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Post by **Zamani** » Fri Mar 04, 2005 10:55 am

Just curious, that means the 155 TS 8V had a different crank than the 75 TS? It seems that the bores are the same? If so, seems kind of dumb for Alfa to do that. Changing cranks just to go from 1962cc to 1995cc?

Mats · Post by **Mats** » Fri Mar 04, 2005 2:39 pm

1995cc is the Lampredi engine. Iron block and so on.

1962cc is the old hopped up Alfa mill

1970cc is the new Fiat/Alfa modular 16v engine (as in newer TS and JTS)

Post by **Zamani** » Fri Mar 04, 2005 5:34 pm

No. 1995cc is not Lampredi. Lampredi only went into the Q4. I'm talking about the 1995cc Nord in the 155 TS 8V and face lifted 164 TS 8V. The heads are different than the 75 TS and pre-face lifted 164 TS.

Maurizio · Post by **Maurizio** » Sat Mar 05, 2005 2:05 am

hmm, posted twice

Maurizio · Post by **Maurizio** » Sat Mar 05, 2005 2:09 am

old forum:

By Zamani on Unrecorded Date:

Bore X stroke
75 TS 84 x 88.5mm = 1962ccm
155 TS 84 x 90mm =1995ccm

I suspect a different crank and the heads must
have been revised. Some guy in the US
bought both heads and he confirmed that the
155 TS had a narrower angle head.

the 155's have the cast iron bottom end, heads are interchangeable. Here the Dutch trofeo like the 155 head over the 75 for it's better flow due to the narrower angle

Alfaross69 · Post by **Alfaross69** » Sat Mar 05, 2005 5:52 am

Maurizio wrote:Some quick math.....

Offset piston pin 1.75 mm
Skim piston crown 1.6 mm
And a 3mm 45 deg chamfer on the outside +
--------------------------------------------------------------
all together will added give 1:11.5

there is also some more material that can be lost, as there has to made some more valve relief (155 have the valves in a steaper angle) .

Maurizio,
I too am interested in a similar build up. How was CR of 11.5:1 determined?.
By observation and/or calculation?
Was this established from a previously done engine?.
Were the combustion chambers cc'ed and what is the typical volume for TS 75 head chamber and a 155 head chamber?(1st component of CR)
How was volume of piston above the block deck calculated (2nd component of CR) with a burette and a dam of known volume?

Just to clear up my confusion about the piston pin (height) relocation(offset?). I might assume that the pin is being raised higher on the piston (micke's numbers indicate it was lowered by .5 mm in relationship to ring lands/ you show 1.75mm, up or down?) to lower it in the bore to accomodate the longer rod length and you not wanting to remove all of that 4.7mm of extra height although some of that height is being used to bump up the CR.
You mention "rod bore offset", do you mean the hole in the rod bush will be bored offset up or down and not concentric with the rod end itself? please explain. Up is bad, down is better

I don't think you mean pin "offset" or "rod bore offset" do you mean maybe just pin height (relocation) specification? please explain how this will be done.

To me "pin offset " is normally the dimension of how far fore/aft of the vertical centerline of the piston the pin is. This move is to reduce thrust forces on long/ short ? stroke motors where rod angularity needs to be reduced?.

Also you mention "more that can be lost " or must be lost to accomodate steeper valve clearance. Was this extra gained volume calc'ed into CR.

You mentioned 155 pistons on the way ( EU purchase or US?), will you rework pistons or custom order similar to the Arias with spec's all provided by manufacturer with no additional work. What is cost of stock 155 piston set with additional work performed versus custom pistons. Which brand are you purchasing. What kind of numbers made you decide the way to go?

Ross

Maurizio · Post by **Maurizio** » Sat Mar 05, 2005 10:58 am

Ross,

first of all this engine has never been built (at least I know off).

I have never rebuilt an engine , but when you start, you got do it right.
I have found a machine shop chef who is very willing to help on my wild plan. (and who has a weakness for alfa's, he owned a 1300 gtv which revved 9000 rpm all the time

)

Piston pin offset I meant the hole in the rod. (down)

CR calculation was done theoretical
So combustion camber volume would be (stroke x bore) / 10 on a standard engine.
To get 1:11.5, the piston has to move up 1.35 mm in the combustion chamber.

Valve relief has to be altered due to the different valve angle of 155 and 75.

The machine shop ordered a standard 155 piston to see what we can do. (I'm from the EU) This would then be reworked to go into my engine

more to come..... It is at the moment just an idea

Maurizio · Post by **Maurizio** » Wed Mar 09, 2005 4:47 am

Zamani wrote:Just curious, that means the 155 TS 8V had a different crank than the 75 TS? It seems that the bores are the same? If so, seems kind of dumb for Alfa to do that. Changing cranks just to go from 1962cc to 1995cc?

liners are the same from a 155 TS 8v, 164 TS and the 75 TS

Maurizio · Post by **Maurizio** » Sat Mar 26, 2005 10:07 am

Who can tell me the exact length of a TS or 2.0 Nord conrod from center crank to center piston pin?

Jim K · Post by **Jim K** » Sat Mar 26, 2005 11:49 am

Nord rod: 156,950/157,050mm (from AR shop manual)
The TS length is not specified in the official literature, but is a little shorter if I remember right. MATS...HELP !!!

(HE knows!)
Jim K.

Micke · Post by **Micke** » Sat Mar 26, 2005 12:30 pm

TS is exactly about 156.0 mm

Maurizio · Post by **Maurizio** » Sun Mar 27, 2005 1:31 pm

OK thanks, knew about the mm length difference, but will measure what is in my problem engine. There was slight exhaust valve/piston contact and I am looking for a cause. Timing was ~2 deg early but still should not be a cause for contact.

Mats · Post by **Mats** » Mon Mar 28, 2005 9:05 am

Like Micke says, 1mm shorter...

One sweet little millimeter. moahaha!

Maurizio · Post by **Maurizio** » Tue Mar 29, 2005 9:57 am

. Checked the rod and it is 156,02 mm. So where the "$&% does the piston\exhaust valve contact come from.

Removed the cams, put the head on its back and filled the combustion chamber up with some very thin oil. (measured cumbustion camber volume also) And after two days only one exhaust valve leaked a very small amount of oil into the exhaust port. Contact must be very marginal, not to bent a valve.

Is the exhaust timing that critical, is 2~3 deg early enough to let the valve hit a piston? Or do I have a head which is skimmed to much.

Jim K · Post by **Jim K** » Tue Mar 29, 2005 10:47 am

Maurizio, here's a very practical and reliable way to measure valve to piston clearance on an assembled engine: Bring to TDC overlap phase (both valves open) and wedge a flat-blade screwdriver between follower and cam body. Twist the screwdriver so as to push down the follower until the valve contacts the piston (still at TDC) and there you have it: valve to piston clearance! Do this for both valves and record. If you repeat after retorquing the head, you will see less clearance! I once went from 2,2mm down to 1,4 just by retorquing 3 times to 10,5kgm (2liter Nord). You are safe with at least 1,5mm intake and 2mm exhaust with good valve springs and no 8000rpm trips!!!
Jim K.