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Tech QuestionsMarch 2003 Tech Q & A

Answers by Technical Editor Rex Chalmers

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March Topics:

GTV6 Engine - Worn Cams and Upgrades | GTV Muffler Removal | LSD Transaxle Lube
Brake Booster Rebuild | Poly Bushings | Cam Timing | Gear Box Noises

GTV6 Engine - Worn Cams and Upgrades : question by Robert Abatecola | 1986 GTV6

I have questions on two GTV6 engine topics:

1. I've been told by my Alfa shop that the cams in my 2.5L V6 are worn to the point that valve clearance can no longer be adjusted properly. Could you explain how cam wear can affect valve clearance adjustment?

2. With the cams worn, almost 160,000 miles on the car and the fact that I've always wanted to play with the engine a bit, I am considering building a mildly upgraded 3.0L for street use and possible eventual "just for fun" track events. S-cams are an obvious choice, but what about pistons? Is it possible to run 10.5:1 on California's 91 octane Premium? Would I be better off going with S-pistons instead? What else would you recommend for my purpose?
Answer : Well Robert, I am not aware of how a worn cam can affect the actual adjustment. The duration, lift, profile, and follower condition can be adversely affected by a worn cam. Generally the cam lobe itself and the follower are what becomes unevenly worn when a cam is said to be “worn.” At 160 K on your cams, I am not surprised that they are worn out. When you replace the cams be sure to inspect all the intake and exhaust followers very closely for wear. Worn followers can destroy a new cam very quickly.

In my humble opinion, the 3.0L is the absolutely best way to go. To quote the late great Smokey Yunick, “there ain’t no substitute for cubic inches,” or cubic Liters, as the case may be. For street and occasional track use, I would definitely go for 10:1 pistons and 164S cams. I would also strongly consider porting the cylinder heads, and at least adding big intake valves. If you have the budget, I would go with tube headers, modified intake runners and plenum, larger air flow meter, or possibly programmable fuel injection and programmable crank fire ignition, in that order. In any case, a stock 3.0 is a vast improvement over the 2.5, even a street modified 2.5.

GTV Muffler Removal : question by Vickesh Kambaran | 1972 GTV 2000

I currently have a healthy GTV, with everything original Alfa parts. The current exhaust system is stainless steel (original headers/exhaust manifold). This is a three piece muffler set.

I am looking at modifying this car into a hot street and occasional track car. The system at the moment seems great, but i was wondering if i would benefit by removing one of the mufflers in order to remove some back pressure??? The last muffler, towards the back is quite small and the piping does a loop upward then back out towards the rear of the car. The diameter seems stock. Is it worth putting on the dyno and removing one of them? or leave it stock? some of the modifications i am looking at include: cams 11.3mm, port polish head, larger valves etc, skim the head, larger venturi's 36mm? etc. will the current system become a bottle from hp? thanks for any help
Answer : First and foremost, before you do anything else, install a set of tube headers!! I say again, install a set of tube headers. I generally recommend a system with no front resonator or tailpipe muffler. Install a free flow center muffler. Yes, the current system will cost you HP with the modifications you are listing. Even a stock engine can benefit from a good set of tube headers with out changing any of the other exhaust components. Remember, an engine is basically an air pump, the object is to get as much mixture into the combustion chamber, burn it as efficiently as possible and as much exhaust out of the cylinder as efficiently as possible.

Milano LSD Transaxle Lube : question by Ed Argalas| 1987 Milano Platinum

Thanks for all the great tech news. I am following up on this month's question about gearbox oil: which do I use in my Alfa Milano transaxle, the Redline 75W90 or 75W90NS? Considering the unit contains both the synchros and an LSD, should I mix the two?
Answer : The folks at Redline recommend only 75W90NS for use in any Alfa gearbox or transaxle (except 164). Their 75W90 is just too slippery for the type of synchromesh mechanism found in 4 cylinder and transaxle Alfa Romeos. The only other synthetic gear oil I have found that works well in Alfas is available though you friendly, local Ford dealer. It is Motorcraft synthetic 75W140 Rear Axle Lubricant.

This gear oil is used primarily in differentials of F series trucks, Expeditions, and Excursions. I have been using this gear oil in my personal Alfas, mine and customer’s Alfa Race cars, and in the Hewland gearbox of my Formula Ford, all with excellent results. My daily driver is an 87 Milano with an LSD rear end. Even after sitting outside all day in zero degree weather, the transmission will shift quite easily into all gears after warming up for about 2 minutes.

Brake Booster Rebuild? : question by Rich Hanning | 1965 Sprint GT

I would appreciate your comments on the feasibility of rebuilding the brake booster on this car. I have owned the car for nine years and have replaced the Dunlop brakes with ATE units on both ends. I just installed a new proportioning valve and while bleeding the system, "something" happened to the brake booster allowing fluid to be sucked into the intake manifold. Disassembly of the accumulator portion of the booster revealed brake fluid on both sides of the diaphram. I had a used, spare booster which I installed. The brake pedal is now firmer than it has ever been but the booster is not working -- no vaccum assist. Do you have any ideas regarding what failed in the original booster to allow fluid into the vaccum accumulator and/or why the new booster might not be working? Is rebuilding one of the two boosters a reasonable idea or should I spring for a new booster?
Answer : When an Alfa comes into my shop displaying booster problems, I always recommend replacing the booster. With the cost of labor and re-build parts, it is generally a wash as to whether rebuilding or replacing is most cost efficient. Most of these units are over 30 years old, and as wonderfully engineered a unit as the booster is, IT'S 30 YEARS OLD!!!!!! If you are one of those engineer types, with time on your hands, by all means go ahead and rebuild the booster. If you are going to rebuild the booster, get a complete kit and rebuild the diaphragm and cylinder parts of the booster. Disassemble the unit, strip it down to it’s base parts and clean to hospital operating room standards. Be certain to inspect the cylinder bore very closely for scoring, corrosion, and scratches or wear marks. Use a very fine ball flex hone to put a new finish on the cylinder bore, clean it again, clean it again, and then inspect very closely for any imperfections. Re-assemble the unit and use a good quality brake assembly lube in the cylinder bore and seals.

As to what failed in your original booster, it was probably one of the seals on the cylinder bore that allowed fluid to leak by and make it’s way into the vacuum booster chamber of the booster. Be sure to verify that the one-way vacuum valve on the back of #4 cylinder on the intake manifold is functioning properly, as it can cause the hard pedal you are describing.

Polyurethane Suspension Bushings : question by Frank| 1967 Duetto

Polyurethane Bushes. Do you think I should change my rubber bushes to these polyurethane ones? Are they really better? what about the ride, will it be harsher?

How long does a normal rubber bush last anyway? My car is now 35 years old and I am kind of sure it had probably never had its bushes changed before. I want to change the bushes but if rubber bushes last a long time then I may not bother with polyurethane ones.

Can you recommend a brand or one that you had experience using since there are so many brands out there. Also, they do not appear to have a complete list of bushes for the front and rear suspension of the car. In this case if changing to polyurethane is an improvement, which are the major bushes I should change and which one I can keep using normal rubber bush?

Thank you for helping me get my car back into shape

Answer : I never recommend poly bushings for anything other than an Alfa that is used for performance driving at least more than half the time. The stock bushing work well and last quite a long time. The poly bushings are stiffer and the result is a noisier harsher ride. That is not to say that use of the Poly bushings won’t provide an advantage in handling. Because of the added stiffness of the poly bushing, there is less deflection in the suspension and the result is less change in suspension geometry. In theory, this will make the car handle better. I seriously doubt that most, if any, drivers will be able to detect a noticeable difference in handling in a car that is used mainly for street driving. In my view, for street driving, the disadvantages of the poly bushing outweigh the advantages.

Cam Timing : question by Marc Zebouni| 1962 Giulia Sprint 101 (Veloce)|

Hello, I bought the car in '99 and it came with high lift cams of 11mm and Webers, 1600 engine. When checking the valve clearance the first time, I did not observe how those cams were set: retarded or not. Today, my exhaust cam is set at 102' and the intake at 116'. It was 118' before but the car would idle bad. My question is how close can I advance the intake cam to 102' and still have good low end power. My webers are DCOE2s and have 120 mains and 180 correction jets. The valve clearances are 15 intake, 18 exhaust. Do I have good volumetric efficiency now? Can I improve it? I love that car.
Answer : First of all, let me say that with the information you have provided me, it is very difficult to give you specific information about tuning your cams and carburetors. There are many different 11mm cams out there with wildly varying duration and timing. You didn’t mention what the idle jets are. The mains and airs will have no affect on how the engine idles. I have smoothed out the idle of countless Alfas by synchronizing and balancing the carburetors. Depending on the specs of the cam, choke size and the ignition timing, an 11mm cam will generally like more fuel and less air than you are currently running. As a general rule, Alfa engines like lobe centers of 102 degrees. You can play with cam timing to some degree, but 102 is usually a good place to start. Valve clearance will directly affect the timing and duration of the opening and closing of every valve, i.e. valve timing. So the best thing you can do is identify the cams that are in your Alfa. Contact the manufacturer or retailer and get the lobe centers and valve adjustment the manufacturer specifies for that particular camshaft and install them on your engine.

I don’t know what pistons are in your engine, so I would strongly suggest that before you start adjusting your cam timing and valve adjustment, you should place a length of 0.100” solder down a spark plug hole between the valve and valve pocket and, by hand, turn the engine through one full revolution. Measure the solder after rotating the engine. You want a minimum of .040” piston to valve clearance on the intake and .060 on the exhaust. At my shop, I will use a degree wheel to set and check cam and valve timing on every engine I rebuild or assemble. After setting the valve clearance and cam timing, I will check the piston to valve clearance and piston to cylinder head clearance with modeling clay.

Hope this gives you some things to think about.

Gear Box Noises : question by Frank | 1967 Duetto

My gear box shifts fine when cold but becomes notchy after travelling a few miles. When cold, the 2nd gear slots in abit notchy but still relatively smoothly and never once grind the gears. But if I try to engage 1st or reverse quickly, sometimes I might grind the gears. I was thinking of having the transmission rebuilt but I decided to change the gearbox oil first to see if it improves things. I am glad to say that 2nd gear is now really very smooth when cold and only becomes abit notchy when warmed up. Things did improve on the 1st and reserve gears too but even then I would still grind 1st and reverse if I try to slot it in too quickly. Also, sometimes I cannot seem to shift into 1st gear at all as there seems to be something blocking the shift. I would either need to force it into gear or I need to go back to neutral before I can shift it into 1st and its very notchy but at least no grinding of gears.

I should add that 3rd gear shifts fine but is abit notchy. 4th is smooth but less notchy and 5th is smooth. I have performed the following test while travelling at about 35-40mph and with clutch depressed all the time I can down shift into 2nd gear smoothly without grinding gears.

I should also mention that there is this relatively loud "grinding" sound from the transmission which lessens when I depress the clutch and comes back when I release the clutch.

So which is it, the gear box or the clutch release bearing etc is at fault? I am willing to change the clutch as it has not been changed in the last 5 years or more and I would like to avoid a costly gear box rebuild if I can. How long do you think I have before I have to have the gear box rebuilt?

Really appreciate your kind assistance in helping me understand what is going on with my new old car.
Answer : To answer the last part of your question first, the noise you are hearing is, most likely, the throw out bearing. It’s difficult for me to tell you how close your meeting with impeding doom is without hearing it for myself. Let me just say that I can count the number of throw out bearings that I have seen fail, in over 30 years of working on Alfas, on less than all my fingers and toes. Yes, I do have a full compliment of both. If it starts getting louder, changes pitch noticeably, or starts screaming at you, replace it.

As to your problems with first and reverse gear engagement, try engaging 2nd gear before going to first or reverse. This is a common complaint of many Alfa owners. The reason for engaging 2nd before trying first or reverse is that it will slow down the speed of the main and countershafts of the transmission and allow easier engagement of the gears. I have also found that sometimes it is necessary to depress the clutch and slightly rev the engine before trying to engage reverse. Reverse has no synchro mechanism and is a combination of 3 straight cut gears. When you engage reverse, what you are actually doing is moving a small straight cut gear into position between two larger straight cut gears to engage reverse motion. Sometimes the gears line up in such a way that the smaller gear hits the teeth of one, or both, of the larger reverse gears. So slightly revving the engine re-aligns the gear teeth.

Doesn’t sound to me like you are near needing a gearbox rebuild as yet, but that’s just my opinion, I could be wrong.

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