Holley jetting questions
08-09-2006, 12:12 PM
#22
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Re: Holley jetting questions
I am using a Navman fuel flow indicator for the gallons of gas consumed and a gps for miles of distance traveled. I have also double checked several times, the number of gallons of gas used when I fill my tank against the mile markers on the river. I live in Minnesota and run the Mississippi River and it has visable navigation mile markers every mile that give numbers to the 1/10 th of a mile. The numbers of the two sets of figures are reasonably close. What is TPS,MAP,and Lambda? Sorry for being dumb about this. I will check what my power valve is after I get a vacum reading on the engine. I am using a digital tach that reads to within 20 rpm. I am amazed at the way one little tap on the power trim button or trim tabs effects speed, gallons of gas burned per hr and rpm . Thanks again for the replies.
08-09-2006, 12:23 PM
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Re: Holley jetting questions
OK, didn't realize you were use fuel flow so you're going in the right direction.
TPS = Throttle Position. You may be able to run the cruise Speed you want will less throttle opening depending on the prop used to give you better fuel economy.
MAP = Manifold Absolute Pressure (Vacuum) Help in tuning your Power Valve circuit. Again you may be able to change your TPS so that you are maintaining enough to keep the Power Valve closed to help with fuel economy.
Lambda = Air Fuel Ratio. The only true way of knowing how "Safe" you really are.
With what you have done to date and where you're at Vacuum Readings would be the next must have.
TPS = Throttle Position. You may be able to run the cruise Speed you want will less throttle opening depending on the prop used to give you better fuel economy.
MAP = Manifold Absolute Pressure (Vacuum) Help in tuning your Power Valve circuit. Again you may be able to change your TPS so that you are maintaining enough to keep the Power Valve closed to help with fuel economy.
Lambda = Air Fuel Ratio. The only true way of knowing how "Safe" you really are.
With what you have done to date and where you're at Vacuum Readings would be the next must have.
08-09-2006, 12:47 PM
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Re: Holley jetting questions
Originally Posted by the duke
changing from the 2bbl to the 4bbl is a tottly different thing. On the 2 bbl, you were always using all of it. When you went to the 4bbl, at cruise you most likely were only using the primary 2, and they were drawing less cfm than the original 2 bbl.
On a 454, I think a 600 cfm carb is too small for the engine,(Using the Holley chart which is pretty conservative, they say 700-750) and I love most edelbrock products, EXCEPT for their carbs, which are pretty much a Carter carb with their name on it.
By the time you buy the new carb/intake etc you will have spent how much? $500? at $3.00 a gallon, thats 167 gallons of gas. If you could double your fuel economy (not likely) how far can you go on that much gas? and that would be to just break even.
On a 454, I think a 600 cfm carb is too small for the engine,(Using the Holley chart which is pretty conservative, they say 700-750) and I love most edelbrock products, EXCEPT for their carbs, which are pretty much a Carter carb with their name on it.
By the time you buy the new carb/intake etc you will have spent how much? $500? at $3.00 a gallon, thats 167 gallons of gas. If you could double your fuel economy (not likely) how far can you go on that much gas? and that would be to just break even.
08-09-2006, 01:13 PM
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Re: Holley jetting questions
A vacuum guage is also fantastic as a load indicator. Keeping the throttle the same, working with drive and tab settings can show a difference. Higher the vac for the same throttle setting means less load.
Carb calibration and timing is #1 for engine effeciency. Bolting on a universal carburetor means fine tuning will usually be needed.
Do not overlook your idle mixture screws - use vac guage for this too.
Carb calibration and timing is #1 for engine effeciency. Bolting on a universal carburetor means fine tuning will usually be needed.
Do not overlook your idle mixture screws - use vac guage for this too.
08-09-2006, 04:53 PM
#26
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Re: Holley jetting questions
The idle screws were set using the digital tach. I hope to get the boat out sunday for a vacuum reading. Should the reading be taken at idle speed and in gear, and are there any other readings that would be of value while I have the boat in the water? pourman do you know what color vacuum spring was in with the 10.5 power valve and what color the spring is with the 3.5 power valve.Thanks for all the replies, I hope they will keep coming.
08-09-2006, 07:17 PM
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Re: Holley jetting questions
The color coded springs control the opening of the secondaries. The power valve has a number on it. Here is a link that covers it pretty well.
Ty
http://www.mortec.com/carbtip1.htm
Ty
http://www.mortec.com/carbtip1.htm
08-10-2006, 05:16 AM
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Re: Holley jetting questions
Pourman, The spring and power valve both controll the secondarys opening. I was wanting the spring colors of yours to compare to mine when I tear down my carb. We both have the same carb, but they are probably calibrated differently. A lot depends on cu in and the cam. What year is yours, how many cu in, and is it a stock cam for that engine? This carb was used on many different applications with different calibrations. I am going to stop at my dealer to see if he can pull up what my boat came with from the factory, and go from there. Thanks again for your time.
08-10-2006, 06:07 AM
#29
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Re: Holley jetting questions
PV is enrichment circuit - ie: fuel only.
Secondary spring controls when secondaries open and when they are totally open...of course all points in between.
The vacuum secondaries aren't actually controlled by engine vacuum. They are controlled by a vacuum that is created thru a passage(s) between the primary/secondary bores that get's created from airflow thru the bores. Basically, as the primary bores get more and more air, the passage creates more 'vacuum' within itself and starts to pull on the secondary diaphragm.
Since it is based off of airflow, comparing one spring, the larger in cid the engine the quicker the secondaries will start to open and the quicker they will fully open compared to a smaller cid engine.
PV works off of engine (intake) vacuum only. It's an 'on/off' device with no inbetween. Making sure this opens/closes at correct times can have a decent effect on mileage.
Hard to type vs talk. Sorry.
===================================
Can we talk about performance upgrades too ? This fuel mileage thing can hurt one's style/personality/ego/meaning of life/ etc,etc,etc. Lol.
Secondary spring controls when secondaries open and when they are totally open...of course all points in between.
The vacuum secondaries aren't actually controlled by engine vacuum. They are controlled by a vacuum that is created thru a passage(s) between the primary/secondary bores that get's created from airflow thru the bores. Basically, as the primary bores get more and more air, the passage creates more 'vacuum' within itself and starts to pull on the secondary diaphragm.
Since it is based off of airflow, comparing one spring, the larger in cid the engine the quicker the secondaries will start to open and the quicker they will fully open compared to a smaller cid engine.
PV works off of engine (intake) vacuum only. It's an 'on/off' device with no inbetween. Making sure this opens/closes at correct times can have a decent effect on mileage.
Hard to type vs talk. Sorry.
===================================
Can we talk about performance upgrades too ? This fuel mileage thing can hurt one's style/personality/ego/meaning of life/ etc,etc,etc. Lol.
08-10-2006, 07:34 AM
#30
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Re: Holley jetting questions
S B, thanks for the information I must have had a brain fart when I said they both control secondary opening. If I was to open the secondaries later by changing the spring one color would I just loose performance and possibly get a backfire or could it be enough to fry the engine by not having enough gas there when the engine needs it? Before I do anything I need to do some more research and get a vacuum reading on the engine.Thanks for your time.
