On my 38 Chrysler I've put in a GM "Canned Ham" P/S pump with the built-in reservoir, and the TRW rack and pinion that was used on 89-96 Cavalier/Grand Am and about a zillion other vehicles. Everything is in and working fine, and it feels great at low speeds. My problem is that freeway speeds it seems awful touchy, like if you look down to turn on the lights you wanna be extra careful to keep it going straight. Noticably touchier that my modern cars. It turns out that there are 2 versions of the rack: A sport version that is 2.5 turns lock-to-lock, and the standard version that uses 3 turns. I have the sport version: could this make it feel twitchier, or would they have the same feel? If that isn't it, I have seen a P/S flow limiting valve in my Speedway catalog that says it is for using a GM pump with a Mustang rack. It cuts the flow from 3gm to 2gm. Think this would help?? What else can I do to make it a bit less sensitive?
Take it to a hot rod friendly alignment shop. Possibly need to add more camber (positive 3-4 degrees). Also, the pressure reducer valve or pump shims will help some. Running bias ply or radials?
Sounds like the pump is pumping in proportion to engine speed. Cars in the 60's were like this. Faster you went, more power assist you got.
I did a post on this earlier. See http://www.jalopyjournal.com/forum/showthread.php?t=179379 The verdict here is that after a trip back to the alignment shop for more caster it has improved. It goes straight but is still a little twitchy. I'm driving it but I use caution at 65+ mph. My money is on Heidts pressure bypass valve. It'll be a winter project here in North Iowa. I've learned that factory engineering sometimes is tough to beat.
I'm running radials. Been to the alignment shop: Right now camber on the driver's side is 1.8 degrees positive, and .7 degrees positive on the passenger's side. That was the least the alignment guy could get. Front end is original (in this respect at least). Maybe I have to reposition the upper control arms to get slightly negative camber numbers? That would be a big job I'd like to avoid. What should the ideal camber numbers look like?
50flathead- I just read your post. I was thinking camber, but your deal was caster. Hmmm. It may be the pump, but I definitely need some good alignment target numbers. I'm not sure where the alignment guy got his "specified range", but what he was shooting for was quite different from what was sugested in your post. My caster numbers are 1.2 degrees on the driver's side and 2.4 degrees on the passenger's, with total toe of .16 degrees. These numbers all are sounding too small, and there is something funny going on with the driver's side, 'cause the range of adjustment just isn't right. Would the OEM alignment specs for a 38 Chrysler still be right for my car with P/S, discs, modern driveline, etc? If not, how should they be adjusted?
I'm having the same problem with my wifes '66 Mustang. I converted to power steering,new Flaming River 16:1 steering box, all new front end parts. Had a local shop align it but it is touchy and wanders at higher speed. It has neg.0.14 deg.caster which I feel is not enough and is causing the problem. I have it back there right now trying to have them put in more caster; hopefully pos 2-3 deg. Only problem is they're not experienced in working on old cars so they have to keep it overnight to continue working on it tomarrow. I'll let you know how it works out.
modifieddriver, 50flathead or anyone else How about a point in the right drection for the shim kit for the front end of my 49 Plymouth. Right now I have 0 caster and I think that is going to be somewhat of a problem with the rack and pinion power stearing. Any one have any help on this? thanks kai
Modified- Is there an easy way to calculate (or approximate) axle load? I've only seen software intended for big rigs. Also a ref to a tire site with the load vs inflation info would be appreciated. I did some Googling but couldn't find anything. I like the idea of working with the inflation first since it is easy and free. If I'm understanding this, 3-7 degrees is probably the right range for caster. What would be a good range for camber? Slightly negative, but how much?? Teardrop- I have a 50 Plymouth, and if I remember right shims were just slid under the "Control Arm Bars" as necessary, and they looked like basic body shims.
Right. There is no caster adjustment except to shim. The manual says that ZERO degrees is the preferred setting, with the acceptable range running from -1 to +1 degree, so whatever problems you're having may have some other cause. oops- just reread your question: you are just anticipating the problem...I'm reading everything I can find and it sounds like more caster (than zero) is in order.
I think your problem lies in the quick steering sport rack. I would start off with the fluid flow restriction and see what you end up with. I think getting near 7 degrees of caster is going to be hard on the upper control arm, I wouldn't want to try more then 2 or 3 degrees myself. Gene
Caster split on a street car? Does it pull left when you let off the gas or hit the brakes? Maybe I'm all wet, but that was one of the techniques I used to use to set up circle track cars. Yours is not as extreme (I shot for a 4 degree split) but double seems like a lot of difference for a street car. If you have a flat area (paved or concrete) that you could work on the car some of the basic suspension tools are fairly cheap (home garage kind, no computers or lasers) or can be fabbed out of a welder's angle finder. The motor sports community has several tools that are somewhat nicer to work with and aren't that much more money. Just a thought, if you have to make too many trips to the alignment shop they could easily pay for themselves.
I'm putting a Fatman rack kit into my '50 Ford and thought they recommended removing the spring from the pump and cutting 1/3 of the length off to decrease pump pressure and then re-install it (but I don't know if you leave it at that length or stretch it to the original length). I'm working from memory at this point and will need to go back and review info but that seems like what it is supposed to be. If you used a kit, call the manufacturer.
Some simple definitions of front alignment terms: CASTER: The purpose of caster is to create a tendency on the part of the front wheels to line up in the direction travel. CAMBER:The purpose of the camber angle is to place the load on the larger inner wheel bearing.
Some simple definitions of front alignment terms: CASTER: The purpose of caster is to create a tendency on the part of the front wheels to line up in the direction travel. In general more caster makes it easier to steer at highway speeds and harder to steer at low speeds. The more positive(kingpins tilted back from vertical at the top) caster the more difficult is steering at low speeds. Zero caster generally makes steering very "touchy". CAMBER:The purpose of the camber angle is to place the load on the larger inner wheel bearing. The best specs to follow for alignment are those factory settings for the front suspension you are using, i.e., 38 Chrysler specs for 38 Chrysler suspension, Pinto/Bobcat/Mustang II specs for PBMII suspension.
Here is a short tech article on the effects of caster, camber and cross caster and camber. Maybe this will help. Remember more caster more steering effort required, less caster = less effort. http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4
As a matter of fact I have. I've dropped the tire pressure to 32 on the front and left the rear at 35. You are correct, it has settled the effect some. I'm running 215 70 R 14 radial TAs on the front, how low would you try? I've also noticed that 195s and 205's on similar vehicle setups are better behaved at speed. I like to make only one adjustment at a time. Chassis tuning is sure dynamic.
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