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Tech QuestionsMarch 2001 Tech Q & A

Answer by Technical Editor Rex Chalmers

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March Topics:

Hot GTV Suspension | Sodium Filled Valves | GTV-6 Cat Burning? | 164 Tire Wear
Hot-Rod Verde Idle | 105 Brake Pedal - Pump Once?

Hot GTV Suspension : question by Michael Moore | ’ 74 GTV

I have a stock GTV in almost concours shape which I autocross a dozen times a year and drive only in the nice weather. I have rebuilt every thing on the car except the suspension. The bushings, A arms,tie rod ends,springs etc. are original [car has 70k miles]. My Alfa friends have given all sorts suggestions from springs to poly bushings. My question to you,which suspension rebuild would you recommend, considering the use I will be doing. I would like to beat more porsches.

Answer : If your suspension is truly original, after 27 years and 70k on the odo, I would suggest you completely rebuild the entire front and rear suspension, replace the springs, sway bars, and shocks. For autocross, the stiffer and less compliant you can make the bushings the better, so poly bushings would be nice, but they wear fairly quickly and are noisy and harsh. Spherical bearings are even better, but they are extremely harsh and would require adding a panhard rod or watts link and a new differential trunion. The bushing choice is a subjective one. You have to weigh the advantages and disadvantages of each and make your decision on that basis.

I would pick a matched set of springs and sway bars from one of the Alfa suppliers such as International, Centerline or Alfa Ricambi. Don’t just throw a set of springs and bars at the car, the spring rates and bar stiffness vary, each delivering different handling characteristics. Ask the suppliers for the characteristics of their set-up as well as bar diameters and spring rates. Adjustable bars would be a great benefit as it would allow you a means of easily adjusting your Alfa’s handling bias. I would also suggest that you get adjustable upper arms as they make camber adjustment a breeze. I prefer Bilstein shocks, but as you know, opinions vary.

Some excellent books have been written on the subject of race car preparation and chassis tuning. Two of my all time favorites are Tune to Win and Prepare to Win, by Carroll Smith. I suggest very strongly that you procure copies of these books. Now, gather as much information from people whose opinion you value as you can, and go for it. Good luck chasing down those Porsches, BMWs, and Rice Burners.

Sodium Filled Valves : question by Robert Clauss | ’ 65 Giulia ti 1600

Is there any value in staying with sodium filled exhaust valves? The head is being redone for my car, and I want to put new valves in, but can't find sodium. I have purchased a set of Cross exhaust valves, but have held off delivering them to the machine shop while I looked further for the original spec type.

Answer : As you know the original Alfa valves were made by ATE and were sodium filled. The thinking behind this was that sodium cooled valves would dissipate heat better than solid steel valves. This is a sound engineering principal that was a good solution in 1966. I talked to Stuart at Sperry Valve Works about your concern. He assures me that with modern valve guide material, and the higher seat pressures that result from a quality high-performance valve job, the modern solid steel valve will give service life that compares favorably with the OE ATE valve. If you have any doubts about the valves that you have purchased Stuart can provide you with suitable valves. International Auto Parts also carries a complete line of quality valves.

GTV-6 Cat Burning? : question by Michael Williams | ’84 GTV-6

I get a strong sulfur smell when I drive the car hard (full throttle esp). I've had my local shop check the mixture... is it something they can't duplicate/diagnose under no load? The problem started after a new Cat was installed. The car passes CA smog fine and has plenty of power. What could it be? Am I burning up the cat?

Answer : I assume that the cat you replaced was the original and that it was replaced because it was no longer functioning. A new cat will make up for a multitude of mixture sins. I would suggest having the mixture checked upstream from the cat by an experienced Alfa technician. Check the mixture at idle and at a mid-range rpm. Pay close attention to the hydrocarbon levels. These levels indicate the amount of unburned fuel in the exhaust; too much HC in the exhaust can cause a cat to burn up in a very short period. Make certain that the oxygen sensor and fuel pressure regulator are in good working order. Verify that the ignition timing is correct. If all of these items check out fine, find a chassis dyno and an experienced tuner/operator. Sounds to me like the mixture is too rich under a load and that you are burning up your new cat.

164 Tire Wear : question by Judy | ’95 164S

Is a feature of the 164 to wear the inner circumference of the front tires? I had the alignment checked when we bought the car, which had this wear pattern, and was told that it was aligned to the factory specs. We just replaced the fronts again with the same problem (worn to the cords with the remainder of the tire quite unworn/intact). Is there any adjustment for toe, or is this a camber problem? Are there better-than-factory settings, and is this something we could do?

Answer : Yes, premature front tyre is one of the less desirable features of the 164 suspension. The factory specification for camber is 1deg. 37’ +/- 20’. This spec combined with having a front engine / front drive layout does generally cause premature wear of the inside of the front tyres. I would make sure that the vehicle is within spec, go for the minimum if you want to slow down the tyre wear. Bear in mind that the more camber will keep more of the rubber in contact with the pavement when your right foot is firmly planted on the go pedal. Also, make certain that the castor and toe-in are set correctly. Another tactic that works well is to perform more frequent tyre rotations.

Hot Rod Verde Idle Problems : question by Tony Brucia | ’88 Milano Verde

My car just got Stage 3 Sperry heads, S cams, new cat, custom center straight through middle exhaust in place of center muffler, new plugs, and new temp. sender, new O2 sender, new dist. cap & rotor. The problem is poor idling when cold. The car tries to idle at 600 rpm. I verified that aux. air valve is open when cold and closed when warm. I spoke to Sperry who said to check for air intake leaks, but I can't find any. The car ran smooth before. Sperry says their modifications wouldn't cause this. Any ideas? Car idles and runs ok when warm. I have air/fuel mixture meter and it appears to be correct. I'm baffled.

Answer : Interesting problem. I’ve a few suggestions for you. Mike and Stuart at Sperry Valve Works are correct, the mods and parts you have installed won’t cause this problem. However, I have seen incorrect cam timing cause this exact problem. If, after making certain that you have the engine at absolute TDC, check the alignment of the cam timing marks. If they are not spot on, it is possible that the cam timing could be the cause of your poor cold idle. Sperry machines special cam wheel keys to alleviate this problem. BEFORE you check cam timing, make sure that your ignition timing is correct, check to see that the cold running timing retard switch on the thermostat housing is NOT connected, check the aux. Air valve when it is cold against a known good unit at the same temperature. This valve may not be open far enough when cold. Check the butterfly hard stop setting. Finally, since you just had this unit apart, I would make absolutely certain that there are no vacuum leaks and that the mixture on the air flow meter is not set too lean or rich. Try adjusting the idle mixture with the engine cold to see if there is any change in the idle.

Sorry for the shotgun diagnosis, this e-tech gig is tough! [ Ed - you're doing a great job, Rex! ]
Hope that this information helps.

105 Brakes Pedal - Pump Once? : question by Steve Smith

There's been a thread on the Alfa Digest regarding the brakes on 105 cars with bottom pivot pedals and the need to pump once before the pedal takes it's highest position. On all your cars, did you ever fit an anti-bleed-back valve to keep the pedal high? I've seen them offered in race catalogs and wondered if they really were effective or just hooie.

Answer : Good to hear from you, Steve. The problem you describe is one that I often hear, usually from my customers with competition Alfas. It is a characteristic of the ATE and Bendix/Bonaldi master cylinders found on 105 Alfas. I have not experimented with anti-bleed-back valves as I have found several tweaks that minimize the condition that your describe. First make absolutely certain that your brake calipers are functioning properly and that your brake discs are absolutely flat. Any warp in the brake disc will push the piston back. Even a slightly warped disc will cause the piston to be pushed back, even more so on a competition vehicle operating at high speeds. Next, use stainless braided/Teflon brake lines to minimize flex line swelling. Also check all wheel bearings for excessive play. Now, flush your brake hydraulic system with a high quality fluid

My final tweak is one that takes some testing to tune properly. I fabricate an insert and attach it to the plate that covers the pedal pivots. Place the insert so that it physically limits how far the brake pedal can travel towards the rear of the car. Then move the brake master adjusting rod in the direction that would simulate putting pressure on the brake pedal to the point where the brake calipers are being actuated. Then back off the adjuster about half to a full turn. Next drive the car and get the brakes hot to make sure that the expanding brake fluid is not actuating the brakes on it’s own. By playing with the position of the insert and the adjusting rod, you will not only be able to get the brakes to actuate at a higher position, you will also have the ability to adjust the brake pedal to a position that suits your driving style, not to mention your inseam. This modification doesn’t eliminate the problem you describe completely, but it’s very inexpensive and certainly makes a vast improvement in pedal feel.

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