Limited disassembly of a 1980 IC 196

Just got the manifold back from the machine shop. This was done on a large surfacing machine with cutters, not ground. All six mounting pads are now flat. Either side of the wedge lays against the manifold without rocking or daylight peeking through. Now suitable for mounting.
 

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Since the surfaces are now flat, I believe the oem shim style is best to use for this application. Might put a skim of high temp rtv on it.
 
Since that castiron is now well seasoned that will probably work fine. I think I've seen that 3 bolt flange manifold in 392 loadstar applications.
 
No, this is a different manifold. I hear they only made something like 500 sets or so. The center-dump horn on the one you're thinking of is longer. If I were to ever go back to a normal installation this "shorty" would bolt right up and with a 3-bolt flange fitted to a down-pipe, never leak. Someone should repop these!
 
Just an update: I am at a point where I can consider putting on the turbo parts, but I am also at an important crossroads. I have followed with great interest an individual (dave binnie) who has successfully converted his corvair corsa from draw-through to blow-through. He originally used the single 1-bbls and now moved up to the 4 carb version. His conversion is absolutely top rate and worth googling. The pro's of going this route are now compelling. I think I can simply rotate the compressor housing to dump upward and then craft a simple u-shaped tube to go up, over, and down onto the stock Holley 1940 1-bbl throat. Sealing the throttle shaft should be easy using "air seals" as this individual has done (as shown in mcginnis' book on turbocharging). My carb presently has brass floats but they make replacements in nitrophyl, so they shouldn't collapse. I can get a rising-rate regulator as used on the maserati bi-turbo, so that takes care of that problem. The electric efi pump used on Ford trucks will supply fuel - same type pump used by bill for the efi conversions. So that is no problem. Except for blocking off the carb bowl vent, I have all the necessary check-valves so that I can retain all of my emissions devices and power brake booster. Here is the only area that will require some development. In his original conversion, dave used the stock corvair rochesters that had no enrichment circuit ("power valve") because the carbs with the pv channels were huge and flowed way too much fuel. So he opted for larger mains to cover this. His later version with the 4 one-barrels uses the secondaries for this purpose. Okay so far. My problem with the Holley is that once boost begins, I will run progressive leaner and I don't want to simply mask things with an overly large main jet. What to do: it appears feasible (maybe) to drill out the pv restrictor and make it flow right, but it would then be too Rich for normal enrichment, but that May not be a terrible situation. The other notions I'm investigating are adding a single small fuel injector to trigger when I hit, say, 2-3 lbs. Boost. Or this: I'm asking bill usn-1 his thoughts on configuring a efi computer to simply trigger a small injector in a linear fashion in response to boost pressure. Efi parts are so common these days.... In any event, dave binnie tells me he runs a wide-band sensor and is running around 12.8:1 a/f which is towards the leaner side of lambda. With datalogging I could fine tune the boost enrichment phase.
 
One issue would be is that on a blow through design a Holley pv won't work because they work off vacuum. Perhaps that's why the rochester's?

While I'm not a big fan of FI in na applications, for your turbo app it might be the best way to go.
 
That's what I said. Pv enrichment all in when manifold pressure is near ambient. Then one needs to begin enrichment to account for boost. The rochesters were interesting. The early corvair versions had no pv or equivalent. Later versions had a simple passage with a small weight that blocked the passage under vacuum and when it dropped, so did the weight and flow began. Sort of hinkey, but it worked. Binnie says those passages could be over 0.020", which is huge, making things waaaay too Rich.

I sent bill a pm on this, and am awaiting his response. Another option is to use a nos fogger nozzle and hook up the output from the efi pump to a nos solenoid. On/off, but better than nothing. An efi computer tailored to progressive flow is ideal, but will require a bit of development. Except for the megajolt ignition, retaining all the smog junk - and great tail pipe numbers - just might Make my vehicle amenable to the referee station granting an exemption, if I ever got to that point. And was still in CA.
 
Actually the pv worked off of delta-p. P1 is the air horn (fuel bowl) p2 is the manifold pressure. The differential between the two p's motivates the pv to open/close. The spring being the calibrating factor and constant.

On the draw thru application you'll need to boost reference the pv with the pressure signal from after the turbo. So anytime the engine is seeing above x map you enrichen the afr. How much is up to the pv metering orifice.
The 1904 pv needs to see the airhorn inlet so plumb the bowl vent to the air filter housing and push a beebee in to the existing 1904 pv signal port and port the cover to the manifold pressure.
 
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Kinda. The stock pv sigs can still be under vacuum from the turbo drawing on the carb, while the engine map is at 2 psi or whatever above ambient pressure.
The reason to boost reference the pv. :icon_rotate:
 
Just so I understand what Robert is saying, the vacuum rating of a pv is relative to the difference across the venturi and not absolute to the atmosphere. Correct? Similar to psig vs. Psia.
 
More on pv function imo. :icon_xd:
it serves two purposes.
1) supplement the metering system with fuel when venturie velocities are low and fuel sigs are weak so it keeps the transition smooth with no dead or lean spot.

2) enrich the arf to say 12-1 at wot and high power conditions so peak power is given.
 
fdchappie said:
just so I understand what Robert is saying, the vacuum rating of a pv is relative to the difference across the venturi and not absolute to the atmosphere. Correct? Similar to psig vs. Psia.
Click to expand...

Yes, only because the pv motive diaphragm sees the p1 and p.
On holly's (2300 for reference) the pv sees bowl pressure which is plumbed to atmospheric + air horn, and manifold pressure to the other. Both can be variable to some extent.

If you only consider sea level standard pressures 14.7 psi, the spring and the manifold pressure side, it functions on absolute.
At altitude and under some boost applications the calibration sees the other variable. Then the calibration is more differential.
 
To be clear, I think we are talking of two different conditions (I think). Regarding a draw-through, I get that. You can have a strong vacuum in the carb, and the pv circuit not activated, while making boost on the other side. Lean = boom! So the signal to the pv is moved to the downstream side of the compressor. Explained in mcginnis' book. The thing, then, is you have the right signal, but then need to richen accordingly. Now, I am talking about a blow-through. Here you go wot, but no boost - yet. Little or no vacuum, pv is activated. Now as the engine continues towards boost, the pv is contributing all it can already, and then you encounter lean unless you can richen things up past that point. Which means a pv that provides a certain level of additional richness up to 0 vacuum, but would somehow need to increase this when going to positive pressures.

Regarding the 1904 used on the 152t. It appears that they just used a bigger main jet and used the stock pv. The main covered the sins of leaness under boost. Probably terribly Rich when not under boost, or most likely, terrible all the time! But not leaning out and detonating into oblivion.

I am seriously considering blow-through using the stock Holley 1940 (not a 1904). It has a similar pintle that opens when vacuum drops, and fuel entering the pintle well flows to a small restrictor, a jet, really, that provides whatever richness the pv is supposed to provide. But while the pv won't provide added richness commensurate with positive pressures, you also won't have the draw-through situation of having a vacuum signal on one side and boost on the other. Just a lean-ness that grows in a linear fashion as manifold pressures go from negative to positive. Still a problem that needs a solution. :crazy:
 
In blow through application and an odd bird like the 1940, it will need to go in a box that encapsulated the entire carb in compressed air.
Bad thing on that is that the variable air density can not be fully dealt with by the venturies. Once on boost up stream of the carb, limited by the waste gate it'll be ok assuming you calibrated it there.
Off boost it'll be like driving a carbureted engine in mammoth, pig Rich. :idea:

I have weighed the choices and feel either go with a non pv carb on blow thru or draw thru on whatever, which is what I plan on doing.
 
Maybe I should revert back to the original plan. A draw-through using the side draft yh. At least I know it will work at least as well on the corvair, and there are choices in metering rods. So getting to an acceptable (read: not ideal) a/f under boost is doable.

So back to casting a carb-to-compressor adaptor from aluminum.
 
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