Hamish Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) Hi learn-ed ones. for some reason I have a yearning for a pair of weber carbs on my 3a i have looked at the Teri Ann site http://www.tr3a.info/WeberDCOEinfo.htm but at what stage of set up do they improve upon my H6’s ? Either performance and or driving characteristics. i have a very reliable car, it’s 116bhp at flywheel, 138ft/lb torque at 3750 rpm, 87mm, 4branch big bore exhaust. Old performance cam but no idea as to profile. It does need revving tho since fitting big bore manifold. The crank is nitrided and flywheel lightened. I understand I could go to 40DCOE Or 45’s ? i understand Which ever type, that all the chokes and jets will have to suit my engine on a rolling road. but if I did go this route I’d have to find a second hand set. Which bring up the carb numbers to get a matched pair ? hope you can share your experiences and wisdom thanks H Edited June 28, 2020 by Hamish Quote Link to post Share on other sites
MilesA Posted June 28, 2020 Report Share Posted June 28, 2020 That will stir the pot Hamish! On the one hand you 'have a very reliable car'. On the other, finding a suitable matching pair, expense, installation, version (40s probably), choke, set up, associated mods (cam, trumpets, etc.), material improvement to performance....? Others will be along with the detail and views as I only sit on the edge of this pot with a brace of 45s on a road going car which only starts to relax at about 50mph and slurps fuel like a demon! Interested to see what the wise ones say though. Miles Quote Link to post Share on other sites
cvtrian Posted June 28, 2020 Report Share Posted June 28, 2020 Hi Hamish, just sent you a pm Cheers Ian Quote Link to post Share on other sites
Motorsport Mickey Posted June 28, 2020 Report Share Posted June 28, 2020 You need 42s Hamish, they can be choked up to 34 (performance) or down to 32 for your normal road running spec. The last pair I've just finished refurbing with chokes at 34mm and as near as can be anticipated the correct jetting etc but you can't buy them new, Or you can just get a professional to work on your head and balance the system fitted (with 89mm pistons exhausts, inlets and bigger valves fitted and with a bit of work on an offset head and a talented rebuild get 148 hp AT THE BACK WHEELS on SUs...blow your mind. Mick Richards Quote Link to post Share on other sites
Hamish Posted June 28, 2020 Author Report Share Posted June 28, 2020 5 minutes ago, Motorsport Mickey said: You need 42s Hamish, they can be choked up to 34 (performance) or down to 32 for your normal road running spec. The last pair I've just finished refurbing with chokes at 34mm and as near as can be anticipated the correct jetting etc but you can't buy them new, Or you can just get a professional to work on your head and balance the system fitted (with 89mm pistons exhausts, inlets and bigger valves fitted and with a bit of work on an offset head and a talented rebuild get 148 hp AT THE BACK WHEELS on SUs...blow your mind. Mick Richards Mick i think you beat me to the last 42’s on eBay. Are you selling them ? are you saying the webers are worth the engine work you suggest as an “or” option ? Ian thanks I have replied. Quote Link to post Share on other sites
DavidBee Posted June 28, 2020 Report Share Posted June 28, 2020 43 minutes ago, Motorsport Mickey said: Or you can just get a professional to work on your head and balance the system fitted (with 89mm pistons exhausts, inlets and bigger valves fitted and with a bit of work on an offset head and a talented rebuild) and get 148 hp AT THE BACK WHEELS on SUs...blow your mind. Mick, But let's say, for the sake of argument, that you had to make a comparison of like with like. What if you have done all that with H6s fitted and then replaced them with 42 Webers? What would hp would you have at the wheels, in your opinion? Quote Link to post Share on other sites
Motorsport Mickey Posted June 28, 2020 Report Share Posted June 28, 2020 Hamish, The work required upon the engine to gain hp and performance are equal with both Webers and SU. The same engine that gave 148hp at the back wheels gave 165 hp at the back wheels with Webers (enough that TR6 drivers marched over to see what was under the bonnet). I think that the physical appearance of the Webers "sells" the idea to many owners, but without the attendant work the gains will not deliver fully, a typical increase of fitting the webers is about 15hp with a fully integrated system from a reworked head with bigger valves with offset etc etc. I've been told of only 8 hp increase (not on mine) when the "package" hasn't been fitted, it's the Olympic ideal "the aggregation of small advantages" delivers a bigger result. Mick Richards Quote Link to post Share on other sites
Motorsport Mickey Posted June 28, 2020 Report Share Posted June 28, 2020 17 minutes ago, DavidBee said: Mick, But let's say, for the sake of argument, that you had to make a comparison of like with like. What if you have done all that with H6s fitted and then replaced them with 42 Webers? What would hp would you have at the wheels, in your opinion? Hi David, Our posts were being worked on together and I think my post answered it...however beware the comparison between Rolling roads..some use horses and some use ponies. I've never built a 4 cylinder engine that made 200 hp at the back wheels, but I've beaten cars that were said to have had ! Having had a 27 year sabbatical and knowing what I know now I believe a 215hp car at the back wheels is quite achievable, and reliably, but it would be a mother to drive on the roads ! Mick Richards Quote Link to post Share on other sites
Motorsport Mickey Posted June 28, 2020 Report Share Posted June 28, 2020 27 minutes ago, DavidBee said: Mick, But let's say, for the sake of argument, that you had to make a comparison of like with like. What if you have done all that with H6s fitted and then replaced them with 42 Webers? What would hp would you have at the wheels, in your opinion? The Webers can give you what the SUs can't...flow, lot's of flow. So as an absolute modification the Webers...well we can't rediscover the wheel, in the late 1950/60s Webers were being fitted as the ultimate power modification and that still remains so today, easily better than the DU6 carbs that I ran as an experiment back in1988, the needles and insides not as clean as the Webers. As regards which Weber, although I've never run on them yet I think the 42s will outperform the 45s, not on absolute power where I'd expect the 45s to pinch a couple hp maybe but on snappy delivery mid corner and midrange which is where the cars spend far more time than balls out top end power and I'd be disappointed if the 42s didn't show a time advantage. Mick Richards Quote Link to post Share on other sites
Hamish Posted June 28, 2020 Author Report Share Posted June 28, 2020 Mick thanks for your insights. I need to know my car better. I don’t know the cam and i don’t know what head work was done, previous owner undertook kas Kastner chamber shaping in the ‘70’s I think. does crank nitriding last for ever ? or is it a surface treatment that wears off ? i think I’ll still keep looking for a pair but 40’s or 45’s ? H Quote Link to post Share on other sites
DavidBee Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) 1 hour ago, Motorsport Mickey said: Hi David, Our posts were being worked on together and I think my post answered it. It did, it did, Mick! Very interesting indeed. Thanks, I guessed as much. Presumably, a limited slip differential would be required with that much power? You've already answered the other question; namely, which Webers are best suited, given the qualities of TR torquey engines: the 42s. Edited June 28, 2020 by DavidBee Quote Link to post Share on other sites
BlueTR3A-5EKT Posted June 28, 2020 Report Share Posted June 28, 2020 Why not a line of Nikuni s ? https://www.gomog.com/allmorgan/MikuniConversion.html Quote Link to post Share on other sites
Motorsport Mickey Posted June 28, 2020 Report Share Posted June 28, 2020 7 minutes ago, BlueTR3A-5EKT said: Why not a line of Nikuni s ? https://www.gomog.com/allmorgan/MikuniConversion.html Nice... Mick Richards Quote Link to post Share on other sites
david ferry Posted June 28, 2020 Report Share Posted June 28, 2020 I can’t remember, but may have a spare set of 45s and manifolds knocking around in the workshop. If you’re really after a pair of 42s, budget for a lot of money to buy them. The last pair I had went to a Maserati restorer in Italy. They are not easy to find. David Quote Link to post Share on other sites
Hamish Posted June 28, 2020 Author Report Share Posted June 28, 2020 (edited) Always interested in seeing What is available David. but I know 42’s are beyond my budget, sadly. Edited June 28, 2020 by Hamish Quote Link to post Share on other sites
DavidBee Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) 1 hour ago, BlueTR3A-5EKT said: Why not a line of Nikunis? Well, Peter, I read the article about conversion from SUs to Nikunis for a Morgan or other classic running on SUs, and am none the wiser, as to your question. Yes, the line up looks nice. But the writer does no more than state that they are better (than either SUs or Webers), and produce more power than the latter. No evidence provided though, and no technical comparison either. Do they work on the same principle of multiple jets, for example? How do they compare? Edited June 28, 2020 by DavidBee Quote Link to post Share on other sites
Dic Doretti Posted June 28, 2020 Report Share Posted June 28, 2020 No one has mentioned the poor old stressed crankshaft, for the webers to perform at their best the engine needs to be revved which the standard crank will not like. For the ultimate performance a steel crank is needed or it will be an ultimate big bang! Cheers Richard Quote Link to post Share on other sites
Motorsport Mickey Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) Richard, My last Championship winning season in a TR4 (1988) I ran on a standard but lightened crank, prepared in the usual way Nitrided and with a stress relieving undercut in the appropriate place with main journals at -10 thou and the big ends offset on the grind by a 30 thou extra throw meaning the big end bearings had to be Massey Ferguson - 60 shells. MINUS 60 thou. Running on 1 3/4 SUs and a 6000 rev limit the engine put out 148HP AT THE BACK WHEELS and maintained it's power and torque all season. The car completed 19 races and practices (over 380 racing laps) that season. It also represented the 4 Cylinder TR Team at Snetterton in the Birkett 6 Hour relay race using a 6000 rev limit and using 45 Webbers which gave 165HP AT THE BACK WHEELS (still on it's standard crankshaft with -60 big ends) in 4 sessions of about 20 minutes each (about 15 laps each session, 60 laps total) where we had a tremendous dice with Chris Carter in his TR6 and fooled around with a brace of Lotus 7 who were in the way. Finished off the season with a 93 lap session at the British Heart Foundation Race day at Snetterton at the end of the Year, where I broke the car...1st motion shaft on the gearbox. The revs required are dependant upon the camshaft used, the Webbers will certainly flow enough to go higher but with the cam used max power was at 5000 revs, maybe with more modern cams I would change where the revs were used. The car was sold at the end of the season to Trakway (my sponsor) and I was asked to again rebuild the engine and prepare it for the next Championship season. it was stripped and measured and the bearings (minimum wear) mains and big end renewed along with new piston rings, pistons were in good condition. It again won the TR Register championship in 1989 with Chris Conoley driving it, still on it's standard crankshaft with - 60 thou big ends. I don't see how a steel crankshaft would help that car or how it would increase it's reliability, if you drive the car within it's rev limits the power is delivered at areas within the standard materials capability. If you set out to use 7000 revs continually then yes steel crankshafts will be required. Mick Richards Edited June 28, 2020 by Motorsport Mickey Quote Link to post Share on other sites
timhum Posted June 28, 2020 Report Share Posted June 28, 2020 Hamish, Have you considered the Jenvey Heritage throttle bodies? My car has these fitted with an Emerald ECU set-up. all the best Tim Quote Link to post Share on other sites
Paul Hogan Posted June 29, 2020 Report Share Posted June 29, 2020 10 hours ago, Dic Doretti said: No one has mentioned the poor old stressed crankshaft, for the webers to perform at their best the engine needs to be revved which the standard crank will not like. For the ultimate performance a steel crank is needed or it will be an ultimate big bang! Cheers Richard Which is exactly what happened on my TR4! After a very large hole appeared in the side of the block one day - which was handy for taking bits of #3 con rod and piston out of it, I fitted a new engine with a steel crank and H beam rods. I should add that I wasn't responsible for wrecking the engine. that was done by the idiot at the MOT station! Hoges. PS That car AAD769B is now for sale again at TRGB. Sadly it seems to have been rather neglected since I last owned it. Quote Link to post Share on other sites
Andy Moltu Posted June 29, 2020 Report Share Posted June 29, 2020 But was it the crank that went or the rod which then demolished the engine? The rods are more of a weak link than the crank. As has already been pointed out significant power gains can be made but there is a significant difference between the requirements of a road car and a race car. A car with peak power at 7000+ rpm is likely to be an utter git to drive in traffic. There needs to be significant work done to the engine to really benefit from Webers and it may be that the cam and other mods you opt for will be influenced by your choice of carb so careful thought as to which componenets you opt for needs to be made as part of that process. Weberising a stock engine may unleash a few Hp at the cost of mpg - yet Weberising a well planned uprated engine may well make a significant gain for a road car. If correct Webers are getting scarce would efi be an option worth considering? Quote Link to post Share on other sites
Hamish Posted June 29, 2020 Author Report Share Posted June 29, 2020 Thanks guys i use my car on the road and it has very good tractable manners. its now more Revvy as it has a 4.1 rear end. i use it in sprints and hillclimbs as many of you know but only 5 or 6 events in a “normal” season. And only done 3 seasons this one being effectively cancelled. Despite this I have Been 2nd in class twice and 10 over all twice and 7th oa last season. this lock down and on furlough I spent my time and event refunded money on the front suspension. i know engine performance should be done in one go matching everything together! But just don’t have the budget for that. I don’t even know what cam I have ?! It’s an old warmed up version I think ? I’ve never changed a cam and I have seen a few on here Who have had to try A few cams before getting it right !! for all I know a set of 45’s may ruin the characteristics? but the H6’s have been rolling road tuned and the chap knows his carbs and polished profiled the needles as best he could. thus wondering if second hand webers may give me a little extra? A first world problem I understand that !! but all you folks will get that. please share your carb experiences and characteristics of driving and best cam carb pairings etc im still very much learning as you can tell H Quote Link to post Share on other sites
stuart Posted June 29, 2020 Report Share Posted June 29, 2020 Im running Dellorto 40`s on my 4a and its still running a standard cam so still easy to pootle round in traffic even with a slightly lightened flywheel but it does go if you want it too, since Ive gone up to 89mm it took a while to get the jetting right again but I think its pretty much there now, the secret ingredient is when the engine was originally built more than 25yrs ago it was built by an ex Brabham engine specialist while he was working the night shift at Reynard racing and he did the head work on their flowbench. Stuart. Quote Link to post Share on other sites
roy53 Posted June 29, 2020 Report Share Posted June 29, 2020 just to through a spanner in the works i run 48s . Dyno figures show webers only gain being at the very top end. Hamish did you think of 2" SUs ? I found that SUs seemed to make it rev quicker but probably my ears. Roy Quote Link to post Share on other sites
Hamish Posted June 29, 2020 Author Report Share Posted June 29, 2020 1 hour ago, roy53 said: just to through a spanner in the works i run 48s . Dyno figures show webers only gain being at the very top end. Hamish did you think of 2" SUs ? I found that SUs seemed to make it rev quicker but probably my ears. Roy No not thought of bigger SU’s anyone done it ?? Quote Link to post Share on other sites
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