Changing to an alloy head

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Printed on: 13 Sep 2024

Topic:

Topic author: Paul
Subject: Changing to an alloy head
Posted on: 15 Nov 2011 08:43:06
Message:

It has often been said that all it takes to convert an iron-headed engine to take an alloy head is to change the camshaft and I admit to being someone who went along with that. - Well it isn't true!

In the head there are kidney-shaped holes which match similar holes in the head gaskets and two round holes in the block.

During the discussion of the sandwich style gaskets with the iron head valve order (still not identified by the way) the following photo was posted on the French Sunbeam forum of a gasket for an alloy head on a block for an iron head:-


Photo © Clead. - Posted with permission.

As you can see, the gasket, which is for a 1,592cc and 1,724cc alloy head, masks two of the holes in the block which is from a Series II Rapier - a 1958 1,494cc block for an iron head. The two lower red arrows show where the masked holes are.

The owner of this car was having excess water loss and it turns out that a previous owner has fitted the Series II Rapier block, kept the Alpine head and changed the camshaft accordingly. I suspect that the leak of water was from those holes into the tappet chest as the gasket clamping pressure won't be so high in large areas as it is where the steel is folded around the edge of a hole and which makes the gasket thicker at those points.

My advice to him has been to drill and tap the two masked holes to take steel plugs and to drill two new holes to match the end of the kidney-shaped holes in the gasket.

It also occurs to me that if there is the extra hole by no.1 but not one in the gasket because Series III Rapier and (Series I Alpine) gaskets are no longer available, then that hole could cause a leak for the same reason and would need plugging as well.

Someone on the S.A.O.C. forum has now suggested that later blocks were the same for both iron and alloy heads which would make sense for economies of production.

Does anyone here have experience of this?

My Alpine won't float! I need one which does!!

Replies:

Reply author: 1922
Replied on: 16 Nov 2011 19:46:49
Message:

The 1972 parts book does not distinguish between the 1725 and 1500 block - they are the same part number.
Likewise only two head gaskets are listed, for aluminum head and for iron head, no mention of 1725 or 1500.

Is that an "arrow" type head gasket?
Maybe this is just a difference between "series" cars and "arrow" cars.

Reply author: Paul
Replied on: 16 Nov 2011 23:18:27
Message:

Yes, if you read my post carefully, you'll see that I'm referring to the 1,494cc block which is completely different from the 1,496cc block (which is the same as the 1,724cc block but fitted with a short throw crank etc.).

This is why it's sometimes very important not to just refer to a "1500".

My Alpine won't float! I need one which does!!

Reply author: 1922
Replied on: 17 Nov 2011 19:37:47
Message:

Yes that was clear - and I was only talking about the '67 onwards Hunter type engines where it certainly is possible to change from iron to alloy head because the blocks are all the same. This is why I used "1500" and "1725".

My point was that the head gasket looks very like a much later gasket - could it be part of the problem?
I stopped using that type of gasket years ago so I haven't got one to look at to compare.

Also the Alpine I was concurrent with the Series III Rapier. Might the problem be that is a Rapier II block and that the a Rapier III block would match the head?

Obviously this is just a theory - I'm no expert on series cars

Reply author: Paul
Replied on: 17 Nov 2011 22:46:50
Message:

Yes, you've inadvertently hit the problem that there is a vast difference between 1,494cc, 1,496cc (and 1,498cc!!) engines and that is why it is very important to be precise when discussing so-called "1500" engines in order to avoid this confusion. I was extremely careful not to say "1500".

The problem with head gaskets is that few people understand the difference between the early blocks made for iron heads, the similar era blocks made for alloy heads and later blocks which appear to be made for both heads and which don't have the water passage on the exhaust side of No.1 and, therefore, the differences between the gaskets and which ones are meant for them, which ones can be used with them and which ones cannot be used with them (without some modifications to the block).

Raising the matter of the 1,496cc engine, which is just a 1,724cc engine with a different crank and rods, is totally irrelevant and simply confusing the discussion in this case which is about 1,494cc and 1,592cc blocks and swapping their iron heads for alloy heads and the resulting problems with gaskets.

I believe I made it quite clear that the problem I was referring to involved the fitting of an alloy head to an early block intended for an iron head.

What you say about the Series I Alpine and the Series III Rapier is correct because from Series III onwards, the Rapier had an alloy head. What I have already explained is that the Series II Alpine in question has been fitted with a Series II Rapier block - a block intended for an iron head.

The whole point of the thread is that most people will be unaware that early blocks did not come in a universal version which took both heads but in different versions, one for iron heads and one for alloy heads and that you cannot simply plonk an alloy head on any old block and just change the camshaft. The additional point is that early blocks of both types also have an extra coolant passage which can result in leaks if a later gasket is fitted and that early gaskets (of at least the sandwich type) are obsolescent.

Maybe we can get back to discussing the conversion of 1,494cc and 1,592cc iron-headed blocks to alloy heads and ignore the irrelevant 1,496cc engines.

What would be helpful is some input as to when the blocks became universal rather than iron or alloy specific and when the extra coolant hole on the exhaust side of No.1 was deleted.

My Alpine won't float! I need one which does!!

Reply author: 1922
Replied on: 18 Nov 2011 20:42:26
Message:

From your reply it seems that I may have offended you, this was not my intention.

At the end of your first post you wrote “Someone on the S.A.O.C. forum has now suggested that later blocks were the same for both iron and alloy heads which would make sense for economies of production.

Does anyone here have experience of this?”

It seemed reasonable and relevant to answer your question about “later blocks” to the effect that yes this was true, there being only one block regardless of head by 1971 and presumably with the introduction of that engine(in 1496cc and 1725cc) in 1965 – even to the extent that same block was used for both capacities. This is something that I have experience of (this piece of information has been very useful in the past when hunting for Hunter/Rapier engine parts in breaker's yards).

That aside here is something that you might find interesting...
The part number for the engine block of the Rapier II and Rapier III is the same, 5220964 and they are both 1494cc. If the Rapier II has an iron head and the Rapier III an alloy head and they use the same block then it follows that the alloy heads and iron heads can be interchanged on the 1494 engines, including the Alpine I.

The Alpine II was introduced in 1960 with the 1592cc engine and the Rapier IIIa got this engine in 1961. I suspect that all 1592 blocks might be the same but I don't have the part numbers for the 1592 Minx engine (iron head of course) to verify this.

If the heads can be swapped among 1494 engines and the same is true of the 1725/1496 family of engines then it seems likely that heads can be interchanged between the 1592 family of engines.

I'm just trying to be helpful...

Reply author: Paul
Replied on: 19 Nov 2011 03:09:53
Message:

The Series I Alpine block (1,494cc - alloy head) is 5220097 superseded by 5220450.

The Series II - IV Alpine block (1,592cc - alloy head) is 5220339 superseded by 5220404 and superseded again by 5220965.

I don't know what 5220964 is but it doesn't appear in the '59-'68 Alpine parts list but from the appearance of 5220965 I would guess 5220964 superseded something earlier.

If you look at the gasket in the photo from the French club's forum which is a gasket for a 1,592cc, 1,724cc and 1,496cc engine with an alloy head and no hole by No.1 and which doesn't mate with an original Series II Rapier block and compare it with a gasket for a Series I Alpine and Series III Rapier which are both 1,494cc engines with alloy heads and with the hole by No.1 :- you can see that the kidney shaped holes are identical. This means that the Series III Rapier (and Series I Alpine) gasket also doesn't match that Series II Rapier block and that means that the original Series II Rapier block is different from the Series III Rapier block.

I suspect that the part number you have is not for the original Series II Rapier block or even for the early Series III Rapier block but for later Series III IIIa or IV Rapier blocks which were fitted with alloy heads but would also mate with a Series II iron head and was therefore also the part which superseded the original Series II Rapier block which wouldn't take an alloy head.

Could you post the full sequence of part numbers for the cylinder blocks for Series II, III, IIIa and IV Rapiers please? I'll dig out the Alpine Marine Parts List and see what that lists. (Sadly, I don't have the Minx or Gazelle Parts Lists either.)

My Alpine won't float! I need one which does!!

Reply author: Paul
Replied on: 19 Nov 2011 12:19:30
Message:

quote:

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Originally posted by Paul

. . . . . . . there is a vast difference between 1,494cc, 1,496cc (and 1,498cc!!) engines and that is why it is very important to be precise when discussing so-called "1500" engines in order to avoid this confusion.

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My Alpine won't float! I need one which does!!

Reply author: 1922
Replied on: 19 Nov 2011 18:59:37
Message:

Information from Parts List "Sunbeam Rapier Series I-V" Part No 6601222, subtitled Sunbeam Rapier Series I, II, III, IIIA, IV & V.
I've also included part numbers for head gaskets in case you have something to match them to.

Rapier I, II, III block


The head gasket is listed as P.103887 superseded by P.114478 for Rapier I and II.
The head gasket for the Series III is 1201091.

Rapier IIIa & IV


Head gasket is "1206899 superseded by 1214624" up to engine B3062664, then "1214624". This coincides with a cylinder head change from "5220474" to "5220609 superseded by 5220806".

I don't know of the publication date of the parts list but it must 1965 or later because it includes the Rapier V with the 1725 engine.
Also it has one more "superseded by" number for the 1494 block than your '68 Alpine list this probably means it is later than your book.

You can see that the numbers you quote for the Alpine I "5220097" and "5220450" are both there, and both superseded by "5220964".

The numbers for the Rapier IIIa and IV match your numbers for the Alpine II-IV.

The Rapier I-III (1494) and the Rapier IIIa (1592) never have the same number. So the 1494 and 1592 blocks must always have had physical differences - it is more than just the bore size as the crankshaft part numbers do not match even though the stroke is the same (76.2mm).

If there is a change to the 1494 block to accept the new alloy head then it seems likely that it happens with the "5220097" block which is the first Alpine block number that you list. Though whether this is during the production of the Rapier II or at the point that the Rapier II becomes the Rapier III we cannot tell.

Not sure there is anything conclusive here so far, except that trying to fit a 1592 head, regardless of whether it's iron or alloy, on to a 1494 block is not something the factory ever expected someone to try!

Reply author: Paul
Replied on: 20 Nov 2011 10:00:53
Message:

That's extremely helpful - thank-you.

Firstly, I can explain the difference in the crankshaft numbers between the 1,494cc engines and the 1,592cc engines. It's down to a change in the big end diameter from 1 7/8" to 2" (nominal).

My Parts List is the final bound edition (with no coloured stripe) of 6600992 "Sunbeam Alpine Series I-V" and my copy dates from the early to mid 1970s but I do know from buying parts at Barlby Road that many numbers were still being superseded way after Rootes had finalised the Parts List. There are reproductions available which can be identified by the grey stripe down the pages which shows that they were produced using a loose-leaf version as a basis although I believe that they still have the final version. Anyway, your Rapier Parts List appears to have later updates so was probably finalised later or Rootes stopped updating the Alpine Parts List earlier. - Rather odd because the Alpine was still being manufactured in '68 whereas the Series V Rapier was discontinued in June '67.

My Alpine Marine Parts List is 6601120 dated April 1964 and covers engines numbered from RM.10001 which is a 1,592cc unit. I believe a 1,494cc unit was advertised but may not have been sold as such. Up to engine number RM.10037 the specification matches the Series II Sunbeam Alpine and from engine number RM.10038, it matches the Series III. I don't know if Rootes ever produced a later version of that Parts List but here are the relevant numbers:-

Cylinder block - 5220404, head - 5220609, gasket - 1214624. So no additional useful information there.

The cylinder head numbers you have, 5220474, 5220609 and 5220806 also appear in the Alpine Parts List and all have the 3/8" threads in the manifold face but there's an earlier head, 5220137, which has 5/16" threads and was used on the 1,494cc block and the early 1,592cc block up to Series II Alpine B9104228 which was built between the 3rd and 7th of April 1961. So the alloy heads were identical on both the 1,494cc alloy headed engines and the early 1,592cc alloy headed engines and the only later change (apart from Harringtons (head part number 5220630) and Holbays) was the beefing up of the manifold threads so all alloy heads are basically interchangeable but some 1,494cc blocks won't take them. This means that Data Sheet 2A/342 might have the answer as to which 1,494cc blocks will take an alloy head.

Anyway, your very helpful information clears up what 5220964 was and identifies an earlier change to the 1,494cc block! Many thanks.

So far then, to summarise, you appear to be able to fit an alloy head to any 1,592cc and 1,724cc/1,496cc iron headed engine by changing the camshaft to match but you can only fit one to some 1,494cc blocks without modifying the waterways and I would totally agree with your theory that P.48842 is the block which only takes an iron head and 5220097 is the first block which takes both. and we so far have no way of telling a P.48842 block from a 5220097 or later block without removing the old iron head.

My Alpine won't float! I need one which does!!

Reply author: 1922
Replied on: 20 Nov 2011 11:48:55
Message:

Hurrah!

I do wish they hadn't abandoned the OHC Singer engine, this might have led on great things such as an twin cam engine for the Alpine or a "Holbay 16v Twin Cam" for the Rapier

My Rapier I-V Parts List is very similar in appearance to my "HUNTER RANGE 1971-1972" Parts List 76601712. Something about the style of the print gives the impression of it being a little older, and the part number is lower. This might make the Rapier I-V Parts List pre '72.

Here it is:



Great stuff, mystery solved. But I still don't much like the idea of putting a 1494 block where a 1592 should be - even if it can, sometimes, be done. But certainly useful information if you are hunting for a replacement block for 1494 Alpine I or Rapier III.
I wonder if the Rootes Archive centre have a copy of that data sheet "Data 2A/342".

Reply author: Paul
Replied on: 20 Nov 2011 15:43:33
Message:

quote:

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Originally posted by 1922

I do wish they hadn't abandoned the OHC Singer engine, this might have led on great things such as an twin cam engine for the Alpine or a "Holbay 16v Twin Cam" for the Rapier

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My Alpine won't float! I need one which does!!

Reply author: turbinecol
Replied on: 21 Nov 2011 22:25:24
Message:

Great marathon post guys, but what a total nightmare as well to figure out!!

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