Steering issue

[blown motor]

I have a 340 Challenger with 15" wheels and factory power steering. When I drive down the highway I barely move the steering wheel. The car is really steady. I also have a 68 Charger with a 440, 17"wheels, power steering, Borgeson box and Firm Feel steering and suspension. Both cars have Bilstein shocks. When driving the Charger it seems I'm always fighting the steering, constantly correcting or adjusting. It just doesn't drive straight and easy like the Challenger.
What's up? Is it just that the big block is more of a lumber wagon? Is it the Borgeson box? Is it out of alignment?

[340Challman]

I have a 340 Challenger with 15" wheels and factory power steering. When I drive down the highway I barely move the steering wheel. The car is really steady. I also have a 68 Charger with a 440, 17"wheels, power steering, Borgeson box and Firm Feel steering and suspension. Both cars have Bilstein shocks. When driving the Charger it seems I'm always fighting the steering, constantly correcting or adjusting. It just doesn't drive straight and easy like the Challenger.
What's up? Is it just that the big block is more of a lumber wagon? Is it the Borgeson box? Is it out of alignment?

I was going to suggest the alignment. If you get too close to 0 toe-in it will change directions with very slight steering input. More toe-in means more stable, but also means more scrubbing. I'm sure you have low profile tires on those 17's that just amplifies the condition. They are much more responsive than 60 series 15's. If you are fairly certain you have no bad steering components that would allow your toe-in to fluctuate, then I would start with checking the alignment. 

I should also mention the tread pattern and road surface. I don't know if you have it, but here in the US some genius thought that running grooves on the pavement in line with the direction of travel would minimize hydroplaning and supposedly reduce noise. However, some tread patterns and tire compounds skitter like crazy on those stupid grooves. So if you have the same geniuses up there, make sure you check the handling on some smooth asphalt before assuming that it is a fault of your cars.

[blown motor]

@340Challman 215/65R15 on the Challenger. 245/45ZR17 on the Charger. Will the wider tires on the Charger affect it also? I don't know what the Z indicates.

[340Challman]

@340Challman 215/65R15 on the Challenger. 245/45ZR17 on the Charger. will the wider tires on the Charger affect it also? I don't know what the Z indicates.

The "Z" is the speed rating. The tire can withstand higher rpm and heat before disintegrating. Yes, the wider the tire, the larger the contact patch, the larger the coefficient of friction. All translates into more feedback to the automobile. Running a 45 series tire you will feel all of the road imperfections more than the 65 series tire. The 65 has more sidewall to absorb the imperfections. At the same time, the 65 series tire will absorb more of the slight misalignment in the front end there may be.

[blown motor]

Just for shits and giggles I should swap the front wheels and see how it feels.

[Bullitt-]

I'm guessing you might have more caster in the Challenger which makes the car want to steer itself back to straight better but makes it harder to turn all else being equal..

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4
Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tire lean when cornering (almost like having more negative camber) as the steering angle is increased.

What's the downside to positive caster? If the vehicle doesn't have power steering, a noticeable increase in steering effort will be felt as positive caster is increased. Other than that, the effects of positive caster are pretty much "positive," especially increasing the lean of the tire when the vehicle is cornering while returning it to a more upright position when driving straight ahead.

[340Challman]

Just for shits and giggles I should swap the front wheels and see how it feels.

Well, it will definitely feel massively different than what you are used to in your Charger. You are now used to the feel of the 45's. The 65's are going to feel mushy compared to the 45's. If it drives as solid and steady as your Challenger, then you may just be feeling the limits of 50+ year old steering geometry running modern high performance low profile tire technology. Also the alignment specifications on todays cars designed for wide low profile tires is much tighter than on say a Honda civic running a 65 series tire. The larger variances allowed on the car with 65 series tires would drive poorly with 245/45 tires. The 65 can absorb those wider tolerances without negative feedback to the automobile. Also, modern cars today have way more caster than our old cars. Caster makes a world of difference in the car driving straight and steady down the road.

[RUNCHARGER]

Less caster in the Charger or the toe is off in the Charger.

[Brads70]

I'd bet the Charger is aligned to stock specs ( for bias ply tires)  You don't want that....

[Scooter]

Anyone have a copy of the Skosh chart they can post up?

[Burdar]

You probably have a combination of a couple issues.  Alignment and tires.  Wider/lower profile tires will definitely follow cracks and uneven spots in the road.

[dodj]

Less caster in the Charger or the toe is off in the Charger.

I'd second this....