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Discussion Starter · #1 ·
I have a 1956 750D Giulietta Spider that I have been restoring at home for a couple of years now. All the nasty, dirty work is pretty much done, and I am now getting into the fun part. The body shell is on a rotisserie at the paint shop getting finished up, and the rest of the car is in my garage in pieces. I have all the restored mechanical parts are on racks ready to be installed, all the hardware is plated and bagged, the chrome are done, and new rubber parts are all in a box waiting to go on. The car was all original, but I wanted something more fun to drive, so I am installing 4 wheel disc brakes, 5-speed close ratio trans, stiff springs and bar, Bilstein shocks, etc. I am keeping and restoring all the original parts so it can be converted back to stock is a later owner really wants to do it. I built a couple of Carrera Panamericana cars to this spec years ago, and they were a blast to drive.

The last part to this puzzle is the engine. I want more power, but I don't want the oil pan sticking out the bottom of the car like you have to do with bigger engines. My solution is to use a 1600, which will fit under the hood without too much tweaking, but bore and stroke it out to 1779cc. I am using a 1750 head as well. At the same time, I have installed 1 mm oversize valves in the head, mild porting, 45 DCOE carbs, big cams (high lift, short duration), lightened steel flywheel, etc. I have a 1750 crank, Mahle liners I will bore out to 80 mm, Crower rods to 1600 dimensions, and have just ordered a custom set of CP pistons to make it all work. I plan to run it on an engine dyno before installing it in the car, so I should be able to get a pretty good idea of how well this all works when it is finished. My goal is to get 150 hp with a tune mild enough for my wife to still drive the car to work and back (I forgot to mention this is her car).

Flow data for the cylinder head before and after big valves and port work is below. Basically a 15% increase in flow across the board.

Rectangle Slope Plot Font Parallel


Rob
 

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You can get plenty hp for the car with a 1600 or a 1750 without redesigning a 70 year old design. Spending money on the body suspension and having a good solid car is probably more reasonable than some of the things you have in mind. Enjoy the car for what it is. This is just my opinion and I wish you luck in which ever way you go and mostly to enjoy the awesome car.
 

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Discussion Starter · #3 ·
Hi Otteud,

A stock 1300 Normale is a fine car, but just a little more tame than we were looking for. I have had the opportunity to enjoy many Alfas during my time as a professional restorer, but this car is one my wife and I want to keep for ourselves as a weekend driver. It is certainly financial suicide on my part to do a full rotisserie restoration to concours standards, then spend a small fortune on modifying the drivetrain, but again, I plan to keep the car for a long time. Everything I have done can be easily undone by a future owner. It is all bolt in, except for the section I cut out of the tunnel to clear the later trans, and even then I saved the old piece and welded in a lip and threaded inserts so it can be screwed right back in.

Rob
 

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Hi Rob,
I once had a '67 GTV that was set up for mild autocross and time trials. After several years the 1600 motor got tired, so we decided to rebuilt it for more performance. I had a set of stock 1750 pistons, so we sent them and the 1600 liners to a local machine shop to bore them out. After fitting all the new rings and bearings etc., it fired right up and for years it ran great. More power, more fun. I eventually sold it and missed it so much that within a year a bought another '67 GTV which I still have.
Regarding the liners, initially I was concerned about the amount of material removed to fit the bigger pistons. I can report that I had no problems while she was mine, for over 10,000 miles.
Vic
 

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Discussion Starter · #5 ·
Thanks Vic, that's very useful information. I am a little nervous about a 2 mm overbore on the liners, but I have gotten several reports like yours that give me confidence it will work for a street car. I also bought Mahle liners, which I am told are a little stronger material than the Borgos, just for insurance.

Rob
 

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Any of the engines will easily handle a 1mm overbore. SCCA rules allow for it, and it is common practice to take the additional displacement. It isn’t unheard of to bore a 1750 to 82mm.
 

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The car was all original, but I wanted something more fun to drive, so I am installing 4 wheel disc brakes, 5-speed close ratio trans, stiff springs and bar, Bilstein shocks, etc. I am keeping and restoring all the original parts so it can be converted back to stock is a later owner really wants to do it. I built a couple of Carrera Panamericana cars to this spec years ago, and they were a blast to drive.

Obviously you know what you are doing. For some this will always be Alfa heresy but, back in the Portello days, there were all manner of tuned Alfas being run by Italian Alfa guys, factory and otherwise. What you are planning is thoroughly doable, I think, and promises to be tremendous fun. My friend Bob built two similar cars: a Sprint Coupe and a Spider. Both were much modified (full-tilt 2 liters which still had enough oem1300 hardware to look like stock Veloches) but still looked oem stock . . . unless you really knew what you were looking at. We took the Sprint Coupe on a Hill Country tour and the ride was electrifying. With your engine and those close-ratio gears you are going to have quite a ride. By all means keep us posted.
 

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Discussion Starter · #8 ·
Hi 180 Out,

The way I see it, I am just building the car Alfa, or at least Conrero, would have built in 1956 if they had access to the technology. I am using mostly original Alfa parts, admittedly from a decade later, but they all bolt into place. Similar to your friend Bob, I will be using a stock 750 Veloce airbox and filter, exhaust headers, yellow fuel line, etc. to keep it looking original.

Rob
 

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Discussion Starter · #10 ·
I just checked out the blue car on BAT; thanks for pointing it out. Seems it was incorrectly listed as a 750F Veloce initially and there have been a ton of posts about that. My guess is all that "noise" will depress the final selling price, so it might be a real bargain in the end. Sadly reinforces my opinion that what I am doing to my car is financial suicide. I think the blue car is not as nice as what I am going for, but if it is cheap enough, it could all be fixed. For example, I really hate the engine sticking so far out the bottom of the car, but I have an engine in process here that could fix that. I am sure I could find a convertible top frame without too much trouble.

Rob
 

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A good 750 top frame may be more difficult to find than you imagine. But I agree that making an “abnormale” from a normale is better than making an “abveloce”!
 

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The BaT car is .. as are most Giuliettas.. totally fair weather cars. I like the idea of no soft top...a PITA that has only usefulness for judging. The ****pit tonneau cover would be my choice with that kind of car. and a golf umbrella in the trunk and nearest gas station awning for a sudden outburst of rain. Can't say I ever needed my soft top
 

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....but I wanted something more fun to drive, so I am installing .... stiff springs and bar, Bilstein shocks, etc.
Be careful about installing truck suspension on so light a car as a Giulietta. Not only will it give you miserable ride quality, but I doubt it will cut your lap times much. I had KYB shocks on my 101 Giulia for awhile, and the feather-light rear end would just hop over bumps, rather than roll over them. You don't get much resistance to lateral forces when your tires are off the ground!

I built a couple of Carrera Panamericana cars to this spec years ago, and they were a blast to drive.
It sounds like you know what you are doing. But will use this latest Giulietta in events like the Panamericana?
 

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Discussion Starter · #14 ·
Hi Alfajay,

No more Panamericanas for me (I think I did four of them), but I did think that I might AutoX the car occasionally if I can get it away from my wife. To make a short story long, I did a bit of a study when I built the PanAm cars (we are talking 30 years ago). I bought several sets of aftermarket springs which I measured and compared against some stock Alfa springs I had in the shop. The results were:

Front spring rateFront free lengthRear spring rateRear free length
Stock 750 Giulietta Spider 170 lbs/in16"60 lbs/in17"
Stock Giulietta Sprint Zagato200 lbs/in15" 60 lbs/in15.4"
Alfa Ricambi Sport280 lbs/in14.4" 90 lbs/in13"
Ward and Deane Race410 lbs/in12.5" 115 lbs/in13.2"
John Norman Race560 lbs/in11.5" 150 lbs/in11.5"

For the first year we ran, I used the Ward and Dean racing springs (roughly double the stock spring rates). The car was great fun on smooth roads, but on the rough roads and huge speed bumps in the south of Mexico they were just too stiff. About halfway through the 10-day event the fuel tank strap mounts actually started to rip out of the trunk floor. We did very well (3rd place overall) but the next year we opted for the Alfa Ricambi sport springs (50% stiffer than stock), all with Spax gas shocks. The absolute grip limit of the car went down, but the driveability was improved. That car is still in road use today with the same springs, and it is remarkably nice to drive. Alfa Ricambi doesn't exist anymore, but I was able to purchase a set of springs with just about the same dimensions and rates, so I am hoping for a similar result.

As to the rear end hopping around, I never experienced that even with the Ward and Deane springs. I have had similar problems when I used KYB Sport shocks and some Bilsteins, so it may be that the KYB rates are just way too high. FYI, I misspoke when I said I was using Bilstein shocks on my car; I am actually using Konis. Hopefully they will work as well as the Spax shocks did back in the day.


Rob
 

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Uncle,
Regarding the Blue Giulietta on BAT, I first saw this car in a Monterey Week report by Centerline International. I think it must have been 4-5 years ago. I was immediately smitten! I love the color of both exterior and interior, though an under-dash photo seems to indicate it was originally red, but who cares.

I have to say that I really like the wrinkle finish on the dash of the 750 cars much more than the padded dash of the the 101 cars. Maybe harder to keep clean, but it's another who cares.

The rollover hoops do nothing for me, but I would buy this car today if I had the extra coin.
Ray
 
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Discussion Starter · #16 ·
I am hoping to get back to the engine build here. My plan is that this will end up being a relatively low-cost but high output build that still looks stock on casual inspection. I am getting ready to have the Mahle liners bored this week, so I am getting the crank ready to install once the block gets back and cleaned up.

Photos show the liner retainers I used to hold them all in place so the boring and honing can be done on a standard machine. There used to be a motorcycle shop in town with a fixture to hold single liners in place, but they are out of business.

Automotive tire Bumper Motor vehicle Automotive exterior Toolbox
Material property Font Drinkware Cylinder Electric blue


I also drilled extra oil passages to the #2 and #4 main bearing saddles, as I never liked Alfa's idea of only supplying oil to #1, 3, 5 main bearings and then relying on the crank passages to carry oil to the other two main bearings. I realize that Alfa built a zillion of these engines and didn't have a lot of trouble, but we all have our superstitions. I figure it does no harm. Crank journals and bearing bores were measured to determine bearing clearances, which are all right about 0.0015". I always use Plastigage during assembly just as a final check, but I admit this is probably unnecessary. Interesting that the Plastigage and measurements seem to agree very closely, but I still do both.

Motor vehicle Product Automotive tire Automotive exterior Camshaft
Automotive tire Rim Engineering Automotive wheel system Auto part
Finger Tool Rotary tool Metalworking hand tool Gas


One thing I always do that I am convinced makes a difference is removing the plugs out of the crank so that I can run bore cleaning brushes through all the passages. I am surprised at the junk that comes out of there. It seems the centrifugal forces during running force any particles in the oil to pile up against these plugs and collect there. The only way I can see to get them out is to remove the plugs. I drill out the stock plugs, then tap the holes for either 1/16" NPT taper plugs or M8 x 1.0 straight set screws; I have used both in the past. You need to use a new, good quality tap and be careful. The cranks are hardened and if you break off a tap you will have to get it EDMed out, which is expensive and tricky.

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I will post more photos when I get my block back from the machine shop and start assembly.

Rob
 

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... My solution is to use a 1600, which will fit under the hood without too much tweaking, but bore and stroke it out to 1779cc. I am using a 1750 head as well. At the same time, I have installed 1 mm oversize valves in the head,...
Is the 1750 head not the same as the 1600 head (intake valves are both 41 mm)?

Maybe it's too late but the LDS-trick could be a nice option, "install" 10 mm spark plugs in stead of 14 mm, this would make it possible to install bigger valves.

If bigger valves are really a bonus for a fast street car is an other discussion (at a certain moment Alfa Romeo reduced the inlet valve size of their 1600-engine for better drivability).
 

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Rob, I have no idea if it is really required. But the machine shop I have trusted for boring liners always does so using a torque plate. When I get them back, they are labeled 1-4, and I put them in that specific hole. He claims that is the only way to ensure that they are perfectly round.
 

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I've been thinking about the out-of-round liner problem. Gordon Raymond sends his liners to a Ferrari specialist machine shop which hones his liners rather than boring which almost always produces slightly out-of-round liners. We supply a torque-plate to our machine-shop which then does a good job of boring our liners.

I think a viable alternative is to hone liners, although this takes an industrial strength hone. When we rebuilt my hot rod 2 liter, the hones liners were 3 thousandths oversize. With Motronics and Hastings rings, every worked just fine.
 
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