Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 Speed

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Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 Speed

Postby VairKing » Sun Feb 09, 2014 10:08 am

Project started in 2011.

I've been dreaming up this project for the last 6 years after the day a club member asked me what I would do different when building a V8 Corvair. I told him I would use a GM supercharged 3800 (L67) instead of that thirsty V8. I spent a good year or so trying to convince him to build such an animal, but then realized I would have to do it myself. So here we are. I've been collecting pieces and parts and its time to do a little more white board planning and get this thing on track!

Car: 1966 Corsa Convertible, I bought this 2 years ago, it was fully restored, partially reassembled. All suspension, 140, etc was brand new. New paint job is about a 6/10, and the reason the seller did not want to finish putting it together. He was flipping the car and another paint job would have killed the deal. Great candidate for a sawzall!

Engine: 2002 Pontiac Grand Prix L67 3800 Supercharged V6, 240 HP from the factory, will be over 300 when installed. Engine was pulled out of a babied car that had 120,000 miles on it. Lots of life left in her!

Transmission: 2006 Pontiac G6 6 speed manual (F40) This transmission is brand new and will bolt up to the L67. The Stage 3 clutch will be custom made by Spec, and a stock 3.8 powered Camaro flywheel will bolt to the engine.

Brakes/suspension: S10 2wd drop spindles and disk brakes up front. For the rear, I am custom building trailing arm with a custom SLA setup. The trailing arms are longer than stock so the locating arms clear the rear of the engine cradle. Coilover shocks and stock Pontiac G6 front disk brakes w/ factory G6 wheel bearings are being used.

Cooling: Front mounted radiator, as small as possible with openings under the bumper like my V8VAIR.

Frame upgrades: I am thinking a semi tubular frame incorporating a somewhat hidden semi roll cage with a roll bar. Mostly to stiffen the car (convertible) and allow me to race/autocross in Corvair/vintage events.



Goals: 25+ MPG on premium pump gas

300+ HP

100% turn key reliability

Good trunk space (front and rear)

Good heat and A/C

4 bucket seats (Yes this car will have a backseat)

LED lighting where possible (it is 2014 afterall)

Front mounted battery (help w/ weight distribution)

Stock gas tank

Those of you who have seen my V8VAIR build page should know this is within my reach.
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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Sun Feb 09, 2014 3:08 pm

Here is my goal board, as it was written in 2010. Some stuff has been changed in the last 4 years and will continue to be changed as the build continues.

And my inspiration for some of these crazy ideas comes from consuming quality micro-brewed beverages...

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Last edited by VairKing on Tue Feb 11, 2014 9:59 am, edited 1 time in total.
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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby Louisville Lanning » Mon Feb 10, 2014 9:44 am

Ryan

I've got to tell you that your planned build looks really exciting. Personally, I can't wait to see the finished product. A Mid-Engine Conversion with modern components. This could start a new direction for Corvair conversions. We all look forward to seeing your progress on this project.

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65 Corsa 4.5L Cpe
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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Tue Feb 11, 2014 8:35 am

This car is going to be my idea of a pro touring Corvair. All the things I wished I did different after my Kelmark coupe was done will be incorporated into this car. I hope when finished I will be able to enjoy this car for years and years without much trouble along the way.

That is some of the reasoning for choosing the 3.8 L 3800 90 degree supercharged V6 for the engine. With 240 HP from the factory, these engines are known to go over 300,000 miles, and are known to handle upwards of 500 HP with stock internals. I will be changing the pulley, intake and exhaust, along with a custom tune to help with the manual transmission. I am expecting somewhere in the 300 HP range.

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I hate automatic transmissions with a passion. Try buying a new car today with a stick. Good luck! So when building my ultiamte pro touring Corvair it had to be a stick. A ton of research 5 years or so ago led me to the Saab F-40 6 speed transmission found in super rare 2006-07 Pontiac G6 GTP cars, and a few Saab 9-5 and 9-3 overseas. From Wikipedia:

The F40 has a three-axis design, with first, second, fifth, and sixth gears on an output shaft behind and below the input shaft, and third and fourth gears are on an output shaft in front of and above the input shaft. Both output shaft pinions drive a helical gear with a conventional differential. The clutch is mounted on a dual-mass flywheel to dampen vibrations on whichever output shaft is idle depending upon which gear is selected.
Triple-cone synchronizers are used on 1st and 2nd gears. These synchronizers have three friction surfaces, which increase their ability to transfer the flow of torque more smoothly from one gear to another. Synchronizers act as clutches to speed up or slow down the gearsets that are being shifted to, and greater friction area results in easier shifting for the driver. The 3rd, 4th, and reverse synchronizers are double-cone, while the 5th and 6th gear synchronizers are single-cone. All of the friction surfaces on the synchronizer rings are sintered bronze. The ratios in the 6-speed are widely spaced for versatile performance and efficiency.
To adapt the F40 to North American applications and maximize performance, 3rd through 6th gears have been changed to higher-ratio gears starting in 2007 model year. The ratio for 3rd gear is now 1.37:1, and the ratio for 4th gear is no longer an overdrive, with a new ratio of 1.05:1. The 5th gear ratio is 0.85:1 and the 6th gear ratio is 0.71:1.
The addition of a ball-and-spring-type detent on the shift sleeve and detents on the shift rail assists the driver in shifting quicker. The detent raises the force required to move the shift lever which prevents excess movement of the shifter by the driver, and reduces the chance of double bump. Tension between the shift sleeve and the shift rail also prevents the sleeve from vibrating while in gear.
The F40 is cast in aluminum, and weighs 124 pounds (56.2 kg). It has been certified for up to 295 ft-lb ( 400 Nm) of engine torque.

The moral of all this technical babble? It's a 6 speed with a 3.55 final drive and a .71:1 6th gear overdrive. Should make highway MPG fantastic. Other important facts is it is rated for 295 ft lb of engine torque . This is pretty close to what my motor will be putting out, and with the lighweightness of the Corvair being almost 1000 lbs lighter than the Grand Prix counterpart, it should hold up just fine.

A few years ago the Fiero guys stumbled upon this transmission and discovered since both the BOP 60 degree and 90 degree engines share the same bellhousing bolt pattern, it might be possible to adapt this transmission to the 3800. It does bolt together, and Spec clutch makes a clutch kit just for this conversion.

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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Tue Feb 11, 2014 8:57 am

The first thing to do was to strip the freshly restored and nearly finished Corsa back down to the shell of the car. Front suspension, Corvair uni-pack, rear suspension, interior, and convertible top were removed. The brand new front and rear suspension made their way into my '65 Monza sedan, while the brand new 140 sits on a cart serving as a backup spare for my racecar.

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Last edited by VairKing on Tue Feb 11, 2014 1:01 pm, edited 1 time in total.
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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Tue Feb 11, 2014 9:04 am

Next I got the manual 6 speed bolted to the engine (It Fits!) and then started looking at what I am going to do to hold the complete motor/trans in place while engineering crossmembers and motor mounts. Since I will need the motor mount locations clear, and because I can't use a chain from overhead, I made a small cradle that bolts to the center of the engine and trans in 5 places, and this cradle bolts to my HF adjustable transmission holding platform. Hopefully with a ratchet strap around the entire thing it will be stable enough on the jack or engine crane to get the engine into the proper location.

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Ryan Counterman
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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Tue Feb 11, 2014 9:07 am

Some cutting, leaving the single layer firewall behind the back seat. There is 2" of "dead space" between the back of the back seat and this firewall that I can protrude into if I need to.

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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Tue Feb 11, 2014 9:27 am

I ended up hacking quite a bit more than that. Little by little until I had the motor where I want it. The back seat is still 100% in its original position, and its looking really good for keeping it there.

I tried different combinations of engine angle in order to get the axles to be somewhat close enough for the CV joints, while keeping it low enough in the car to clear the convertible top when down, while keeping some respectable ground clearance.

After all this, I have settled on tipping the engine about 10 degrees towards the rear of the car. This lines up my axles very nicely, gives me about 4" of ground clearance at the worse point (My V8 car is much much worse with about 2" at the worse point and I have never scrapped anything)

Before I run the car I will pull off the oil pan and make sure the oil pickup is going to be okay to pickup oil at this angle or I will modify it to make it happen.

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Ryan Counterman
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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Tue Feb 11, 2014 9:53 am

In lieu of using the factory Pontiac engine cradle and struts (the easy way out?) I have decided to custom build my own engine cradle and custom build the rear suspension from scratch. To save weight, I have decided to build the cradle out of aluminum 6063 box tubing, 2x3 .25" wall.

Some of the mounting pieces raw:

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Finished:

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Ryan Counterman
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Re: Build Thread: '66 Convertible Mid Engine S/C 3800 V6 6 S

Postby VairKing » Tue Feb 11, 2014 10:25 am

After the cradle was built it was simply a matter of positioning it and drilling the mounting holes into the frame of the Corvair. I designed it so it can be removed fairly easily for future service.

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