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Intent is to drill 1/2" holes in 3/16" thick stainless steel.  I am no using a step drill, because I figured that the 3/16" thickness precludes using the step drill.  First question is, can I use the step drill bit for 3"16" thick material?  Second question is if I can't use the step bit, and I drill progressively larger holes until I get the 1/2" hole that is my goal, what is the best way to center the drill bit in the existing hole?  I have a centering bit, but it is height challenged and I would have to readjust the table height each time I use the centering bit and by bit would no longer be centered.

Drilling-larger-holes

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First off, drilling through most stainless steel is really, really tough, mostly because the metal, being an alloy, is really hard (think tool steel hardness).  Expect to totally dull any drills you use on it.

Second, I have had no luck with step drills on Stainless - they tend to take too big a bite of the metal and/or overheat and dull prematurely, but I've only tried them one time so your mileage may vary.

I use a set of Cobalt or Titanium drill bits and keep increasing every other size til I get where I want.  They tend to self-center in the previous holes so that hasn't been an issue.  Usually after 3 - 4 holes the bits are really dull and may or may not take a sharpening (I use a Drill Doctor).  Look for extremely heat resistant drill bits for the best results.

I have found that if you can drill from both sides a step drill can work in a little thicker material. Some grades of stainless are really tough; you may not have much success with cobalt or titanium coated bits. The carbide bits I used to lighten transaxle parts (a lot of trans parts are surface hardened to a depth of .030- .040" and even a cobalt bit barely made a mark) may be the answer, though; just be prepared to pay more. Use a fluid to keep temps down and they last longer.

Hope this helps. Al

You know how sometimes you just have to verbalize something to make clear what your next step is?  The step bits that I have are real cheap Harbor Freight bits, so I figured what do I have to lose?  I chucked one up, clamped and drilled.  I did have to drill from both sides, and my drill press made a little fuss, but the holes turned out ok.

engine-to-frame

The piece on the left is composed of two pieces of plate stainless and the 1/2 round is two pieces of stainless, cut from round stock, and then bent to fit one inside the other.

The piece on the right is similar, but the flat stock is just one piece.  They started out being my practice pieces, but they turned out good enough that I can use them, I think.

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Here they are installed for a test fit.  The portion that will be welded to the frame is the upper 1/2 round portion.  I never thought about drilling holes so provide extra welding area.  Is that permissible?  Does it affect the structural integrity of the part?

And how long will I have to work with metal before I stop grabbing pieces that I have just cut, or grinded on.  I need an ice maker in the garage, so it doesn't take so long for me to get ice on the burns.

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Dilema:  What to do with wasted space?  The first photo is looking at the rear window and the shelf where there is normally a "back seat" in a coupe.

Through-rear-window

The 2nd and 3rd photos are looking over the driver seat at the space where there is normally a rear seat, but is now occupied by a fiberglass box.

behind-seat

behind-seat-2

The size of the fiberglass box is about 1' x 1' x 3' and the cutout is the transaxle sticking through.  The 4th and next photo is the cavity resulting from the fiberglass box as seen from the left side looking to the right side.  The rectangular steel tube in the upper right of the photo and the threaded rod are no longer there.  They were the temporary engine support, but they have been replaced by the permanent engine support.

cavity-from-left-side

The 5th and next photo is showing the cavity from the rear of the car looking forward.  The cavity/space is just above the transaxle.  Portions of the frame were removed to accommodate the transaxle and frame support still needs to be welded in.  So, ..., to the point, what to do with this space.  I can't afford to have any wasted space.  My wife and I will probably want to take weekend or longer trips in our coupe when it is finished, and you all know how little trunk space there is.  I have drawn it up, and if I put the radiator and fan and the gas tank and battery all in the trunk, there is no room for any luggage or anything else.  Here are some options:  I cut out the frame material that is partially removed already and relocate it where the temporary engine support was, cut out the existing fiberglass and remold it so that the 1' x 1' x 3' space is located in the car behind the seats and becomes useful luggage space.  Or, locate the radiator and fan in the existing cavity, drawing air from underneath the car and out through the engine hood vent, and relocate the air intake to the wheel well fiberglass.  That photo is next.  Or build and install the gas tank in this space.  What do you think?

cavity-from-rear

engine-side-wheel-well

That triangular sheet of fiberglass above the frame to the right of the engine is inside wall of the wheel well.  And the last photo is of a nice piece helping me to duct the intake air from wherever I want.

intake-curve

Opinions?

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Last edited by Todd M
Todd M posted:

Dilema:  What to do with wasted space?  The first photo is looking at the rear window and the shelf where there is normally a "back seat" in a coupe.

Through-rear-window

The 2nd and 3rd photos are looking over the driver seat at the space where there is normally a rear seat, but is now occupied by a fiberglass box.

behind-seat

behind-seat-2

The size of the fiberglass box is about 1' x 1' x 3' and the cutout is the transaxle sticking through.  The 4th and next photo is the cavity resulting from the fiberglass box as seen from the left side looking to the right side.  The rectangular steel tube in the upper right of the photo and the threaded rod are no longer there.  They were the temporary engine support, but they have been replaced by the permanent engine support.

cavity-from-left-side

The 5th and next photo is showing the cavity from the rear of the car looking forward.  The cavity/space is just above the transaxle.  Portions of the frame were removed to accommodate the transaxle and frame support still needs to be welded in.  So, ..., to the point, what to do with this space.  I can't afford to have any wasted space.  My wife and I will probably want to take weekend or longer trips in our coupe when it is finished, and you all know how little trunk space there is.  I have drawn it up, and if I put the radiator and fan and the gas tank and battery all in the trunk, there is no room for any luggage or anything else.  Here are some options:  I cut out the frame material that is partially removed already and relocate it where the temporary engine support was, cut out the existing fiberglass and remold it so that the 1' x 1' x 3' space is located in the car behind the seats and becomes useful luggage space.  Or, locate the radiator and fan in the existing cavity, drawing air from underneath the car and out through the engine hood vent, and relocate the air intake to the wheel well fiberglass.  That photo is next.  Or build and install the gas tank in this space.  What do you think?

cavity-from-rear

engine-side-wheel-well

That triangular sheet of fiberglass above the frame to the right of the engine is inside wall of the wheel well.  And the last photo is of a nice piece helping me to duct the intake air from wherever I want.

intake-curve

Opinions?

Be very careful about space consideration. Careful space management may give you a pleasant surprise up front. I had an older speedster ( IM on VW chassis ) with a rad with fan, battery and fuel tank up front and also room for some baggage. Baggage here and there in small packages but also room for a jack, small spare tire, booster cables and a small spares / tool kit. It can be done. 

My heater core ( Subaru conversion ) was placed in that dreaded cavity between the rear seat rear bulkhead and the front of the engine " firewall" and the airflow in there is somewhere between berserk and who really knows. It is not rad friendly. A scoop to jamb air up in there will be very low to the ground and you'll likely try to make the upper roof of the scoop flat to the body of the car. Right away that is a no no. Look at any air cooling belly scoop on a Spitfire or Mustang ( or any jet engine intake ) and you'll see they are offset to the body to maximize clean air to the intake scoop. 

Want to go with what people already know  ?....put the rad up front. Mine was near horizontal...just about 3" up in the front with a 24 square inch scoop and it will run in any Key West weather. My install also included mostly straight 1 1/2" aluminum coolant tubing running from front to back in and out and that added a cooling feature too. My rad was Saab 9000 and it worked fine . YMMV. Good luck, Amigo. 

That frame is pretty incredible looking, Todd.  It looks like a little redesign in the cavity area could give you some more space, but it would be tough to do with the body on.  You could cut out a opening panel on the top of that space and have sort of a storage well there.  That might be the easiest thing to do.  It would also give you the option of making it a secure, lockable space.

@David Stroud IM Roadster D - " and the airflow in there is somewhere between berserk and who really knows. It is not rad friendly. "

Now, there is the rub, right?  No one really knows.  The fact that the Porsche engineers use the top of the airfoil to draw air is confusing, because basic physics tells us that area is low pressure, thus the vent will tend to suck air out of the engine compartment.  And the same physics tells us that large flat pan under the car is a high pressure area compared to the area above the vent, and thus air from under the car would tend to move from the bottom through the engine compartment and out the vent.  I wish I could talk with one of the original engineers who could tell me that the location of the vent was a cost compromise and not an optimal solution.  Also, the engine tins in the 356 seal off the engine compartment from the high pressure area underneath the car possibly making the pressure difference between the top of the car and the engine compartment negligible.  My car has no engine tins and the engine "firewall" is located farther forward with no air seal.  Hmm.

A part of me wants to locate the gas tank in that cavity because it would take the gas tank away from the front in case of an accident and put it in a safer location, and a part of me wants to put the radiator there just to see what happens, and a part of wants to make it into interior cabin space.

Luckily, some stair parts showed up yesterday and I have to go back to work on the stairs which will give me some more time to mull over my dilema.

I Had a Porsche 914 some years ago and learned some things about air flow. The 914 being a mid engine car needed clean cool air to the engine cooling fan. They had a strip of plastic running across the bottom of the car right before the firewall and engine compartment. It was about 2.5" wide. I asked and learned that this strip was an air dam to create a low pressure area directly behind it thus allowing the cooling fan to draw clean air over and through the engine heads and cylinders. If you did something like this it may do the same thing and allow the air to flow to and through your radiator if you locate it in that area. You may need to run the electric fan all of the time to keep the temps. within range to  make it work but it should work.  I would try your plan I think it may work using the air dam across the bottom of the car. They used a semi rigid material (plastic landscaping edging) that could bend if something hit it but not break off.  I looked for pictures of this air dam and couldn't easily find any. I think many 914's have had it removed or knocked off before or during restoration but believe they came from the factory with one. I know my race shop mechanic installed one my car and the engine temps dropped and he is the one who educated me on it. Good luck and thanks for taking us on the journey with you.

Last edited by Jimmy V.

I like the idea of putting the fuel tank in the "void" area thus making the frunk ideal as a frunk !  From your photos Todd, I think I would cut out all of the glass barrier on the front of the "void". This would allow you plenty of room to re-work that part of the frame that was removed to allow the transaxle to fit in. It looks like you could bend up a couple of curved tube pieces to jump over that transaxle. They should be low and trussed and gusseted to give you maximum floor space in the rear seat area for the fuel tank. Put the radiator up front. With it tilted it really doesn't take up much room up there and certainly allows cool air to flow thru it nicely. With the fuel tank gone, there's even more room below the floor up there. Probably collision safer too ? Glass is so easy to work with and is secondary to the car frame structure. Once the frame is completed to your satisfaction, and the fuel tank is in,  just replace or modify the  Fglass   you cut out to fit the new configuration. Same in the frunk. Fabricate a new Fglass  floor to take advantage of all the room left by the fuel tank re-location.

By the way, where did you get that green elbow for your air cleaner duct work ? I like that a lot and it has a very tight radius for it's tube diameter !  What is the tube diameter anyway ? Don't know if your interested in one of these air cleaners but it is what will be on my Subaru Engine. I call it an "Air Gobbeler". There K&N filter inside is large enough to handle a V-6

 

 

 

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aircooled posted:

I like the idea of putting the fuel tank in the "void" area thus making the frunk ideal as a frunk !  From your photos Todd, I think I would cut out all of the glass barrier on the front of the "void". This would allow you plenty of room to re-work that part of the frame that was removed to allow the transaxle to fit in. It looks like you could bend up a couple of curved tube pieces to jump over that transaxle. They should be low and trussed and gusseted to give you maximum floor space in the rear seat area for the fuel tank. Put the radiator up front. With it tilted it really doesn't take up much room up there and certainly allows cool air to flow thru it nicely. With the fuel tank gone, there's even more room below the floor up there. Probably collision safer too ? Glass is so easy to work with and is secondary to the car frame structure. Once the frame is completed to your satisfaction, and the fuel tank is in,  just replace or modify the  Fglass   you cut out to fit the new configuration. Same in the frunk. Fabricate a new Fglass  floor to take advantage of all the room left by the fuel tank re-location.

By the way, where did you get that green elbow for your air cleaner duct work ? I like that a lot and it has a very tight radius for it's tube diameter !  What is the tube diameter anyway ? Don't know if your interested in one of these air cleaners but it is what will be on my Subaru Engine. I call it an "Air Gobbeler". There K&N filter inside is large enough to handle a V-6

 

 

 

That is probably the smart way to go, and the most likely way I will go, but also like the idea of putting the radiator in there just to see how it works.  Yeah, that isn't smart, but rarely am I accused of such.  I am thinking that I will have to cut the glass no matter which of the three options I use, because installation of anything in that space will be tough, unless I uninstall the transaxle.  I will at the very least have to cut enough fiberglass to remodel those cut cross frame members.  The intake elbow, (came as bare metal, but stuff rusts), came as part of a package deal when I bought the Subaru to Vanagon engine support.  I don't remember the vendor name, but will get it for you.  Thanks for the offer, but I don't think my plans for the intake will work with the gobbler.

FWIW, I placed my aftermarket heater core in that cavity behind the rear seat bulkhead / ahead of the engine firewall and the two hot air outlets from the core were routed via aircraft scat hose to the door rear bulkheads on either side of the car.

With or without coolant flow to the heater, there was always a slight flow of air into the car through those hoses without any heater fan turned on. With the fan turned on to speeds 1, 2 or 3 there was no shortage of air flow. Evidence of high pressure  in that cavity ? 

Last edited by David Stroud IM Roadster D
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