Will A 1750 head bolt right on a 1600 engine?
If so would you use a 1750 head gasket?
If so would you use a 1750 head gasket?
xxxxxxxxdoulikecars
1750 head on 1600 engine
I rebuilt my 1600 about 12 yrs. ago not realizing until much later that it had a 1750 head. Used the 1600 gasket set. I've put about 35K on it since. Leaks like a sieve (for other reasons) but runs like stink.
Bill Sinclair
67 Duetto
69 Berlina (project)
73 Berlina (for sale)
73 GTV basket case
I rebuilt my 1600 about 12 yrs. ago not realizing until much later that it had a 1750 head. Used the 1600 gasket set. I've put about 35K on it since. Leaks like a sieve (for other reasons) but runs like stink.
Bill Sinclair
67 Duetto
69 Berlina (project)
73 Berlina (for sale)
73 GTV basket case
It should work out fine. I did do that to one engine when I couldn't find a good 1600 head. Valve size is the same. I could only find very minor differences in the chambers and figured it couln't make much difference in compression. 1750 head has nice small ports. 1750 uses 12mm studs, 1600 11mm, so the stud holes are bigger but that shouldn't be a problem. Use a 1600 HG for a 1600, I think the 1750 one is on the edge of too big for a 1600. The 1750 one is 1 or 2mm larger in diameter than the 1600 one.
Difficulties in building a 1650
I am building a "1650" engine. What's that you ask? Well, it is a 1600 crank + 1750 pistons, which produces around 1650cc of displacement. Why am I doing that? Well, right now, I'm wondering too! Read on...
I used a 1600cc head, and a 1750 head gasket, as the bores are now 1750 sized (80 mm - I had my machine shop bore out my 1600cc liners). I had a little trouble re-assembling it, as the piston-head clearance wasn't sufficient (my machinist advised .040" minimum). I had to chamfer the edges of the combustion chambers where they meet the head-block surface on the underside of the head. The interference was greater at the rears of cyl #1 & 2, and at the fronts of #3 & 4, since Alfa heads have the combustion chambers at wider centers than the cylinders (weird, I know).
Anyhow, when I got it back together, I was a bit worried about having too high a compression ratio - after, all, the 1750 pistons are 5.2% greater in area, so they will displace a proportionately greater volume. However, when I measured the compression, all four cylinders were way too LOW. Like 50psi. Upon looking at my old 1600 pistons, I see they have a fairly high dome, while the 1750's have a shallow dome.
I know, low compression could be caused by a variety of things. However, I doubt all 4 cylinders would be equally low if the problem was a leak in the new headgasket, or an improperly ground valve seat, or ...
So, it would seem that going with a 1750 head would be the simplest solution. Anyone have one laying around? Would like to get the cam caps, but could use the valves (and of course cams) from my existing 1600 head.
Thanks
Jay Mackro
San Juan Capistrano, CA
I am building a "1650" engine. What's that you ask? Well, it is a 1600 crank + 1750 pistons, which produces around 1650cc of displacement. Why am I doing that? Well, right now, I'm wondering too! Read on...
I used a 1600cc head, and a 1750 head gasket, as the bores are now 1750 sized (80 mm - I had my machine shop bore out my 1600cc liners). I had a little trouble re-assembling it, as the piston-head clearance wasn't sufficient (my machinist advised .040" minimum). I had to chamfer the edges of the combustion chambers where they meet the head-block surface on the underside of the head. The interference was greater at the rears of cyl #1 & 2, and at the fronts of #3 & 4, since Alfa heads have the combustion chambers at wider centers than the cylinders (weird, I know).
Anyhow, when I got it back together, I was a bit worried about having too high a compression ratio - after, all, the 1750 pistons are 5.2% greater in area, so they will displace a proportionately greater volume. However, when I measured the compression, all four cylinders were way too LOW. Like 50psi. Upon looking at my old 1600 pistons, I see they have a fairly high dome, while the 1750's have a shallow dome.
I know, low compression could be caused by a variety of things. However, I doubt all 4 cylinders would be equally low if the problem was a leak in the new headgasket, or an improperly ground valve seat, or ...
So, it would seem that going with a 1750 head would be the simplest solution. Anyone have one laying around? Would like to get the cam caps, but could use the valves (and of course cams) from my existing 1600 head.
Thanks
Jay Mackro
San Juan Capistrano, CA
Of course you would end up with much lower CR !!! You used a 1750 head which is made for 9,5:1 but you decreased the stroke from 88,5 to 82mm !! What you should TRY to do, is use the 1600 head suitably modified so the pistons fit, and obtain the safety clearance of 0,060". I don't know what the resulting CR would be, but its worth a quick try, since valve sizes are the same. (I don't even know if this will work, I've never encountered it before).
No I don't, but the 1750 head has a larger diameter at the gasket surface. Since valve sizes are the same, I think the 1600 head could have better squish characteristics when used with 1750 pistons. Its an interesting combination. As far as cc'ing goes, if you have both heads with valves, its very simple to use a flat glass/clear plastic plate with a hole, to measure head volumes. These are NOT combustion chamber volumes however. For those, you must bolt the head (with gasket) on and measure the volume with the piston at TDC. Then, you can easily do the math for the resulting CR.
Head volumn for 1600/1750
I have measured the chamber volumn for the average 1600 head to be 75cc, and for the 1779 head to be 79cc. Everything else appears to be identical between the two heads. Just the roof of the chamber is lower in the 1600 head to get the reduced volumn.
One thing I have found is that the pistons in the 1600 engine do not come to the top of the liners, they are .010 to .015" down. That must be why the Compitition Advisory Book has the block and liners milled down .010" to prepare a 1600cc engine for racing. The pistons recessed do more to lower a compression ratio than anything else. (Everything else being equal, bore/stroke, etc).
Also there appears to two 1779 pistons for the US cars, one for the early 1969 cars with an advertised CR of 9.5:1, and later pistons with a lower dome for the 9:1 CR.
Incidentially, every engine that I have measured has a lower compression ratio than advertised.
I have measured the chamber volumn for the average 1600 head to be 75cc, and for the 1779 head to be 79cc. Everything else appears to be identical between the two heads. Just the roof of the chamber is lower in the 1600 head to get the reduced volumn.
One thing I have found is that the pistons in the 1600 engine do not come to the top of the liners, they are .010 to .015" down. That must be why the Compitition Advisory Book has the block and liners milled down .010" to prepare a 1600cc engine for racing. The pistons recessed do more to lower a compression ratio than anything else. (Everything else being equal, bore/stroke, etc).
Also there appears to two 1779 pistons for the US cars, one for the early 1969 cars with an advertised CR of 9.5:1, and later pistons with a lower dome for the 9:1 CR.
Incidentially, every engine that I have measured has a lower compression ratio than advertised.
Interesting. I'm the guy who replied above about the 1600 engine that I rebuilt 12 yrs. ago w/a 1750 head. So I guess I've been running with a lower than stock CR. Would this account for the fact that I can run this engine on 87 octane with no pinging?George Willet said:
Bill Sinclair
Long time since last update to this thread so here goes. I've just discovered my "1600" Junior actually has a 1750 head. (triangle stamped on engine) I'm pretty sure the block is 1600 from the distance between water pump & gasket.
I can't decipher the engine number: AR01600*020624, I've looked but can't work it out- if anyone else can I'd be grateful.
I always thought the 1600 in the number gave it away, but now I think it's just a coincidence.
Quite happy with how she runs-(obviously faster now I know it's 1750! ) but is there anything else I should be aware of ? Settings, gaps etc.
(I know about the lower compression) Everything I've done so far has been assuming it's a 1600.
Thanks.
I can't decipher the engine number: AR01600*020624, I've looked but can't work it out- if anyone else can I'd be grateful.
I always thought the 1600 in the number gave it away, but now I think it's just a coincidence.
Quite happy with how she runs-(obviously faster now I know it's 1750! ) but is there anything else I should be aware of ? Settings, gaps etc.
(I know about the lower compression) Everything I've done so far has been assuming it's a 1600.
Thanks.
1600cc engine type AR01600 is shown to have been fitted to the 113 Giuliettas, 116 Nuova Giulietta and Alfetta GT in the early 1980s. There may be other fitments as well.
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