Bfg

. Hi all, not a lot of news on the American frontier, re. my buying Chance, as the seller continues to have a difficult year. Nevertheless undeterred I stride ..or trip over, forward and am now looking to buy a TR4A engine. The plan is.. to rebuild or have that rebuilt through the winter months so that as and when I finally get the car it'll be a leap forward to getting her on the road. I'll then have the car's original engine to rebuild at my longer-term convenience. And then I'll sell whichever is 'spare'. I recognise the risk in buying and rebuilding an engine before I even get a car, but I'm prepared to commit to the TR4 ..and then also want things to happen next year rather than the year after. So that's the plan, here's the engine I'm going to look at tomorrow. This is the engine I'm looking to buy tomorrow, as a 4A engine. Seemingly with a hot climate six blade fan, and a side-screen car's rocker cover ? This supposed to be a US import TR4A one. Clearly it is to be rebuilt. The question I'm faced with is this actually a TR4A engine or an earlier one with a high port head fitted ? From reading up - this is what I gleaned : 4A cyl head is slightly reworked to breather better with the later manifold, but this is not apparent from the outside. Likewise the engine bore / capacity, compression ratio and camshaft profile are is not outwardly apparent. TR4 has steel push-rod tubes, whereas the 4A has aluminium ones. ( is this correct ? ) starting handle dogs on the TR4, deleted on the 4A. (B.Piggot) the breather of the 4A is a closed system via a tube from the rocker cover to a PCV valve. The TR4 has a pipe in the side of the crankcase, below the petrol pump. Later TR4 from CT14234 has a tube from the rocker cover to the air filters. However a TR4 engine might have been fitted with a core plug - in which case you can't tell from that. TR4A inlet manifold (if original) has the triangles cast into the balance pipe, and the vacuum takeoff is not on such a large raised boss. Exhaust manifold on the 4A went to 4 into 2 down-pipes. TR4 has a single down-pipe. (B.Piggot) Stromberg carbs were standard on the 4A until CT62191. thereafter SU were used. Fuel pipe and throttle linkages changed with the carbs. (B.Piggot) Flywheel is slimmer / lighter on the TR4 clutch on TR4 is dry plate spring type, whereas the 4A has a diaphram clutch. (B.Piggot) The clutch splines however are the same size. there is some difference (?) between how the camshaft or its seal is retained. engine plates are the same on TR4 and 4A. ? commissioning numbers : TR4 from CT1 to CT40304 (06/01/65). and 4A were CTC 5001 to CTC78684 (10/06/67). But were the engine and comission numbers the same ? Are there any other visual indicators as to what this engine was from ? Thanks, Pete.

By the time I went to bed last night - it felt as if I had been in lectures all day ..after reading what John Thomason wrote about about the single v twin carb on his Spitfire and then following through to his previous discussions on the why and wherefores of manifolds. 216 - June 1998.pdf 111 - Sept 1989.pdf 112 - October 1989.pdf 107 - May 1989.pdf It was well written and a great read - I've learnt a great deal. I can't honestly say that the Dolomite 1300 manifold looked to be the most refined in world, but it did make for an easy conversion (back from single to twin carbs in 20 minutes !) ..and most likely was dirt cheap too ! Very noticeable also was that the standard 13/60 Herald air filter trumpet does look very restrictive for a tuned 1500 Spitfire. Neither of these things take away from the results achieved but who knows - they might imply that slightly better results might be achieved with a single carb setup.? Thanks All - great thread. I look forward to going back into the archives and reading more of his reports. Pete

OK. ...being a newbie (..actually a returnee to the club after a few decades away ) I didn't know about this resource nor how to access it. But I have just explored the TSSC website, found COURIER in the left hand side bar, clicked on it and found 29 years worth of excellent courier magazines and their articles in pdf format, freely available to us.! - FANTASTIC !! And Thanks Please, where might I find the index ?

Thank you Richard. I understand your conclusion ..derived from their direct relationship. This is also my understanding. Power is the work done in any unit of time, it may therefore be a measure of ; force x distance / unit of time. (NB. 'distance' may be linear or around an axis) Torque is the gauge of force x radius (..with neither distance-moved nor time coming into this equation). But as 'force' is directly proportional to the results in both equations - it must be true that if the force is greater in the single-carb's power curve, then it would be proportionally so in the torque curve. Of course from the result suggested, a 2% difference is unlikely to be felt in everyday road use. Interesting nevertheless. Cheers.

It used to be said that the surest way to better performance is to increase the capacity (maximum re-bore size) and to increase the compression ratio (skim the cylinder head gasket faces + new pistons). At the same time a few lumps in the induction tract would be smoothed out, and the gaskets and ports better matched to the size and shape of their manifold. The existing carb(s) would simply be re-jetted, and the air filters replaced with those which claimed 'free flow' ..or else open bell-mouths used instead. Ducting (for cold air) might be run from in front of the radiator to point in the general location of the carb(s). And, as the machining was needed on any old and worn (dry liner) engine anyway - the additional cost in achieving more torque would be negligible. Swapping to a four branch 'extractor' exhaust, along with contact-less ignition, and possibly an improved inlet manifold - were the next stage in 'home tuning'. And only then, were things like replacing the carbs considered, upgrading the camshaft, altering the advance curve, and actually paying someone to tune the car on a rolling road. Next tuning stage included lighter engine components, re-balancing and more advanced porting to safely achieve higher engine revs. Why.., have things changed since I were a teenager ? ..in the world of Triumph Heralds ?

As I'm hankering after TR4a with O/D, and the standard gearing is 4000 rpm @80mph without overdrive - I'm sure I would be content with loosing something in the 80-100mph acceleration range in exchange for having a little smoother idle, plus another 3 mpg ..and the servicing / tuning advantages of just one carb. Yes, I know the TR4's supposed to be a sports car, but it's also a classic two-seater convertible with bags of torque for long-legged touring ..so it needn't be driven at ton-up speeds to be thoroughly enjoyed. I'm sure when I read this post yesterday evening - you mentioned higher torque at the lower engine speeds from the single carb. I guess that was not wholly correct and so edited to correct ? I like the idea of these manifolds, which provide more-or-less-equally to all cylinders, but the TR4 bonnet is so low to the carbs that even with a 45deg adapter it (possibly) wouldn't fit. It already has a bonnet bulge to clear the standard carb's dashpots. However I'd recently spotted photos of the TR6 with a downdraft carburettor . . Although this is a twin-carb twin-choke setup - the adapters to its standard (??) inlet manifold are off the shelf, and clearly fits under the TR6 bonnet line. But what if any are the advantages (or disadvantages) with down-draft versus side-draft carburettors ? Thanks. Pete. p.s. If anyone can send me a digital copy of that article, it would be appreciated.

With all other things being equal (ie.cylinder head inlet tract, valving, cam choice and exhaust flow being the same) ..surely the only difference between single and twin carbs is the inlet manifold, carburettor(s) and filter(s). I recognise that each manifold would induce a different swirl effect, and a crossover inlet manifold would be different again to that of the standard single carb type. Is this what you mean by "air flowing through more effectively" ..and because of improved swirl it uses more fuel ? I'm not trying to being funny or a smart ass - I honestly don't understand ..yet. So for the sake of discussion, if a single carb is 1-1/2" dia, and twin carbs are each 1-1/8". The smaller twin carbs are 3/4 the radius of the single so their air-flow resistance is 12 times as great ..but there are two of them. Tbh., I'm not knowledgeable enough to work the maths. But as the resistance depends on the size of carbs used, then - if a BIG single carb is used rather than two smaller ones, there will then be less drag. And I guess there is a balance point on the graph - where resistance is the same. But as very big carbs don't work so well at low engine speeds, then a two-staged / twin-choke carburettor is used ..such as the 32/36 DGVAS Weber mentioned by Richard. ?

I'm probably boring you all now but I'm enjoying learning about this, so here's another question . . Why do multiple carbs use more fuel ? ..when the engine is of exactly the same capacity and the optimum air-fuel mix must remain the same ..let's say 14:1 for the sake of this discussion. I can imagine the mix / swirl effect might be more effective, but that doesn't alter the air : fuel ratio. So a logical interpretation may be that twin carbs offer more ram effect (if that's the right terminology for this context ? ). ie. both more air and more fuel (at the optimum mix) gets to fills the cylinders, which when ignited gives more powerful combustion. Is that right ? Ok, I'm thinking as I write that "ram effect" is an incorrect term because that mix has not pushed / rammed / forced into the cylinder, and is only drawn-in by the descending piston. So might I conclude that induction through twin carbs (or twin chokes) simply offers less resistance than a single (..even larger) carb. ?

That's really interesting, I was not aware of 'crossover' inlet manifolds. Unassuming little blighters aren't they ! ..but see Lynx still make them for Ford 1600 and the Volvo P1800. I'll have to research / see what Lynx claims performance wise. Following on from Clive's excellent prompt .. < here > is Lynx's explanation. I like it ! Thanks.

Sounds interesting - would you happen to have any photos of that ?

I recall reading about shared induction tracts on motorcycles ; as two cylinders alternate in their opening - the air-fuel flow is repeatedly reversed. ie. when one cylinder's inlet valve opens the air is sucked from behind the other (now closed) cylinder's inlet valve. Then flow is reversed again as that other cylinder's inlet valve opens. The reference endorsed sharpening the divider in the shared tract Sunbeam 500cc in line twin cylinder motorcycle shared induction port, seen here with its standard (rounded) divider between the two cylinders. Air/Fuel is expected to change / alternate direction dependent on which inlet valve is opened, and as one opens the airflow to the other is reversed as air is sucked out of the void behind the valve. The blunt radius of that divider is also a surface for the fuel particles to impact and so loose their 'suspension in the air flow'. The advice was that this edge should be sharpened to lessen that impact face and to minimise the air reversal. I did that on this engine but the result was inconclusive because so many other factors were changed at the same time (the engine was rebuilt with rebore and new rings etc.).

Out of interest ; do all 4-cylinder in-line car engines have this firing order ? or have some been changed to balance out the induction pulses ? Did it work ?

Thanks Clive, I didn't know about John Thomason, but did a google search and see that he's published. It would be of interest so perhaps one of the lads in my local group here in Suffolk has a copy they'd lend me for a weekend, otherwise I'll look out for a copy of that. " single was a little more economical, the twins a little more power. Maybe 10%?? " is in the region I'd expect, which would knock the sharp edge off acceleration but be more noticeable at the top end. I wonder what effect it had on low to mid-range torque ? Yes even though I couldn't tell you what the Essex engine's Weber was, except it had a collar for LPG which worked exceedingly well - I'd forgotten the Citroen's Weber was twin choke of different sizes. I've driven the A-series Citroens a lot, usually driving on a single choke ..with the positive feedback of the second choke's spring making driving 'economically' very much easier to gauge. agreed .. for direct comparison. But of course there's also building an engine for either one or two carburettors. I'm thinking for example when rebuilding an engine, a specific camshaft might be better for one carb rather than two. So perhaps although more involved, the difference might be 'better optimized' than is apparent when simply changing the manifold and number of carbs. ? Likewise it may be that an SU is a better carb in its twin carb setup than a Solex which for whatever reason seems to relishes being single ? (or vice-versa, or Weber, Mikuni or whomever ?) Indeed ! does seem to complicate things, as JohnD recently pointed out. But it was used on the E-type and on cars like the Toyota 2000. I'm thinking that it must have had advantages to have been introduced by those manufacturers. 2134 but your point is valid. 4 into 2 into 1 branch exhaust manifolds may be intertwined to balance this, but that's not practical with short inlet manifolds. So I guess part of the issue with single carbs is that the middle cylinders have shorter induction tracts than the first and forth cylinders. ? Thanks all.

. Just an idle enquiry., but I'm wondering if twin carbs really makes that much difference ? or whether with a suitable manifold a single carb might be that much easier to keep in tune ..and therefore in daily use just as powerful and perhaps more economical than two carbs which are rarely perfectly synchronized. ? It's not exactly the same but my Norton 850 motorcycle (sold very recently) had a single carb conversion, as did the previous one I owned many years ago. Similarly Triumph (motorcycle twins) were spec'd with single or twin carbs, ie., modeled as the Triumph Tiger and Triumph Bonneville. Certainly my experience of Norton and Triumph twins is that the single car bikes are always a little easier to start and feel smoother around town. Perhaps that's because the air flow through their venturi is steadier at low engine speeds.? I might hazard a guess that top speed might suffer from being a bit wheezy with a single carb (which has been sized for normal road use), but as I have only ever driven or ridden over 120mph a dozen times in my lifetime, I can't see that is now a serious problem. Similarly many sports cars have twin carbs whereas their kindred saloon, fitted with the same engine has a single carb. And that is expected to provide ample pulling power for the heavier car and payload, as well as being more economical ..and to be more reliable. Of course it's not so easy to compare the performance of a sports car and a saloon with the same engine, because vehicle weight and aerodynamics, camshaft & compression ratio, and even gearing simply confuse any direct comparison. But on my Norton I felt no lack in acceleration nor pulling power when I switched to a single carb. Seems to me that adding a second carb (OEM price £50 ?) was a sales ploy used by manufacturers to charge buyers another £1000 for a car with only half the interior trim.! I note that car's like my Scimitar with a 3 ltr Essex engine (also used in the Granada and Capri, and possibly in the Transit van ? ) had one twin-choke Weber, as indeed did my flat-four Citroen, and so then wonder if one twin-choke might be more practical to live with than twin carbs, their control linkages, extra plumbing, starting choke, twin air filters, etc. ? Thanks, Pete.

. Interesting project thanks for sharing, I'll enjoy following progress and its development. ..aside from which I sorta like the idea of a Spitfire built with German mechanicals

^ yes aluminium food trays are a very useful source of this beautifully ductile metal. And even though mine just comes from an Aldi supermarket and not M&S ..you posh sort you - I find they're also useful for simply pressing into a corner for an imprint, to take to the bench as a rough shape guide template when making the more awkward bits. They can save a fair bit of back n' forthing especially if you're working in a hard-to-reach spot. Also handy for imprinting angles or holes, which are then easier to measure, and you can even scribe markings on the alum. All sorts of little jobs like that. Also as a small but still very useful heat and splatter shield to wrap around things you'd prefer not to have red-hot weld splatter or grindings burn into. Why this wonderful stuff even clings onto things like rubber pipes or carburettors ! Of course, everyday use is as a sorting tray, which then funnels ..to guide nuts n' bolts back into their jars (the clear plastic peanut-butter jars are very handy indeed for sorting different size fastenings into). And occasionally I might sacrifice one to the Murphy's law of dumbest places to put a drain plug, such as the one under the gearbox of my motorcycle ..which drains straight onto the bike's centre stand. An aluminium tray suitably-bent diverts said oil into a container. My apologies to the O.P. for this little off-thread diversion. There is a thread for home made and adapted tools, so any further comments I think we ought to put on there... < here >

^ that's a pain, but very do-able. Not so easy for a first time welder though. Aside from some skill in welding (..practice on a bench first with rusty thin metal) - the ease, or difficulty, of such repairs comes down to the accurate shape and size of infill patches. Please be aware that it's not unusual to spend an hour or more making awkward repair piece(s) when it only takes five minutes to weld them in place and to clean up the weld. This is where most garages cut corners. They roughly cut a piece of reclaimed metal (a bit of another car) and slap it behind, crudely weld that in place and then smear panel sealant or bondo over to hide it from sight. It's Ok to make the car safe n' strong for a while, but far from the ideal repair on any classic. This why (the very few) really good restoration shops charge ten times the price - it's that they spend ten times the time getting it right. Of course the question is always ; how good do you want it done ? and this is usually balanced against how much the car is (monetary or emotionally) worth, either now or in the foreseeable. For a decent repair you need to cut the rot out, translated ; rot is seen as deep pitting in the cleaned up metal. But many who are new to welding cut out too much at once ..and then it's almost impossible to remember exactly what shape was there. Folding (bending) sheet steel is quite easy along a straight edge, or if you need gentle folds - bending the sheet metal over a piece of tube. But forming a piece of steel around a compound corner is difficult. Use a piece of cereal-packet thickness cardboard and use that to try and make your repair pieces. You'll find you can easily cut and make the straight bits, but the cardboard doesn't want to go around the corners. So the answer, for the newcomer to sheet metal-work, is to make the straight pieces separately, to the corners. Unless you're handy with a hammer and dolly in shaping metal, a corner piece will most likely needed to be darted and perhaps even made in two or three parts (like a tailor or seamstress making fabric go around corners). So, the surface rust, paint and grime needs cleaning off and the deep pitted (wasted away) metal needs to be cut out ..but only do this along one straight edge at a time. How much to cut out is a matter of choice. If seven-eighth of the metal surface is very deeply potted then you'd probably cut it out, but if there's only one deep pit in a square inch then you might live with it or else individually fill that with weld. You have to make the call based on how deep and much pitting there is. Template a new straight edge in card or aluminium foil ..the trays which food is cooked and sold in is useful for this because its easy to cut with scissors and when folded it doesn't spring back to being flat again). Once shaped it can be flattened again as a flat template to be reproduced in steel.. fine tune its shape and trim to match the corner at either end. NB. The final definition of intended cutout holes are best done later (with a file or grinder) ..so those edges are best left just a little oversize. Once you are happy with the accuracy of fit between corners, then tack-weld it in place. Only now do you do the same with the first corner, cut out one small patch at a time, so that you can always see what edge shape you're trying to make it to. Make that, and tack it into place. Piece by piece you can rebuild really complex shapes. When it's all together tacked in place - start filling in weld between your tacks. Just short (1/2") welds at a time and then let it cool, or else cool it with a damp rag. Move onto welding another area which is cool. Heat will expand metal, and when it's constrained by the surroundings it distorts and buckles. If you're not careful - you then weld the next bit which is buckled out of shape ! So by welding a short 'stitch' at a time and allowing it to cool, and perhaps a little tap of a light hammer or tweak with the pliers to straighten things up again - the distortion is kept to a minimum. It sounds like a whole lot of effort for something that's hidden under carpet or a trim panel. And that's why many people do a nasty job.. Always the choice is yours. It's lasted all these years as it was, and only you will know what's hidden out of sight. Of course with experience - things speed up considerably. Assessing what patches are needed and where best to cut them, cutting the right shape ..the first time around, the quality of your welding, being familiar with the power tools to prep and thereafter clean things up, etc. etc. It's a very useful 'craft skill' to have and the job satisfaction is rewarding. And even if nobody else ever sees it - you know. ! Best regards, Pete.

. Sold, paid for, and ready for collection ..around 10 am this morning. Second person to view bought her without hesitation. The significance of this is that this money goes straight into my Triumph TR4A restoration fund. And the floor & shelf space, and 'project time' are all freed up. It's a beautiful motorcycle but I now feel a touring in a 4A will be more fun than clobbering up and riding a motorcycle long distance

Barry, Just a thought, as I don't have a six.. but the inlet manifolds on the Vitesse is a big convoluted aluminium casting with cold water running through it, and then a blinking great big heat sink of an cylinder head and block. So I'm wondering if your starting issue at this time of year is not one of the fuel condensating before it gets into the combustion chamber.? How fast is the engine spinning over ? And how well does she start when the engine is warm ? Pete.

It was a hassle and the price was ' disappointing ' but at least I have US-dollars, more space, and one less ' project ' to nag at me and keep me poor (and no I'm not talking about wife n' kids). I now have two beautiful motorcycles for sale ...if you'd like to buy Funds needed to pay for the TR's restoration. Yes I hope / look forward to being there tomorrow evening. Pete.

Yes, I told him it's an ohc boxer engine ..so perhaps he's expecting a Porsche

I relate to that !

.. Ami super has gone to live in New York .. The ship departed on the 27th. Following a number of silly offers from the UK, and even more people trying to scam me (..clearly we don't even have a police farse any more), and then a couple of guys from the continent who couldn't get their ducks in a row, the gentleman who is Sales Manager for Bonhams Auction house in New York bought it (..cheaply).. I guess he ought to know an investment. Anyone else over here is just looking for 'a steal '.

. I bought the Clarke 151 simply because that just happened to be the best machine at the price ..within a sensible collection distance of where I live. Likewise it is on a standard 13a plug. I was actually hoping to find a 135, but for what I need would have been happy with a still smaller one. I do prefer one on wheels though, so its bottle is safely stored and carried on it. A bottle falling over is likely to smash its regulator gauge. These small machines are only designed to carry small canisters (..without a gauge), but by fitting my own strap I adapted it to take a 2-foot tall gas bottle, plus regulator gauges. That amount of gas lasted long enough to be practical for home-garage use. I did the inner wings and other minor repairs on the Citroen, did some minor jobs and made a tow-bar for an old Jag saloon I had a few years ago, and also made the wood burning stove with (I think) just one bottle. Then when I last refilled, the local BOC depot had non of that size of bottles in stock, so I had to accept a 3-foot-tall bottle (they didn't charge me more deposit nor rental, and the gas per cc is cheaper). But now I have to be careful when moving the welder because it wants to wheelie and topple over backwards.! I really ought to modify it and move its rear wheels back by 3" (like the Clarke 160). It shouldn't be too difficult ..as I have a welder ! Pete.

..I've just found a couple of pictures *1 of my repairs to a 1973 Citroen Ami, done in March '17 when I first bought the Clark 151. These lightweight Citroen inner wing flanges were made of thin gauge steel and then frayed with rust and otherwise split. Before . . . During the repair . . . And thereafter fettled and painted . . . Although the Clark 151 are said to weld metals up to 5 or 6mm thick (..huh, on a good day !). These repairs were made using so low a setting (the repair pieces were 18swg) that they might just as equally have been done using a Clarke 90 mig welder. *1 Sorry the photos are all small and low resolution but they are off my website, as the originals were lost when my computer's hard-drive crashed.