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DavidHill
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« on: 07 July, 2023, 07:47:57 AM » |
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Morning All,
Finally on the road, taking my Aprilia down the by pass with a GPS speedometer I can only register a maximum speed of 65-67 MPH flat out with the throttle wide open. I am running the standard Zenith carb, with a standard exhaust. The motoring reports describe an easy 70mph with an 80mph maximum...should I be able to achieve that??
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lancialulu
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« Reply #1 on: 07 July, 2023, 11:36:57 AM » |
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is it a 1500?
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Its not the winning but taking part! or is it taking apart?
Lancias:
1955 Aurelia B12
1967 Fulvia 1.3HFR
1972 Fulvia 1600HF
1972 Fulvia Sport 1600
1983 HPE VX
1988 Delta 1.6GTie
1998 Zeta 21. 12v
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GG
Megaposter
Posts: 543
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« Reply #2 on: 07 July, 2023, 11:59:37 AM » |
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Have you checked the hole in the main carb jet? We rebored one in a vintage Appia to original specs, and found another 10+ mph.
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B20 s.2, Appia C10, Flavia 2000
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ColinMarr
Permanent resident
Posts: 1635
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« Reply #3 on: 08 July, 2023, 08:02:18 PM » |
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Remembering former times when Aprilias were less precious than they are now, I recall 80 mph was quite realistic. Flickering speedo needles were not reliable, but by the late 1960s electronic rev-counters were available and I remember putting one to the test. On my car, which had a Series 1, 1352cc engine, fitted with a “big Weber” and straight-through exhaust, it would readily pull 4000 rpm and cruise at 3500. At the time, we thought 1000 rpm in top gear equated to 20 mph and it seemed reasonable to claim 80 mph.
The attached photo from 1969 is a ‘still’ from an 8mm cine camera filming while driving a Morris Minor in pursuit. At times, its speedo read over 80 … and I burnt out its exhaust valves, but that’s another story.
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DavidHill
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« Reply #4 on: 12 July, 2023, 08:54:47 AM » |
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Thanks for the thoughts re carb jets etc...any information on what the bore size is on the main jet for my Zenith carb? (it looks clean and unaltered so am fairly sure it is ok). My engine is a 1500cc and has recently been rebuilt. (last 500 miles).
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Spider2
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« Reply #5 on: 12 July, 2023, 01:21:53 PM » |
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with a rebuilt engine is it wise to attempt top speed? Not familiar with the Aprilia engine but would not a more gentle approach to running it in be quite a good idea?
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Kari
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« Reply #6 on: 12 July, 2023, 01:31:51 PM » |
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The main jet size on the Zenith 32 VIM and the VIML 3 is 110.
Recent engine rebuilt: The rings have seated properly? Valve timing on the spot? Just a thought.
Karl
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Sliding Pillar
Permanent resident
Posts: 1697
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« Reply #7 on: 12 July, 2023, 06:10:35 PM » |
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1955 Aurelia
1961 Lamborghini
1985 Y10
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davidwheeler
Permanent resident
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« Reply #8 on: 16 July, 2023, 11:14:18 AM » |
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Mine is also (almost) 1500 cc and has a twin carb Nardi setup. After having run it in over some 2000 miles! I find it easy to cruise on the motorway at 70mph with quite a bit in hand so it should attain 80mph. Remember Vincenzo when taken for a ride in the first Aprilia said nothing until the end of the test when he said "Magnificent motorcar" (or something of the sort, in Italian) but also said it was too fast so the top speed was reduced to 80mph.
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David Wheeler. Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
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LatheJon
Member
Posts: 17
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« Reply #9 on: 19 July, 2023, 07:59:09 AM » |
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Hi David, If your Valve and Ignition Timing is ok, it may be Fuel. If you have a standard Fuel Pump it may not be getting enough. I think I remember Harry saying "using a thick gasket on the fuel pump, the car wont go above 50"
A thick gasket and a worn actuator rod may not help top speed.
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davidwheeler
Permanent resident
Posts: 1450
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« Reply #10 on: 20 July, 2023, 12:54:46 PM » |
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Part of the reason I use an electric one!
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David Wheeler. Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
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DavidHill
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« Reply #11 on: 06 August, 2023, 09:16:02 PM » |
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Some progress to report...i have checked the main jet size - and it is 1.1mm, so the jet is fine. Interested in the report that it could be a too thick gasket on the fuel pump. How much is too thick? My fuel pump is mechanical - but has new parts in it so should be ok...but could be the issue. On a drive down the duel carriageway this afternoon it was very happy at 50 mph, but i have decided to properly run it in first before trying for higher speeds...so far 400km in from the engine rebuild...
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