Archive for May, 2009

Exhaust System

May 30th, 2009 No comments

So, I want the car to sound mean. I don’t mind loud, but I’ve got an upper limit. Laguna Seca limits sound to 92db, and my car must pass that limit. That’s good anyway, because I will drive it on the street. Some guys have 2 systems, one especially for Laguna, but I’m hoping to just use one system that’s good for everywhere. I think I can do this without much real compromise. So far, my plan is:

  • Long tube headers with 1 5/8″ primary, 3″ collectors
  • 2 1/2″ aluminized tubing for the exhaust pipes
  • An H pipe or an X pipe
  • Flowmaster 3 chamber (50 Series?) mufflers

I think this will give me all the power I need, and keep the sound below 92.

Categories: Engine and Drivetrain Tags:

Exhaust Headers

May 30th, 2009 No comments

I’ve been learning a lot about headers and exhaust recently. The way headers work is pretty amazing. I’d heard references to “scavenging” before but never quite got it. For my own notes, I’ll put what I’ve learned here. As always, if I’m off-base, leave me a comment and straighten me out!

I have to start with the exhaust stroke. In my car, as in many higher performance cars, there’s a bit of  “cam overlap”. That means that the intake event and the exhaust event will overlap a bit. The 4 strokes of the internal combustion cycle are Intake, Compression, Power, and Exhaust. Somewhere around 80% through the power stroke, the cam begins to open the exhaust valve. It might seem like you lose power this way, but in practice, most of the energy from the explosion has already been used and the inertia of the crank is enough to carry it through the end of the stroke without really losing much power. The exhaust valve beginning to open a bit early allows it to be fully open for the exhaust stroke, and the gasses can escape very efficiently.

So the piston is traveling up the cylinder, pushing the exhaust gasses out the exhaust valve. Somewhere near the top of the stroke, the cam begins to opent the intake valve. The inertia of the exhaust gas flowing so quickly out the exhaust valve actually helps to draw in the new combustibles through the intake valve. There are 2 things going out the exhaust valve at this point: a pulse of gasses, and a compression wave (sound) from the explosion. The compression wave is traveling at the speed of sound (around 760mph depending on the dynamics of the gas, temp, etc.) – the gas pulse somewhat slower (I don’t know the speed). When the compression wave exits the header’s primary tube and enters the collector, a negative pressure wave heads back up the tube at, again, the speed of sound.

The length of the header primary tubes has to be calculated so that this negative pressure wave, travelling at the speed of sound, reaches the exhaust valve at just the right moment to help pull the exhaust gasses from the next combustion out of the cylinder. This plus the inertia from the gas pulse movement also helps to pull the intake gasses into the cylinder for the combustion after that. This is what they call the  “scavenging effect” of the headers. The more combustible material you can pull into the cylinder for that next power stroke, the more energy it can release, and that energy will push the piston down faster, turn the crank faster, and the smile will get bigger on your face.

The staggering thing is how fast and how often this happens. In the 4 stroke motor, it takes 2 revolutions to complete. So in one minute at 4000RPM, each valve has cycled 2000 times. That’s 33 1/3 cycles per second that this whole process has to execute. This is why the exact timing is so critical.

So the length of these tubes is critical and needs to be designed to match the flow characteristics of the intake/cam/heads. Furthermore, each one has to perform similarly in order to send the gas pulses out the exhaust pipes in the rigt order, and not on top of each other (which would create pressure and in effect, blockage). So the primary tube lengths must be calculated, and must be proper in their relation to each other. In my application, that pretty much means equal length, within, I’ve heard, .5″

Where this may be leading me is toward getting some pipe and laying out and welding my own headers. It depends on the final design of the motor, and what its characteristics will be. If I can buy something that’s close enough to what I need, then I’ll likely do that. If not, I may be building them myself, which will be a ton of work, but fun. The challenge with making my own is in trying to lay out the pipes so that they all are the same length, and end at the same spot, but start in very different spots (each exhaust port). That, and making them fit in the limited space that exists between my engine and my car’s body. Luckily, I won’t have to actually bend tubing. I can buy u-bends and j-bends, and cut them to the lengths I want. I can imagine that this will be a long process, with possibly a lot of waste involved. Fun though! And the pride of ownership would be high.

Pressure Isolators are Cool

May 28th, 2009 No comments
Autometer pressure isolator, P/N 5282

Autometer pressure isolator, P/N 5282

Pressure isolators are the coolest thing since sliced bread. This is one area where I probably went overboard and spent money I didn’t strictly have to spend. However, it gave me some peace of mind. I have in the car mechanical fuel and oil pressure gauges. So, if they fail, fuel and 200 degree oil could come into the cabin under pressure and in theory, ignite.

In reality, the quantities we’re talking about are quite small so I probably shouldn’t have worried about it. Disclaimer out of the way, I’ll explain why I think they are so cool. The brass bit has a diaphragm in it. The hose on one side goes to the pressure source. The hose on the other side is filled with a mix of antifreeze and water, and goes to the gauge side. You mount the isolator in the engine compartment and run the line inside the car to the gauge (in the kit, they even include the right rubber grommet for your firewall). The diaphragm transfers the pressure change from the source fluid to the non-flammable fluid and thereby to the gauge.

Cool right? AN-4 fittings are used, but AN-4 to 1/8 NPT adapters are included so that you can adapt to the standard gauge fittings.

A Word on Cheap Tools

May 28th, 2009 1 comment

OK, so we all know about -insert your cheap tool store here-  and how incredibly cheap the stuff is. I’d love to be able to say “stay away from there and only buy the best high-quality tools”. But, I’m not made of cash, and as much as I love and  respect good tools and have some of them, sometimes it’s not practical to spend top dollar on something. You have to judge how much you’ll use the tools and how many “cycles” you’ll put them through. With some tools, you have a high tolerance for inaccuracy and some you don’t. With some tools, you’re going to use them 10 times and be done, so you don’t care if they last any longer. For instance, I went to Harbor Freight to buy my sheet metal nibbler. I knew that I would use it probably just for this one project and you know, it was great! I got a great hammer and dolly set there too, for very little money.

Here’s what I would not buy at *cheap tool store*: sockets, wrenches, micrometers, tools that you will use a long time or for close-tolerance stuff.  I think your basic trade-offs will be in the areas of accuracy and duty cycles. Cheap tools will often be inaccurate from one to the next, so I wouldn’t get measurement tools that have to be very accurate. That includes sockets. You use sockets all the time and for years, and you can ruin fasteners with ill-fitting ones.

Here’s what I would buy: anything you won’t use a ton that can handle a degree of imprecision. Or – if you will use it a lot, but it’s so cheap you can afford to just buy another one!

Basically, don’t waste your money on stuff you don’t need! You have more than enough stuff to spend money on if spending is your aim 🙂

McMaster-Carr has good quality cheaper stuff in their economy lines, along with the super-high quality expensive stuff.

Categories: Tools and Equipment Tags:

Safety Equipment

May 28th, 2009 No comments

Just in case there is anyone reading this, and looking at the tools post, I’d be remiss if I didn’t say something about safety. If you are planning on undertaking the kind of project I have, you really need to get some basic safety gear. Anyone who’s done a fair amount of work with power tools has probably had some experience that has made it known, on no uncertain terms, that they are to be respected.

Just recently, I was grinding my floor pans. I’d become tired, but persisted, single-minded about getting the dang weld or whatever ground down nice and flat. In a moment of distraction I lost focus and zip! the grinding wheel hit my finger and in a fraction of a second it went through my glove and almost 1/8″ into my finger. I cleaned the hell out of it and it healed fine, as injuries often do, but the point is, this happened in just the briefest moment of distraction. This, I told myself, was the last time I’d buy cheap gloves. Even better would have been to take a rest!

Both presence of mind and safety gear are important, so here is a list of some of the safety gear I have found important:

  • Fire extinguisher – keep one in easy reach whenever you are doing welding, grinding, etc.
  • gloves – good ones. You need to be able to feel, but you also need protection, so you’ll need a selection of appropriate gloves. For welding, it’s important that you have some large welding gloves, probably leather ones. For other tasks, other gloves are appropriate.
  • face shield – I’m talking about one of these clear shields that covers your whole face. So useful for keeping showers of sparks at bay, or protecting you when you don’t feel like wearing goggles
  • eyeware – you need safety glasses and there’s no way around it.
  • Welding helmet – get one that is auto-sensing. Even a cheaper one will do unless you are doing hours upon hours of welding
  • Welding cap – simple little fire-proof cap that covers the top of your head. you’d be surprised how far up the sparks can travel, and how very easily they can burn through your skin.
  • Long leather welding jacket. Like many of these things, it doesn’t have to be expensive. I bought mine from AirGas for $60 I think. It’s long, has snaps around the neck, etc.
  • Welding blanket
  • Good protective shoes appropriate to what you’re doing
  • Ear plugs – I bought a box of a couple hundred pairs for not too much and I use them when I do any impact stuff or other loud stuff. It helps fatigue as well as your hearing.
  • Respirator – get a decent N-95 respirator. Use it while grinding, painting, etc. This is some toxic stuff and N-95 should be good for most vapors and particles (read the label).
Categories: Tools and Equipment Tags:


May 25th, 2009 No comments

This new motor is at a really good machine shop right now. The rotating assembly will be balanced really well. This will make a great difference in efficiency and longevity.

One thing I’m trying to sort out right now is whether to go with internal or external balancing. The stock small block Ford was externally balanced, meaning that the rotating assembly was balanced with 28 Oz weights in the flywheel and harmonic balancer. Basically, the weights on either end counter the crank’s imbalance. At this RPM level (6500 max), external balancing should still work pretty well.

Instead, one can go with an internal balance or “zero balance” setup. In this setup, the flywheel and harmonic damper (now called a “damper” rather than a “balancer”) are balanced only with themselves – no counterweight is installed.The damper is now allowed to do just it’s intended function – help keep the crank from snapping back after being twisted by the rod on its power stroke. The damper is 2 pieces – an inner and and outer ring, usually connected by some kind of flexible elastic material. The damper is “tuned” to a certain set of frequencies specific to the motor. It uses the inertia from the outer ring to damp the tendency for the crank to snap back in reaction to the power stroke.

The disadvantage here is only cost – the balancer, flywheel have to be replaced, and the crank must be balanced accordingly. Sometimes extra cost is incurred in that process.

The advantages to internal balancing are a few. Firstly, it makes the rotation of the rotating assembly more efficient. I don’t understand the physics of it well enough to explain it, so I’ll have to do some research. It partly has to do with having less inertia out at the extremities of the crank. Secondly, if I do need to replace a flywheel or damper in the future, it is as simple as swapping in another zero balanced unit. If I replace either of those on an externally balanced motor, the whole rotating assembly really has to be spun and balanced again.

Really I guess it’s just more front-loaded cost. it saves later on and makes for a more efficient motor.

I was originally going to just get the current balancer refreshed and go with the stock flywheel. I’ve found out though, that I really ought to replace the balancer with a new unit. Also, it seems there are some safety issues with cast iron flywheels on a higher-power motor that’s revving high a lot. Something about explosions… If I’m replacing the flywheel and the balancer anyway, it’s not much of a leap to go internal balancing.

Categories: Engine and Drivetrain Tags:


May 24th, 2009 No comments

So I’ve read some great books along the way that have helped me out with my journey. I mentioned Carroll Smith already. Here are some, titles:

Carroll Smith:

  • Drive to Win
  • Engineer to Win
  • Prepare to Win
  • Tune to Win
  • Nuts, Bolts, Fasteners and Plumbing

These all work together as a great set. They’re old, but so is my car! And the basics are all still good. I learned a lot by reading this set (a couple times).

Paul Van Valkenburgh: Race Car Engineering and Mechanics – great, in-depth discussion of race car engineering. A dose of physics and math but nothing too out of control.

Paul Van Valkenburgh and Mark Donohugh: The Unfair Advantage – this is Mark Donohugh’s story of his racing career, mostly with Penske Racing. He was intensely involved in the development of their cars, and Penske Racing made a lot of breakthroughs during his time there. Reading it makes you feel like you’re there. Great stuff.

I just ordered Race Car Vehicle Dynamics by William F. Milliken. I think this one will be on the more hard-core side. I expect there will be a lot I don’t get, and I’ll have to go back and study my math. I can’t avoid it!

I’ve also learned a lot from the magazine “Race Car Engineering”. This is a great magazine that has some stuff I understand, and some stuff I don’t. In a lot of cases, the stuff they work on is about 35 levels above what I’ll be working on, (and 40 levels more expensive), but it’s still very interesting and very useful. I find that most magazines have very little substance and can be consumed in 20 minutes. Not so with RE. It keeps you thinking. Right now it’s one of my 2 favorite magazines (the other, for different reasons, is MotorSport).

Categories: Uncategorized Tags:

Oil Pan

May 24th, 2009 No comments

Since 315 will be encountering some hard corners, I got a proper oil pan for the job. I opted for a pan from Armando’s Racing Oil Pans. Armando worked for Aviaid for many years, and produces a high-quality product for a decent price.

The traps at the bottom are doors that hinge inward. They let oil in any time, but when the car is in a corner, they keep the oil from being pulled over to the side of the pan (away from the pickup). A stock oil pan won’t do this – it will allow the oil to move away from the pickup in a corner (or heavy accelleration), and the system will go dry for a moment – damage!

Categories: Engine and Drivetrain, Photos Tags:


May 24th, 2009 No comments
The car as it was before the project

The car as it was before the project

This is the car as it was before I put it up on stands and tore it apart.

Categories: Exterior, Photos Tags:

Why Progressive Rate Front Springs?

May 24th, 2009 No comments

I went with the progressive rate fronts, hoping to have a “best of both worlds” scenario since my car will be on the street and the track too. You really get your best handling with springs that are as soft as possible, while still resisting body roll. “Stiffer is always better” is really a myth. The function of the spring is to absorb the energy from a bump, store it, and then use it to push the wheel back down onto the road, maintaining traction. If it’s too stiff, a bump comes and the spring can’t absorb the energy – it might just pass it to the body, and the wheel then just skips along, not following the contour of the road, and therefore losing traction.

The springs should be soft enough to absorb the energy from whatever bump you go over, but stiff enough to stop too much weight transfer in a hard corner. Those things don’t really go together! Modern suspensions have ways to cope with this, but this old Mustang is not terribly sophisticated.

The soft side of the progressive rate springs is 480 lbs – just right for a firm but good ride during street driving (the original squishy stock stuff was closer to 250 I think). Under a heavy load, like  a fast corner, the suspension will compress, and the springs will hit their higher rate of 680lbs, which should give some significant push-back to resist roll and weight transfer, making for a predictable corner.

Combined with good shocks and the roller perches, the suspension should be responsive and firm.

Ideally, progressive rate suspensions are the way to go when they are properly calibrated. Is that the case here? We’ll see!

Categories: Suspension and Brakes Tags: