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Depends on what you want, what you need, and what you can afford. The 9.1 set is out there because most 1600 heads have been milled, and many owners do not know how much. As such actual compression may not end up as 9.1.
Both Webb and JE have offerings up to 12 to one. Pump fuel won't work for those, but, if you know your head height, and combustion chamber volume, you can have them made up any way you wish. A set from Spruell is a little more money than a P & L set.
 

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Discussion Starter #3 (Edited)
Exactly. I would hate to shave a nice original head if not necessary.

Is there no in-between stock and race piston?

I have the original 1600 engine sitting in my garage. The one in the car was from a '67 Super. It's been in the car since probably the early 80's.

I would like sometime (after reading about it all these years and doing heads etc) to learn to rebuild an engine from scratch and do it right. As part of the exercise, why not improve the breathing and make a stock but quick street-only car? My Duetto is a nearly original 3-owner car, so I won't be dropping in a 2 liter or that sort of thing - I like the way a 1600 drives.

EDIT - I just found these at Spruell. Bored out liners, 1690cc, 10.5:1...
http://www.spruellmotorsport.com/piston-liner-81mm-1600-1700-p-3902.html
 

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If you send your old liners you save some $. This isn't to crazy at 10.5 and is probably exactly what you are looking for.
 

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A lot depends on the head, cams, ignition and Weber tune. I run higher than that on pump gas (BP Premium) in 1600's without problems.
 

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Just asking what u intend to achieve with higher compression pistons? I know tha u may see a little increase in power but r u really going to get that much per cost power? When u start to increase the compression over about 10, thing start getting more challenging as well. Might be more cost effective to put a 2.o liter engine easier to get most all perf parts and save your 1600 for when u wish to return to stock. Please forgive me if I have offended you , Good luck
 

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Discussion Starter #8 (Edited)
Not at all, good point. The cost per HP is probably not that great.

My thought is, if you were going to buy new P&Ls anyway to rebuild, why is it we're stuck with 9.1:1 pistons. Even the Motronic 2 liters had 10:1. I think something around 9.5 to 10:1 would make a nice street engine.

I don't want to lose low end drivability either.

I have two good heads - is it considered excessive to mill the head down to get that kind of compression? Would there be valve clearance or timing chain issues?
 

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An interesting modification. Increases the bore from the stock 1600's 78mm to 81mm. My calculator shows that this would push the displacement to 1690cc (note that the stock "1600" engine displaces 1567cc). I wonder how thin the liners become at their bases with 1.5mm taken off the walls?

Installing 1750 pistons in a 1600 requires a 2mm overbore (from 78 to 80mm) - the resulting displacement is 1649. I'm sure the Spruell kit is more sophisticated, but acquiring 1750 pistons plus boring the 1600 liners can be done for less than $950.
 

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I would not mill a stock 1600 head. Good spares for the 1600 are are more difficult to come by these days and tend to command a price outside of my "fun budget", especially when 2 liter parts are so plentiful and relatively inexpensive. I play with the Spiders and preserve the Sprint.

You can certainly mill the head to achieve the slight increases in CR you propose. There would not be a timing chain issue and I doubt you would have any valve interference at 10:1 using stock pistons. Gordon and others can provide a more authoritative answer.
 

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Hi Jay & Mark,
For street use 80 mm bores in 1600's work pretty well. With pure race engines, I stay with 79 mm for just the reason you mention, skirts get very thin. Some report liner shift as related to thin skirts. I have never had this problem, but prefer 79 mm bores perhaps for security.
Any older Alfa head, no longer in production, is a bad candidate for milling to get compression increases. Pistons and liners are cheaper than no longer available heads. If you spend much time reading the BB posts, you will uncover sad stories from owners of 750 & 101 1300 heads, as well as GTA heads, that have been "milled-to-death". Some are no longer salvageable, others require serious over-bore to prevent the intake valve being shielded by the edge of the liner. There was just such a GTA head for sale on e-bay last week, at a fair price. The catch was, it required a 1750 engine with a bore greater than 80 mm's for the head to work properly.
As I have said before, the older Alfa heads should only be made FLAT by one skilled at flattening aluminum heads with a hydraulic press. NOT MILLING. Pistons and liners can be secured that will give desired compression without altering a non replaceable casting.
Paul Spruell can easily modify the 10.5 pistons in 78, 79, or 80 mm to give ANY COMPRESSION you wish. For street use, a 1600 with an 80 mm bore is just fine. Depending on your normal operating altitude, 9.7 to 10.5 is reasonable compression, assuming you will run premium fuel. Increases in bore and compression will result in power increases, along with increased, low end torque. IF the engine is to be rebuilt, as a street engine, pistons and liners other than "standard" have little downside.
This is my opinion from my experience.
My two "1600 engines" are a GTA engine with a 79 mm bore and about 10.7 to one compression, and an Ausca race "test" engine with a 79 mm bore and 10.5 compression.
 

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Discussion Starter #12
OK, the head stays stock thickness - you've reinforced my vague recollections of previous advice.

I very much appreciate your experience and advice here, as well as in past posts I've read. Thanks also to other posters.

I asked essentially the same question over on the Spider forum where maybe more eyes are watching. Someone brought up 9.7:1 101 forged Veloce pistons. The P&Ls fit a 105 1600, but are of course no longer available. Another Holy Grail motor part.

So, Spruell would take the overbore 10.5:1 piston and cut off some of the dome thickness in order to drop the CR? There's enough meat there to do that? Are they heavy to begin with?

Second question - How would you decide on a point between 10.5: and 10:1? (or 9.7: for that matter) It really does need to be a tractable, reliable, long-term but fun engine. I'm not selling it. I use premium anyway and it got hardened valve seats when leaded gas went away. I suppose this is all leading to cams and porting and jetting next.

Oh...third question...can anyone join TCAI, or is it a closed, one-member kind of thing?

Thanks -
 

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The forged JE pistons have plenty of material for modifications, intentionally. They are not overly heavy, and are designed to last for more than one rebuild. For racing use, they can be lightened further, but for street use, this is not necessary.
As far as a decision on compression, you need to consider if you may wish other modifications in the future. Paul feels 10.5 is a trouble free ratio. I would agree, but this becomes an individual choice. A customer has just completed a custom 1600 using a 79 mm bore and 9.7 ratio for his street engine. He will have no problems.
There are plenty of us as members of TCAI. If you work on Italian cars, membership is assured. Contact AlfaVeloce (Larry) on the BB for information.
 

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Discussion Starter #14 (Edited)
There are plenty of us as members of TCAI. If you work on Italian cars, membership is assured.
It appears, then, that I am way behind in my dues payments...

I had an interesting conversation today with Wes Ingram about unnecessary align boring of blocks and how it moves the crank up, which messes with the lower chain tension and sometimes alignment of the input shaft at the transmission. Very very rarely needed.

Where do I measure my extra head to see if or how much it has been milled? Your comment made me wonder if the head's been milled, then you install 10.5:1 pistons and end up with a slightly higher CR.

Thanks -
 

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Wes knows how easy it is for a well intentioned machinist, unfamiliar with Alfa blocks to ruin those as well. Like Alfa heads, most blocks will be straight, with a flat head and good crankshaft. Exceptions are when main caps have been swapped, but it it easy to make one cap match the rest of a block!
Heads are measured as pictured by the red and blue lines with arrows on this 105 1300 Jr head. Forget my numbers here, they pertain to this head only. As it is, this one measures 112.26 mm, the blue (safe) line. It needed some minor repair and I wrote in red, it's minimum allowable height for my application, which was 110 mm. Less and it would not be a good choice. This measurement is a little different for different heads.
If the head was milled by a machinist who does not know Alfa heads, it can have the combustion chamber face possibly milled ****eyed across ANY axis. This is NOT FUN to try to correct, and the correction can leave the head at less than minimum height. In other words, "flat" is NOT good enough. Particularly if it is ****eyed, or cams won't turn!
The 105, 1300 head pictured turned out to be a very good one. For the price I paid on e-bay, I was ... LUCKY!
 

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Sorry to get a bit off topic, but:

unnecessary align boring of blocks and how it moves the crank up
There is two commonly used methods: Align (or line) Honing and line boring. I used to work in an engine shop and have line bored a few blocks. With both, the cap is closed down (machined).

With honing, a whopping big hone is used to open out the main tunnel to the correct size. If the caps require 1 mm to be machined off the mating surface to correct the defect, the crank will move up about .5 mm when the honing takes place as equal amounts are removed from both the caps and block.

With boring, the boring bar axis is set to the axis of block tunnel, plus a poofteenth (machine shop technical term) more to ensure that the last cut will -just- clean up the block tunnel. The bulk of the material comes out of the caps.

Line BORING is far superior!

But unless you have a particularly valuable block, not really worth the effort once you have had a failure.
 

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Upping compression / line boring

I agree with the comments re line boring. The material should come from the caps. (see for sale section)
However I strongly disagree with Gordon`s position on milling the heads.
These heads can be milled quite a bit (up to .080) and be perfectly usable.
Building with off the shelf pistons/liners and shaving the heads to up the compression makes far more sense (cents as well) as cost for custom pistons/liners being bored/rings are further complicated on rebuild if parts (pistons/liners/rings) are needed. As well the small increases resulting from boring these little motors is not productive in cost/HP output.
On top of the equation is the fact that the high dome pistons interfere with and slow flame propagation in the combustion chamber. Only applicable in reality to pure race motors.

Buy a set of standard 9.0 pistons & liners shave the head .040 (1mm) and you will have a fun daily driver. 10 to one and will run on mid grade fuel.
Process is even better on the 2 Liter where both 10.0 & 10.4 pistons are available to build with.

Outside perhaps the 750 series, these heads are hardly "collectables" or "scarce" and what is your car really for, driving and enjoying, or sitting and ("appreciating" (IE: rusting:p )
 

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Discussion Starter #18
Thanks all. I will do some measuring and see what I've got.

Then I'll open my wallet and do some measuring and see what I've got. It won't be pretty.
 

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Head Gasket

Do you use the standard 1600 head gasket when increasing the bore and piston size on the 1600 liner?
 

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You can, up to a point. 79 mm bore works fine with 1600 Reinz, but 80 mm sometimes might be better served with a 1750 Reinz gasket. You might check though, perhaps both gaskets are the same bore now. I have several different ones I choose from that are NOT current production. The fire ring should not be at the very edge of the bored liner or hang over the edge. The ring needs to have as much of the metal contact area on the upper liner surface as possible. If the liner top surface has a groove cut for a better seal, the rolled edge of the fire ring should be between that groove and the bore.
 
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