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Originally posted by CHampshire:

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Originally posted by TOP38:
I don't think its converter related. My guess is fuel also. Have you checked your floats? Alky is not kind to them. Brass floats can collapse and the black ones can become alky soaked messing with the fuel level in the bowls, check those. If you have O2 logged you know right away if it was fuel related.

Also have you noticed it using more fuel on a run now vs at the start of this swap, this would be another indication you got float bowl issues. Alky can run fine even when it's pig rich unlike gas...

No o2 unfortunately. Thanks for the info on the floats. They are the black ones. They were new with the carb and have 50 passes on them. As far as fuel useage, we used 5 gallons yesterday on two warm ups, two time runs and first round. That doesn't seem like a lot to me, but I am new to alky so I don't know for sure. It's a lot compared to race gas though!

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Originally posted by Mike Rietow:
Have you got a engine rpm graph from before you changed the bypass pressure, you can post? Any difference in that graph?

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Originally posted by TOP38:

Sounds high to me,,, warmups need a lean out valve or even a primer plus system that allows you to warm up on gas and also just before you put it away for the day.

With the car idling slowing increase rpm and note at what rpm the boosters begin to flow fuel. High floats will start flowing fuel much earlier than normal and you will use much more fuel than you should.

If you carb is relatively new, your floats are likely ok. What normally occurs is as the floats become heavier due to fuel soak, the fuel level rises in the bowls, without knowing, racers readjust the floats, this reduces float drop which restricts fuel flow at WOT which causes a lean condition to occur.

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Originally posted by rusty:
that fuel system will not run my alky setup,i did try it before going back to a belt drive system

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Originally posted by TOP38:
The air bleed lean out deal works but if it raise the rpm high enough to start fuel flowing from the boosters your defeating the goal.

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posted September 21, 2020 03:15 PM Hide Post
quote:
Originally posted by rusty:
that fuel system will not run my alky setup,i did try it before going back to a belt drive system

i cant recall with the electric pump ,but after low 4.5s to high 40s
How fast were you running at the time? I do feel like the car should run faster than it does even when running good, but I also see guys running an Aeromotive setup going 4.60's with an electric pump. I am torn on this.

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Originally posted by CHampshire:

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Originally posted by ts393c:
I will say 8 pounds of pressure is a lot. Every time I ran that much it would blow the bowls over.

How much do you run on alky with an electric pump?

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Originally posted by CHampshire:
Thanks everyone for the feedback. I have an update...well sort of. At the start of the season, a few races in we had a fuel pump issue. Long story short we were aerating our fuel and had to change our return line in the tank.

When we put it back together we added a fitting to the bottom of the regulator to check pump bypass pressure. In doing so we may have created this issue. The line from the pump to the regulator has a nice twist to it now. See the photo below.



We think this may be our culprit and will be re-plumbing this to see. We are most likely going to be changing the lines out of the regulator to the carb as well, mainly for piece of mind.

What do you guys think? Smoking gun?

quote:

Originally posted by CHampshire:
Update on this. First off, thanks to everyone that pitched in and gave me some suggestions. Here is what we did.

Took the Magna fuel stuff off, and went to APD. Bought a belt drive pump, fuel log, regulator and gear for the crank mandrel. Re-plumbed per their instructions. Set fuel pressure per their instructions. Hauled butt. Car went from 4.98 at 136 last time out to 4.90 at 141 yesterday. Here are some photos for reference.





Very pleased with the results for now. Water temp didn't climb during the run either. What it was staged at was what it was when it got back to the trailer. Hardly ran the fan at all.

I still think it should be going faster with that mph. We will be borrowing a convertor from a friend for the coming weekend and making some shock changes as well. Will see if we can get it into the low 4.80's before the end of the year.