Peter,
Thanks for the great explination! Definitely makes since. I'll reset the timing
with the vacuum disconnected. I got a feeling that I'm going to end up pretty
close to my orginal setting before I started all this. That would make since,
since the MD266 is supposed to have the most power/torque from 1500 - 4000 rpm,
which is where is was.
Thanks again - Bryan
BTW - I will probably try using a smaller main jet in my carb, and also
readjust
the accelerator pump(man that thing really squirts out the fuel)
>X-Accept-Language: en
>MIME-Version: 1.0
>To: Bryan Vandiver <Bryan.Vandiver@eng.sun.com>
>CC: spridgets@autox.team.net
>Subject: Re: Speed timing, and gas mileage
>Content-Transfer-Encoding: 7bit
>
>Brian,
> The vacuum connected gives a false reading since the engine is not
>under load and has a high vacuum which it would not have if the engine
>was under load pulling the weight of the car. Fro example in your test
>you probably did not have the throttle open anywhere near where it would
>be if the car was actually doing 4000rpm in 4th gear. The wider the
>throttle is open and the more load on the engine the less vacuum there
>is. An advance of 32 degrees with no additional vacuum advance simulates
>the most advance there will be when the engine is working its hardest
>and will normally give the best power without causing the engine to
>knock ping or overheat.
>Under lighter loads the vacuum advance mechanism allows greater timing
>and improves gas mileage and driveability.
>You should have your 8 - 14 degrees of initial timing set first then see
>how many degrees you are advanced at 3500 rpm. All the centrifugal
>advance should be in by 3500 rpm or a little under. If the total advance
>is greater than this it should be limited by the stops on the
>distributor base plate not by retarding the initial advance, if the
>advance is less, then the base plate is binding or the springs are too
>strong or the weights are too light.
>So what you are looking for is an initial setting of 8-14 degrees, and a
>total centrifugal advance of 32-35 degrees at 3500rpm. With the vacuum
>attached you will probably pick up as much as an additional 10 degrees
>depending on load, Light load = higher vacuum = more advance = better
>gas mileage.
>
>As far as gas mileage I do not have much experience with webers or
>dellorto's but there are a couple midgets around here with similar specs
>and 10.5 to 1 compression using stock SU's that are pretty peppy and get
>about 25 mpg city driving.
>
>The timing marks jumping around are normally a sign of a worn
>distributor or worn timing chain or plug wires allowing spark to jump
>between them. You could switch back to points to eliminate the
>electronic ignition from the picture. I use a Crane XR700 on my car with
>no jumping around of the marks.
>Hope I did not confuse you too much.
>
>Peter S.
>Charlotte NC
>59 Bugeye
>71 Midget
>71 Fiat 850 Spider
>
>
>
>Bryan Vandiver wrote:
>>
>> Peter,
>>
>> No, I didn't have the vacuum disconnected when I timed at 4000rpm. I didn't
>> think I was supposed to. Doesn't it need to be connected to make sure the
>> engine is timed at 'full advance', or am I missing something here. Would that
>> also explain why I two distinct timing marks with my strobe light?
>> In any case, what exactly am I shooting for?, what is setting the timing at
30
>> degrees supposed to do for me?
>>
>> regards - Bryan
>>
>> >X-Accept-Language: en
>> >MIME-Version: 1.0
>> >To: Bryan Vandiver <Bryan.Vandiver@eng.sun.com>
>> >CC: spridgets@autox.team.net
>> >Subject: Re: Speed timing, and gas mileage
>> >Content-Transfer-Encoding: 7bit
>> >
>> >Did you have the vacuum advance disconnected when you did the 4000 rpm
>> >total advance?? The engine is not under load so would have a high
>> >vacuum. The total advance should be done with the vacuum disconnected,
>> >and should be around 32~36 degrees.
>> >Peter S.
>> >Charlotte NC
>> >
>> >Bryan Vandiver wrote:
>> >>
>> >> I have some questions about 'Speed timing' my 1275 engine in my bugeye.
>> >> First of all here's ,my setup.
>> >> Freshly 'rebuit' 1275
>> >> - .020 over piston
>> >> - Kent md266 cam/springs/lifters set. (timed in at 7degrees from TDC)
>> >> - 12g940 head (mildly ported, and port matched to manifolds) w/K&N filter
>> >> - dellorto DHLA 40 (simular to weber DCOE)
>> >> - Maniflow LCB for 1275
>> >> - 1.75 exhaust system
>> >> - Ignitor electronic ig in stock Distributor ('71 1275)
>> >>
>> >> When I timed the engine by ear, my timing setting ended up being between
>> >> 18-21Deg at 1000RPM, with smooth idle, and plenty of power between
>> 2-4000RPM.
>> >> I then speed timed the engine at ~4000RPM and the setting from above
showed
>> it
>> >> was running 40+ degrees at full advance.
>> >> I then reset the timing to ~30 degrees at full advance.
>> >> Now I have a much rougher idle, and It seems like my power band shifted to
>> >> between 3500-6000 RPM. The timing mark at 1000rpm with the vacuum advance
>> >> disconnected, is now at about 6 deg.
>> >> I also noticed when speed timing that my timing mark wasn't 'jumping
around
>> >> randomly, but that I saw two pretty stationary timing marks about 5 deg
>> apart.
>> >>
>> >> The car does start and idles well, although a little rougher than I'd
like.
>> I'm
>> >> wondering if now I'm running too retarted at low rpm.
>> >> Anyone have any experience with this that they'd like to share?
>> >> Please remember this is a 'street' car, NOT for track.
>> >>
>> >> Also, even though my plugs look good after 2-tanks of gas, (nice tan
>> deposits),
>> >> I'm getting less than 18MPG! this sounds way too low for a car/engine of
this
>> >> size. Not to mention the fact that this is with a 5-speed OD 210 tranny.
>> >>
>> >> Regards - Bryan Vandiver
>> >> San Jose, CA
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