Tony’s Garage: Readers' Tech Questions - July 2014

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Tony Huntimer Jul 31, 2014 0 Comment(s)

Q. Hi Tony.

First, let me say I love your column and usually look at it before any other feature in the magazine. I have a ’69 Camaro with a stock 350, stock intake manifold, and a four-barrel carburetor. The car has stock exhaust manifolds and a chambered exhaust system. I’m interested in upgrading the engine and would like your advice on what makes sense as I start, and also in what order to do things. I’d like to add long-tube headers but rarely see anything in your magazine (except for last month) about a chambered exhaust system. Are they compatible? Also, I’d like to upgrade the manifold and carb to something like an Edelbrock Air-Gap and a Holley carb. Finally, I’d like to have a little more performance oriented cam. What order should I do these upgrades? Eventually, I’d like A/C and a front drive system, too. I’m not racing or autocrossing the car. I’m just looking for things to make it a little cooler with a little more power and better sound.

Thanks for any help you can offer!

Mark D.
Via email

Hedman Hedders Camaro Headers 1/3

Hedman Hedders (from left to right): ’67- 81 Camaro super short tube headers PN 68396 (uncoated, PN 68390), ’67- 69 Camaro long-tube headers PN 66003 (uncoated, PN 65003), ’67- 81 Camaro mid-length Elite Heavy Duty headers PN 68608 (uncoated, PN 68600). Photo courtesy of Hedman Hedders

A. Mark,

Thanks for the kind words.

Since you’re asking where I would start, I assume you’re going to do this in stages. Anytime you install a freer flowing exhaust system, you will need to adjust the carburetor to make up for the increase of airflow, for the best possible performance. This is one of the reasons I would probably install the headers first.

With some basic and typical modifications performed by your local exhaust shop to your chambered exhaust system, it will work with any type of header or exhaust manifold setup. They will cut the system back to the proper length and install some flanged reducers to adapt the header collectors to the 2.125-inch chambered system. Are you dead-set on running full-length headers? There are mid-length headers out there that don’t hang down as much. Camaros that sit a little lower than stock ride height benefit from these mid-length headers and can get plenty of performance gains from them.

When you’re ready for carb and intake manifold, it’s a good idea to pick the ones you want to run in the long run and consider installing a high-performance camshaft at the same time. This will save money later on. If you choose a carb and intake that work with a low/stock performance camshaft and you decide to upgrade the camshaft to a higher performance level, you’re going to end up buying a second carb and intake manifold. If you can swing it, do all three at the same time.

Just in case you’re new to the hobby, each intake manifold is rated for optimum performance within a specified rpm range. That range is determined by your end goal performance. Be it mild performance, street/strip, Pro Touring, drag racing, etc., be realistic when choosing what you want. Don’t shoot for the stars and get something you won’t be happy with. Once you’ve decided on a performance level, you’re ready to choose an intake manifold. For best performance, a carburetor and camshaft need to be matched to the intake manifold. A mild street Camaro can deliver plenty of power from an Edelbrock 650 carb, Performer intake manifold, and Performer cam and lifter kit. If you’re looking for more power, choose a Performer RPM intake manifold and a larger carburetor from Edelbrock or Holley to match. Then choose a cam and kit from Edelbrock or COMP Cams. Both companies have excellent tech support to help you get the right parts for the best performance.

If you haven’t yet looked into front drive systems, make sure that you choose one that allows an easy upgrade that includes an A/C compressor. I’ve always been a big fan of the Vintage Air FrontRunner system. To make sure everything lines up correctly, it includes a water pump and alternator, along with everything else you’ll need. Other kits that don’t include the water pump and alternator are just leaving too much room for possible fitment issues. You can always install a FrontRunner with an A/C pump and run it without hooking it up until you’re ready, just as long as you keep the caps in place until you’re ready to hook it up.


(Note, this letter originally appeared in Tony’s Garage in the Dec, ’13 issue. – Ed.)

Q. Tony,

Back in the day, I bought a new ’78 Z28 with a 350 and a four-speed. Since the day I drove it off the lot it has had a bad vibration starting around 75 mph and gets worse all the way up to 90 mph, where the vibration doesn’t get any worse or better. The dealer changed the harmonic damper, rebalanced the tires, and may have changed out the flywheel.

None of these fixes worked. Over the years, I have replaced tires and rims, had the engine rebuilt (balanced and blueprinted) with 9:1 pistons and a mild Isky hydraulic cam. I have also had a new driveline built with a larger diameter tube. The engine runs like a sewing machine up to 5,500 rpm in Neutral. No vibrations. The only way I can describe the vibration is that it is related to the speed of the car and is a very tight or short-wave type of vibration. If the shifter is against the rear stop, the vibrations are transmitted to the shifter. If I move the shifter off the rear stop, the vibration goes away from the shifter, but is still present. There’s no vibration in the steering mechanism. I have not done anything with the rearend as far as troubleshooting. The car has never been wrecked, raced, or excessively abused. Any suggestions as what I may try next to troubleshoot this problem.

Thanks for your help.

Bill Pedersen
Via email

A. Bill,

WOW! It sounds like you’ve been pulling your hair out for a while trying to find this vibration issue.

One of my first thoughts was that the driveshaft may be out of phase (universal joints clocked 90 degrees off of each other). Properly phased universal joints are in the same clocked position in the front and the rear. Universal joints out of phase are not a common occurrence, but it has happened. Since you said that you’ve replaced it already, that turned into a fleeting thought. It truly sounds like it has to be in your rearend. Not the one you sit on. I’m referring to the one mounted to your leaf springs.

Have you attempted to check how “true” your axles are by using a dial indicator with the brake drums removed? An axle could have been machined improperly from the factory. An axle could be slightly bent. I used to work at GM, and I’ve seen some cars get seriously abused before they end up on the lot of a dealership. A Teamster or a truck driver could have taken your car for a joyride and hit a curb before you received the keys to your brand-new pride and joy back in 1978. Most likely you would have noticed the brake shoes on one side wearing more than the other. It doesn’t take much to cause a vibration like the one you’re experiencing.

If you haven’t already, check the pinion yoke on the rearend to see if it may have been machined slightly off-center. If the pinion yoke universal joint cups are improperly machined, the driveshaft could be whipping around and cause the car to shake at higher speeds. You would probably need to measure the runout of the rear of the driveshaft with a dial indicator with the car up on jackstands. This would allow you to rotate the driveshaft.

If the problem increases or decreases while accelerating or decelerating in the trouble range, you may have pinion angle problems. Also, check the angles of the driveshaft. Changing the ride height of your car can change your pinion angles and cause unwanted drivetrain vibrations. Since you’ve had this problem since you purchased the car, pinion angles are probably not your issue but still worth a look. You can measure the angle of your crankshaft/transmission output shaft as well as your differential pinion angles with a basic angle gauge. For best results, the car should be level (easiest to accomplish on a drive-on rack). A production leaf spring car should have about 3 degrees down on the transmission output shaft and about 3 degrees up on the differential pinion angle. These add up to 6 degrees of difference. Seven degrees is about the maximum for long universal joint life. Three down and three up should get you a pretty smooth ride. If you’re way off of these measurements, you can get some angle shims to adjust the pinion angle or you’ll have to figure out a way to shim the transmission mount to get it within spec. If your car was a moderate- to-high-performance Pro Touring leaf spring car, you can adjust the differential pinion angle to as much as 3 degrees down before you may start noticing chassis vibrations. The variation from stock and high-performance angles has to do with combating the amount of leaf spring wrap-up from applied power/torque.

Good luck!

Tci Dampers 2/3

TCI makes one of my preferred higher-quality dampers.

Mystery Vibration, Part 2 …

Q. Tony,

I had the driveline shop technician take the Camaro for testdrive yesterday. He thinks there is a slight vibration from the engine, which could be felt up through the shifter. He recommended a fluid-type harmonic damper. He also mentioned about having a new pressure plate/clutch/flywheel assembly that has been balanced as a unit. While the car was on the lift, we ran it in First gear. The driveline and pinion yoke looked good. No noticeable problems. However, the passenger rear brake drum did have some noticeable vertical (up and down) motion. Possibly a bent axleshaft. He also said to keep my hand off the shifter while driving. I wouldn’t notice the vibration as much and, more importantly, holding the shifter back against the stop puts pressure on the shifting forks, wearing them out. Who knew?

I’m not familiar with the fluid-type damper. Any comments?

Thanks,

Bill Pedersen
Via email

A. Bill,

I’ve never personally had experience with fluid-type dampers. The few engine builders I trust have all steered me to non-fluid-type dampers from reputable manufacturers. For that reason, I’ve only used conventional dampers from the factory on my stock engines, and from TCI or BHJ Dynamics on my performance engines.

Your mechanic was on the ball about keeping your hand off the shifter. He’s correct that you will prematurely wear out shift forks and sliders. I would have mentioned it, but when it comes to manual transmissions, I assumed everyone knew to keep their hand off the shifter and their foot off the clutch pedal unless they were shifting.

Have that questionable brake drum and axle checked. I really hope you find the culprit. Good luck!


Got a burning tech question?
Email Tony Huntimer at camaroperformers@racehome.com

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