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Learning how to build Lotus Seven replicas...together!
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PostPosted: Wed May 14, 2014 7:33 pm 
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Joined: Sat May 10, 2014 1:47 pm
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Location: Birmingham, AL
Here's to the beginning of my GM L67 (3800 Series II) SC build! :cheers:

Step #1 - Planning!

My Dad donated to me their mid 90's Buick Regal GS with the supercharged L67. Car was parked several years ago (running), but with an electrical issue that was never found. Car has around 70,000 miles on it. So I have the engine sourced and excited to have this powerplant with such low mileage. I also have some experience with MegaSquirt and plan to use on this build.

I am curious what else can be used from this Regal besides the engine? Please chime in!


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PostPosted: Fri May 16, 2014 7:40 pm 
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Location: Birmingham, AL
I have spent passed couple of days studying suspension setups and the information is dizzying! Where's the simple answer? LOL!

So, I am going to go with IRS and want matching front/rear hub bolt patterns and run 17" wheels. Brake clearance shouldn't be an issue and I want the larger diameter wheels for looks and better ride on these horrible Birmingham AL roads.. With that said, I think I need to concentrate on selecting the IRS setup first since the front spindles *should* be easy to match to the rear. And I plan to wring out the L67 and get closer to 300 HP out of it, so I will need an LSD. Any other criteria to consider when choosing an IRS?


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PostPosted: Fri May 16, 2014 10:16 pm 
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Always Moore!
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I think your wheel size logic may be a bit backwards. Larger wheels are heavier and usually result in a smaller sidewall. Higher unsprung weight and smaller sidewalls are the enemy of ride comfort.

I would sit down and make a list of what needs to happen to make it a car rather than what needs to happen to make it a supercharged 300 hp Locost with IRS and an LSD.

Unless the "better" stuff falls into your lap for a reasonable price and ends up being straight forward I'd go for the simplest/quickest/easiest route possible. The sooner it becomes a driving car the better the chances of it actually being completed. A pile of parts isn't very motivating but a working vehicle sure is. As long as you pick parts that are compatible with the "better" stuff, you can improve the winter after its finished.

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PostPosted: Sat May 17, 2014 12:27 am 
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a.moore wrote:
I think your wheel size logic may be a bit backwards. Larger wheels are heavier and usually result in a smaller sidewall. Higher unsprung weight and smaller sidewalls are the enemy of ride comfort.

I would sit down and make a list of what needs to happen to make it a car rather than what needs to happen to make it a supercharged 300 hp Locost with IRS and an LSD.

Unless the "better" stuff falls into your lap for a reasonable price and ends up being straight forward I'd go for the simplest/quickest/easiest route possible. The sooner it becomes a driving car the better the chances of it actually being completed. A pile of parts isn't very motivating but a working vehicle sure is. As long as you pick parts that are compatible with the "better" stuff, you can improve the winter after its finished.


Very, very wise words, couldn't have offered better advice myself.

Build a base model, have fun, add hop ups, can't go wrong.

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PostPosted: Sat May 17, 2014 5:43 am 
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Location: Mobile, Alabama
Welcome aboard. There is much to be gained from a single source donor. My car was put together from several different cars at the local pull a part, this approach did cause some headaches.
What kind of car do you want to end up with? Let the answer guide you in the build. Build a car that suits you. We like to cruise country roads in ours, occasionally hit some antique shops and thrift stores. So ours is built oversized with a radio, locking glove box and a trailer hitch
As far as horsepower goes. My car is very heavy compared to most locost a, little over 2100 lbs, I estimate our 5.0 ford to be about 300hp ....the car will get sideways and stay sideways as long as I hold the pedal down. Fun at first then you figure out thT it can be a pita trying to keep the thing out of the ditch. A friend of mine thAt used to own a company that built several hundred of these cars swears that in a typical book chassis car, 150 horsepower will thrill you.
Like I said at first. Build a car that suit you!


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PostPosted: Sat May 17, 2014 6:44 am 
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a.moore wrote:
I think your wheel size logic may be a bit backwards. Larger wheels are heavier and usually result in a smaller sidewall. Higher unsprung weight and smaller sidewalls are the enemy of ride comfort.


Lower sidewalls do make for a harsher ride that's true, but a larger diameter tyre also rolls over bumps much easier and with less deflection than small wheels do.


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PostPosted: Sat May 17, 2014 9:28 am 
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Location: Birmingham, AL
Thanks for the all the replies, keep them coming!

Regarding wheel size, I was thinking along the same lines as CheapRacer above larger diameter tires rolling over bumps better. I also like the look of larger wheels/tires.

As far as what I want the car to do...I am with SMartin99 and want something a little more on the comfort side. I don't plan to be ultra-competitive in autocross, just go as fast as possible and have fun. That being said, I am not going for an ultra lightweight build.

Totally agree on not buying a bunch of parts and focusing on getting a running/driving car together, but I also don't want to have buy the same parts multiple times. And I would rather go ahead and engineer in the IRS, otherwise I may never come back and do it!

So let me step back for a moment and say I don't have the answers, but that is why I am here and that is to get advice from all of you who have been down this road. I am all ears!

P.S. - What parts could be used from the Regal?

Image


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PostPosted: Sat May 17, 2014 10:47 am 
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Location: Carlsbad, California, USA
Welcome!

It's nice to see another Buick 3.8L V6 Locost started. I doing a Locost using it's (reverse engineered) cousin, the Ford 3.8L V6 :lol: . I've had a 3.8L in two cars and it's a very nice engine with plenty of power and torque. Even stock, your supercharged V6 is going to give you a lot, so no harm in postponing engine modifications until a "Phase II" project instead of in the initial build.

I'll be looking forward to your build.

Cheers,

Lonnie

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PostPosted: Sat May 17, 2014 11:58 am 
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Regarding tires, cheapracer and a.moore are both right in regards to specific issues. ..
A larger diameter tire will bridge a void with less suspension movement because it will reach both sides of the void more readily, reducing the droop that happens, a taller sidewall will absorb more shock than a short one.
Sidewall deflection can be "sort of" controlled by the tires construction but it will include some sideways deflection in corners that's harder to adjust for, an argument for short tires. ..
If you're more interested in track days I'd go with a short sidewall but for a primarily street driven car I'd go with a taller sidewall.
With some research you should be able to figure out two sizes (rim size that is) of tire that will give you a similiar enough tire diameter that having two sets of rims/tires will give you good performance in both situations.

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PostPosted: Sat May 17, 2014 12:07 pm 
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Location: Birmingham, AL
oldejack wrote:
With some research you should be able to figure out two sizes (rim size that is) of tire that will give you a similiar enough tire diameter that having two sets of rims/tires will give you good performance in both situations.


Good idea on having two sets of wheels/tires with overall same diameter. Keeps same geometry and suspension/steering setup. Run a smaller diameter wheel and larger sidewall for everyday driving, and have a second set with larger diameter wheels and shorter sidewalls.


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PostPosted: Tue May 20, 2014 8:57 am 
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Location: Southern Ontario
I think I would determine the gearing in the tranny and diff (get your tranny and diff)before considering tires. Your tire diameter is pretty much determined by your gearing. There are formulas that consider gearing, tire diameter and rpms to give speed.
Once you know what diameter tire you need- then you can decide what diameter rim you want to stick in there and how big or small the sidewall will be.
If you end up with long gears, then you don't want to put large diameter tires on. Doing 70 in 1st really isn't fun. Nor is pulling 6000 rpm in high gear at 50mph.

I have some 13" tires with a diameter of 25". I also have some 18" tires with a diameter of 24" so rim size is less important than tire diameter.
Doug


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PostPosted: Tue May 20, 2014 7:52 pm 
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h20loo wrote:
I think I would determine the gearing in the tranny and diff (get your tranny and diff)before considering tires. Your tire diameter is pretty much determined by your gearing. There are formulas that consider gearing, tire diameter and rpms to give speed.
Once you know what diameter tire you need- then you can decide what diameter rim you want to stick in there and how big or small the sidewall will be.
If you end up with long gears, then you don't want to put large diameter tires on. Doing 70 in 1st really isn't fun. Nor is pulling 6000 rpm in high gear at 50mph.

I have some 13" tires with a diameter of 25". I also have some 18" tires with a diameter of 24" so rim size is less important than tire diameter.
Doug


Well, I'm looking at mating a T5 (or variant) using a bell housing from a '92-'94 S10 4 cylinder. For the IRS, I am still looking at options. The best I have seen so far is a C5 setup, but haven't priced it yet. If I go the C5 route, there should be some ratio options or change the ring/pinion. Overall, this combo would allow an average diameter tire to be used and won't narrow my choices.


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PostPosted: Tue May 20, 2014 8:11 pm 
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I's recommend considering the ford 8.8 irs diff, the factory ratio's are; 2.26, 2.47, 2.73, 3.08, 3.27, 3.31, 3.45, 3.55, 3.73, 4.10 & 4.56. ..
Somewhere in there is the number that will work for you and those diff's can handle some major power especially in a lightweight car.

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PostPosted: Tue May 20, 2014 8:34 pm 
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Location: Birmingham, AL
oldejack wrote:
I's recommend considering the ford 8.8 irs diff, the factory ratio's are; 2.26, 2.47, 2.73, 3.08, 3.27, 3.31, 3.45, 3.55, 3.73, 4.10 & 4.56. ..
Somewhere in there is the number that will work for you and those diff's can handle some major power especially in a lightweight car.


What are some Fords the 8.8 IRS was available in? Quick Google search shows they aren't double wishbone and use the half-shaft as a support. Appreciate the info and ratio listing, plenty to choose from!

EDIT: I was searching google pics on my phone and see now the 8.8 IRS came in double wishbone. Also found a nice link another Locost member posted on the 8.8 IRS.

viewtopic.php?f=5&t=14439&start=0


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PostPosted: Wed May 21, 2014 7:06 am 
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We are Slotus!
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I think you'll find the 8.8 from a late model Explorer has the best mounting design. The "ears" on the diff cover make all the difference, plus it's stronger. You can mix-n-match that cover with other diffs, if that works better for you, but that cover is the one you want. Do a search for "Grasshopper Legs" (no kiddin!) and you'll see what I mean.
:cheers:
JDK

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