What type of aluminum for a firewall

I'm assuming you want to put it over the existing firewall; it doesn't have to be very thick (I think)- 18 (.0403") or 20 (.0320") gauge maybe? Kevin (Coolryde on here) has done it so let's hope he chimes in. I would think construction panel adhesive would do it; again, Kevin has experience here. If you're creating a firewall- 12 gauge (.808")?

Re a hole in the firewall where the fan is- it's for air intake to the motor; if you omit the hole you have to be sure the motor is getting enough air or it will overheat. Bigger motors with dual carbs (the carbs alone can draw as much as 1000cfm at full throttle vs a Solex 34-3's 128? cfm capabilities) need way more air than an earlier stock motor (the .2" wider doghouse fan requires about 250 more cfm at 3500rpm than the earlier fan)   Gene Berg reported (in his book of technical articles) a motor only lasting 4300 miles in a kit car that had no air intake at all to the engine compartment. And that was the longest any of the person's motors had lived. 

In the thread "More air, please"   https://www.speedsterowners.com...2313073951079/page/1

I explained how to use aquarium air tubing and a glass of water as a manometer to see if your engine compartment is getting enough air. My post is about 1/4 down the page.

I hope this helps. Al

I used 1/8" sheet aluminum which seems plenty stiff enough to mount most things to. After all the fitting, I ran my belt sander over all pieces with 80 grit to give it the brushed look.

Applied a few coats of a solution called Sharkhide (you can find it online easily) which seems to be holding up quite well, any oil splatter I might find seems to wipe off easily. And, btw, I just wiped the Sharkhide on with a non-lint-type paper towel and it dries very quickly. As per cost, I'm lucky, my neighbor gets this stuff from his place of employment and charges me 15-20 cents a pound or something like that...pretty cheap. Someone even remarked awhile back to me that aluminum sheets can be purchased in the "pre-brushed" stage.

No the old piece is missing so it would need to stand on its own.  Thanks for the replies so far.

A picture and manf would help.  In looking at Rich's Beck engine compartment it's completely different on sides than my CMC.  If I recall, the ThunderRanch has much more engine space above the flywheel area - perhaps missing the extra "firewall there".  

If no fiberglass firewall to bolt aluminum to, you could fiberglass 1x1x3" hunks of wood to the fiberglass side pieces and screw the aluminum to it. Simply rough up FG where you intend to attach, use dab of Liquid Nails to affix, then cover with fiberglass cloth and resin to make it permanent.  

I paid $90 for a 4x8' sheet of polished 1/8" diamond plate (from a metal supply place).  HD/Lowes sells smaller pieces (maybe 2x4'?) and simple smooth pieces (not diamond plate or polished). 

i'm in the middle of redoing my firewall

build form fitting cardboard template

trace on 18awg clear anodized

(wait until daughter is not sleeping to cut)

fyi - that much aluminum was $50.  8' wide x 3'.  He gave me the extra 1'x 8' for freeee

Mango, are you going to be able to fit that in in one piece? Good for you if you can.

Do any of you guys seal up the engine area and just cut a hole for the fan instead of using that rubber flap cmc says to use?  There never an issue with crap flying into the fan with the cutout?  

Mango you are putting that over the fiberglass right?

A LOT of people have sucked debris into their fans....  Some ( probably most ) from things left in the engine bay after maintenance....Others sucked in via the hole....   Once done, a piece of "expanded metal" is cut to shape and attached to the fan shroud, or hole opening...

Some of us do the "overkill" and screen both openings....  

I wouldn't seal up the front (front is front of car) of the engine compartment completely even with the air access hole in front of the fan; the more air coming in the better. As for the fan taking something in, if you're running a cylinder head temp gauge (always a good idea, along with an oil temp gauge with a modified VW motor) you'll see the cht start to spike (before the oil temp gauge starts to react) for what seems no apparent reason. Pull over, reach in and pull out the debris (rag, plastic bag, big honkin' leaves...) and away you go. Oh, turn the car off first...

And Leon's advice to screen the opening is right on.

Leon wrote: A LOT of people have sucked debris into their fans.... 

Seriously I confess to this, I somehow left a shop rag in the engine bay, it got sucked into the fan transfering itself onto the head at # 3 cylinder...after the motor overheated, I found the problem.

Me too----two times. (Slow earner!)  The CHT gauge saved me.

it's hard for me to see a rag getting past the fan and you not knowing about it, as it would create a major unbalance & shake the crap out of the thing,&2 probably take a while&possiably shread, be kinda hard for it to just go through1 pair of vanes quickely,and then there is the airfoils inside the shroud for the rag to get cought on(there are about 6-8 in there to get the air going the right way).is it possiable you/somebody just left the rag on the motor before you/somebody instaled the shroud??or rag was already in the shroud??. not saying it cant be done but....also if yours still has the thremostat flaps in the shroud there is another thing to grab the rag.

Alan is 100% correct. The second time this happened to me was on our trip to Morro Bay 3 years ago.  We left Morro Bay and all was normal. 60 miles later going up the Temblor mountains the CHT shot way up and I knew immediately I had left a rag in the engine compartment.  Sure 'nuff there it was in one piece siting in the fan.  I can't imagine how I did that blunder but I sure did.  The key is finding out quickly before frying the engine!

yup.  like origami.  it's only 18awg and there is no engine in the bay.  easy-peazy.

oh ya - i sucked a rag in my fan once.  made a hell of a racket.  you'd have to be def to not hear it