Questionwould i benefit from changing my gear ratio to 3.55, a friend at work recommended it, i am currently totally restoring this car and it is a frame off restoration, i would like for this car to be the best in acceleration, also before i began restoring my car the engine would not go past 65mph, it wouldnt redline, it would sit at 3000rpm with the foot fully depressed to the accelerator, would this be timing? acceleration up to 65 the car would act perfect . thank you.
AnswerIf your objective is acceleration at the expense of top end speed and MPG, then a 4.11 gear set from an earlier year SPIT is your best choice. if maximum MPG is desired, then a 3.27 gear set from a GT6 is your best choice.
SPIT/GT6 gearing options are 4.11, 3.89, 3.62 and 3.27, as those were the differentials in GT6s and SPITs, with 3.89 being the most common. If you are talking about another make of triumph, I am less familiar with gear sets that are available.
Given how you are describing the 65 max issue, I would have first looked at your throttle linkage to see if the accelerator pedal is fully opening the butterfly valve in the carb. There are stops and adjustments that can be made to the linkage to make sure when the pedal is to the floor, the butterfly valve is open to the maximum position.
A complete loss of power at that low of a RPM is more indicative of a fuel/compression issue than an ignition timing problem. For SPIT race applications, if you don't run strong enough springs, the valves start to float at higher RPMs, in which the car will seem that it won't want to rev any more. At a lower rev, like 3000 RPM, I suspect something with the throttle linkage or fuel starvation.
