Why 1725? (No, not a V6 issue)

[Jay Laifman]

I've always wondered what the relevance was of 1725. I assume my knowledge is incomplete. I thought that at the time, there were racing classes for 1600cc and 2000cc. So, the early Series had some chances in the 1600 class. But, then going to 1725 puts Alpines out of the 1600 class. Was there a class between 1600cc and 2000cc?

If not, why would Rootes pick an engine size that didn't match and completely blow out the "win on Sunday..." opportunities?

Must be a European racing class for something.

 

[husky drvr]

Jay,

Pure speculation on my part but I doubt Rootes had much to do with the choice. I am guessing that Chrysler had the most influence on the size chosen. I think somebody told the engineers to develop an engine that had the most displacement for the least money to develop and build. I am not totally sure but I am thinking that these engines' basic design dates back to a flat head side valve design which was modified to allow the use of an OHV setup ( MOD 1 ). When the Alpine was developed, the "new" alloy head was put in service ( MOD 2 ). The alloy design works but it is a compromised design in many ways > poor sealing, marginal performance, and probably a better choice of alloy could be found today.

When Chrysler bought into Rootes, I would say that a return on investment was most important. The American market was the single biggest market for Rootes and none of the then current Rootes models were going to be able to pass the upcoming American vehicle safety standards. New vehicle models were required before development of a sorely needed new design engine. In America we all know bigger is better but how do you get the most engine for the least cost as a temporary solution? Enter the 1725 ( MOD 3 ). By not changing the bore, the head, head gasket, and pistons remain the same or as off the shelf items. That means that for practical purposes the block casting cores were changed to include five mains and their required machining, a new oil pump and sump design to match the new wider block ( was that to clear the new longer stroke crank ?), a new set of cam cores to match the oil pump drive, new cranks, and new rods were developed to build both a 1500 and 1725 engine with the same tooling and basic parts. I think if Chrysler could have made the stroke longer and the engine stay reliable it would have been done.

I am sure all this is over simplified.

 

[Tom H]

This is covered extensively in Graham Robson's book. It was not a Chrysler issue. The market , and Rootes sales people, demanded more power. The new TR-4 had 100 hp, for example. Rootes designers hoped to keep as much of the original design to save money. The block had already had its bore expanded twice since the original design and there was little room for expanding further without moving watr jackets etc. So they decided to add stroke and chose a convenient 1/4 inch increase , from 3.00 to 3.25. Thus you get 1725 ccs. No magic in the number. Of course this stroke increase added stress and vibration to the crank and thus they found they needed to add 2 more main bearings. This added more design effort , but resulted in a nice engine. And after adding some improvements to the head and valves they moved from 82.5 to 92.5 hp. ( I think i have these numbers right, but could be off a bit)

Tom H

 

[todd reid]

Why 1725

Also keep in mind that the 1725 was used across the Rootes product line. Rootes sold a heck of a lot more sedans (Hillman, Singer, Humber & Sunbeam)than they did Alpines. Also the Alpines primary competiton (the MGB) was close by at 1798cc.

 

[husky drvr]

This is covered extensively in Graham Robson's book.

Tom,

I guess I will have to try and find a copy to read. As stated, I was speculating.

 

[Jay Laifman]

Thanks Tom.

As to the book, I do have it. And while it seems to have good information, I have to say that it is my least favorite Sunbeam book. The author clearly has quite a bit of disdain for the Alpine. It comes across in his tone throughout the book. Then, while he did work with Rootes, it was not until years after the Alpine and Tiger ceased production. So, while he has written many books and is seen as an authority on many, this is clearly just an attempt by him to make money by selling on his other books and his non-connection connection to Alpines.

 

[Series3Scott]

Thanks Tom.

As to the book, I do have it. And while it seems to have good information, I have to say that it is my least favorite Sunbeam book. The author clearly has quite a bit of disdain for the Alpine. It comes across in his tone throughout the book. Then, while he did work with Rootes, it was not until years after the Alpine and Tiger ceased production. So, while he has written many books and is seen as an authority on many, this is clearly just an attempt by him to make money by selling on his other books and his non-connection connection to Alpines.

The last time this came up both Jay and I chimed in with this opinion, and I still hold to it. The best book on Alpines is still the McGovern book.

 

[sunbeam74]

I tried to see if the FIA regulations might have influenced the capacity but it appears the cut off for the class 10 was 2000cc's. Class 9 was 1600. (In the early 60's)

It seems the size difference was a matter of convenience.


Steve

 

[mikephillips]

It may be that this was the largest they could go before the changes to the block would cause a new cylnder head to be required.