Rootes 1725 engines : the differences ?

Paul Goldsmith

Paul Goldsmith

0
Hi,

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 [8D]

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 ?
 
Hi Paul

We tried and failed to get a 1725 Alpine lump into our 65 PA which had a 1500 lump in due to the sump (and indeed the oil pickup) clashing with the steering!
 
hi paul
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
 
in answer to paul, the ali head can use more compression without detonation/pre-ignition issues,and i believe it has a more efficient combustion chamber design :)

"you were only supposed to blow the bloody doors off no.3"
 
This might be of interest Paul. Paulfordy's ecellent efforts with a Hunter GT engine in his old Highwayman.

http://66.129.69.181/forum/topic.asp?TOPIC_ID=208&whichpage=14

'Harvey the RV'
 
Hi
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
 
Jon,
Slight reading error here or missing comma.
Meaning was that when alternator is charging due to electrical load being placed on a carb fitted car at idle revs the engine tends to slow, but on modern vehicles and retrofits like this, the EMU compensates and maintains the idle speed
 
just one small point on compression, the more you have then the more torque you will get as well as thermal efficiency.
its more to do with the cam timings and lobe centreline angles as to where the power is.:)

"you were only supposed to blow the bloody doors off no.3"
 
All sounding very tempting, particularly as when they come up the engines seem to be 'cheap as chips' (perhaps with the exception of Holbays). I understand they're pretty straightforward and affordable to rebuild too.

I saw the first instalment in PC with the fuel injection conversion and await the follow up with interest ;)

I've been reading the A5 maintenance handbook which states that 2nd gear should be used for moving off with 1st only required for laden hill starts ! I'm thinking that even the standard PB engine might handle a better ratio on a camper which is unlikely to ever be fully laden like as a van - what are your thoughts or experiences on this ?
 
I must admit when I was driving mine 1st was only used for cliff climbing. I found 2nd was best for pulling away and was almost brisk.

'Harvey the RV'
 
Steve
This is a conversion I hope to undertake soon. Have the Holbay engine, just waiting on time & ability. If you or anyone else has any further pointers it'd be great to post them here.

Cheers
Jules

RatSport www.ratsport.co.uk
 
quote:
Originally posted by Cally

Hi
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




Yes indeed. I am about to emabark. I have the 1725 Holbay unit ready (complete with twin 40s which I very much doubt will fit - anyone any suggestions on alternative carburation other than CD150s ?)
I am hoping to also used the O/D box, I assume the prop will need shortening, any other issues anyone knows in this area?

Cheers
Jules

RatSport www.ratsport.co.uk
 
Hi Jules,Tim has so far settled for the bank of four carbs,perviously shown under "ran" in readers rides,Today some very small K&N's arrived ebay :)if you have a look at the cylinder head(Holbay) there are some nice curve's,where the inlet manifold joins the carbs to the head.Tim has said he is going to trim them so the carbs can be mounted at an angle on modified stacks,will post some pic's of his idea later,& as he makes progress not sure how soon every thing will happen but when he gets an idea in his head he does get cracking :D:p[^]

"RAN"the van & N0.1
 
Thanks people, I would really like to see a pic of the carb work when its done, that sounds interesting!!

Tim,I had a look at the prop today - its so gauged its never going to balance up (although I dont know how critical this is on a commer) - I may start again with a CV joint type.

Cheers
Jules

RatSport www.ratsport.co.uk
 
jules, i have done several props and never had any balanced, they all worked well :)

"you were only supposed to blow the bloody doors off no.3"
 
Right, so if I change the mount plates from my Commer motor, and use my original gearbox (I have an auto), a late 70's Hillman/Chrysler Hunter motor will fit and be upright? Will the Hunter sump clear, or do I need to use my Commer sump? Are the sumps interchangeable? I take it I would need to fiddle around with clearance/linkage for the carb/air filter if I fit the Hunter engine - that's OK. Someone else mentioned swapping the thermostat housing and/or water pump too - again no biggy. Can anyone tell me if any of the 1725 motors can run on unleaded fuel? Or do they need hardened valve seats? Thanks in advance!
 
Yep the motor will sit upright with the Commer front plate/mountings. You will need to use the Commer sump but again it will go straight on, fit the Commer water pump, thermostat housing and alternator bracket (you may want to use the Commer rocker cover as well because of the oil filler position) and job done:)
The engine will run on unleaded but you will need to use an additive. If it's an iron head engine then the Commer carb and exhaust will fit as well, bit more of a fiddle if it's an ally head.

41fa30c8-22ce-43e8-bd12-188475a80292.jpg

Harvey & Bonnie
 
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