19-10-2018, 05:48 AM
(This post was last modified: 19-10-2018, 05:54 AM by Ian Williams.)
As promised the first instalment of my detailed feed back on these Accuspark distributors. The unit under examination is new and the first thing I noticed was the large amount of side play in the spindle, so before installing it on a car for testing I decided to dismantle the unit, take measurements and compare them with genuine Lucas components.
So first up side play in the spindle bearings was 14 thou, even some fairly clapped out DK4's in my parts shed have trouble matching this achievement in authenticity! The reason for this was revealed once it was apart, the bearings are roughly machined from steel and pressed into the aluminium body, the top one being 1/2" to low in the body leaving the top of the spindle poorly supported.- see pictures comparing with a bronze bushed original.
Once dismantled it was apparent none of the components were hardened, in fairness the Lucas distributors have not got all of the important wear surfaces hardened either, but some items like the cam are. There were no lubrication scrolls or oil drillings other than the bit of bent tube attached to the side of the body. Once the smear of grease has been exhausted it will be almost opposable to re lubricate unless dismantled. I guess virtually nobody ever did, and very few now actually lubricate their distributors anyway. Next I measured slop in the advance mechanism, for reference all the pins on the Lucas Distributors were 3/16" or 187 thou, I have a number of New Old Stock spares to compare with. On our Accuspark they varied quite a bit from 181 thou on the cam pins, 182 thou on the base plate, and 185 thou on the steel advance weights - the original weights were lead with steel pins. Side play in the toggles which fir over the pins measured 8 thou and were quite sloppy on the pins, new Lucas parts are a snug fit and clapped ones are often worse the Accuspark, wear in this area, the toggles and pins particularly is why many advance mec's don't work properly. The accuspark springs were both the same weight and much lighter than the originals, this would create a different advance curve and partly explains why some people have difficulty timing the units accurately. Lucas units use a two stage advance, a light spring controls initial advance and a strong spring takes over as speed increases, the end of the strong spring should be loose over the pin fully retarded and is shaped to accommodate this- see picture
Side play between spindle and advance cam was measured at 4 thou, a new Lucas has negligible play in this area, The Accuspark base plate has 10 degrees of advance giving 20 degrees engine advance, any owner fitting one should take this into account. In summary I found excessive play in every component and many of the bearing surfaces were roughly finished, as a result I would anticipate quite rapid wear.
Pictures below, Accuspark is on the left Lucas the right
So first up side play in the spindle bearings was 14 thou, even some fairly clapped out DK4's in my parts shed have trouble matching this achievement in authenticity! The reason for this was revealed once it was apart, the bearings are roughly machined from steel and pressed into the aluminium body, the top one being 1/2" to low in the body leaving the top of the spindle poorly supported.- see pictures comparing with a bronze bushed original.
Once dismantled it was apparent none of the components were hardened, in fairness the Lucas distributors have not got all of the important wear surfaces hardened either, but some items like the cam are. There were no lubrication scrolls or oil drillings other than the bit of bent tube attached to the side of the body. Once the smear of grease has been exhausted it will be almost opposable to re lubricate unless dismantled. I guess virtually nobody ever did, and very few now actually lubricate their distributors anyway. Next I measured slop in the advance mechanism, for reference all the pins on the Lucas Distributors were 3/16" or 187 thou, I have a number of New Old Stock spares to compare with. On our Accuspark they varied quite a bit from 181 thou on the cam pins, 182 thou on the base plate, and 185 thou on the steel advance weights - the original weights were lead with steel pins. Side play in the toggles which fir over the pins measured 8 thou and were quite sloppy on the pins, new Lucas parts are a snug fit and clapped ones are often worse the Accuspark, wear in this area, the toggles and pins particularly is why many advance mec's don't work properly. The accuspark springs were both the same weight and much lighter than the originals, this would create a different advance curve and partly explains why some people have difficulty timing the units accurately. Lucas units use a two stage advance, a light spring controls initial advance and a strong spring takes over as speed increases, the end of the strong spring should be loose over the pin fully retarded and is shaped to accommodate this- see picture
Side play between spindle and advance cam was measured at 4 thou, a new Lucas has negligible play in this area, The Accuspark base plate has 10 degrees of advance giving 20 degrees engine advance, any owner fitting one should take this into account. In summary I found excessive play in every component and many of the bearing surfaces were roughly finished, as a result I would anticipate quite rapid wear.
Pictures below, Accuspark is on the left Lucas the right
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