My thought is it will be ready to test once you have the blowoff on it. That will ensure all the boost can be bled off when the throttle is closed. Thats a safer setup than the 2 smaller bleed valves you have now i think.
Ok, so I ordered a blow off valve and it has a vacuum reference. It looks like there is a port on the Weber carbs that has a location after the throttle plates (butterflies) but I don’t have a fitting on there - just the block off screws. I am wondering if I can try it with no vacuum reference…
The function of the blowoff valve is to blow off boost when the throttle is shut. The only way it knows the throttle is shut is the vacuum created by throttles being shut. That's how most blow off valves work anyway.
Sorry I can’t help you! It could be air and fuel mixture or timing! But hopefully someone out there watching that knows could help you with those issues! Or maybe you’ll get get it done with fiddling around with it!
Sorry my comments are all over the place... the engine appears to have plenty of fuel, even at idle...as evidenced by the carbon output of the exhaust at idle.
Yeah - I think there is some cycling of the boost pressure the way I am releasing the excess. So I got a BOV but I am not sure where I will get the vacuum to connect to the fitting on the BOV. I may be able to just use the spring portion of the BOV without a vacuum line, and just set it at 10 lbs and see what happens…
I think creating boost at idle is a problem though. Using manifold pressure before the throttle plates is also an issue, like on the fpr. I think if you take the manifold pressure from after the throttle plates for the bov and fpr, it will have a better chance of being happy at idle. What the cylinders get is the pressure after the throttle plates.
I think a vacuum driven blow off makes sense so you have very uniform boost (or lack of it) at idle. Once you get into the gas, the blowoff should close (because it sees less vacuum from the open throttle). The vacuum reference needs to come from after the throttle plates though... which is the only place you have vacuum normally.
More advance back to a more normal position will give it stronger idle. Bit you don't want it there at wot where you can hurt the engine. It's nearly impossible to hurt the engine at idle.
@@2dougsgma Agreed. Especially with 8.8:1 compression I think Mike said. In fact, the tricky part is that you won't get the most power out of it unless you push timing to an optimum place, which is scary when you don't know how far to go. At 4 deg of base timing advance, the car may be slower than stock. At 8 deg of base timing, it could be faster than it was. But push it too far without knowing the signs of detonation (and no knock sensor), and you can hurt the engine. But as you say, hard to hurt the engine at just 5 psi. If you are running good gas (91 or higher octane), 4 deg base timing, 8.8:1 compression, and only 5 psi.... driving around and doing some basic careful accelerations (not WOT... just normal driving stuff)... should be a good first step. And then go a little deeper in the throttle.... and creep up on WOT, especially sustained WOT for more than a second or 2. That's where you are most likely to hurt the engine. The car should accelerate smoothly and without misses or hesitations. If you are acceleration and you get even a hint of hesitation (like a subtle miss), get out of it. That "miss" feeling of the engine bogging a bit is really the pre-ignition (or knock).... and if that goes on for a second or 2, it can cause damage. But again at 5 psi, 91 octane, and 8.8:1 compression, it's not likely... especially if you are seeing a rich enough mixture. I saw 10:1 AFR with a little bit of free revving; so I'm guessing it's going to be plenty rich the first time out.
My thought is it will be ready to test once you have the blowoff on it. That will ensure all the boost can be bled off when the throttle is closed. Thats a safer setup than the 2 smaller bleed valves you have now i think.
Ok, so I ordered a blow off valve and it has a vacuum reference. It looks like there is a port on the Weber carbs that has a location after the throttle plates (butterflies) but I don’t have a fitting on there - just the block off screws. I am wondering if I can try it with no vacuum reference…
The function of the blowoff valve is to blow off boost when the throttle is shut. The only way it knows the throttle is shut is the vacuum created by throttles being shut. That's how most blow off valves work anyway.
Sorry I can’t help you! It could be air and fuel mixture or timing! But hopefully someone out there watching that knows could help you with those issues! Or maybe you’ll get get it done with fiddling around with it!
I ordered a “blow off valve” BOV because I think my issue may be with the boost pressure variance…. We shall see - it gets here first week of Jan…
Sorry my comments are all over the place... the engine appears to have plenty of fuel, even at idle...as evidenced by the carbon output of the exhaust at idle.
Yeah - I think there is some cycling of the boost pressure the way I am releasing the excess. So I got a BOV but I am not sure where I will get the vacuum to connect to the fitting on the BOV. I may be able to just use the spring portion of the BOV without a vacuum line, and just set it at 10 lbs and see what happens…
I think creating boost at idle is a problem though. Using manifold pressure before the throttle plates is also an issue, like on the fpr. I think if you take the manifold pressure from after the throttle plates for the bov and fpr, it will have a better chance of being happy at idle. What the cylinders get is the pressure after the throttle plates.
give it more timing for a test.
More retard or advance? It is set on about 3.5 degrees advance at idle…
I think a vacuum driven blow off makes sense so you have very uniform boost (or lack of it) at idle. Once you get into the gas, the blowoff should close (because it sees less vacuum from the open throttle). The vacuum reference needs to come from after the throttle plates though... which is the only place you have vacuum normally.
More advance back to a more normal position will give it stronger idle. Bit you don't want it there at wot where you can hurt the engine. It's nearly impossible to hurt the engine at idle.
More advanced is what I’m thinking. Get it running and driving around and tune it from there. Don’t think you’ll hurt it with 5 pounds of boost.
@@2dougsgma Agreed. Especially with 8.8:1 compression I think Mike said. In fact, the tricky part is that you won't get the most power out of it unless you push timing to an optimum place, which is scary when you don't know how far to go. At 4 deg of base timing advance, the car may be slower than stock. At 8 deg of base timing, it could be faster than it was. But push it too far without knowing the signs of detonation (and no knock sensor), and you can hurt the engine. But as you say, hard to hurt the engine at just 5 psi. If you are running good gas (91 or higher octane), 4 deg base timing, 8.8:1 compression, and only 5 psi.... driving around and doing some basic careful accelerations (not WOT... just normal driving stuff)... should be a good first step. And then go a little deeper in the throttle.... and creep up on WOT, especially sustained WOT for more than a second or 2. That's where you are most likely to hurt the engine. The car should accelerate smoothly and without misses or hesitations. If you are acceleration and you get even a hint of hesitation (like a subtle miss), get out of it. That "miss" feeling of the engine bogging a bit is really the pre-ignition (or knock).... and if that goes on for a second or 2, it can cause damage. But again at 5 psi, 91 octane, and 8.8:1 compression, it's not likely... especially if you are seeing a rich enough mixture. I saw 10:1 AFR with a little bit of free revving; so I'm guessing it's going to be plenty rich the first time out.