Herb calls it right in my book. Bang for the buck, a turbo really takes
advantage of the high revving abilities of the 1275. Simply put, normally
aspirated engines suck. Now that it seems to be well dialed in, the power
range is fairly broad. From about 3K to 6.5K it pulls very strongly.
These days, with the RAYJAY overpriced, I would look for a nice, small,
intercooled turbo unit like the one on the Volvo's with a waste gate. Make
a manifold as my PO did with clever welding and pipe, rig a single 1.5 SU
and adjust the waste gate to open around 8-10 lbs. Now watch the
Weber-equipped cars get small in the rear view.
>Jeff,
>
>While at the you-pull yard, I spotted a Shelby Daytona Turbo. Turbo
>still intact. I'm sure you could find a small displacement car near you
>as well. They shouldn't want too much for the turbo. Make your own
>manifolds, linkage, oil supply/return, etc. And in the event the turbo
>needs rebuilding, average cost runs between $250-$350.
>
>You won't find a better way to improve the torque curve on your engine!
>
>Glen, give Jeff some pointers.
>
>WFO Herb
>Keep the sticky side down.
>
>Jeff Boatright wrote:
>
>> Spridgeteers,
>>
>> Let's all take a deep breath. This is supposed to be fun!
>>
>> OK, back to the original question. How does one increase torque
>> output on a BMC A series engine? In my case, the engine is a 1275
>> with 40 overbore and a Kent 266 cam. However, I hope that what we
>> discuss could be applicable to all spridget motors.
>>
>> One response was that intake gas velocity must be kept high. How does
>> one do this? Vizard, in his inimitable way, shows the use of long
>> (15+ inch) ram pipes with detailed discussion, but then mentions that
>> none of this will really work with twin SUs. I don't understand why.
>> But, is the only answer to switch to a single carb setup? As close
>> readers of his book probably know, he spends most of his effort in
>> increasing flow to increase ultimate power. Does anyone know of other
>> sources of opinion backed by real data or anecdotal experience?
>>
>> Also, according to Vizard's charts, it is not necessarily always true
>> that a modification that increases power at the high end results in
>> loss of torque at the low end. Several of his charts show that torque
>> often increases with flow. What does seem to occur frequently,
>> though, is that that the power increase is proportionately larger
>> than the torque increase. However, his data are all a little suspect
>> for purposes of this discussion in that his goal is nearly always to
>> increase power and let torque take care of itself; he doesn't
>> systematically study torque. Of course, some would argue that he
>> doesn't systematically study anything.
>>
>> Another response was to go with nitrous or increase capacity. The
>> nitrous idea would be fun but maybe hard on the engine. It may be
>> hard on the wallet. It does sound fun, though. Increasing capacity is
>> something for engine rebuild time. I have upped mine a bit (to a
>> calculated 1312 cc, I think, though the recent thread on cylinder
>> volume has me second guessing). One downside, in addition to cost and
>> time off the road, is that as the size increases, the engine does not
>> idle quite as smoothly - it's the one advantage I've ever heard
>> discussed about the 948 vs 1275.
>>
>> A final response was to go with supercharging. Now _that_ is
>> expensive. But, it sure seems like the way to go for increase torque
>> and power, particularly as complete, new systems can now be bought
>> off the shelf (from MM and from the group in Australia). I'd have to
>> win the lottery, though, to go this route.
>>
>> Anyway, there it is. I guess I'm looking for sub-$300 DIY torque
>> solutions. But mainly, I'm simply ignorant to the extreme on this
>> topic and would love to hear your thoughts on it.
>>
>> Thanks,
>>
>> Jeff
>>
>> _____________________________________________________________
>> Jeffrey H. Boatright, PhD
>> Assistant Professor, Emory Eye Center, Atlanta, GA, USA
>> Senior Editor, Molecular Vision, http://www.molvis.org/molvis
>> mailto:jboatri@emory.edu
>
>
Regards,
Glen Byrns
'59 Bugeye
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