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Discussion Starter · #21 ·
I agree with all the above, primarily that I should look into making a torque plate. I am switching machine shops as all the other shops here in the Carlsbad area seem to have closed, and my new machinist is not an Alfa guy. I will meet with him tomorrow and see how he wants to handle it. It is getting hard to find anyone who wants to do anything "hands-on" these days. I can't recall the last time I met a restoration shop owner who didn't have grey hair.
 

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Discussion Starter · #22 ·
Hi Koenraad,

Neat trick with the 10 mm spark plugs, I had never thought of it. I opted to use off-the-shelf parts on this build in an effort to keep the cost down. I used 1 mm oversize intake and exhaust valves with stock stem diameters so I could use stock guides, seals, retainers, locks, shims, etc. The 1 mm oversize valves fit on the stock valve seats as well. If the engine output on the dyno is disappointing when I am done, the first place I would turn to try to make more power is the head, but I hope it doesn't come to that.

FYI, my cylinder head man told me that he can get better flow out of a 1750 head than a 1600 head. I believe that Mike Sperry of Sperry Valve works told me the same thing 30 years ago. The guy I bought my used engine parts from told me I could have either one for the same price, so I picked the 1750 head. The better flow thing might just be an "old wives' tale", but I figure the chambers might be shaped better for matching up to my 80 mm bore.

Rob
 

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750 Sprints, Spider, 101 Sprint, Spider & Ti, 105 Sprint GT, 105 Juniors, others
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I put a 1600cc into my '60 Spider Normale, tweaked the head a bit by matching ports etc, my extremely talented engineering friend built me a 1600 Veloce branch for it, we sorted cams till we had a nice non-matched pair, a 1750 Euro 00548 on the intake and a 1600 Giulia Sprint GT 00502 on the exhaust, fitted twin Webers & a full Veloce intake system. The cams give it such a nice spread of mid range torque and it pulls like a steam locomotive. Owners of proper Giulia Spider Veloces are smiling as they've known this all along....

1300 is oiled & wrapped up under the bench.

Ciao
Greig
 

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Hi Koenraad,

Neat trick with the 10 mm spark plugs, I had never thought of it. I opted to use off-the-shelf parts on this build in an effort to keep the cost down. I used 1 mm oversize intake and exhaust valves with stock stem diameters so I could use stock guides, seals, retainers, locks, shims, etc. The 1 mm oversize valves fit on the stock valve seats as well. If the engine output on the dyno is disappointing when I am done, the first place I would turn to try to make more power is the head, but I hope it doesn't come to that.

FYI, my cylinder head man told me that he can get better flow out of a 1750 head than a 1600 head. I believe that Mike Sperry of Sperry Valve works told me the same thing 30 years ago. The guy I bought my used engine parts from told me I could have either one for the same price, so I picked the 1750 head. The better flow thing might just be an "old wives' tale", but I figure the chambers might be shaped better for matching up to my 80 mm bore.

Rob
I think you will find the 1600 and 1750 combustion chambers identical with the exception of a very small chamfer at the interface on the 1750.
 

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... The better flow thing might just be an "old wives' tale", but I figure the chambers might be shaped better for matching up to my 80 mm bore.
I checked Jim K. famous book... just before the inlet valves both heads can be enlarged to 37 (between valve and valve seat) and 39 mm (1) (valve seat). Just before the valve guide a 1600 head can or should (2) be enlarged to 34 mm, the 1750 head to 36 mm.

Jim K. advises to enlarge the intake manifold to 37 mm for the 1600 head and 40 mm for the 1750 head.

On the exhaust side, there are no differences.

(1): For a 2000 head this dimension is (only) 39,5 mm.
(2): The numbers indicated by Jim K. can be read in two ways: as in "should" (for ideal performance) or as in "this is the maximum possible", that's not clear to me.
 

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I think what you are doing is great and probably what I'd do if I still had my 750F. And talk about class, I mean what car has such an elegant petcock on the side of the block! It was things like that made me love Alfas even more.
 

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I am so happy that you and your wife enjoy driving a car from a simpler time. Most importantly a car that has a built in theft deterant...... a clutch pedal. 🤯🤣🤣👍
 

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Discussion Starter · #29 ·
Thanks everyone for your comments. I suppose that what I am trying to build is just a 1750 with a shorter block. As Ipalmer pointed out, I will end up with a 1750 with a less desirable rod length/stroke ratio, but it will fit under my hood. Everything is a tradeoff.

Thanks, Koenraad for the port dimensions. I was not aware of this book and will be interested to see how my port dimensions compare. Interesting that the dimensions are different for the 1600 and 1750, but I wonder whether that is due to casting differences or just an adjustment for larger displacement?

Rob
 

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Thanks, Koenraad for the port dimensions. I was not aware of this book and will be interested to see how my port dimensions compare. Interesting that the dimensions are different for the 1600 and 1750, but I wonder whether that is due to casting differences or just an adjustment for larger displacement?
It was Domenico Chirico, a long time Alfa engineer, who said in his book that the 1750 engine uses the same head as the 1600, so casting wise, I think they are the same.

The combustion chamber will probably have a trimmed edge to adapt the bigger bore.
 

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Discussion Starter · #32 ·
I will have to get my head down off the shelf and measure the ports to see how well they correspond to Jim K's book. I will also have to get a copy of the book.

I don't know if anyone noticed, but the blue Abnormale we discussed earlier in this thread sold for $80k on Bring a Trailer ($84k including commission). That makes me feel a little better about all the work I am putting in.
 

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Discussion Starter · #33 ·
There has been a delay on my project due to the lead time for pistons from CP. Winter is always the busy season for these guys as all the race teams are ordering parts to build engines for the next season, but this year it got really crazy. 14-16 week lead time for new pistons. All I have been able to do is modify my intake manifold, order some parts, and try to make sure everything is ready to go once I have my pistons in hand.

I am using an (I think) early 105 intake manifold, but I want it to look more like a 750 part. I ground off all the sharp corners to get a more rounded shape, welded up all the holes and ports I will not need, then prepped the whole surface to give it a uniform "cast" look. I also cut the ears off my head for fastening the front of the cam cover, then filled the notches with weld and gave it the cast treatment. You can still notice it from below, as in the photo, but when it is installed in the car it will look good with a 1600 cam cover on it.

The cams I am installing are 286 deg intake duration with 11.0 mm lift and 282 deg. exhaust duration with 10.5 mm lift. I got these from Jon Norman and he reported great results using them in a similar engine recently. I was originally thinking of bigger cams, but it is a street car after all.

I also looked up the build sheets and engine dyno sheets for a pair of 1750 engines I built years ago for the Carrera Panamericana. They were similar spec to the one I am building now (low compression, ported heads, 45 DCOE carbs) but with slightly bigger cams. I got 157 hp out of one and 154 out of the other at 7000 rpm, but with slightly better peak torque (129 ft lbs @ 6000 rpm). I think that makes my goal of 150 hp @ 6500 rpm for this motor realistic, hopefully with better low end torque than the Panamericana engines. Can't wait to find out.
 

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Discussion Starter · #34 ·
So, a big delay in getting my liners bored due to making a torque plate, but it is all done now. Just cleaned the block, liners, and oil passages this morning, so I am ready to start assembly. I bored out the block to feed oil directly to the #2 and #4 main bearings while I was at it, something I used to do on race engines. Not sure whether it makes any difference in a street car. Photo shows running a bristle brush through the block oil passages while flooding with solvent in the tank. Have to get out all the debris from the machine shop before assembly.

I know most of this is boring detail, but I found something ineresting in my dyno records while doing my research. When I was building those 1750s for the Carrera Panemerica, I tested out a camshaft change on the engine dyno. I think it was interesting because normally you have to give up low end torque to get top end power gains. In this case, I improved both, or at least I didn't lose anywhere. The engine started with 300 deg, 10.5 mm lift cams both intake and exhaust. Peak power was 152 bhp @ 6500 rpm, which I thought was quite good for a 1750 on 87 octane pump gas. I then changed just the intake cam to a 280 deg, 12.0 mm lift cam. Much of the Panamericana is run at high altitudes, up to 10k feet if I recall. I was trying to reduce overlap to improve mid range torque and close the intake valve earlier to help build compression in the thin air at altitude. By using a cam with shorter duration but greater lift, I got an increase in area under the lift vs. duration curve while also reducing duration. The results was 158 bhp @7000 with no significant loss in power lower down. I wasn't able to simulate high altitude on the engine dyno, but the driver reported much improved performance all around on the actual event. I thought this was a good example of how increasing cam lift improves performance everywhere.

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Discussion Starter · #35 ·
I finally have everything I need to continue my build in-hand, so I am starting to assemble my engine.
Just for review, my plan is to use a 1750 crank in a 1600 block along with an 80 mm bore to give me 1779 cc in a 1600 block. The crank drops in because all the bearing journals are identical, so that part is easy. I also want to use stock 1600 length connecting rods, so the only custom part I need to accomplish this are the pistons. There are no off-the-shelf pistons that are going to work for this, so I had to design my own. First thing I had to do was to figure the dimensions of all the parts I want to use. Rod length is easy, as I found that published several places as 148 mm. The next thing I needed was the crankshaft’s stroke, which was also easily found, of 88.5 mm. The dimension I could not find published anywhere is the 1600 block height, the distance between the crankshaft centerline and the top of the deck. I was able to calculate this by using a large set of calipers and measuring the distance from the top of the front main bearing saddle to the head gasket surface. I could then take that distance and add half the main bearing bore diameter, which gave me 222.5 mm. This seems a funny number, but compared to the published 1750 block height of 235 mm, it sounds about right. This means the 1600 block is 12.5 mm shorter than the 1750 block, almost exactly 0.5”.

Since I knew that I wanted the edge of the piston to be exactly level with the top of the liner at TDC, this gave me enough info to calculate the pin height or compression height of the piston. This is the distance from the centerline of the piston pin to the deck of the piston at its outer edge. I needed the compression height to be equal to the block height, minus half the stroke of the crank and the length of the con rod center-to-center. 222.5 mm – (88.5 mm/2) – 148 mm = 30.25 mm, which is the compression height I need.

The next thing the piston maker needs is the piston dome volume. First, I needed to choose the compression ratio I want. The number I always heard for hot Nord engines in the past was 9.7/1 if running on pump gas. I have been told by smart people that if you use the flatter dome of the later Motronic pistons you can tolerate 10.5/1 on pump gas (91 octane is the best we can get in CA). Not wanting to push it, I decided to shoot for 10.0/1. The first thing I needed to do was to measure the volume of the combustion chamber. My head was already assembled with all its new parts, so this was relatively straightforward. I sealed a flat plate with two holes drilled in it onto the bottom surface of the head with a thin film of grease, then used a burette to add ATF until it was full. This test showed the combustion chamber volume to be 75.0 cc. I used this number to calculate the volume I would need to fill with piston dome to get the 10.0/1 compression ratio I was looking for. This gave me a piston dome volume of 32.8 cc. I now had everything I needed to order the pistons. I told them I wanted 80.0 mm bore Alfa 1750 pistons with a 30.25 mm pin height, a 32.8 cc dome similar in design to the newer Motronic pistons, and I paid a little extra to have the underside of the dome machined to reduce weight. That gave me the last piece that I needed to place my piston order.

I now have pistons in my hands and bored liners to match. I will give an update when I get a little farther along. In the meantime, if someone wants more detail on the piston design, I would be happy to provide it.

Rob
 
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