RPM
The Rat Master!
Have to wonder about that dyno tune with 20psi of fuel pressure.
6 MPG is costly...
- Thread starter Ezheimers
- Start date
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donsrods
Well-known member
Yeah, fuel injection cars run 20 psi, the carbs you are running would like something like 3-4 psi max.
Don
Don
WickedFast1
Well-known member
gotta be a LIKE button here somewhere
Old Iron
Well-known member
At 20 psi, I'm assuming your pump is an electric one then.
Either, put a regulator on the fuel line just before the fuel line manifold or take the electric one off and put the correct mechanical fuel pump on the engine block.
You can dump a lot of fuel in an engine before you ever see any black smoke.
How much Hp & Tq did the engine dyno at ????
Either, put a regulator on the fuel line just before the fuel line manifold or take the electric one off and put the correct mechanical fuel pump on the engine block.
You can dump a lot of fuel in an engine before you ever see any black smoke.
How much Hp & Tq did the engine dyno at ????
Ezheimers
Well-known member
6 MPG is history now...
Thank You to those with the knowledge that I lack... The regulator just had to be calibrated back to something like 3# - 4# Solving loads of flooding problems and I'm sure will help with the gas mileage... We'll see this weekend.
I've also taken spring off the throttle stem and while there I removed the pull stop that pulled the secondary carbs into play. I've yet to run it down the highway but it's great around town. The secondary carbs were being pulled into service even tho I wasn't stomping on it... Just don't always need all three dumping fuel..............
Again... "Thank You" to those who helped... -EZ
Thank You to those with the knowledge that I lack... The regulator just had to be calibrated back to something like 3# - 4# Solving loads of flooding problems and I'm sure will help with the gas mileage... We'll see this weekend.
I've also taken spring off the throttle stem and while there I removed the pull stop that pulled the secondary carbs into play. I've yet to run it down the highway but it's great around town. The secondary carbs were being pulled into service even tho I wasn't stomping on it... Just don't always need all three dumping fuel..............
Again... "Thank You" to those who helped... -EZ
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MercuryMac
Builder Junky!
Hi Ezheimer,
The trouble with a store-bought computerized tune-up is that no hotrod experience has been put into the technician's education. One example is the 20 lb. fuel pressure.
The guy who sold me my Holley 94 carb kits, told me to block off the idle circuits and the power valves in the two secondary carbs, so I did because it made sense to me. I have not run my three deuces yet though, so I can't prove anything. Maybe your vacuum is lower than the stock value and your power valves are dribbling gas most of the time. This could be another example of the dyno-tuner's lack of hotrod education.
Keep on tinkering.
The trouble with a store-bought computerized tune-up is that no hotrod experience has been put into the technician's education. One example is the 20 lb. fuel pressure.
The guy who sold me my Holley 94 carb kits, told me to block off the idle circuits and the power valves in the two secondary carbs, so I did because it made sense to me. I have not run my three deuces yet though, so I can't prove anything. Maybe your vacuum is lower than the stock value and your power valves are dribbling gas most of the time. This could be another example of the dyno-tuner's lack of hotrod education.
Keep on tinkering.
donsrods
Well-known member
I've been thinking about the 6 mpg you are getting, and something is very, very wrong. I had a 70 Cadillac with the 472 engine, the car weighed about the same as a 3 bedroom house, and even towing my boat I never dipped below 10 mpg. Something is either blowing fuel straight out your tailpipe or you have miscalculated how much gas you are using.
Even the two four barrel 331 stroker I am running in my 27 with 4.30 gears nets me about 20 mpg on the highway and about 15 around town. And I am cranking 3,000 rpms at 60 mph. Something is very wrong with your setup.
Don
Even the two four barrel 331 stroker I am running in my 27 with 4.30 gears nets me about 20 mpg on the highway and about 15 around town. And I am cranking 3,000 rpms at 60 mph. Something is very wrong with your setup.
Don
Don, at 20psi, I'd think it's got to be blowing that fuel out somewhere. Probably blowing it past the needle valve of the float, maybe some of the fittings, etc. But, like was said, if the guys that tuned it didn't catch the fuel pressure problem, who knows what else they got wrong?
Ezheimers
Well-known member
6 mpg
In all honesty - It's me the un-knowing owner - who turns and twists and screws the little things up. I installed the regulater after the tune-up cause they told me too. Said without one I had too much pressure to the carbs. I just didn't set it correctly. My bad...!
After setting the carbs to run only on the center carb unless needed - The darn rod runs better than before - so she was definitely getting drunk on too much fuel. I'm betting that changes this weekend out on the highway........ EZ
Again "Thanks"
In all honesty - It's me the un-knowing owner - who turns and twists and screws the little things up. I installed the regulater after the tune-up cause they told me too. Said without one I had too much pressure to the carbs. I just didn't set it correctly. My bad...!
After setting the carbs to run only on the center carb unless needed - The darn rod runs better than before - so she was definitely getting drunk on too much fuel. I'm betting that changes this weekend out on the highway........ EZ
Again "Thanks"
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BlueNorther
Well-known member
I would put the secondary carb linkage back in the top hole like in the first picture.
that gives you the largest ratio of movement before the secondary's start to open,
back off both "open" and "close" collars to start with, with the linkage in the top hole, have some one push the gas pedal all the way to the floor and hold it there. manually open the secondary's and adjust the rear(opening) collar up against the secondary pivot. this will co-ordinate all carbs full throttle at the same time. now have the person take their foot off the pedal completely, and set the safety closing collar to about 1/8" clearance to the secondary pivot.
now you should have about 3/4 throttle on the primary carb and still get full throttle on the floor.
close the 4 end carb idle screws, only center carb should be used to set idle speed and mixture richness. leave power valves in secondary carbs, they should not be a problem.
make sure all 4 throttle plates are centered and tightly closed on secondary carbs or they will FU your idle adjustments.
using lighter springs on the weights in the distributer. shoot for having the timing fully advanced by 2800-3000 rpm, set it to as much total advance as you can without pinging under load. should be 36-42degrees total. SBC's looooove advance early. use a vacuum advance pot that needs high vac numbers to move the advance plate. later model vac units move and stay advanced at way too low vac numbers and cause pinging under medium throttle loads. I bought one from moroso that was adjustable through the vacuum hose port. vacuum advance should be connected to manifold vacuum source.
these changes should put you in the 20 mpg area, I did it with a 4500 lb. pickup with a turbo 350c and 3.08 gears.
that gives you the largest ratio of movement before the secondary's start to open,
back off both "open" and "close" collars to start with, with the linkage in the top hole, have some one push the gas pedal all the way to the floor and hold it there. manually open the secondary's and adjust the rear(opening) collar up against the secondary pivot. this will co-ordinate all carbs full throttle at the same time. now have the person take their foot off the pedal completely, and set the safety closing collar to about 1/8" clearance to the secondary pivot.
now you should have about 3/4 throttle on the primary carb and still get full throttle on the floor.
close the 4 end carb idle screws, only center carb should be used to set idle speed and mixture richness. leave power valves in secondary carbs, they should not be a problem.
make sure all 4 throttle plates are centered and tightly closed on secondary carbs or they will FU your idle adjustments.
using lighter springs on the weights in the distributer. shoot for having the timing fully advanced by 2800-3000 rpm, set it to as much total advance as you can without pinging under load. should be 36-42degrees total. SBC's looooove advance early. use a vacuum advance pot that needs high vac numbers to move the advance plate. later model vac units move and stay advanced at way too low vac numbers and cause pinging under medium throttle loads. I bought one from moroso that was adjustable through the vacuum hose port. vacuum advance should be connected to manifold vacuum source.
these changes should put you in the 20 mpg area, I did it with a 4500 lb. pickup with a turbo 350c and 3.08 gears.
deerchooper
Well-known member
- Joined
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check your brakes after you drive a while. I don't have fenders on my rat and after a while I could feel the car being held back. I was able to look at the rotors and noticed the rotors had a turned blue. I found some drag between the mount and caliper, did a little grinding for clearance and took that slight drag that I was getting away.
