engine and driveline setup on type 105 - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 4 (permalink) Old 10-14-2018, 07:36 PM Thread Starter
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engine and driveline setup on type 105

Hello --

I am new the site and excited about all the information I've found so far!!

I'm starting a build of a '50s style racing sports car with Alfa and Ferrari influences. I had a Duetto many years ago and decided to use an Alfa 105 inline 4 DOHC engine and drive train. This is not my first car project but certainly the first "from scratch" build.

I've start making drawings of the body, chassis and placement of components. But I need some info that I haven't found with simple searches. I want to follow Alfa specs on these items to avoid complicating things.

my questions:

1. At ride height, is there an specific angle the engine expects to be mounted (from front to back)? I know some American cars require a few degrees to angle so the nose of the engine is up slightly.

2. What pinion angle should I use on the rear axle when installed at ride height? Again, some US-made cars can range from 1-2 degrees or more depending on the suspension type.

3. And related to #2, what do the specs call for on a 105 driveshaft angle?

Any insights would be greatly appreciated as I start this journey.

Richard
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post #2 of 4 (permalink) Old 10-15-2018, 06:31 AM
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If you use an Alfa driveshaft then you want the two U-joints to move through the same angle when the car is normally loaded. That means that the front tube of the driveshaft should be parallel to the input shaft of the axle when the rear suspension is loaded. Vertical alignment is accomplished by lowering either the center support or the transmission mount.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #3 of 4 (permalink) Old 10-15-2018, 11:19 AM Thread Starter
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Thank you Ed for the quick reply.

So if I understand you correctly, when set up properly there should ideally be a straight line through the engine crankshaft, transmission, drive shaft and the rear axle input, meaning there is no pinion angle at the rear axle - am I reading this correctly? and the adjustments to achieve this state is through movement of the transmission mount?

Sorry to restate what I think I heard, but I want to get this correct.

I sure appreciate your time and knowledge!!
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post #4 of 4 (permalink) Old 10-15-2018, 01:17 PM
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No. The front driveshaft (the input to the first U-joint) should be parallel to (not necessarily in line with) the input shaft of the differential (the output from the second U-joint). Imagine a stretched Z The middle line of the Z is the rear driveshaft tube. The horizontal lines are the front tube and the diff input shaft but in practice they are not horizontal. The slope of the diff input varies with suspension drop so you put the weight of the car on the wheels, measure the slope and make the front tube the same slope.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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105, 115, dohc, gtv, spider

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