vuser@druhi.UUCP (GerardenC) (03/05/86)
reply-to: eshelman@tekigm2 Eshelman.UUCP (Douglas Eshelman) >References: >I am considering weberizing my MGB. I would be interested in >hearing from anyone that has had experience with MGBs and either >side draft or down draft Webers. I would also be interested in >hearing about any other performance oriented modifications that >have been done on MGBs ( other than engine swaps ). > >Thanx in advances, Doug Eshelman. If you plan to drive the car on the street I would suggest using a weber down draft they are much easier to tune. the side drafts work best at high rpm, High velocity air flow is needed to keep them pulsing correctly. The sidedrafts will usually bog at low rpm no matter how you tune them. A good carb for the MG would be a DGV 32/36. Headers would also make a good improvment ( dont forget a low restriction exaust). I used this combination on my triumph (almost the same engine) and the performance was quite good. If you want to use strombergs and want to get rid of flooding and loading problems in the corners, try a Grose-jet valve in the float chamber. They advertise in the back of auto week. I am now installing some in my carbs, I dont know how they work yet, but I have heard many good things. chuck gerarden ihnp4!drutx!druhi!vuser
bae@fisher.UUCP (Shiva the Destroyer) (03/07/86)
> If you plan to drive the car on the street I would suggest using > a weber down draft they are much easier to tune. the side drafts > work best at high rpm, High velocity air flow is needed to keep > them pulsing correctly. The sidedrafts will usually bog at low rpm > no matter how you tune them. I have been running a DCOE45-13 sidedraft on my '66-'67 B for 7 months now, and it works great. I had no major difficulties tuning it to run well at both low and high end. To go into the gory details: Suggested Performance Modifications: HEAD ---- You did not state what year your MG was. You want to use the 'hi-compression' (8.8:1) head from the earlier non-smog MGBs if you have a late-model B. Then you want to hone down the heads until, in combination with your hi-performance FORGED pistons you have a compression ratio of 10.3->10.5:1. This will allow you to run on 92 pump octane Super-Unleaded without difficulty. You should polish the ports of your head, but DO NOT have some machine shop 'port' your head for you. The water jackets are very near the surface near the valve ports, and it is quite easy to ruin a very expensive head. Do not purchase an aluminum hi-compression head. This head is not manufactured any more, as the valve guides fall out after ~12k miles, however some shops still have a few hanging around which they are trying to get rid of. Use stellite valve seats and bronzed valve guides, as this will allow you to run hotter, and on unleaded most of the time. The extra expense is worth it, as leaded gas is fast disappearing. Fit a new set of early-model DOUBLE valve springs, but do not install high-performance competiton springs, as you will have to renew your cam every 6k miles. You don't really have to increase the valve crash speed (6230 RPM) unless you plan on serious racing, and it's not worth the extra bother of lightening and shortening pushrods, balancing pistons, soft main bearings, etc. Renew your rocker assembly and bearings while you have the thing apart, as old rocker assemblies do not take to the increased power, and often destruct. Note that the inner two cylinders will run hotter than the outer, as their exhaust ports are very close together, and they share a common exhaust path through the head. This should influence your choice of plugs. CAM --- You can purchase through Moss Motors a 'competition' cam, or you can have yours machined to your specifications. Unless you are going for full b*lls-out performance, I recommend a milder cam than the full race. Slightly increased lift and duration will be sufficient. If you increase the lift, make sure to machine the head properly to give clearance, as there is already a tight fit in there. CRANK ----- MGB cranks for the most part are nicely balanced, still it is worth checking while you have the engine apart. INTAKE SYSTEM ------------- The Weber DCOE45 is the way to go, as it requires far less skill and time to maintain, ONCE IT IS TUNED PROPERLY! It will run like garbage unless it is correct. Suggested tuning for modifications presented here: Stock Warmed Up Full Race ----- --------- --------- Auxiliary venturi: 4.5 5.0 4.5-5.0 Chokes: 33 34 36 Main jet: 135 140 150-170 Air correction jet: 170 170 170 Emulsion tubes: F15 F15 F16 Idling jets: 50,60F9 55F9 50F9,55F9,60F8 Pump jets: 55 55 60 There is quite a bit of variance in the idle jet setting, depending on the idle speed you set, and the amount of pick-up condition you are willing to tolerate. (Pick-up condition == belching fire) The recommended method is to pick your desired idle speed, then try idle jets until you go one step too rich, then back off one step. Setting your mixture too rich is bad, as it has a tendency to wash out your main bearings after 5k miles :-) Polish the intake manifold supplied with your carb conversion kit, it will get you 2-3 hp. Do not use the supplied gaskets between carb and manifold, as they quickly develop leaks. Edelbrock supplies an Australian-manufactured single-piece dual-o-ring gasket assembly which is far superior, for about $12.00. It is a limited-availability part, as the two Australians who fabricate the assembly evidently only work 1/2 time... Also beware of vacuum leaks between manifold and engine block - the intake manifold mounting ears are very roughly machined, and need to be hand-ground to fit your bolts/exhaust manifold/header assembly, or else! DO NOT WEBERIZE A WORN ENGINE - it will surely die. EXHAUST ------- Headers and free-flow exhaust system. MAIN ENGINE ----------- You can go oversize up to .040 if you want. I have kept mine stock displacement for aesthetic reasons. Do not use the soft high-performance competition bearings on your mains (incidentally, do not hype an early 3-main bearing engine - it won't last long), as you will have to renew them quite often. Do use the best rod-bearings you can get - it's worth the confidence. There are also special performance rings available - these take a long long time to seat properly, but if you are willing to baby the engine until they seat, you should use them. DRIVETRAIN ---------- Competition clutch and pressure plate are necessary. I suggest putting some ballistic nylon or wire mesh between you and the clutch if you enjoy walking, and plan to drive the car hard... The rear end is sufficiently strong to handle the added power without modification. If you are rebuilding your gearbox at this time and you have an early-style gearbox, it is possible to make first, second, and third gear a bit closer in ratio, thus avoiding the classic MG 'missing-syncro-in-second' syndrome, if you can find the necessary parts, which consist of a different ratio second gear assembly, and the corresponding layshaft. These parts are next to impossible to locate, unless you have a friend in England with old racing parts in his basement. SUSPENSION AND HANDLING ----------------------- The Armstrong lever-arm shocks are good performers, if in pristine condition. Fit competition shock valves to these if you are using them, preferably the adjustable sort. You may wish to convert to tube-type shocks. There are two kits available, one for Gabriel gas shocks, and one for Konis. The Gabriel mounting system is better. The disadvantages of these are that a) they are expensive ($400-500) b) they increase unsprung weight. The advantage is that minimum maintenance will be required once installed. Good anti-roll bars front and rear are essential. Moss Motors has a couple of pages devoted to MGB suspension modifications in their big catalog, I suggest you look there for details. Be careful not to disturb the neutral handling characteristics of the car by installing Godzilla-size bars... Polyurethane Bushings. Strengthened arch springs - stock MGB-GT springs work fine. Strengthened coil springs in front. Clean your stearing gear, and replace the boot seals. I do not suggest you lower your MG much, unless you have a late-model raised MG (to meet Fed. bumper-height regulations), in which case you ought to ASAP. MG's do not have enough ground clearance for American city driving as it is, no need to complicate things. Any more than 3/4 inch lowering, and you will have problems with speed bumps, sewer drains in driveways, small rocks and branches on the road, etc. A good roll cage or properly braced bar will go a long way in stiffening up the MG frame, which is normally quite flexible. A brace in the engine compartment is also useful. Replace the two 6v batteries in the rear of the cockpit with a good 12v battery located in the right rear of the boot. This will save you time and money in maintaining your batteries. If you are philisophically opposed to this, you can place a single small-import 12v battery in the right battery well, and get much the same effect. Wires wheels are not the most performance oriented wheels available, but what the heck - they sure look nice if you've got them. If you don't, avoid them like the plague, if you do, you might as well learn to live with them. Tires make a world of difference on the MG. I run Yoko A008's, 185/70 R14s. These are pretty bad in the rain though. See the latest tire comparison arguments for details. IGNITION -------- If you have fitted the Weber system, make sure that your stock Lucas distributor has the proper advance abilities, as there is no vacuum outlet on the Weber, so you will be using centrifugal advance alone. Mallory makes a distributor which fits your MG which has adjustable advance characteristics, and which will work fine without vacuum, if you do not wish to play with the Lucas. Lucas makes a good high-energy coil which seems to lead to more reliable ignition, particularly at high rpm. See the previous note on plugs. BRAKES ------ The Lockheed braking system normally fitted by the manufacturer is quite adequate, but maintain it very regularly. The front hoses like to break. Often. You may wish to fit a dual master cylinder if you have an early single master system. It won't help much though - just keep your handbrake adjusted properly, and be alert. MISC ---- British Leyland put out a Performance Tuning Guide and a Special Tuning Guide, which contain detailed information on the machine work you can do on your engine to achieve various levels of performance and reliability (inversely related, of course). One of these is reprinted in 'The Complete MGB', a very good shop manual. Parts sources: Moss Motors: 800-322-6985 ask for their big MGB catalog Victoria British: 800-255-0088 Dolphin Coventry: 415-964-2414 Weber conversion specialists -- Brian A. Ehrmantraut Ad Maioram Gloriam Hasturi! UUCP: {allegra, astrovax, princeton} !fisher!bae BELL: (415) 962-7192 USnail: P.O. Box 476, La Honda, California, 94020