I myself, like you, always had everything with a vacuum advance hooked up to ported vacuum, until recently. I bought an old Chevy truck that was constantly shutting down, starving for fuel due to vapor lock when the temperature gauge would get up to about 215 degrees. When I would open the hood, the heat coming off engine was unbearable, making you immediately have to step back. I tried replacing everything in the cooling system first, new radiator, new water pump, new thermostat, new fan clutch and it still would get too hot. Then I tried insulating the fuel lines, adding a return line from a filter right before the carburetor, still had vapor lock. Then I noticed a pattern where I could hear the fan clutch just start to engage and pull more air through the radiator right before it shut down from being too hot, so I "recalibrated" the little thermostatic clock spring on the front of the fan clutch so it would pull more air all the time. Only had to turn spring like eighth of an inch (think it was counterclockwise) and now the fan pulls much more air. Then I added a carburetor spacer, and blocked off the heat riser passages in the intake. But, even after all that it still got too hot and would get vapor lock. Then I did a little research and decided to check my vacuum advance. All I did was switch the vacuum advance from a ported vacuum source to a manifold vacuum source, adjusted the vacuum pot screw one and a half turns to maximum, and that is what finally fixed it. Now the temperature gauge stays around 170-180 degrees, even in traffic!! My gas mileage got much better too. Anyway, I guess it all depends on the combination of parts, some like ported vacuum and some like manifold vacuum.. Cool video, good luck!
Ever try using a combo vacuum advance pressure retard canister like some of the ford and chrysler units of the 60's & 70's ? You can possibly adapt these units to other makes with a little bit of modification.
Thanks for the video. I really enjoy what you do. On most engines, I run full manifold vacuum to the distributor. I usually setup all distributors myself, adjusting the centrifugal advance as well as the vacuum advance. I usually limit the total travel of the vacuum advance cannister. I find the additional advance from the vacuum gives a cleaner, smoother idle, and improved response off idle. If I do this with just the centrifugal advance, I end up with an odd curve, or too much total, or some other goofy timing condition. My question is do you think the supercharged engine would not benefit from vacuum advance at idle in the same way?
I think it depends more on what type of cam is used....If it is a bone stock factory cam, then I think ported vacuum is usually better. If it is a performance oriented cam, then running manifold vacuum would be better.... and then for an all out race cam, then I would completely eliminate vacuum advance all together. Thank you for your interest, I definitely like getting feedback on these videos and learning from other people's experiences.
Saw your comment on Mod Everything’s TT 260 SBO. Birds of a feather? BTW, love your diagrams. Are the factory turbo Q-jets 800 CFM as someone has suggested on CZcams? My ‘75 Toro Q-jet is badly bent from over torquing and I may need a replacement body. None of these cars seem to be nearby anymore. It managed to fill the crankcase with fuel and doubled the fluid level to about 12 litres
Quadrajet you can plug off the power piston and run straight off the jets. I run one on a weiand 144. But i never thought of this !! Thank you. One question are you routing it to the bottom or top of the blower?
Yes, it is better to plug off the power piston and run straight off the jets versus leaving the Quadrajet stock on a supercharger... Definitely. But if the engine is mostly street driven and has a mild cam, then plumbing the power piston vacuum to the bottom of the blower is the better way to go for a smoother running street engine and fuel economy
Hey Ray’ I have 750 street demon would you do the air valley the same as the Quad jet you did or would you have to look and see if it’s the same I picked up a 174 super charger with an machined intake for a 460 ford that is pretty much stock but freshly rebuilt and I was thinking about running that new carb because they run so clean and no maintenance Thanks Rob
Looking at the design of the street demon carburetor, it looks like in order to get external boost reference to the metering rods, the street demon would need to be modified almost exactly like the edelbrock carburetors.
I leave the dashpot alone. It seems to function fine as-is in a draw through application. Probably not the case in blow through. I usually set the choke completely open. It doesn't get too cold around here... and when it's really cold, I don't drive the oldies
@raysoto1969 ok. So you leave the rod to the dashpot from the secondary air valve on it as well? I know it controls the air valve on the secondary is why I ask.
@davidgrowii4809 Yes, because if you remove it, the secondary air flaps will open too quickly, and you will notice an annoying hesitation when you mash the accelerator
Comment….. Your a genius!
Thanks
I myself, like you, always had everything with a vacuum advance hooked up to ported vacuum, until recently. I bought an old Chevy truck that was constantly shutting down, starving for fuel due to vapor lock when the temperature gauge would get up to about 215 degrees. When I would open the hood, the heat coming off engine was unbearable, making you immediately have to step back. I tried replacing everything in the cooling system first, new radiator, new water pump, new thermostat, new fan clutch and it still would get too hot. Then I tried insulating the fuel lines, adding a return line from a filter right before the carburetor, still had vapor lock. Then I noticed a pattern where I could hear the fan clutch just start to engage and pull more air through the radiator right before it shut down from being too hot, so I "recalibrated" the little thermostatic clock spring on the front of the fan clutch so it would pull more air all the time. Only had to turn spring like eighth of an inch (think it was counterclockwise) and now the fan pulls much more air. Then I added a carburetor spacer, and blocked off the heat riser passages in the intake. But, even after all that it still got too hot and would get vapor lock. Then I did a little research and decided to check my vacuum advance. All I did was switch the vacuum advance from a ported vacuum source to a manifold vacuum source, adjusted the vacuum pot screw one and a half turns to maximum, and that is what finally fixed it. Now the temperature gauge stays around 170-180 degrees, even in traffic!! My gas mileage got much better too. Anyway, I guess it all depends on the combination of parts, some like ported vacuum and some like manifold vacuum.. Cool video, good luck!
Very well done
Ever try using a combo vacuum advance pressure retard canister like some of the ford and chrysler units of the 60's & 70's ? You can possibly adapt these units to other makes with a little bit of modification.
Thanks for the video. I really enjoy what you do.
On most engines, I run full manifold vacuum to the distributor. I usually setup all distributors myself, adjusting the centrifugal advance as well as the vacuum advance. I usually limit the total travel of the vacuum advance cannister. I find the additional advance from the vacuum gives a cleaner, smoother idle, and improved response off idle. If I do this with just the centrifugal advance, I end up with an odd curve, or too much total, or some other goofy timing condition. My question is do you think the supercharged engine would not benefit from vacuum advance at idle in the same way?
I think it depends more on what type of cam is used....If it is a bone stock factory cam, then I think ported vacuum is usually better. If it is a performance oriented cam, then running manifold vacuum would be better.... and then for an all out race cam, then I would completely eliminate vacuum advance all together.
Thank you for your interest, I definitely like getting feedback on these videos and learning from other people's experiences.
Saw your comment on Mod Everything’s TT 260 SBO. Birds of a feather?
BTW, love your diagrams.
Are the factory turbo Q-jets 800 CFM as someone has suggested on CZcams? My ‘75 Toro Q-jet is badly bent from over torquing and I may need a replacement body. None of these cars seem to be nearby anymore.
It managed to fill the crankcase with fuel and doubled the fluid level to about 12 litres
I know the 301 turbo Q-jet is indeed 800cfm.... I'm not sure about the Q-jet on the turbo Buicks
Quadrajet you can plug off the power piston and run straight off the jets. I run one on a weiand 144. But i never thought of this !! Thank you. One question are you routing it to the bottom or top of the blower?
Yes, it is better to plug off the power piston and run straight off the jets versus leaving the Quadrajet stock on a supercharger... Definitely. But if the engine is mostly street driven and has a mild cam, then plumbing the power piston vacuum to the bottom of the blower is the better way to go for a smoother running street engine and fuel economy
Hey Ray’ I have 750 street demon would you do the air valley the same as the Quad jet you did or would you have to look and see if it’s the same I picked up a 174 super charger with an machined intake for a 460 ford that is pretty much stock but freshly rebuilt and I was thinking about running that new carb because they run so clean and no maintenance Thanks Rob
Looking at the design of the street demon carburetor, it looks like in order to get external boost reference to the metering rods, the street demon would need to be modified almost exactly like the edelbrock carburetors.
Can I send you my elderbrock 750 to get it ready for a turbo 350?
On the quadrajet, what do you reference or do about the dash pot or choke full off? Do you reference it differently or eliminate it all together?
I leave the dashpot alone. It seems to function fine as-is in a draw through application. Probably not the case in blow through. I usually set the choke completely open. It doesn't get too cold around here... and when it's really cold, I don't drive the oldies
@raysoto1969 ok. So you leave the rod to the dashpot from the secondary air valve on it as well? I know it controls the air valve on the secondary is why I ask.
@davidgrowii4809 Yes, because if you remove it, the secondary air flaps will open too quickly, and you will notice an annoying hesitation when you mash the accelerator
@@raysoto1969 awesome! Thank you!!!
Hmm i think doesn't make sense because you have a bypass
The bypass valve is closed during boost. That's when fuel metering needs to boost referenced
@@raysoto1969 I've thought about it and you're right.