A Stag with Rover Power-and Reliability
Blown head gaskets and finally a comprehensive engine blow-up when the timing gear fell off the end of a camshaft of his Triumph Stag had driven to despair Mike Stephens, proprietor of Western Models in Redhill, Surrey. When Mike's first Stag had exasperated with similar maladies his answer had been to swap the car for a Renault. But the call of the comfortable Stag's idyllic open-air/ fixed-head, four-seater concept had proved too much and a later model, blue Stag replaced the reliable Renault. The glutton-for-punishment refused to be ground down by this second Stag's expensive unreliability and found the answer to all his problems by transplanting one Leyland V8 for another—the more reputable, all-aluminium Rover V8.
The transplant has proved so successful that the weak-hearted Stag's Barnard, Douglas Hall, who runs May Engineering at 142A, East Street, Epsom, Surrey (Epsom 28228), has decided to build Stag 3500s on a commercial basis, in conjunction with Western Models, whose latest offering on the miniature side of its business, an exquisite 1/43rd-scale model of the Tyrrell Project 34 prototype, has a place of honour on Ken Tyrrell's desk.
I'd long wondered why nobody, in particular Leyland themselves, had not previously offered up the Rover engine to the convertible Stag body, at least so far as I knew. By coincidence, I'd been talking about this selfsame subject to our rally-man, G.P., whose Stag temperature gauge was currently showing an attraction for the red segment, just a couple of days before I heard about the May Engineering car. We thought the fact that Leyland should produce two V8 engines at all seemed a nonsense; that they should produce two with such dissimilar reliability reputations seemed crazy. However, the Stag project, with basically a double-banked Dolomite engine, had been too far advanced when the Leyland Group began to pull Rover, Triumph and the rest together to adopt the Rover engine at that stage. In fact, since I tried the May Engineering car, I have heard from Leyland that they too have experimented with a Rover engine in the Stag. Whether or not they were satisfied with the conversion I don't know, but for their production purposes the project is unviable on several scores, apparently, in so much as re-vamping a production car in this way would entail a complete new series of safety and emission tests and retooling, unjustified by the Stag's low volume.
If the idea of dropping one V8 in the home of another only 500 c.c. smaller V8 sounds simple, it is not quite so straightforward in practice. For one thing the deeper, longer-stroke Rover engine's twin SUs fail to clear the Stag bonnet. For another, the Rover engine revs to a modest 5,200 r.p.m. (disregarding the new 3500's 6,000 r.p.m.limited engine, being unavailable yet on the second-hand market) compared with the Stag's 6,500 r.p.m. Thus, Rover maximum revs would offer a mere 103 m.p.h. on the Stag's 19.9 m.p.h./1,000 r.p.m. potential direct top, using the standard 3.7-to-1 final drive ratio, were something not done to make the hydraulic tappet, push-rod V8 rev somewhat better. This will be less problematic with manual-overdrive cars; Stephen's Stag has the standard Borg-Warner Model 35 automatic gearbox with 1.0-to-1 highest gearing, equivalent to the manual's direct 4th gear. Hall is still developing a clutch, flywheel and adaptor plate to mate up the Rover engine to the manual Stag box.
Such a conversion on the automatic Stag requires few amendments to the drive-line; the gearbox and propshaft position and length are unaltered and the Rover engine's torque-converter housing bolts straight to the Stag's Borg Warner Type 35 box. Different tailshaft lengths make it impossible to use the otherwise similar Rover Type 35 box. If the Rover engine used happens to have been made in the last two years it will have been mated to a Model 65 gearbox, the torque-converter housing of which has to be changed for a Type 35 to suit the Stag box. Stephens' car uses the Stag torque-converter, with slightly different characteristics to those suited to the torquey Rover engine. In future, Hall will lit the Rover item.
Adapting engine mountings for the Rover unit is a straightforward-enough job. But the Rover engine is longer than the Stag. the nose on the top pulley needing to sit right where the Stag radiator would be positioned. A subtle application of cutting equipment to the tin-work ahead of the radiator allows it to be moved forwards and downwards at an angle. A header tank is fitted to compensate for the consequential loss of pressure height and to accommodate the Rover's greater coolant requirements. Twin, Kenlowe thermostatically-controlled electric fans replace the engine-driven item. The cast-iron Rover exhaust manifolds won't clear the front body rails, so Mike (the Pipe) Randall, of Wallington, Surrey, has fashioned tubular extractor manifolds, which curve forwards and down before heading towards a link-up with the standard Stag twin-exhaust system. As an incidental, these new manifolds should let loose a few of the horse-power strangled by the Rover manifolds. The remaining major headache is to graft a glass-fibre bulge into the bonnet to clear the angled SUs atop the engine, which breathe through a single paper-element filter per unit and necessitate a revised throttle linkage. Hall is considering eradicating the clearance problem by fitting the horizontal SL` arrangement from the MG-B V8. I feel this is unnecessary; it would mean the loss of some power and torque and the nottoo-unattractive, yet distinguishing, bulge.
Mike Stephens' Rover engine came from a crashed 3500. It was rebuilt completely by Hall, ex-SuperSport engine builder and Brabham mechanic. who had it balanced as a matter of course and made one or two other improvements to extend its rev range. The source and attention paid to engines for customers' cars will be similar, with the possibility of using the improved hydraulic tappets from the new 3500. Though the necessities of life dictate that May Engineering's work incorporates bread-and-butter repairs and servicing, which was how Stephens, Stag and Hall-came to meet, Hall is primarily a competition engine specialist, mainly with Ford BDAs„ so these V8s ought to he put together properly.
On paper the slow-revving 88.9 mm. x 71.1 mm., 3,528 c.c. pushrod, all-aluminium Rover engine isn't necessarily all that superior to the higher-revving, 86 mm. x 64.5 mm., iron-block, aluminium -head, single o.h.c. per hank Stag unit. Indeed, in standard form its 143 b.h.p. DIN maximum power is 3 b.h.p. down on the Stag's, thoughproduced at 5,000 r.p.m., 700 r.p.m. less. It is in sheer torque that the Solihull lump gains: 202 lb ft. at 2,700 r.p.m. against 167 lb. ft. at 3,500 r.p.m. Furn the key to fire the Rover engine, using the Stag's existing manual choke control if necessary, and there is a much gruffer note to the irregular V8 beat. Otherwise; there is only the bonnet bulge ahead to remind the driver of the changed power source.
The deeper bark is matched by a fiercer bite. I have always found the automatic Stag to be a shade lethargic; put your foot down in this May Engineering version and the message is much more emphatic, whether from rest or at speed. The torque characteristics more than overcome the Rover's less extensive rev range in manual hold or on kick-down, producing a splendid surge of power through the range. The Stag torque-converter's unsuitability showed with a touch of sip on kick-down, but this failed to disguise or spoil the much pleasanter performance characteristics. Without an opportunity to take comparative figures. I can't be much more specific than this, but would imagine the 0-60 time to be well under the 8 sec. mark and maximum speed, assuming this modified engine will pull its maximum 6,000 r.p.m. in top, which it should on the Stag final drive ratio, to be standard Stag-like at 120 m.p.h. A standard Stag weighs more than 2 cwt. less than the Rover 3500, while the Rover engine saves another 1/2 cwt. compared with the other V8.
Koni shock-absorbers all-round are a standard part of this May Engineering conversion. Combined with the later-model Stag's smaller wheel and improved steering, these help produce surprisingly taut and balanced handling at the expense of a firmer ride. Hall and Stephens quote a high £1,500 plus VAT for this conversion, but this does include low-profile tyres, which the customer is not obliged to have, the Konis, Kenlowes, all the other conversion paraphernalia and a full engine rebuild. And the Stag engine reverts to the customer, presumably to dispose of for cash. Stag owners who can't understand the logic of this conversion have Obviously not been amongst the unlucky ones who have suffered multiple engine disasters. But the only alternative to the Stag-type concept is even more expensive—they-call it a Mercedes.—C.R.