Welcome to our resource for MG Car Information.
MG MGB GT V8 Factory Originals Technical - Lumenition - Lucas & Mallory Dual Point - Long
This is _very obscure but I thought I'd document it in case anyone is thinking of doing the same.
The saga - I bought a Lumenition Performance Ignition System which includes a matched Coil & variable dwell ignition amplifier. You also need a fitting kit to match your distributor. I bought the Mallory kit as I had a new Mallory Dual Point with Vacumn advance - I checked this with the MGOC who I was buying it from and they assured me this fitting kit would work fine with my distributor. Of course it didn't. <G>
Tech - The Mallory I use is a 27 series YL mech. advance with Vac. adv. can. It allows a max of 28deg mech (adjustable) + 15 degs vacumn. At 3500rpm I had her set to around 51deg at small throttle openings (max vac.) which although this sounds high, it is a recommended figure for max. fuel economy. My settings were (12 deg at <1000rpm initial + 24 mech + max. 15 deg additional Vac. advance). I averaged 26/27mpg (UK) on my last trip (3 tanks) around Ireland with this setup and Weber 500.
The kit Lumenition sells for Mallory distributors is only for Single points, NON vacumn advance distributors. So in frustration I decided to r&r my Lucas Factory V8 distributor. I got this all up and running fine but felt miffed that the new Mallory (which is a much sturdier, adjustable, and free revolving unit) was left unused. I also really wanted Vac. adv as it is a street car so I kept the Lucas until I could sort out the Mallory.
With the Lucas, I've found that I was lacking mid range punch and I put this down to the advance curve in the Lucas - I don't think it's steep enough for the Weber/Offy combo so I took another look at the Mallory Single point fitting kit with a view to installing it in the DP Vac. Adv. dizzy. Another incentive was the arrival of a Mallory Advance spring tuning kit which I ordered prior to the Lumenition. A $25 spring kit is a lot cheaper than the Lumenition Fully Programmable Control (400 UKP) which removes the need for advance springs altogether and must be the ultimate upgrade for the Std. Performance Ignition Kit if u can afford it! :)
Today I disassembled the Mallory and found that the supplied plate in the Lumenition Fitting kit could be epoxied to the base plate of my Mallory, simply by removing the spring & circlip securing the existing advance plate to the base plate, discarding the advance plate and glueing the Lumenition plate in it's place - location unimportant so long as it is centred perfectly. By doing this I have lost the Vacumn advance facility. I think this will be offset simply by the steeper curve and having almost as much advance all the time as I would have crusing under high vacumn conditions. The V8 hardly ever gets north of 2500rpm at any rate unless it's at WOT, the gearing sees to that.
I don't think the Lucas springs were weak in my distributor either as I did decellerating tests and matched to the figures given in the workshop manuals. If I had more tools I would have tried to retain the vacumn advance by drilling and tapping new holes in the Mallory advance plate and also removing the points retaining posts so they don't interfere with the Lumenition chopper. Unfortunately I don't have those facilities here (drill press, taps etc).
Result - I now have full advance in by around 2700rpm - 38 deg. total. 12 deg inital + 26 mech. The throttle response has improved dramatically, punch is immediate and I've discovered the lost torque/pickup I felt the car should have always had around the 1500-2500rpm range (not that it was ever _really lacking! <G>). I'll report back how the fuel economy is after another 3 tanks or so. The car is now much more responsive to quick blips of the throttle, and feels generally smoother in the midrange with no loss WOT up top as I would have expected. As for 'thats too much advance' argument, I dare anyone to get a Factory 8.3:1 V8 to ping!! I can't and I know after talking to Paul H. this weekend he can't either. I can't say any of this would apply with a 9.x:1 SD1 heads and the like.
So!! If you have a Mallory Dual Point, I would recommend their spring kit. Well worth the $ and also if you're considering switching to a Lumenition you can do it with a little bit of work and lose the vac. adv. or a little more work and keep that too. The much easier conversion is a pertronix kit of course as apparently they just fit right into a Mallory, but I preferred the locally supported lumention, the plug and play rev limiters and options to upgrade to the computer when I have more $ than sense at a later date. <G>
FWIW, HTH, YMMV!!
<VBG> and sorry for wasting all the bandwidth! :)
|Oh no! Not even more mid-range punch! When you get to drive mine you'll think it's 4-cylinders short.|
|Once the engine volumetric efficiency is improved then your into 28 to 30 degrees of advance as for maximum power. The greater advance needed with the low compression, small valve less efficient head(ed) V8's is typical, although I would normally expect this to be between 34 and 36 degrees total. The difference is to small to worry about and as engines are individual, so are their ideal settings.|
Just about to fit a Mallory to my 4.6 Motor. Be interested to know what the difference is between the 'standard' mallory spring advance rate & the range supplied in the kit !
This thread was discussed between 08/05/2001 and 15/05/2001
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.