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Posts Tagged ‘decisions’

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:

Moving the Battery to the Back

June 4th, 2009 No comments

A lot of folks move the battery to the back of the car to help out the weight balance. This was done in the early GT-350s, until some time in ’66, when people started complaining about fumes in the passenger compartment, and then they moved it back. I thought about it, but while reading Race Car Engineering and Mechanics by Paul van Valkenburgh, I found the formula for calculating the difference it would make.

The formula is:

((component move distance in inches)(component weight))/(vehicle weight) = (CG distance moved in inches)

This comes out to (144×20)/2500 or so (could be up to 3000 lbs). So I’d only be moving the center of gravity back about 1″. Not worth it! Not to me anyway. That’s the sort of thing that would be a great part of a bigger plan. If you’re moving a lot of stuff and lightening the car a lot, it would be a part of a larger difference. For me, my car is not the sort where I’m getting every last HP and every last bit of handling. I’m not stripping out the interior or putting on fiberglass panels (except for the hood). I doubt I’d notice it at all, though I don’t doubt it makes a difference for someone.

Balancing

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: