Rootes 1725 engines : the differences
As I'm understanding things, the Commer van has a low compression iron headed single carb version of the Rootes 1725cc engine. Rootes cars sometimes have a high compression version Rootes cars sometimes have twin carbs with different manifold Rootes cars sometimes have an alloy head Finally, there's a rather tasty Holbay tuned version Has anybody fitted any of these versions to their Commer PB and was it straightforward ? I'm guessing the main issue will be space to handle the different manifold and carb arrangements Also, what are the main benefits of the alloy headed engine over the iron version, other than weight ? [Paul Goldsmith]
this is a subject which could be invaluable to everyone,ive asked steve yates to come up with the differences if he can or if hugh reads this he will know all the answers,as far as i know you cannot fit an alloy head to an engine with a cast head without changing the cam the basic engine block was used in rootes cars /vans from 1954 with a 3 bearing crank as a 1390cc .then incresed to 1494cc from 1958.to 1592cc from 1961 and then to 1725cc with a 5 bearing from 1965.it then ran until the early 1980s in the iranian peykan hunter. as far as i know the only reason the engine in the hunter family was at an angle was to enable twin carbs to be fitted hunter engines fit easily into the earlier vogue/superminx/sceptre range as each block has two sets of engine mounting holes drilled into it and you just swop from one engine mounting to the other the tuned holbay ran twin webbers and an 8 1/2 inch clutch same as the commer pb,a company called classic car developments in derbyshire offers a air filter weber conversion kit to enable the holbay engine to sit up straight to be used in sunbeam alpines so should be ok for commer van i thought all sump pans were interchangeable but stand to be corrected we are going to install a holbay engine and transmission into our dodge camper soon so can advise on the pitfalls,we are looking into fitting stromberg 175cd carbs as fitted to the later high performance hunter gls as twin webbers are a pain to keep tuned [Steve Williams]
Steve Williams has given you the basics. The Rootes lump is basically the same from early Minxes to last Hunters except for change to 5 bearings with 1725 and also threaded holes in block for engine mountings for Hunter. You can fit the latter engine into earlier vehicles if you take the timing cover engine mounts off your current engine and swap to new lump. Failure to use right timing cover mounts means bolt hole for mountings won't marry up I've seen a Holbay + O/D gearbox in a van > pretty fast I'm told by Bob Allan Imp Spares guy who had it Low Compression engines meant slogging power low down to haul weight rather than high revs and top end power. Engine changes may mean changing prop shaft and diff ratios to match Engine cover can be a problem as Holbay must have matching Cam and Carbs to work > but work by Cananem (see latest Practical Classics A40 project) means you can go to full engine management and injection on old engines for better drivebility, no choke or alternator slowing engine etc. The A40 gave 20% more power!! on this alone. You have better choice to mount components and with no points etc have low maintenance like modern vehicle and coversion uses scrapyard sourced parts to a significant extent.I know Dave Hampshire the guy who does this as he's an Imp Club member who runs a Chamois Coupe on hos own build system which was his degree course work at York University Hope this has weted your appetite for now [Cali]