Modified Tappets

The valve clearence compensation problem on the intake side is solved by modified tappets. The bottom of the right tappet is machined on a lathe down to 6.60 mm thickness instead of 7.30 mm. Alfa 105 tappets (left) usually only have 3.25 mm.


The new tuning tappet (right) has 42 g. This is a 3 g saving over the original Alfa 105 tappet. Now valve clearing compensation with Alfa shims which are available from 1.50 to 3.50 mm thickness is possible in combination with reground camshafts. A good adress to find these tappets ist histo:tec in Germany or tuning shops supplying Volkwagen/Audi parts. So called "mechanical tappets" are available for VW Golf GTI or Audi 20V engines to replace the hydraulic ones to achieve higher revs. They must have a diameter of nearly 35 mm.

Valve-clearance Compensation

NACHTRAG:
DIESE ÄNDERUNG DER STÖßELBECHER WURDE SO NICHT VERBAUT. DER ALFA HAT NORMALE SERIENTEILE.

The new cam with smaller base circle requires a different valve clearence compensation at least on the intake side. The exhaust valves I use have 1 mm longer stems. Here adjusting the correct lash (0.45 mm) with normal Alfa shims is no problem.

J. Kartalamakis recommends to use regrounded Volkswagen Golf Shims (see next photo) or special custom made steel shims. Higher shims than 3.50 mm are reported to be available at Gozzoli in Italy .
In my special case I would need modified shims from 4.85 mm to 5.35 mm thickness.
My solution to that problem are modified tappets with a thicker bottom, see post above.

Intake Manifold Prolongation

Here you you can see the aluminum parts from histo:tec I use to prolong the intake manifold. This is a length of 40 mm. Parts are also available in 25 mm length. A longer intake manifold will produce more torque at a lower rpm range. This is to compensate toque loss below 3500 1/min due to the hot camshaft.
O-rings on both sides seal against the manifold and the Webers. The diameter is 40 mm (45 mm parts are available, too). Please check the necessary room in the engine compartment especially at Bertone GT cars with original air filter box. The carburetor support link and the throttle linkage must be prolonged, too.

High Lift Camshafts

Finally my new camshafts arrived from regrinding. CAMPRO did a good job to get the best benefit from the old Alfa 105480320051 cams. The new grinded base circle is 25,3 mm and they realized a maximum lift of 10,7 mm from the given cam profile.


Furthermore they did nitrating, straightening and polished the slide bearing areas. Clearance between the lobes and the head is ok.

Camshaft Profile

To get an improved 1600cc engine for street driving an adequate camschaft profile is necessary. I've chosen a pair of cams which is quite similar to the Alfa Grp. 1 cam part no. 115010320032. From different sources (original Alfa cam data, IAP, Kent Cams, Schleicher, J. Kartalamakis, Alfa Bulletin Board, Colombo & Bariani, etc.) I have chosen a cam with these data:

- max. lift 10,97 mm
- duration 286 deg @ 0,35 mm clearance
- 243 deg @ 0.05" clearance (for those who are Americans)
- 248 deg @ 1,0 mm clearance
- timing: 110 deg lobe center (on both inlet and outlet cam)
- max. valve opening overlap @ TDC 2,5 mm

To improve the profile I calculated the lobe geometry according to Benzingers Formula using smooth intersections between triangular mathematical spline formulas. These cams are regrinded from original Alfa 105480320051 camshafts by CAMPRO, Bochum/Germany. See http://www.campro-technologie.de.

Valve lift (black), speed (reed) and acceleration (blue)

Valve lift curve, calculated curve (blue), Grp. 1cam (magenta)

Valve timing chart (0 deg = TDC)

Cylinder Head Preparation - Part II

This is a view through the inlet port on the open intake valve before porting an polishing the inlet port. At 1600cc engines the valve guides are not much penetrating into the port. They needn't to be shortened nor machined.
The head is milled to a total heigt of 111.2 mm. As a consequence the diameter of the in-head combustion chamber is only 77 mm. It is 1 mm smaller compared to the engine bore of 78 mm. To avoid collision with the piston a chamfer is often recommended when milling the 1600cc head to achive high compression ratios. I measured the volume of the in-head combustion chambers to 63 cm³ each.


These are the new parts of the valve spring mechanism. You can see the inlet valve (bottom), the sodium filled exhaust valve, spring seat, shim, inner and outer valve spring, spring retainer and two valve keys.
As you can see, the valve keys at the outlet valve are different from the original Alfa inlet valve. They have three "rings" instead of one. I sourced them directly from TRW Automotive GmbH, Hauptstraße 10, D-31699 Beckedorf (TRW No. K8A090M0).

In addition to that there are a set of new valve guides, valve gaskets and valve seats with a three angle valve job (15/30/60 deg). To be continued ...

Air filter housing

I modified the intake system and put a new fine glossy black paint on the air box. All boreholes inside were enlarged to 14 mm diameter and a new K&N-Filter with lower air flow resistance is used.


The tube to the cylinder head cover is not mounted due to an oil catch tank on the exhaust side of the engine.

2nd @ Oldtimerausfahrt Bietigheim

I got another cup at SG Bietigheims weekend on Sunday 8th July 2007. I finished 2nd of 13 participants in the group 1971 - 1987. A late Ford Escort XR 3i was first - damned second-hand car.

Cylinder Head Preparation - Part I

I just started preparing my 1600 cc cylinder head. Stage one tuning consists of cleaning the head, milling -1 mm to increase compression ratio, 3-angle valve job (15/30/60 deg) and porting all air passages. New parts are

• intake and exhaust valve guides
• new valves, exhaust valves sodium filled
• new higher lift performance camshaft (286 deg, 11 mm lift)
  
• prologation of the intake port system
  

I gave the head to Theilacker machine shop. The work is done on this milling maschine. My Alfa head of course is much smaller than this Maybach head on the bench.


Theilacker has a long tradition as a maschine shop for large gasoline (Deutz) engines. In the early days they had a mobile replacement parts service for MWM engines. MWM is Motorenwerke Mannheim. They supplied for example farm tractor maufacturer like Fendt or Eicher.

Compression measurement

Recently I found this compression value sheet from 2001. The compression of each cylinder is between 12.75 and 13 bar measured with a MotorMeter gauge.

Road wheel power

The G-Tech measures horsepower though the formula:

vehicle speed * acceleration * weight of the vehicle = power at the wheels

The more accurate the vehicle weight is entered, the better the measurement will be. I asked the people from a local grain mill to use their scales and got 1145 kg with driver. The G-Tech deliveres rear wheel horsepower. This horsepower includes the loss of power through the drivetrain which is approximately 15%. Rear wheel horsepower is what most people are interested in because that is what they experience when driving. The use of flywheel horsepower measurement is often used in advertising, but not very realistic when it comes to accelerating the vehicle.


For more information about the G-Tech RR device see here: G-Tech-Home

A run consists of a straight on acceleration from stand-still to maximum rpm in second gear.

This is the result of an actual measurement after some work with MS Excel. The red line is the calculated torque at the driven wheels, derived from acceleration and weight.
The blue line is calculated wheel horsepower. The 1600cc DOHC engine with some modifications produces about 90 hp at the rear wheels. This means approximatily 108 hp at the flywheel.

There may be some uncertainties in this result because this is only one measurement. I have to make several measurements and then calculate mean values. This story will go on ...

Bicycle Speedometer

To get an information about average or maximum speed I included a digital speedometer Sigma BC 1200. For calibration it is necessary to input the exact wheel circumference which is also called wheel size factor. It can be measured on the car or it can be determined by the help of this table:

The sensor I use is a wheel sensor with magnet glued on the inner side of the rim. If a cardan-drive shaft sensor is used, the wheel circumference must be multiplied by 0.2195 to get the wheel size factor.

I calibrated the speedo with a GPS based navigation system. The correct wheel size factor for 195/60 R 15 tires is 1882 mm.

Digital instruments unfortunately are not always allowed in historic rallying and this particular one has not backlight function.

Alfa DOHC 1600cc engine at it's time

Engine power of the Alfa DOHC engine was not so bad - compared to other cars and makes at the beginning of the 1970s. The 1600cc double Weber carbureted engine was at the top of the line. Only fuel injected 4 cylinder engines offered slightly more power.

Engines with 1600 cm³ capacity (single carb., double carb. and fuel injection)

Front suspension

There are not much things to make better at the front suspension of an road going Alfa:

• Bilstein shocks
• Superflex Poly bushing between trailing arm and upper lateral arm
• Lemfoerder forged upper lateral link (# 032.311.003.501) with reinforced inner bushing (taken from lower A-arm)

Values for suspension alignment:

Toe-in: 0° 14' (positve toe-in, 3 mm distance between rims)
Camber: 0° 20' +/- 30'
Max. camber difference between left and right wheel: 0° 40'
Caster angle: 1° 30' +/- 30'
Max. caster angle difference between left and right wheel: 0° 20'
King-pin inclination: 8° 35'

Brake conversion

To upgrade and lighten the front brakes I've chosen a pair of Brembo 2-piston fixed calipers from the Alfa 75 1.8 turbo (1779 cm³, 110 kW) which was in production from Sept. 1986 until Feb. 1992. The calipers use exactly the same 48 mm piston diameter, so that the brake force distribution remains equal. But the area of the pads increased from 140 mm² to 201 mm². This should be ok to prevent excessive wear and fading.


A pair of new brake lines (intermediate tubes) had to be manufactured. M10x1 nut thead thread fits the brake hose (steel hose type, see below) and M10x1 screw thread is used for the saddle thread. The brake force diagramm of the GT junior shows that there is not so much difference between the original brake layout and the Brembo/Alfa 75 design.

Calculated brake force diagramm

New steel-flex brake lines from Dickhaut-Specials were used, too. Remember that the Brembo caliper has M10 x 1. The line length is 38 cm at the front and 40 cm at the rear.

Brake assembly in the car

The calipers are made for wider vented brake discs. so I had to open the caliper and remove two spacers - thats all. Brake disk is Brembo, too, matching the GT 1300/1600 (diameter 267 mm). It would be possible to use vented discs. If you like, have a look at the Alfa Montreal disk or at Audi 90 GTE discs. The brake force according to the german TÜV measurement is 220 daN per wheel.