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Who can build a reliable stag engine.


Fuzzy Harris

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My friend is building a stag engined 2500 saloon, he wants to know who can be trusted to build him a reliable and mildly tuned lump, also what is involved in building one of these engines properly and how much is it going to cost ?, i`m sure someone can help.

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Sorry you don`t know my mate, he`d want a life time guarantee, sometimes it`s best not to get involved, if someone could give me a definative answer why these engines have a bad rep i may consider it, was it down to timing chains, casting sand left in the block, poor cylinder heads the list goes on, if it aint rocket science why have i heard so many tales of newly rebuilt units going pair shaped, is it crap parts, crap workmanship or just a crap engine, they do sound nice though.

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Rover V8 more reliable?
Well I s'pose if you mean reliable=oil pressure about 5psi at idle+changing the cam every 40 000 miles instead of the cam timing chains+vast thirst with less power?? I'm not so sure!
I've driven both inc the EFI, and the standard 3.5L is a SLUG.

The Rover is more than 50 years old and the combustion chamber shape is a disaster compared with the inclined valve SOHC Stag.

I'm not so crazy about either but I'll bet if you put some nice cams in the Stag (maybe even IMP!!) and balance it, it's a lot more like a sports car engine than any old yankee push rod engine....that's why no-one want 'em in kit cars any more... ;D

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I agree, the standard 3.5 is a slug, but change the cam for a light performance type, port the heads (very easily done), and add a set of headers and Weber/Holley/ fuel injection and you have 220 BHP.  More work and money and you can easily achieve 300BHP (not that I'd want that much in a standard Stag!).  You can buy stage 1/2/3 heads for under a grand a pair - try finding the same for a Stag!

Cam shafts only fail if you disregard service intervals or use thin oil and radical performance cam designs as Mobil One and TVR found to their cost.

Low oil pressure?  A £10 'tad-pole' oil pressure relief valve sorts that!

Poor MPG?  Mine averages 22-30, depending on driving conditions, the same as the Stag engine it replaced.

There's no denying the Stag engine is a beautiful concept but is and always will be let down by its inherent design faults.  It is weak and therefore has a lower tolerance to tuning.  I was a believer for years, yet after those problems raising their head time and again, (timing chains, failing jack-shaft, poor water flow, even in reconditioned heads) I finally said enough and went for an engine that doesn't have issues.

The Rover unit isn't an angel, but if reliability and power is what you want, it wins hands down.  It was in production for 50 years, ask yourself why?  

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My mate next door had his Stag engine rebuilt by a specialist in Telford 7 years ago - has never missed a beat although over a fairly low mileage.  Looks and sounds amazing.  Unfortunately the chap who ran the business is no longer with us - will enquire if they are still trading.  Perhaps call Fitchetts as I recall there was a Stag specialist on the same trading estate as them?

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The Stag engine has an awful lot of things in common with the Maserati SM V6 DOHC (read sado-maso).
Being as no-one in their right mind uses either for a daily drive, it's worth keeping the original engines.
Jackshafts on SMs ALSO give up BIG BIG time (they're made of cast iron as are the centre cam sprockets,+single row chains and run everything from PAS to hydro suspension off it so you can imagine!)

Now, original SMs use carbs and were plagued with problems just like the Stag.
2 things helped make it better.
Later fuel injection, and one or 2 specialists that put some serious thought into improving it, and some good ppl, that made the jackshaft out of top quality steel....
With the result someone even made a twin turbo one and it was pretty OK!

Being as very few people were every interested in developing the Stag for fast road use, (and BOB at now defunct Holbay owned one) I was astonished when he told me in the late 80s, He owned one, drove it not lightly every day, and was TOTALLY reliable with very very good power....I'm sure he still has it!

Goes to show,- you ONLY need a good engine builder.

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Well I agree with GT on this, the standard Stag lump is delicate but I build my own engines and dont trust anyone!
Rover in a Stag sods up the gearing cos the Stag lump revs way more than the normal untuned Rover.
Lumenition ignition or similar, points on a v8 that hits over 6000 rpm :'(
I fitted the chains and guides then run them for 1000 miles and reset.
I used my Stag for sprints and hillclimbs to good effect (easy 125mph) always beating the Healeys and MGC's.
I would not gaurantee this engine however because just like the Sprint it needs driving gently till warmed..........then thrash it, failure to do this and it will bite you.

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trackerjack wrote:
...I fitted the chains and guides then run them for 1000 miles and reset ... it needs driving gently till warmed..........then thrash it, failure to do this and it will bite you.

Totaly agree on this one  :)

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