2nd gen camaro and howe centerlink

[speedjohnston]

Just to keep this out of Brians build thread, I was going to use the stock centerlink and the Howe idler and pitman arms with there tie rod ends. the centerlink you can see is sitting a little funny when the wheels are pointed straight and wasn't going to work.

I switched to the Howe centerlink and cut the front off the crossmember (still needs to have a plate welded on) and the centerlink sits very square with the engine now. My cut needs to be grinded a little.

My question has to do with the Ackerman. The car is built for the street and high speed road racing, so the Ackerman under racing conditions if its not crazy will have little effect (debateably). I had the cars front wheels raised and turned the steering side to side and took some measurements. I realize this is not the most accurate method but for some using the centerlink the ackerman issue seemed obvious, but I seem to have very little difference one way or the other. This could be because of the pitman arm and idler I am using? How obvious is it when its out? Just looking for opinions while I finish figuring out the front suspension.

[pro-tour79]

using the Howe pitman arm is what caused the issue in the first place , it is like a Firebird pitman arm shorter and bent down, a Camaro used a straight flat longer pitman arm, but the Howe center link is made to work with that pitman arm.

[speedjohnston]

So is the ackerman issue only of concern when you mix the stock parts with the Howe parts?

[mfain]

You might want to look at Bob Bolles suspension article in the Feb 2010 Circle Track. He, and most others, now recommend zero or very near zero Ackerman. If you employ Ackermann at all, it will be in fractions of a degree, not whole degrees. The article briefly describes how to check the Ackermann. The old Woodward catalog used to have a good tech section on how to adjust Ackermann. It was related to rack placement, but the principle is the same for drag link suspensions. Moving the inboard tie rod static mounting positions (i.e. moving the rack or the drag link) forward will induce more Ackermann -- moving it aft will have the opposite effect. This movement can be done by moving both the steering box and idler arm mounts fore or aft, as required; using a differently shaped drag link that moves the tie rod mounting points fore or aft; or using different length steering arms (longer steering arms have the same effect on Ackermann as moving the rack or drag length aft). I assume that your Howe drag link was made for your chassis using the steering arm lengths you have, so you should already be in the ball park. Your car looks great -- best of luck with the build.

[mfain]

Another thought -- it is hard to tell looking at the photos, but it appears that your idler arm is longer than the pitman arm. If that is the case, the two outboard tie rod end mounting points will swing in slightly different arcs, which will make the Ackermann different when turning in one direction vice the other. For visualization, I have had good luck making scale models of the steering componenets (1/2 or 1/4 scale works) out of poster board and pinning them together at the pivot points with thumb tacks. Thumb tack the "fixed" points like the pitman arm, idler arm, and ball joint centerlines to a piece of wood (in appropriate scaled positions). You can then turn the wheels back and forth and measure each wheel's turn angle with a protractor. Its not super precise, but it will let you see what is happening to the Ackermann. You could also just draw it out on graph paper. Here is a quote from the Woodward catalog that may shed some light on your situation. You can replace the words "rack and pinion" with "drag link". "On frames based on the 1971 Camero, it was impossible to locate a rack and pinion far enough to the rear, so it became common to fabricate spindles with a shorter steering arm on the left side, and give a faster steering ratio to the left wheel." This was obviously to help a circle track car with left turn entry, but it gave toe in (negative Ackermann) if you turn right. Having different Pitman Arm/Idler Arm lengths will have the same effect to some degree. Just food for thought -- hope this helps.

Pappy

[speedjohnston]

Thanks for the replys, that deffinately gives me some ideas on how to check it. I will also look for that Bob bolles article. What I originaly tried to do was turn the wheel all the way in one direction untill it stopped on the lower a-arm, then measured tire to tire. Then I did it the other way and took the same measurement. I was hoping if there was a difference right to left I would find the measurement would change if the ackermann changed. It seemed to be within a 16th of an inch, but I just checked quickly since I didn't even know if this would tell me anything at all. I had all these other little issues along the way, I didn't even think about this untill it was mentioned last night in another thread. Thanks again for the help.

[Cris@JCG]

I have a 70 Camaro that I am building for myself.. Please give me some more details about this front suspension!! Are those ATS spindles?? They look like the have extenders on them.. A-arms??? Details please!! I like this setup

[speedjohnston]

They are the ATS AFX spindles, the a-arms are SPC with a tall Howe ball joint. I purchased and got help with this set up from Mark Savitske at SC&C.

[Cris@JCG]

Thank you!

Originally Posted by speedjohnston

They are the ATS AFX spindles, the a-arms are SPC with a tall Howe ball joint. I purchased and got help with this set up from Mark Savitske at SC&C.

[David Pozzi]

GM used 3 different hole spacings on the idler arm during the 70's. The 3rd gen Camaros have slots for the idler arm making it somewhat adjustable for height. If all else is OK on your steering, I'd consider redrilling the idler arm holes, or slotting them to get the center link level.
David