Archive for June, 2009

Why Relocate the Control Arm?

June 27th, 2009 No comments

So, why the so called “Shelby Drop”? First, let me explain just what it is. The “drop” refers to the fact that the inboard mount point of the upper control arm is moved down. Shelby moved it down 1″,  and 1/8″ rearward. It would probably be more accurate to call it the “Arning Drop” because it was originally designed by Klaus Arning, a top suspension designer for Ford. He designed it as part of a full package for the Mustang, which included his 4 link Independent Rear Suspension design. The 4 link IRS didn’t make it into the final car, but Shelby made use of the front upper control arm positioning for the GT350. In my highly approximate picture of the stock setup, you can see why: camber_curveThe circle represents the path of motion of the outboard control arm mount point during suspension movement. You can see here that if the suspension is loaded, as in a hard turn or a bump, the control arm will move outward, pushing the top of the tire out, creating positive camber. This will make it so that the contact patch of hte tire is reduced, with just outer edge of the tire contacting the pavement.

You can imagine what happens when you move the mout point down a bit. The curve becomes more advantageous to the loaded condition. If the car is in a hard turn, it will actually be beneficial to have a bit of negative camber to maximize the contact patch of the tire.

The drop also lowers the CG a little, and reduces the leverage that the suspension has on the body, minimizing body twist. These 3 things together make for more performant handling under the stress of the track.

Internal Balance

June 27th, 2009 No comments

I talked with Bob again the other day about internal balancing, and I found out a couple things.

In an externally balanced engine, like the stock small block Ford, weights are installed on the flywheel and the harmonic balancer that balance the rotating assembly. Pre-1981, this amounted to 28oz or so. After 1981, 50 oz.

This is fine for engines that get mostly street use, with some high revving now and then. When you start revving high a higher percentage of the time, and/or up your revs higher than about 6k, you start to see the disadvantage. The weights on the end can set up an oscillation in the crank at high RPMs. As you can imagine, the bearing clearances aren’t very high – even a slight oscillation can cause damage to the main bearings.

Moving the weight closer to the radial and axial center reduces this tendency toward oscillation (or at least lowers its amplitude) and the bearings last longer in a high-stress motor. This also reduces the stress on the crank itself and it’s less prone to fatigue.

Categories: Engine and Drivetrain Tags:

Engine Project on hold

June 26th, 2009 No comments

Well, as happens sometimes in a project, money runs out! We have a big trip coming up to China, and it’s gotten bigger and bigger. So, I had Bob stop production on the motor for 6 weeks or so. I’ll crank it back up in August. There is quite a bit done already, which is exciting.

Categories: Engine and Drivetrain Tags:


June 20th, 2009 No comments

I have to give a shout out here to my mentors for this project – Scott and Ray. These guys are in Nor Cal Shelby Club with me and they’ve been incredibly patient with my incessant questions, and giving with their time and advice. These guys are both intensely smart, meticulous engineers who are passionate about open tracking their vintage Mustangs and have spent many years building and rebuilding them.

I’m feeling really confident about my project at this point. I think it’s going to be a fast, fun, and safe car. A lot of times when you do a project like this, you’ll buy parts, put things together, realize you got the wrong stuff, and lose money as you buy all new stuff and try to move the old stuff on the used market. Sure that’s happened a bit to me, but remarkably little, and that’s largely because I have some incredible guides in the process. I’m getting the benefit from their long trial and error processes, and their experience and ability as engineers. I wouldn’t be able to take on these kinds of projects without them.

Thanks guys!

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Engine parts decided

June 20th, 2009 No comments

So, the engine config is all settled and the machinist has started to work.

  • Displacement: 331CI
  • Bore: 4.030
  • Stroke: 3.25
  • HP and Torque: ~410-420
  • Heads: AFR 165 #1402, 58CC, P/N 00031561
  • Valve springs: AFR 8019
  • Cam: Isky roller – custom grind
  • Lifters: Isky Hydraulic roller – made to fit standard base circle cam in old style block, P/N3860-HYRT
  • Rockers: Comp Cams Ultra Pro-Magnum – chrome-moly roller rockers, P/N 1632-16
  • Intake: Edelbrock RPM Performer Air Gap
  • Timing set: Racemaster from Australia Muscle Parts – this is a set imported by Keith Craft Racing, that will basically eliminate any chance of cam walk as I understand it – P/N AMP-351W
  • Crank: Scat 9000
  • Bearings: King
  • Rods: Scat I Beam “Scat54”
  • Pistons: SRP forged P/N 206066
  • Rod cap nuts: ARP 8740 “Scat 17”
  • Rings: Total Seal P/N CR 3690 35
  • Pushrods: Manley 25630-16 with 4130 swedged end
  • Screw in freeze plugs
  • Oil pump: Melling “M” Select – P/N 10687
  • Oil Pump drive shaft: Milodon
  • Convert main cap bolts to Milodon studs and include windage tray mount
  • Oil Pan: Armando’s Road Race oil pan #402 – 9.5 qts
  • Internal balance of rotating assembly
  • Harmonic Damper: Pioneer SFI 18.1 rated, P/N 872034 – Scratch that – The Pioneer unit had the timing marks on the wrong side for the timing cover I have. I replaced it with a very nice BHJ unit.
  • Flywheel: Ram aluminum with 10″ and 10.5″ clutch bolt patterns, P/N 2529
  • Clutch: Centerforce I – Pressure Plate P/N CF360030, Disc 280490, Throwout bearing N1439
  • Head Bolts: ARP 154-3601
  • Gasket – Intake: Fel Pro 1262S-3
  • Gasket – Head: Fel Pro 1011-1
  • Gasket – Timing Cover set (with main seal): TCS 45008
  • Gasket – Oil Pan:  OS 13262 T
  • Gasket – Valve Cover: 1684
  • Carb: not positive yet but Holley ~650CFM Vac or Mechanical secondary – UPDATE – 600+ CFM Holley 4150 with Mechanical secondaries, modified to Stage III spec by The Carb Shop
  • Headers: Probably 1 5/8 long tube (still undecided on length and maker) – UPDATE – Hooker Super Comp P/N 6111-HKR – I cut off the collectors and added my own pipe there to the right length and ID
  • de-burr and smooth all oil and water passageways
  • Machine cam bearings for proper oil flow (this involves changing the place where the oil contacts the cam bearing, making it much more efficient lubrication than the stock setup)
  • Port and clearance oil pump
  • Re-machine for single piece rear main seal (the old 2 piece ones are so problematic)
  • Port-match heads and intake

Ray, Dad and I will be doing all the final assembly, port and clearance of the oil pump, dialing the cam, etc. Bob Gromm at Gromm Racing Heads is doing all the machine work and re-working the heads to be sure they are as good as they can get. He’s also port-matching the heads and intake for good flow.

This is a graph of the simulation of the power it should make:315 engine graph

Is this the recipe for your car? No it’s not. It’s based on a ton of decisions and trade-offs. Everything is inter-related and everything has it’s ups and downs. This is my attempt at building a reliable, powerful motor out of my old ’68 302 block. I’m hoping for a balance of streetability and trackability.

As I’ve gone through this process I’ve really gotten some respect for the fact that there’s no simple “bolt on solution”. Everything works together and choices in one area mean choices in another.

Categories: Engine and Drivetrain Tags: , ,


June 16th, 2009 No comments

I just talked with one of the local “friends of the club” here in Hayward. He said that what we could do is have him do the spray work and body work, and I could take the car home inbetween stages and do the sanding and prep stuff myself. Not a bad idea. I’m sure that I could do the sanding/rubout very well. The spray is more of an unknown, especially with metallic. So this might be a good trade-off and a big money-saver. Sanding/rubout represent a good portion of the hours in the paint process.

Categories: Exterior Tags:

Body and Paint

June 4th, 2009 No comments

Since this project has gone way over budget, I’m considering the idea of doing some of my own paint work. I think I could save a lot of money by first stripping the paint off the car, and taking it apart for the body guys, and then doing some or all of the final spray and rub-out. I have skills from my job as a refinisher that I think would translate well.

I recently was hanging out with an acquaintance of mine who works with all the body shops in the area. He said that a lot of them have very slow business just now, and he thinks he could find one that would welcome a guy like me, who would like to rent the booth and a bit of instruction.

Here again, I would be paying what I would for a cheaper job, and have the option of getting higher quality if I busted my butt to do it. Sanding and rub-out are extremely labor-intensive, which is why a good paint job is so expensive.

I don’t feel good about doing the body work, since I don’t have any experience there. A good foundation is so important. I think I’d rather have someone do the prep and then do the finishing stuff myself.

Still not sure on this one, but seriously considering it.

Categories: Exterior Tags:

Exhaust Work

June 4th, 2009 No comments

I figure if I’m thinking of building my own headers, I may as well think of building my own exhaust system. It would be much less complex than the headers would be, and I can probalby save some money on it.

Like a lot of things, I might pay the same amount as I would for a “cheap job” but end up with better quality. For instance, I may be able to do it myself with mandrel-bent tubing for around what I would pay for regular tubing bent in a pipe bender. It would also allow me to make it specifically to fit the car. I had a problem with my last exhaust system – in a bump, the rear diff/axle housing would slam into the exhaust pipes. The brake hard lines are mounted in just such a way that one of them got smashed in that action, and shut off braking to one rear wheel, forever causing the car to pitch to one side under hard braking. That took a while to figure out…

Apparently, welding aluminized pipe is not that different from welding mild steel. The coating is quite thin.

I plan to move the ends of the pipes up to go out the rear valence, as in a GT. I like that look, and I’ve already bought the rear valence for it.

It may be a bit presumptuous to think that I can do such a great custom job with it, but it’s probably worth a shot.

New Trunk Lid

June 4th, 2009 No comments

Again on CL, I found a guy selling an original ’66 trunk lid. Still has its spare tire instructions on the bottom. At $45, it’s much cheaper than getting the body work done on mine, which has a kink in it from an accident I had many years ago. Score.

Categories: Exterior Tags:

New Hood

June 4th, 2009 No comments

Browsing Craig’s List, I found someone selling a fiberglass, GT-350 style (with a scoop) hood. It’s the kind with a full steel frame, so it should be rigid enough, while being lighter and of course, adding the cool-looking scoop. I imagine the scoop will get me a bit of cool air for the intake as well.

I’ll need to get some lighter-rate hood springs for it, so that it won’t bow.

I needed a new hood anyway. My current one is a Taiwanese knockoff, and as such, is thinner metal and has bowed. Also, I put 4 little dents in the bottom (that show on the top) several years ago, when Matt and I tried pulling the engine out without removing the hood first – doh!

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