Classic over carburetion problem?
Elevation: 342m / 1122feet
I still don't like vacuum secondaries though they never even seem to open up.
The only thing I can really answer right now is about the rpm 3000 and yes that's when it starts to go good.
Here's all the cam info.
View attachment 1715738847
Well there you have most of it;
I'll guess;
Static compression ratio of................... guessing 9.5:1.
elevation 1122@ Ica of 63* (in at 108)
Effective stroke is 2.59 inches.
Your dynamic compression ratio is 7.64:1 .
Your dynamic cranking pressure is .................
148.16 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and
boost of PSI is...............................................
7.42 :1.
V/P (Volume to Pressure Index) is ...................
119
That's a nice cam; especially so with the pressure up around 180 .......... in a 360..............lol............. like mine.
But predicted to be 148psi, the V/P of 119 shows it to be about as powerful in the lower rpms, as a 318LA
At 10/1 the Pressure climbs to 158, and VP to 128, so now the bottom end is feeling like a 5.2M might.
At 9.0 the pressure is predicted to be 138, and the VP is 111 decidedly weak.
So now you know why pressure is important.
Until you do a compression test, I sure cannot say what your solution is. I mean if the pressure is down at less than 140psi I know what I would be doing. But if the pressure was already 160, then I would give a different solution. But at 150 it's a tougher call.
Your choices at 150 are;
a higher compression ratio
a higher stall,
or a higher number rear gear.
Of these the higher compression ratio is an across the board power increasing fix; more real power all throughout the rpm band.
The higher stall effectively gives away efficiency below it's stall, and gives you nothing afterwards. It simply allows your engine to spool up to a higher rpm, where the power is.
The gears allow your engine to run up the power curve quicker, and so make the engine feel more powerful, altho it is not.
A lot of builders seem to recommend a compression ceiling of between 9 and 9.5 ; which, with a stock cam would be fine. But with a 230/236/110 cam is terrible, as you may have discovered.
As to the 750 vacuum secondary, hang on to that for a few months. It is the right size carb for your combo. It may just need some light tuning adjustments. If you can feel the Secondaries opening, they are probably opening too soon.
A DP carb may be more fun, but with a 2200 stall, that is gonna hurt performance just as much as the 2200 is hurting the VS carb. The thing is that below 2800 to guessing 3400, the carb don't much care about the secondaries as in most cases the Primaries are well able to meet the air supply demand. If you had a DP and opened all 4 barrels at 2200, the demand would simply be met at a slower airspeed thru the venturies. I mean if the engine, at a certain rpm, can only inhale 300 cfm, you can supply that 300 thru whatever holes will pass at least that much. If your holes are bigger, the same amount of air is still gonna get thru there, allbeit at a slower velocity, cuz 300 is all the engine can pull.. The 750, whether a DP or a VS is easily big enough to feed any SBM even most strokers. At the price of new carbs these days, I'd rather put that money towards getting the pressure up; it will be far better spent in doing that. Or even just a higher stall, cuz 2200 is way too low for that cam, even if the engine was up to pressure...... IMO
