Andy,
Without the aid of a dyno or exhaust analyzer it would be hard to tell whether
or not different needles or jets are in order. Chances are you do need
different jetting. The way your engine is equipped indicates a potential higher
degree of efficiency.
It may not be scientific but I've used the following method on motor cycles
(15:1 flat tracker) as well as a turbocharged car running... are you ready for
this... 32 psi boost. This was a 240Z I ran in AP and decided to try my luck
at the drags with. Best run was 11:98 e.t. @ 119 mph, after finally getting it
jetted correctly for full throttle, long distance (1/4+mile) runs.
Start with a new set of plugs. Find a good road where traffic isn't a problem,
straight as possible. To avoid getting a ticket, third gear may work. Run
hard, put the clutch in as you shut off the engine, coast to a stop. Pull the
plugs and take a "reading". I do this for different rpm ranges. This will give
you a fairly accurate indication of how the engine jetted. More than one run in
each range is advised. I am assuming here you are familiar with "reading"
plugs.
I know I'll get a tongue lashing from some of you out there, but us old hot
rodders have old (and poor) ways! Just my thoughts.
WFO Herb
Keep the sticky side down!
Andy Webster wrote:
> Okay petrolheads,
> I'm trying to get the best out of what I've got:
> A 10CCDAH high comp 1100 (.040 OB so 1136cc) with a 998 cooper head.
> I've got a 3 into 1 extractor with fairly short primaries, about 1 foot
> long.
> Twin 1 1/4" S.U.s as standard with AN needles.
> Anyone know if I should change needles?
> I'm fairly sure my tacho is ~accurate, I cant get it to idle anything like
> smoothly below 1000rpm, Go <1000 rpm and the engine trys to shake itself off
> the mounts
> I'm pretty sure theres a lumpy-ish cam in there as the idle is not smooth
> but a rythmic thing like when you tap your fingers from
> pinky,ring,bird,pointer on the table in quick succession over and over, you
> know, like when your waiting for a web page to load. Is that normal or a
> symptom of a standard cam and some other problem?
> With my flash new timing light I set the ign timing to 8' btdc. Seeing as it
> was at 1000rpm instead of the specified 600rpm should that have been less
> advanced ,say 5'btdc?
> When revved should the mark fly around to 40' or more btdc? Thats just the
> centrifugal advance doin its thing right...?
> I think I have pre-ignition paranoia, I always think its knocking but nobody
> who knows has ever said "hear that?" "thats knocking" so I cant be sure.
> Thanks for any words of wisdom
> Andy
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