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Brunton M-Spec 1,600 pounds and LS POWER!!

 
Old 03-25-2013, 10:30 PM
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Default Brunton M-Spec 1,700 pounds and LS POWER!!

My first exposure to a Brunton was at a track event, several years ago. The particular car I saw was a Brunton Stalker with an LS3, that set fast time of day. It was light, simplistic, and it was powered my my favorite breed of engine. I was racing an 02 Z-28 at the time (the reason for my screen name). I loved the broad power band of the LS1, but wished I didn't have to carry all the Camaro's weight around corners and into braking zones. The Stalker was a car that was less than 1/2 the weight of my Camaro (3,600 pounds w driver), easier to work on, and undeniably faster. I was smitten.

The Classic Stalker uses as solid rear axle (out of an S-10) and front spindles form an S-10 or G-body. These parts are hung on a fabricated chassis on fabricated control arms. The new M-spec uses a CTS rear diff with Miata uprights. Front spindles on the M-spec are also Miata pieces. They good news is that makes consumables like bearings and rotors cheap. And the geometry of the Miata stuff is quite good. Though the pieces seem a bit small for us muscle car guys, remember they only have to suspend and stop 1/2 the weight of even an extremely light muscle car.

After a couple years of messing with other projects, and even dabbling in off-road Jeeps and UTVs, it was time to get back to the road course. I looked into Cobra replica. To much fit and finish work, 500 more pounds than the Brunton, and not really set up for GM power. After digging deeper into the Stalker idea, and speaking directly with one of the owners, Glen, it was clear that the Stalker better fit my wants. And after speaking with Glen, I knew their new M-spec chassis was the way to go. GM LS powertrain, independent suspension at all corners, and a real roll bar that looked like it belonged there. The canti-lever suspension was a huge deal to me. Plus, it is made right here in the good old USA!

We worked out a deal and I flew down to Florida, rented a Penske truck, and met the Mineharts in person. It was great dealing directly with the owners of the company. Glen and Scott are enthusiasts, they know their stuff, and seem to enjoy sharing their product w like minded car nuts. They really made the whole purchase and pick up easy and personalized.

I got to tour the shop, and more importantly got a ride in an M-spec! A quick ride shotgun w Scott made it clear that I had made the right choice. I've had some fast cars, and have had friends w even faster cars. In fact I had just got to drive a friend's new ZL1 Camaro. This Brunton thing blew everything else out of the water! At the time their test car was running a stock, truck 5.3 liter LS engine, right down to the truck cam (though w LS1 intake and headers). My mind was struggling to comprehend what a 6.2 liter LS with say, 500 hp could do!

I couldn't wait to turn my new bare chassis into a running car to find out!!


We strapped it into the cube van, and my brother and I road tripped back to the frozen tundra of Wisconsin.


Picking it up in December meant family commitments kept me from getting started right away. Having it set idle in the clutter of the garage was difficult.






I spent what felt like forever organizing the garage and hanging the body work up on the walls, safe and out of the way. Eventually, I was able to start fabricating some aluminum panels.

Step one, flip it over, and build the floor:




Working with the aluminum was well within the grasp of your basic, do-it-your-selfer.

The pretty bare aluminum and Clecos really made me feel like some pro race car builder. LOL

As a testament to just how light the Brunton chassis is, after building the floors, I was able to just roll the chassis over, and pick it up (one end at a time) and set it on saw horses!


Building the panels just takes patience and basic tools like a jig saw, drill, and clamps. Brunton has videos available to walk a new builder through the process, and are there to answer emails and even phone calls to help you though.

I've had a couple of friends helping me out from time to time, which really helps keep the motivation up. Just focusing on one task or panel at a time keeps you from getting overwhelmed.




I bounced around a little and mocked up the front suspension:




The canti-levers are so well fabricated, I cannot bring myself to paint them!

But I took the rest apart and another friend (networking is key) powder-coated the control arms and spindles.





Wow, according to the date stamp on my photo, this 6.2L L92 has been waiting patiently on a stand for almost 5 years now!! I had planned on putting it in my Buick, but enough waiting. It is time to use this thing!!!


Due to the cramped nature of the chassis, the VVT had to go. That extra 1/2 inch that the cam phaser took up behind the water pump was just to much. You need to use Corvette water pump and balancer. The good news is that opens up pandora's box because a cam swap is necessary. I have now decided to go with a stock LS9 (the ZR1 Corvette's supercharged engine) cam. It is shockingly low priced ($120) and is similar in specs to an LS7 cam. Two friends of mine are running LS7 cams in their L92 swapped muscle cars and got 420 RWHP (that should be more than 500 HP at the crank). I also picked up some Texas Speed valve springs.

I know there could be more power freed up by an aftermarket cam. But I want a broad torque curve, and honestly, this thing makes way to much power for this light chassis already. Traction will be the limiting factor. I also want to take it easy on the valve train. So I'll leave some power on the table for the sake of reliability.

Yet another friend, came up to offer his experience w internal engine work.

Here you can see the cam phaser with the timing cover removed:


Sadly, we were not able to put a cam back in. I had purchased a stock LS7 cam. But when I opened the box, it was not a GM cam, and it was damaged. So, I'm waiting on the new LS9 cam to arrive.





We were able to swap out the valve springs.


And we swapped out the stock rod bolts for Katech ones. This is a supposed weak point of LS engines, so I figure $200 on extreme quality rod bolts is reasonable insurance.

I also installed the Corvette style oil pan (loosely) and pick up. The engine will get a Corvette harmonic balancer and water pump also to clear the chassis.

Side note, I ordered LS9 push rods and timing chain with the cam. Further research shows them to be the same GM part numbers as the L92 timing chain and push rods. Looks like GM puts the good stuff in the truck engines too!

Last edited by subtlez28; 06-26-2015 at 12:54 PM.
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Old 03-26-2013, 08:06 AM
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This is a awesome build! I bet these these things fly! Ill be watchin this one.
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Old 03-27-2013, 10:02 PM
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Dude! I just found my next corner carver. I already liked the super stalker but with miata suspension and cantilever setup, it's a done deal.

Seriously I need to look up the miata suspension option. Subscribed to this thread to see how the miata suspension setup works out.
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Old 03-27-2013, 11:47 PM
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Originally Posted by 89gmcs15 View Post
This is a awesome build! I bet these these things fly! Ill be watchin this one.
Originally Posted by sciff5 View Post
Dude! I just found my next corner carver. I already liked the super stalker but with miata suspension and cantilever setup, it's a done deal.

Seriously I need to look up the miata suspension option. Subscribed to this thread to see how the miata suspension setup works out.
Thanks for the comments guys!

Just to be clear though, the Miata parts are limited to the uprights (spindles) and brakes. Although I chose the Wilwood brake upgrade so I will have 4 pot front calipers. I'm told the Miata front spindles have zero scrub, making them a better choice than the G-body/S-10 spindles on the Stalkers. Though I am disappointed I didn't get to run a GM bolt pattern as I have a supply of GM wheels.

Anyway, suspension geometry is different, you can see the fabricated chromoly control arms in the pics. I'm about to add some more as I just had the rears powder-coated.

The rear suspension is also cantilever and independent, and uses a Cadillac CTS rear diff. Having last raced a 4th gen F-body, I am excited to have independent rear suspension especially because of the adjustable camber.

My powder coater dropped off some more of his work. Engine mounts, rear control arms, and the fabricated piece to mount the master cylinder (reversed):

I sent him off with the pushrods and tie rods. They are gold anodized, but I have decided to black out most parts, leaving the fasteners as is for contrast.

A friend of mine who has been a huge help dropped over today. We made some progress. It is starting to look like a car!


I also got some GM parts in. My LS9 cam, timing chain and pushrod...
I was surprised to see the timing chain was made in France of all places.

I was more surprised that ordering "PUSH RODS" at the discounted price of $15.29 netted me exactly one push rod! I thought it was too cheap to be a set of 16, but also to much to just be one. Especially considering the description label of "push rodS". Not a big deal though since I found out my L92 push rods are the same part number as the LS9s.

Hope to slap in the LS9 cam soon, and button up the engine!


To that end. Can someone advise what the substance is called that GM puts in the corner of the gaskets? It is an off white and stays tacky, sort of like plumbers' putty. Though I realize thats not what it is.
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Old 03-28-2013, 09:46 AM
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Old 03-28-2013, 10:14 PM
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I got a little more work in today. I finished off the top of the trans tunnel. All the clamps, lumber, and square stock are to create the slight bend in the panel as it transitions to flat:


I cut in the rough shape of the scuttle onto the fire-wall shelf, and fit the fiberglass dash to the scuttle's rear side:



We made up templates out of cardboard yesterday. That really helped making the cuts to the shelf and dash.

I completely wrapped the fiberglass dash in painters tape to avoid scratching it.

I only have a couple more pieces of aluminum to fit (the other side panel, 2 trim pieces that go under the hood, and a simple foot well panel).

Now for the fun part! Test fitting the engine and bolting up the suspension and brakes!
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Old 03-28-2013, 10:59 PM
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That is awesome..
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Old 03-28-2013, 11:28 PM
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sweet build!! I say just have the chassis clear coated and done! that color will look killer
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Old 04-06-2013, 09:27 PM
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I was able to finish off the aluminum panels.

My LS9 cam came in. I have been asked, why use a cam intended for a forced induction engine. The reason is it is similar in specs to an LS7 cam, and I have friends who have had success w LS7 cams in L92s. The LS7 cam is more aggressive in an actual LS7 though due to its 1.8 rockers (as apposed to the 1.7s on most LS engines). Oh, and it is $120 new as apposed to around $400 for the LS7 or most any LS cam... Can anyone explain that?

LS9 cam specs: 211/230 .558/.552 (or.562 according to some internet sources...) 122.5 LSA
LS7 cam specs: 211/230 .560/.557 120 LSA
LS6 cam specs: 204/218 .551/.547 117 LSA


I re-used the L92 timing chain and tensioner as they were unused and the same part # as the LS9 pieces.

I purchased a VVT delete kit from Texas Speed that has an LS2 front cover, cam sprocket, and cam sensor.


I installed the oil pan w/out a gasket to align the front cover, and sprung for the GM sealant fro the corners.
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Old 04-08-2013, 04:02 AM
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I cannot believe the LS9 cam has -49* overlap...........Talk about a smooth idle. I have 0* overlap and it's a pretty small lope.

That car will be stupid scary fast. I've been thinking about the Factory Five 818. I'd love to wedge an LS in there but it would never fit.

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Old 04-08-2013, 10:40 AM
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HOLY CRAP man - that thing is going to be just INSANE!!
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Old 04-14-2013, 04:48 AM
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I think I'm next on this car too instead of a FFR cobra that I've always wanted too. I really like the huge weight savings on this thing and a real rollbar as well.
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Old 04-14-2013, 07:02 AM
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cool build!
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Old 04-14-2013, 11:04 PM
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Originally Posted by V8Rumble View Post
HOLY CRAP man - that thing is going to be just INSANE!!
That is my hope! The L92 will move a bit quicker in this than the Buick I originally planned to put it in. LOL

Originally Posted by merim123 View Post
I think I'm next on this car too instead of a FFR cobra that I've always wanted too. I really like the huge weight savings on this thing and a real rollbar as well.
Do it! Join the sickness! Hopefully I can get mine running soon and further convince you!

Originally Posted by HioSSilver View Post
cool build!
Thanks!

With more gracious help from friends I have pulled the L92 from the stand, and bolted up the bell housing to align the oil pan. As luck would have it my torque wrench crapped out. I'm glad I didn't trust it because it wanted to put down way more than the spec 18 ft/lbs on the oil pan bolts! That would have been a bad day stripping treads out of the aluminum block! But I snugged them down so at least it is aligned, and I picked up 2 new torque wrenches the other day. A 1/2" drive to replace the failed unit and a smaller 3/8" in/lb that will be better suited for most smaller fasteners. Hope the old torque wrench was accurate when we were doing the rod bolts!! I think it was though, just the low torque settings that seem to be an issue...

Then we put it back on the stand to install the corvette balancer. I skipped the trick of heating the balancer to make installation easier. That may have been a mistake as installation was quite difficult. In fact I ruined a specialized tool made to install LS balancers. After reading a bit on the inter-webs on how much torque to apply I found it to be 250 lb/ft! So I needed a cheater bar. Problem was the special tool required a large crescent wrench (as I didn't have a large enough open end wrench). So my usual cheater pipe would not fit. After some garage scrounging, we did find a suitable replacement that did fit over the wider wrench handle:

Who knows what that super specialized, high performance cheater bar is?
Lol

I was not able to research a definitive answer on just when the balancer is on fully. This is how the balancer is in relationship to the flange now. Any input would be helpful here. Needless to say we put a lot of torque to it and even went to the old bolt method after stripping the tool (thankfully not the crank!).


In order to run the LS3 intake in reverse orientation, the oil pressure sensor at the rear of the valley cover needs to be removed. After much speculation on just how to remove the bung and machine the surface flat, I went crude and just saw-zalled and flapper wheeled it down.



Now I have yet another decision to make. Katech makes a slick piece that bolts to the flat surface I have created, putting the stock sender at a 90 degree angle. In fact they already had an adaptor for the other LS engines, but the LS3 intake allows even less room than the others. Luckily for me they just released an LS3 specific part that is even more dramatically machined. The alternative is to drill and tap the cap over the oil filter or buy a pre tapped piece.

I'm currently leaning toward ponying up for the Katech piece to keep the harness relatively stock routed, and using the cap by the filer for an aftermarket sender.
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Old 04-15-2013, 12:34 AM
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Did you pick that cheater pipe up at autozone, cause i got to have one lol. Wish i would have checked out this thread from the start.
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Old 04-15-2013, 12:38 AM
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Originally Posted by darren roar View Post
Did you pick that cheater pipe up at autozone, cause i got to have one lol. Wish i would have checked out this thread from the start.
Looks like you have 2! I can see them in your avatar.

You have to do the custom sticker mod yourself though. They don't come that way.
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Old 04-15-2013, 01:25 AM
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I want to build one of these someday!

I believe you should replace that stock timing chain tensioner as they are prone to failure. Do some research on here about it.

I know on my alum 5.3 when I removed the DOD I swapped that out.

What rear end will you be running? I missed that somehow.
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Old 04-15-2013, 01:31 AM
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Originally Posted by gnx7 View Post
I want to build one of these someday!

I believe you should replace that stock timing chain tensioner as they are prone to failure. Do some research on here about it.

I know on my alum 5.3 when I removed the DOD I swapped that out.

What rear end will you be running? I missed that somehow.
I have read a couple threads debating tensioners vs dampeners. I get that there is a bias. What I didn't get as the facts on why.

What made me decide to stay w the factory L92 pieces is they are new and the same as the LS9 pieces. I assume GM power-train engineers when this route on the LS9 for a reason.

For a rear end I am running a CTS center section. Brand new w 3.23 gears and factory G80 limited slip. I know the big power CTS-V guys replace them w 8.8s, but remember I am pulling around way less than 1/2 the weight.
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Old 04-15-2013, 02:21 AM
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this thing looks AWESOME. If you don't mind me asking, how much are you into this build for?
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Old 04-15-2013, 02:26 AM
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In for more progress. I would love to build a car like this from scratch. Is there a way of making one of these street legal?
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