Jets

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amcamx
Posts: 97
Joined: Sat Aug 13, 2011 6:21 pm

Jets

Post by amcamx » Wed Oct 19, 2016 9:24 am

Story goes, that if the car runs faster in good air, the jets are rich, and if slower, too lean.
So, how many racers, have jetted leaner, than the jets the Holley carb came with?

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OLD YELLER
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Re: Jets

Post by OLD YELLER » Wed Oct 19, 2016 9:10 pm

Every engine has different fuel needs...Do some experimenting and see what you learn...Watch out on jet sizes! Some of the jets have the same hole size for two or three numbers....Like for example #80,#81,#82 holley jets have the same size hole......... :arrow: :arrow:
The older I get, the better I was.....

amcamx
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Re: Jets

Post by amcamx » Thu Oct 20, 2016 6:49 pm

Chambered exhaust, was an option, on the 69 Z28 Camaro, but I have not seen one raced with one. So maybe it is not for performance, and I took it off of the Blue car.
With open exhaust, there was misfire for the run. A plug looked white, so I jetted richer, and had the same problem.
Rule of thumb, is to jet richer for open exhaust, but I had to jet 8 sizes leaner to stop the miss.
Spark output, and ign wire resistance, was good, and even new plugs did not help.
I plan to put an air fuel ratio gauge on, to find out what is going on.

amcamx
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Re: Jets

Post by amcamx » Fri Oct 21, 2016 6:41 am

Years ago, I could make a change to the motor, and all was fine, now I may need to change jets too.
I am starting to think, that old school motors, designed 50 years ago, and todays pump gas, do not work very well.
I may need, to mix race gas, 50-50, with pump gas.

amcamx
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Re: Jets

Post by amcamx » Fri Oct 21, 2016 10:33 am

The Black car ran .05 quicker in better air, so the jets must be rich?
1 Stock jets
2 Engine temp, the same.
3 60ft, same.
4 Mph same.
5 Stall, the same, I cannot stall very high, as the car will push in the stage beams.
6 Shift points the same, as I race in drive.
So, what happened?

secondwindracing
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Location: frontenac

Re: Jets

Post by secondwindracing » Sat Nov 19, 2016 8:23 pm

Read your plugs..they don't lie..Dave

amcamx
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Re: Jets

Post by amcamx » Sun Nov 20, 2016 3:08 pm

What would be a correct plug reading with pump gas, and how much would the reading change, driving up the return road, and parking in the pits?
The vacuum during the run, is zero, all through the quarter, and how much does that effect the plug reading? Vacuum is 15, at idle, in drive. The carb is not, vacuum secondary, so it hits all at once.
A good bracket motor, may not have zero vacuum.
The racers that have air fuel ratio gauges, can see the ratio, but where on the run, do they check it?
I would think, that they would want it to be rich at the start, and then taper off, to normal, at the finish line?
The car may be more consistent at higher stall, but because of my age, and back problems, I can go there, but not live there, for more than about two runs per meet.
How can I get the brakes to hold better, with the stall? Cut groves in the shoes, to trap the dust, or drill holes in the drum? They have holes in the disk brakes.

amcamx
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Re: Jets

Post by amcamx » Sat Jan 07, 2017 8:57 am

For a side note.
I checked the oil on the Scooter, and oil gushed out, and slammed the dipstick back in.
What am I doing, I caused an oil leak, then I thought, wait a minute, there is too much oil, and it needs to get out. I messed up twice, with a dipstick.
The Internet said, the thermostat is 10 degrees cold, and causes the fuel injection to put extra fuel in the motor, and can cause the oil to rise.
Aww, come on, they can come up with something better than that.
I put in a hotter thermostat, and changed the oil and filter, and it worked.
So now, I have to jet the Carb, for the correct oil level, too.
What next?
I am waiting, for someone to put up a No Smoking sign, in the burnout area.
The fast cars, come around me so fast, it can cause me the think that the motor died.
Where did they come from, and where did they go?
I told Tom, that it has been so long since I have won a race, that I forgot what it is like, and then he wins, to show me what it is like.
No better than I do, they are starting to think that I am the class Clown.
When things are slow, this time of year, they can try to be funny.

84foxbox
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Re: Jets

Post by 84foxbox » Sun Jan 15, 2017 8:17 pm

Every racer has fought that fight at some point. The way I do it is go to test and tune night with it fat and then drop 2 sizes both front and rear until it starts to lean pop and then go back up so that you know.. also read your spark plug color while testing and It will tell you alot.. to touch on the e.t's being off. My car can run the same mph and drop 4 or 5 numbers because of wind or who knows. If it's that bad just dial a little soft and race your race. But yes my carb is a 750dp on a 393 sbc and has smaller jets than what it originally came with. Raise the number of jet as the weather gets cooler and reverse that as it gets hot out.. I would highly recommend on taking your car to Ken Snyder before the year starts and let him make it as competitive as humanely possible at a good price. I hope this helps you.. good luck this year
1984 Ford Mustang GT (sbc) 6.48
2004 Dodge Ram 3500
2011 Ford Fusion Sport
1979 Ford F100 custom

amcamx
Posts: 97
Joined: Sat Aug 13, 2011 6:21 pm

Re: Jets

Post by amcamx » Tue Jan 17, 2017 6:14 am

Thanks for the information, that leaner than stock jets, may be needed.
Now that I have had more time to think about it, the old style 4160, 660 carb was not updated by Holley, and not designed for street, or foot brake racing, as it did not have a smooth, progressive, ascending transfer of power.
The HP Pro may be more consistent.

84foxbox
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Re: Jets

Post by 84foxbox » Tue Jan 17, 2017 8:32 pm

Sometimes it will take a couple different carb setups to get it right but yes leaner the better as far as power and it will tell you when you are too lean.. personally if I were you depending on where you are located at I would call Luke Siebert in topeka. He is very affordable and the most knowledgeable guy I've ever met when it comes to the right setup for your application and he can put that secret touch to make it work even better.. try to lean the whole system out by timing and jetting and see what happends..
1984 Ford Mustang GT (sbc) 6.48
2004 Dodge Ram 3500
2011 Ford Fusion Sport
1979 Ford F100 custom

amcamx
Posts: 97
Joined: Sat Aug 13, 2011 6:21 pm

Re: Jets

Post by amcamx » Wed Jan 18, 2017 8:58 am

I like to tinker, and have tried about every carb setup there is, except, leaner than stock jets.
I have damaged two stroke Motorcycles, that were lean.
Jim told me that a small block Chevy, larger than 350, can blow the head gasket, and Torch the block in the 5-7 cylinder area, with the secondary of the carb unhooked.
So, leaner than stock is not a place I want to go.
I may need to stall 2,400 min, and it may push into the beams, at 2,800. As responsive as the motor was with the last setup, it is very difficult to race right.
I gave up racing long ago, and am not trying to win, just test and tune, and try to get the car to work better, but I need eliminations to tell how it does.
But, when the numbers go outside the range, and something I do, can help one car, but hurts the other, I can get lost.
Even if the cars are not consistent, they may be predictable, but I like to change cars a lot, and I have problems, keeping book on them.
I am a slow learner, and it can take me 5-8 years to get a car to work as good as it is, and I have reached the end of the line, with the Amc cars.
I hope to get the Rampage drag truck running, and race in SP. There is no hope to ever get it to work right, but it would be a lot of fun trying.

amcamx
Posts: 97
Joined: Sat Aug 13, 2011 6:21 pm

Re: Jets

Post by amcamx » Thu Jan 26, 2017 6:29 am

An air fuel gauge may help, with jetting, but for how long?
Many Oxy sensors, on late model cars, have a heater, for warm up, until a temp of 190f is reached, but bracket cars, may stage much lower than that. Is the heater, used, to keep it from getting gummed up when cold?
The aftermarket, air fuel ratio sensors, do not have a heater, right?

62ChevyII
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Location: Wichita, KS

Re: Jets

Post by 62ChevyII » Thu Jan 26, 2017 10:54 pm

The Innovate wide band O2 sensor I have has a heater built into it... you just turn on the power to it for a few seconds before firing the engine up. I'm pretty sure most of the aftermarket wide band O2 sensors work that way.

amcamx
Posts: 97
Joined: Sat Aug 13, 2011 6:21 pm

Re: Jets

Post by amcamx » Sat Jan 28, 2017 6:36 am

Thanks for the info, that is what I need.

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