if you're interested. I can also ask if he's got anything else from it. Please put me down for one of those oil filter upgrades you're doing for the factory Mann inline filters you've got going in the 4-cam forum.

Keep up the great work!

Justin

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Bill Sargent
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Re: Building a 904

#50 Post by Bill Sargent »

Hi Justin - do you need the 356 carrera filter cup or the taller 904 filter cup?

Regarding the spare 904 seat, it would only have worked if it was the passenger seat. My mods to the driver’s seat mean we will be making a custom seat insert as the seat bottom is about 4” longer. Plus the driver’s and passenger seats are different widths, with the passenger seat being a couple of inches narrower.

As for 904’s painted red, at least 3 left the factory in red. The one in the current issue of Excellence, the one in the Audrain museum and the one Rod Emory just got back in the road.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

Justin Rio
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Re: Building a 904

#51 Post by Justin Rio »

Oh, thats a good point Bill, you'll probably want to actually be able to fit down in there once its all built. I have the standard bowl but a large one would be a nice option. I'll send you a PM as not to highjack your build post here. Thanks again! Justin

Puygranier Antoine
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Re: Building a 904

#52 Post by Puygranier Antoine »

Thanks for sharing all these interesting build details!

Antoine

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Bill Sargent
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Re: Building a 904

#53 Post by Bill Sargent »

Over the last couple of years I have been pulling together a 904 tool kit. Tim Kuser (owns 904014), Pete Bartelli and Victor Miles have all been very helpful. The tool kit is essentially a Carrera 2 Kit with additional tools.

The tools are contained in a normal 356C/SC bag which struggles to hold all the extra tools.
904 tool kit in bag
904 tool kit in bag
A few tools in the photo below are not correct. The two 3/8” extensions should be 4” (100mm). The ones in the photo are the current 76mm long ones. The Allen wrenches are the correct size but are not original.
904 tool kit tools
904 tool kit tools
The jack is a simple (and scary) affair consisting of a threaded rod, small base, folding finger and a ratchet that fits over flats at the top.
IMG_7539.jpeg
Last edited by Bill Sargent on Mon Oct 30, 2023 6:06 pm, edited 1 time in total.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

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Bill Sargent
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Re: Building a 904

#54 Post by Bill Sargent »

I made a 2 week trip to the UK in July to help get the major movable panels installed. I gained a whole new appreciation for the people building the original cars. Assembling 2 doors and getting them to fit properly on the car took 3 days. Installing the rear clamshell was another 3 days. However, installing the hood and latches was quicker, at 1 day. We also installed a gurney bubble to provide headroom with a helmet on.

These photos were taken at the end of my stay.
IMG_1641.jpeg
IMG_1636.jpeg
Installing the doors involved first gluing the front of the door to the inner skin, then installing the hinges and latch. The outer skin in then offered up followed by the door going on/off many times while things are sanded down if the skin is proud of the body or shims being installed if the skin sits too low.
IMG_1612.jpeg
IMG_1624.jpeg
IMG_1629.jpeg
The gurney bubble involved gluing foam to the roof, shaping the bubble, laying up a mold, creating the bubble part, carefully cutting a hole in the roof, gluing the bubble in place and later glassing the seam to prevent later cracking.
IMG_1477.jpeg
IMG_1490.jpeg
71095474699__36A0D5F5-118D-4F1D-BB7F-0FCD34EFF55C.jpeg
IMG_1521.jpeg
The rear clamshell involved installing the rear wishbone on the chassis, setting the clamshell on the car with someone inside to mark the length of the front struts, cutting the struts to length and tack welding the top pivot tubes on - followed by multiple clamshell on/off operations to get it to lign up correctly at the firewall.
IMG_1538.jpeg
This post reached the 10 photo limit so the next post will contain the rest of the photos.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

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Bill Sargent
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Re: Building a 904

#55 Post by Bill Sargent »

The photos below are a continuation from my last post.
IMG_1557.jpeg
IMG_1582.jpeg
Since we moved the driver’s seat down and back, but the front edge of the seat stayed in the same place, we had to mold a new, longer driver’s foam seat. Barrie has molds for the seats and uses a 2 pack foam. We molded the bottom and back, then cut 110mm, the amount we moved the seat back, off the rear of the seat bottom, placed the bottom back in the mold and added foam to fill the gap. We then used the cut off bit to extend the seat bottom. Worked well!
IMG_1486.jpeg
IMG_1502.jpeg
The last thing we did was to trial fit the wiper motor and linkage to locate where to glass in the fiberglass upper motor mount.
IMG_1571.jpeg
IMG_1567.jpeg
After returning home I did some fabrication to convert a set of original carb air boxes from Solex 44 to Weber 46IDA. The Solex Version has integrated velocity stacks and a plate that mounted to the carb top. The Weber version used modified regular velocity stacks that act as an adapter between the air box and carb top. The build sequence is shown below.
Weber on Right, Solex on left.  Thanks to Peter Hofmann for the photo.
Weber on Right, Solex on left. Thanks to Peter Hofmann for the photo.
Band saw surgery
Band saw surgery
Laser cut parts for the conversion
Laser cut parts for the conversion
Modified velocity stacks.
Modified velocity stacks.
The next post will show the completed air boxes.
Last edited by Bill Sargent on Tue Oct 31, 2023 8:00 pm, edited 1 time in total.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

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Bill Sargent
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Re: Building a 904

#56 Post by Bill Sargent »

This post is a continuation of my last post which ended with photos of the air box conversion.

The converted parts ready to install are shown below.
IMG_1994.jpeg
And here they are installed on the motor.
IMG_1988.jpeg
Thanks for following along.
Last edited by Bill Sargent on Sat Feb 03, 2024 1:56 am, edited 1 time in total.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

Puygranier Antoine
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Re: Building a 904

#57 Post by Puygranier Antoine »

Fantastic project, thanks a lot for sharing !

Antoine

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Greg Scallon
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Re: Building a 904

#58 Post by Greg Scallon »

I agree. This thread is super fun to keep up with. Your craftsmanship and attention to detail are incredible. Looking forward to the next installment.

-Greg
'58 Speedster
'56 VW Deluxe Microbus 

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Martin Benade
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Re: Building a 904

#59 Post by Martin Benade »

I am too, although it’s causing insane jealousy!
Cleveland Ohio
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Bill Sargent
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Re: Building a 904

#60 Post by Bill Sargent »

This project is definitely not about instant gratification! I placed my order in August 2015, construction was started in September 2018 and I am at least a year out from the car shipping to the US after which at least another 6 months if assembly will be required. However the longer it takes the more parts I am able to make.
Regards,

Bill Sargent
#151489 59A Cab - Faux Cam
#159176 64C Cab
#460603 67 912
904 clone in the works

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