Triumph TR4 & 4A

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Do you drive this great classic or are thinking of buying one? Here’s how to ensure that you get the best out of your car for years to come

Sporting all the charm, simplicity and nostalgia of the earlier TRs – but with the chunky looks of the TR5 PI, the four-cylinder TR4 sounds like the perfect mix. However, despite the car’s utterly orthodox design and construction, there’s a surprising number of pitfalls ready to catch the unwary during ownership. The good news is that there’s a veritable army of specialists on your side together with magnificent help and back up from owners’ clubs. So have no fear, get tinkering and make your TR terrific!

1. Engine output

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Tractor-derived ‘four’ can easily yield 130bhp for reliable road use. A cheap upgrade is a session on the rolling road, paying attention to optimum mixture and ignition settings with better air cleaners, complementing it with a sportier exhaust. Twin 1.75 SUs ample before going to twin Weber DCOEs. Performance engines cost £3500-£5000 depending upon specification.

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Many say TR4s were under-cooled when new, leading to head gasket woes. If head has to come off then always have an unleaded conversion carried out, even if you’re not envisaging any tuning. An uprated rad, plus an electric fan, is a wise move, especially if you intend to increase horsepower. It’s a trusty ‘wet liner’ engine design that can even withstand supercharging; 40 per cent more power for £3500.

2. Bottom end

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Wet liner block is easy to stretch. TRGB sells 89mm piston/liner kits for 2.3-litres, costing £450 while TR Enterprises trumps this with a 92mm kit giving 2.5-litres, to provide TR6-beating torque although going above 2.3-litres isn’t warranted for most owners. As a racing engine it needs a lot of work to beat 160bhp plus, standard unit is not up to it and so needs a steel crank, rods etc.

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Wet liner design means bores can be re-sleeved, resulting in an almost open-ended engine life; it’s a bodge but you can even rotate the liners to counter wear at the ‘thrust’ side. To prevent liners popping out with head off, you need special clamp-down tool before you can turn crank. 60-70lb oil pressure shows good health but watch for oil leaks at rear of crank scroll seal, TRGB’s modern oil seal kit at £60 is advisable to cure this fault.

3. Front suspension

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Uprated dampers and springs are mandatory, complemented by polyurethane bushes at the same time. Revington TR sells various upgrades, with a full suspension rebuild (including new poly bushes, springs, dampers and anti-roll bar etc) costing around £1700. A TR6-type anti-roll bar is a cheap mod but TRGB says the benefits aren’t that significant.

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Trunnions need periodic care or risk dangerous seizure; ideally should be EP90 gear oil, not grease, but latter is easier to fill with a gun. Lower suspension wishbone mounting brackets are known to fall off so check regularly. Tuners don’t advocate altering ride height for road use. Full poly bush refurb and a geometry reset by TR experts works wonders, more so on the IRS cars.

4. Wheels & tyres

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There’s a wide choice of rims including the still fashionable Minilite designs although there’s something to be said about a plain hub cap look (pictured), we reckon. Don’t go over a 6J size – even competition TRs didn’t! SC Parts’ new 72 spoke wire wheels at £199 at Power steering from 2000/2.5 saloons can be adapted although an EZ electric conversion has the beauty of being reversible plus you can alter the assistance.

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Wire wheels need regular checks for aging and don’t forget the hubs and splines; worn ones can give rise to clunking which you may blame the transmission for! If bad it is best to renew; some good deals are on out there. SC Parts has brand new steering racks at £119, standard or high ratio although the latter will make steering very heavy. When new, Triumph used to recommend the checking and adjusting of the front hubs every 12,000 miles.

5. Transmission

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Rover LT77, Ford Sierra or a Toyota Supra ’boxes can be installed; Revington offers latter conversion at £4400 – pricey but it can be reversed to original spec without any evidence. Don’t instantly ditch standard o/d as it potentially offers seven-speeds and ideal for rally work after uprating. Revington advises a Logic Overdrive Device (£84), which disengages overdrive when you shift-up a gear. Flywheels can be lightened but start with the already lighter 4A one, if possible.

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Biggest problem is the infamous Triumph crankshaft thrust washer wear. You need to watch crank pulley movement at front of engine as the clutch is operated by an aid – if above 0.015in of play they can fall out. Oversized washers can cure this and can be done with engine in situ, but if bad more involved repairs calls for a full stripdown. Layshaft problems not unknown and overdrive units suffer from oil leaks and solenoid problems, but it’s a sturdy unit.

6. Brakes

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DBA discs equipped Mintex or EBC pads are good first step mods at less than £150. Uprated callipers from BCC are next but not essential unless engine is really highly tuned. A cheaper alternative is to find Toyota Hilux pick-up ones (1979-83) but these are rare. Rear drum brakes are adequate for mild performance increases, with just the addition of sportier linings, before opting for alloy Alfin drums.

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Don’t forget that earlier TR4 used disc brakes which are actually larger than the later TR5/6 set-ups so opting for fuel injection hardware is a retrograde step. The rest of the brakes pose no particular problems apart from routine service work – change the fluid at recommended intervals. If wire wheels are fitted, then check the spokes regularly for looseness – a tap with a pencil is the usual policy. Conversion to wires is very simple.

7. Rear end

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IRS adds 100lb and competition drivers like simpler earlier rear end; TR experts say it’s not worth the expense and effort to convert unless fitting new chassis. Adapting to telescopic damping is pretty involved as well as costly but essential to aid handling for competition although you need to watch FIA regs on some categories as many mods have to be in period. Modern u/j kit cures the infamous ‘spline lock’ but costly.

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Axles sturdy but known to leak; full rebuild costs over £1000. Infamous Triumph spline lock affects 4A and later TRs. Again FIA mods allows certain mods but for road use you can opt for modified (SC Parts) driveshafts, but keeping a close eye on their u/js also helps reduce that ‘TR twitch’. If keeping lever type dampers, ensure they are quality recon types as cheap types aren’t known to last that long at all.

8. Body and chassis

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CTM Engineering of Southampton specialises in repairs or new chassis frames. Remember, a new chassis not only rids you of rust problems but it will be much stiffer and aid rigidity, talking of which, TR Enterprises sells a chassis stiffening kit for just £75 although the company adds that you need to decide how much you want to add before altering suspension settings – a roll cage also adds rigidity and too much spoils a TR’s handling.

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Outriggers rot badly and cost an easy £2000 because the body ideally needs to be removed, which is not a bad idea if major repairs are on the cards anyway. The front end hides a lot of nasties while reinforcing the differential and the trailing arms is not only a good move but essential if you contemplate converting the dampers to modern telescopics. Chassis arms residing under the boot also give trouble.

9. Body & trim

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Everything you’re going to need is available off the shelf from a wide range of sources and trim quality is better than when brand new. You can go for a luxury look with posher carpets and wood detailing or you can opt for a stripped rally replica. If you find period accessories all the better. TR6 seats fit and are an improvement if you don’t want an aftermarket look.

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Parts availability for the inside is generally excellent and a full interior refurb is both cost effective and desirable, especially if you also like the idea of making the stark cabin a bit posher as in the picture. The hood is also a simple affair costing under £250. Keep that Surrey top in good order as they are becoming harder to find; check rear window seals for deterioration. If cabin ventilation isn’t good then it may be due to the air vent flap not operating correctly.

And another thing…

With TR5 PI prices already up in the clouds, can you turn a humble TR4 into something that resembles one – after all aren’t the big-six versions TR4A based? Well, according to the TR Register the swap can be done but it isn’t as straight drop in and you don’t need to be TR expert to spot one from the real thing.

For simplicity, use a carb-fed 2.5 engine, ideally, from a TR which has right parts. The basic mods centre around the engine mounts and moving the steering rack forward using TR6 bits on the suspension. You will need to ‘dress’ the engine compartment’s inner wing to make room for the carbs. Cooling ideally requires a six-cylinder rad but the mounting and ducting will need slightly modifying, too. Naturally, you’ll need suitable modifications to the front springs and brakes.

While not that common, it’s not an unknown conversion; speak to a TR specialist, and in particular Colin Matthews at CTM (01489 782054) as he appears to have done this conversion in the past.