Targa Truck '71 GMC build - The first truck in Targa Newfoundland.

[Ethereal]

You could do a fiberglass front clip to save a ton of weight. You can even get a full glass cab if you want to go crazy.

[bovey]

You could do a fiberglass front clip to save a ton of weight. You can even get a full glass cab if you want to go crazy.

Depends on the fibreglass, I've seen 'glass hoods that don't weight much less than a full steel hood. I may lighten the sheet metal, I'd love carbon. Munssey Speed makes some nice stuff. I wish someone would make a the later square hood, the early hood is better for performance, but I have a soft spot for the later brick design.

In other news, my adventure to Holley LS Fest is in print. Performance Improvements produces a magazine, they circulate about 36,000 of these. They are having a huge sale this week-end, stop in for a copy of the magazine and they also have some posters of the truck to give out.

[hotrod56]

Hey Bovey

What does your truck weigh and what is the weight distribution?

[bovey]

What does your truck weigh and what is the weight distribution?

The weight of the truck is fully outlined in posts 276 and 279. But here is a summary:

[Ethereal]

Hey Mark,

I'm looking forward to working with you on your new truck chassis which will be a killer for next year's event ... and helping improve your current truck to perform as best it can in this year's event.

For your current truck, I'm suggesting better shocks & brakes. To keep the cost in line, let's go with Wilwood D52 floating calipers up front in place of your cast iron GM calipers. Then, let's upgrade the pads from BP-10's to Wilwood's BP-20's. That will increase your braking force enough to make a significant improvement. See the chart below.

I feel your current braking torque is less than optimum, especially for the 295 tires you're planning to run. If your master cylinder needs replacing, you could go with option #1 and switch to a 7/8" M/C & leave the pedal ratio alone. You said your brake pedal is 14" long from pivot center to center of foot pad ... and the dimension to the M/C rod clevis is 2.5". That works out to a 5.6-1 pedal ratio.

If the M/C does NOT need replacing, save some money & simply increase the pedal ratio. If you drill a hole for the M/C rod at 2" from the pivot 91/2" above the current hole CL-to-CL) ... that will change the pedal ratio from 5.6-1 to 7-1 as shown in Option #2. That
would be my preference.


Attachment 94363

I'm going through brake calculations right now and referencing yours -- what was the reasoning behind the wilwood calipers up front? The stock calipers have a bigger piston area and thus greater clamping force. Also the Hawk HP+ pads have a coefficient of friction of .55 -- not .41 at 700 degrees... I'm getting a brake force of 2800 lb vs 1600 for the stock front calipers in this configuration with a 7:1 pedal ratio. My calculations can be seen in this spreadsheet.

[bovey]

I'm going through brake calculations right now and referencing yours -- what was the reasoning behind the wilwood calipers up front? The stock calipers have a bigger piston area and thus greater clamping force. Also the Hawk HP+ pads have a coefficient of friction of .55 -- not .41 at 700 degrees... I'm getting a brake force of 2800 lb vs 1600 for the stock front calipers in this configuration with a 7:1 pedal ratio. My calculations can be seen in this spreadsheet.

Those are good questions, questions I don't really have answers for. But I will offer this.

1) I needed new callipers, so upgrading to Wilwood's D52 was easy.

2) The variance in numbers maybe because Ron accounts for actual not theoretical. I believe his numbers are based on tests he has done, or information someone has given him. Can't recall.

3) I was having huge heat problems stock calipers, going to aluminum helped.

4) I seem to recall the larger diameter of the stock caliper was a wash because they flexed under heavy braking. Add heat and thing get inconsistent.

I know Ron is crazy busy at the moment, but I'll shoot him a message and try to get him to chime in.

[Ethereal]

Those are good questions, questions I don't really have answers for. But I will offer this.

1) I needed new callipers, so upgrading to Wilwood's D52 was easy.

2) The variance in numbers maybe because Ron accounts for actual not theoretical. I believe his numbers are based on tests he has done, or information someone has given him. Can't recall.

3) I was having huge heat problems stock calipers, going to aluminum helped.

4) I seem to recall the larger diameter of the stock caliper was a wash because they flexed under heavy braking. Add heat and thing get inconsistent.

I know Ron is crazy busy at the moment, but I'll shoot him a message and try to get him to chime in.

I was looking at Howe calipers because they have slightly larger pistons, but then caught this quote on their product page:
"For higher heat applications we recommend a steel outer half to reduce high temperature flexing that occurs in all aluminum calipers."
I guess this means that the manufacture an outer half made of steel to use with the aluminum portion of the caliper, but I couldn't find it on their website.

http://www.howeracing.com/p-7708-how...le-piston.aspx

For heat dissipation I'm looking at these cool heat sinks:
http://www.fourproducts.com/coolshim-technology.php
But at their price ($120 for two wheels) I might get creative and make my own. They look like a computer heatsink brazed to a metal shim.


How do you know when you have temp issues, does your brake fluid burn up or something?

[kingcrunch]

For a brake setup that does not have vented discs and is hard to upgrade to vented discs, this setup is kind of the last straw before going all out and converting to something expensive.
What vehicle are you working with? Does it have solid or vented discs?

I am asking because a vented disc is a much larger heatsink that the little sinks on the brake pads in that link.
With good brake ventilation that should give a much larger effect on brake cooling.

You will notice that your brake fluid is boiling when you suddenly loose the pedal.
When the fluid boils, air bubbles form and these collapse under the pressure of the pedal, the pedal sinks to the floor.
Fluid that has been cooked will do that again much faster after its initial boiling.

When it gets that hot, the brake pads will glaze aswell, leaving you with a lot less braking power.

[bovey]

I was looking at Howe calipers because they have slightly larger pistons, but then caught this quote on their product page:
"For higher heat applications we recommend a steel outer half to reduce high temperature flexing that occurs in all aluminum calipers."
I guess this means that the manufacture an outer half made of steel to use with the aluminum portion of the caliper, but I couldn't find it on their website.

For heat dissipation I'm looking at these cool heat sinks:

How do you know when you have temp issues, does your brake fluid burn up or something?

How do you plan on using the vehicle? Be mindful of using full on race calipers on the street. They don't always have the same piston seals and will not put up with the dirt and crap associated with a street car life.

In your quest for braking force, don't forget you can have too much. From my understanding, once you get into the 4000lbs of force arena, you need to have your pedal ratio optimized so you can modulate the brakes. To say that another way, you can have so much braking force that every time you hit the petal you risk locking up the wheels, or a lack of control of the force that is unsettles the vehicle. This is extreme, but possible.



Like kingcrunch said, you'll know when you have brake over heating issues. The brakes go soft first, then they go away. And after they cool off, you'll notice you need to pump the brakes going into corners to get them loaded up. Once you settle on a brake package find out what the rotor temp should be and buy a heat gun to keep tabs on things.

The brake cooler attachment is neat. Find out how much they weigh. And not sure what your planning to do with the vehicle, but keep in mind many forms of heavy duty motorsport keep their brakes temps under control with ducting.

[Ethereal]

I'm going to start with autocrossing my C-20 longbed (with vented discs @kingcrunch) and see where I go from there... I'll def. add some ducting and plan on adding a bunch of sensors for rotor, caliper, and wheel temps etc to chart those things during runs. I'm really using this thread as a baseline for my build since it's obvious that a lot of though and effort has already been put into your decisions No need to start from scratch.

I plan to start with stock front calipers and the 97 camaro rears to get a baseline and adjust as necessary. I believe that I'll generate a lot less heat doing autox that you have experienced and I might be ok with these components from a heat standpoint.

I certainly don't understand brake modulation yet but what you're saying about overbraking makes sense. My thought is that pedal ratio is simple to adjust, so I'm trying to design my brakes with as much stopping power as possible and will reduce that via pedal ratio if necessary.

[Josh@Ridetech]

Always nice to see the updates Mark!

[bovey]

Always nice to see the updates Mark!

Thank you. I'm long overdue for a big update. Work has been crazy, I'll be back soon. Big changes are in the works.

[bovey]

It surprising how much time is takes to lock down a plan. Everything is constantly changing.


From the first post of this build, it was my intention to do a Version 1 and Version 2, Ver. 2.0 being a full chassis, etc., etc. Everything was on track, I had worked through the plan with Ron Sutton, I had met a number of builders, I had saved up money. But then the Canadian dollar dropped. At its depth, it cost me $1.47 to buy $1 USD. Needless to say, money conversion broke my budget.

So, instead of Targa Truck Ver 2.0 – I humbly present Targa Truck Ver 1.47 – thank you global economy.

FWIW, the dollar has rebounded to a better place, but this ship has sailed, sadly the chassis has to wait.

Not being able to do the chassis complicated things a lot. My upgrades are intended to make the truck safer, and more reliable. There will be some performance upgrades as a result of these changes, but the benefits of Ver. 1.47 will not be fully realized until Ver. 2.0 happens.

PLEASE KEEP IN MIND, some of this might seem weird. Race spindles, stock a-arms - stuff like that. This is a long term project and I'm working towards a complete vision of the truck, one that I can't complete in one hit.

SUSPENSION/ BRAKES / SAFETY


Ron Sutton and I have had a plan for the truck for a while, but the trigger has been pulled, Ron called a couple of days ago to let me know the following has been shipped:

1) 1 set of RSRT Track Star spindles.
2) Speedway Engineering 9” Grand National Floater w/ Detroit locker and 4:11s
3) Wilwood Aerolite Calipers – 6 piston front, 4 piston rear
4) 13.06” x 12.5 Wilwood Spec 37 rotors x 4
5) 2 of super cool adjustable pan hard bar mounts




Following closely behind are a new set of Forgeline GZ3R wheels. This was a painful purchase. I had bought my first set of wheels with the intension of drilling them out for 5/8” studs, the manufacturer said “No problem”…

Actually, it is a problem. There is not enough meat on wheel design to drill them out. Every garage needs expensive wall are – right???? Sigh.

As usual, trying to save money, cost me money. Oh well, Forgelines are sexy tho. FYI - running a custom spindles allows for a true square set-up with some serious depth on the wheels.




ENGINE


My dad came down for a week-end and we pulled the engine out, it was a great day. The engine is going down to my friends at SDPC (Texas) for a rebuild. Sadly, that has been delayed because I need an approval letter from the EPA to ship an GM LS engine back to it home country of the USA. Seriously.



The engine is going to get an overhaul, maybe a new set of pistons, a new cam profile as the transmission and gearing are changing, more on this below. Nothing is really wrong with it; this is just preventative maintenance. Besides, it’s lived some hard, HARD miles.

I was at PRI this year and it was amazing opportunity to inspect parts and meet the companies/people behind them. The truck is going dry sump so I need to source the front drive and decide on a dry sump supplier.

One of the company’s I meet with was Aviaid, they make a killer product and were beyond helpful with my questions, we have designed a set-up for the truck including a 3-port pump and a 3 gallon tank in the bed. (Not photographed)



My current front drive is a Wegner (WAK-11)street set-up, and they now make a race version, so I just need to buy a few parts to complete the upgrade to accept the additional oil pump.

My dream plan is to go to an electric water pump. Davis Craig has a really neat set-up; it’s just a matter of cost. Not that it’s expensive, but I have a budget.



TRANSMISSION

I was going to stick with my current T56, it’s a wide ratio Magnum. However, a race team reached out to me that has proper endurance race quality Tranzilla t56 they’d like to get rid of, so I’m figuring that out right now. It’s a killer close-ratio version, with a 2:29 first gear, Carbon Synchros… it is sexy stuff. They also have some spare twin disc GS Giken clutches. I need a cold shower.



While this is outside the budget, it’s a great opportunity that I doubt will happen again, so I pounced on it. This was an important purchase to lock down now as it affects the both the engine and 9” gearing. While the cam selection is not decided, we have locked down on 4:11s for the final gear., instead of the 4:30 I was going to use with my wide ratio t56.

WEIGHT

The big experiment is going the be weight. The truck is heavy, corner balance is decent, but I’m going to further perfect the balance and start to move weight back to achieve better a better bias front-to-back.

This amount of work is more than the talent I have, let alone space and time. I’ve found a couple race shops to help redo the fire wall, replacing the massive OEM heater system with a compact light unit, put a pedal box in, and move the engine back 10-12 inches.

Most of the work is mundane, pinion angle… stuff like that. We do need to fabricate a pan hard bar and bracket, but that is nothing crazy. The pan-hard bar height and location will be set once we figure out the spring rates of my current springs, I just need to find someone to measure them.

Here are a couple of idea on the PHB, space is more limited that expected.



WIRING

My truck is long overdue for a rewire job. My original plan was to use a traditional wiring system, fuse panel, relays, etc, etc. But after seeing some demos of PCMs, I’m going that way. Fortunately, one of the people I’ve met along the way is a Motec dealer so we are currently making plans. PCMs and their abilities are mind boggling.

There are loads of details to each thing mentioned above. I’ll dive into that on a part-by-part basis as this juggernaut moves forward. But for now, it’s just a waiting game. Getting stuff out of the USA and into the USA is never easy, let alone the paperwork, but that is another story.

Thanks for following along.

[Dr G]

This is awesome. Can't wait to read more. I love the Forgeline GZ3R wheels. What size did you get?

Gustave

[bovey]

This is awesome. Can't wait to read more. I love the Forgeline GZ3R wheels. What size did you get?

I almost went with the more traditional GW3R, but really liked more, let's call it elegant design of of the GZ3R.

Sadly, they are only 18" x 10", my current chassis set-up will not allow for more width on the front and I want a square set-up with same bs all the way around.

[Dr G]

I almost went with the more traditional GW3R, but really liked more, let's call it elegant design of of the GZ3R.

Sadly, they are only 18" x 10", my current chassis set-up will not allow for more width on the front and I want a square set-up with same bs all the way around.

I'm with you on the square set up. 10" wide is not bad. If you had your druthers would you go 11" or 12" in width?

I like the GW3R style also. To me it looks a lot like the classic BBS wheel that has been on Porsches and BMWs for many years. I think for an American made truck I prefer the GZ3R you ultimately chose.

I note you're doing a full floater. How do folks implement a parking brake with those?

Gustave

[bovey]

I'm with you on the square set up. 10" wide is not bad. If you had your druthers would you go 11" or 12" in width?

I note you're doing a full floater. How do folks implement a parking brake with those?

Going 13" when the time finally comes. Again, square set-up with 335s. I'm stuffing every inch of tire I can under this thing.

As for parking brakes. I have found a product. Now I just need to get it into the country. More soon.

Also, my Ron Sutton Race Technology shipment arrived! SO AWESOME. I'm going to at least look at the crate tomorrow, not sure if I'll have time to open it until Monday/Tuesday.

[Ethereal]

For the panhard, why not a combo of your options 2 and 3? mount the left side as low as possible and the right side as high as possible for the closest to level bar that you can get in order to minimize axle movement.

[Ron Sutton]

I'm with you on the square set up. 10" wide is not bad. If you had your druthers would you go 11" or 12" in width?

I like the GW3R style also. To me it looks a lot like the classic BBS wheel that has been on Porsches and BMWs for many years. I think for an American made truck I prefer the GZ3R you ultimately chose.

I note you're doing a full floater. How do folks implement a parking brake with those?

Gustave

Hey Gustave,

On the floater rear end, if we go with Speedway Engineering's "Mod-Lite" floater with steel hubs, we have 2 brake kits options with a parking brake. One from Wilwood with 12.88" x .81" rotors & Superlite calipers ... available now. The second one, from StopTech that I designed utilizing a 14" x 1.25" Aero-Rotor & ST40 Calipers will be available in July.

But I'd say 2/3 of my clients going with floater rear ends do not run a traditional parking brake. They want to avoid the extra weight out on the end of the axle. So most of them put a line lock solenoid (like drag racers use) in either the front or rear brake line. Then when they want to warm up their car, they fire it up in neutral, put on a little brake pressure, hit the toggle switch (instead of a momentary switch) and lock one set of brakes. Very simple, light & low cost.

[Ron Sutton]

For the panhard, why not a combo of your options 2 and 3? mount the left side as low as possible and the right side as high as possible for the closest to level bar that you can get in order to minimize axle movement.

Just to clarify ... the PHB will be level-ish. The drawing just shows range.