As I recall the roll pins were a desperate attemt to stop the oil leaks between the head and block that are notorious on Alfas. It's kinda a good fix but since there is no groove for the o ring to sit in and thus be pressed against it really doesn't take advantage of the sealing properties of an o ring. An o ring works because the pressure of the gas or liquid presses the o ring against the groove and sealing surfaces it sits against. Since there is no groove in the head or block the o ring is free to expand outwards and thus the sealing properties of the o ring are not fully utilitized. The pins were added to relieve some of the pressusre against the o ring and thus allow it to seal more effectivily.
The Norman items did NOT work for me--seems there was too much play in my oil passages and the o-rings were getting mangled by not being properly constrained at cyl head install/torquing--the culprit being that machined step. I've since "regressed" to the spiral wrapped pins as sold by Centerline--they work mighty fine. I recommend you DO NOT BUY the the split type--they will cut your o-rings.
Simple calculations will prove that the presence of the roll pins will not result in a pressure drop accross the head gasket.
When building serious engines, I tap the block to M6. Then get some short allen head grub screws and drill an orifice about 1 mm (.040" for those of you that don't speak in modern units) through the centre. I have even machined the top of the grubscrew to locate the O-ring a couple of times. Loctite (low strength) the grubscrew in place before assembly.
Ensure before assembly that you have not blocked the orifice with Loctite by blowing compressed air through the oil galleries.
The effect this has is to lower the oil pressure accross the head gasket (reducing the incidence of O-ring leaks). Therefore, reducing the flow to the top end (where the standard engine has more than enough supply), thus making more available to the bottom end (where it is really needed).
This technique, combined with cross drilling the block has resulted in no bearing failures in years of building Alfa race engines.
Of course, if the block has the roll pins in it, then this will be difficult. Good luck to you getting the hardened roll pins out.....
Since I am about to reinstall the head on my 1750, I figured I might ask if this applies to the 1750 engines? I didn't find any roll pins in the front of the engine, but 2 in the rear of the block. Are the 2 at the rear the ones in question, or should there be some on all the passages?
All six passages should have the roll pins or brass restrictors. And if you use the square cut Chevy valve stem seals, carefully seat them in the head gasket holes, place the headgasket down over the alignment dowels in the block, recheck the Orings are in place, then slowly lower the head down to the gasket surface, you won't have any more oil seepage from the head gasket area.
Hope this helps. Remember: the devil is in the details.
__________________
George Willet
willet@q.com 520-374-2220: please do not use PM, email me direct, saves us both time.
Note: I prefer to offer parts to the AlfaBB members first, and eBay second.
THESE are the good old days!
There are no easy answers to complex problems.
All six passages should have the roll pins or brass restrictors. And if you use the square cut Chevy valve stem seals, carefully seat them in the head gasket holes, place the headgasket down over the alignment dowels in the block, recheck the Orings are in place, then slowly lower the head down to the gasket surface, you won't have any more oil seepage from the head gasket area.
Hope this helps. Remember: the devil is in the details.
No roll pins, but I did exactly what you recommend. I made sure everything was in place before lowering it all the way down onto the block. I didn't have any leaks before, so hopefully it will remain the same.
I should find out either Monday evening or Tues, I'm racing the other car tomorrow so I won't be finishing the Alfa. I just need to install the radiator and battery.
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