Holley jetting questions
 

I have a holley 4150# 750 cfm vac secondary on my stock 1992 330 hp 454. The boat turns 4260 rpm wot fully trimmed with 4 adults and a full load of gas and the book says 4200 to 4600 rpm. I am running a new rev 4 wedged and ballenced 4 blade prop. I think I am proped just abought right. I have plenty of power out of the hole, even some extra. Most all of my running is cruising around 2700 to 3000 rpm,hardly ever using wide open throttle.The boat is a 23 ft bow rider and weighs about 3800lbs empty. Like a lot of people I am looking for better gas milage, right now it gets about 1 1/2 mpg and I think it should be a little better then that. As far as I know the carb is set to factory specs. I havent opened it yet to see whats in it for calibration. Can I go to a heavier secondary spring and smaller primary and secondary jets without damaging the motor [how much smaller]. I am willing to give up some preformance for better gas milage. Thanks for any replies.

Re: Holley jetting questions
 

You probably could but if you lean it out to much the money you saved on gas you'll be spending for a new motor. I would say most people here run a little on the rich side to avoid detonation problems, I know I do. Why don't you remove the flame arrestor while under way and note the throttle position just before the secondaries open. Do most of your cruising at this point. That should save some gas.
Dave

Re: Holley jetting questions
 

The amount of gas that you would save by going leaner on your jets is a minimum quanity. The down side is detonation/leaning out the motor and burning pistons. gas is still cheaper than rebuilds.

Re: Holley jetting questions
 

Do any of you think there would be enough improvement to justify a edelbrock preformer manifold and a 600 cfm edelbrock carb? Edelbrock recomends the 600 cfm 1409# carb for a 454 turning in my rpm range. This boat is run only in fresh water. Edelbrock also suggested if I wanted to change cams, to go to Crane or Comp for one of their marine cams.

Re: Holley jetting questions
 

What are your objectives in doing a cam change. Most people change cams to increase performance, not gas mileage. If gas mileage is still your priority as stated in your first post, leave the motor alone!
Dave

Re: Holley jetting questions
 

Your spending money to save on gas money, youll never recoop

Re: Holley jetting questions
 

There is little if anything that you are going to do to a BB to save gas in a boat. The best way is to prop it right, and then just not run it at WOT. If you read any of the boating Mags, you can see how much fuel that the boats use at X rpm. as you back up the economy improves greatly. Like Strip Poker said, if you spend several hundred dollars on a smaller carb, you will never make up that cost in gas savings, let alone losing performance.

Re: Holley jetting questions
 

I did change a 302 cu 2bbl ford 188 hp I. O. to a edelbrock 4 bbl carb, edelbrock preformer manifold and their lowest rpm cam that they had at that time. I gained preformance along with a sizable increase in gas milage. I ran that boat for 6 yrs trouble free. I have good enough preformance with my 454 but a little more is always nice. Edelbrock says that by using a 600 cfm on my set up and the rpm I am turning it should increase my low and mid range but I may loose a couple mph on the high end, I dont care about the top speed. I plan on keeping this boat for a very long time, and at the cost of what gas has been doing it wouldnt take all that much of a gas milage increase for me to get to the break even amount of $$ spent on the engine. I dont care that much about the preformance, either more or a little less would be acceptable to me. I was extremly happy with the changes I made on the 302 ford and looking for opinions befor I do anything to the 454 chev. Thanks for any replies

Re: Holley jetting questions
 

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.

Re: Holley jetting questions
 

I agree with you on the 2 bbl to 4 bbl making the difference on the 302. I just got off the holley web site and punched in my stock 454 cu turning 4600 rpm, that is the max it would ever turn, They also show to use a 600 cfm unless I need a spread bore then it would be 650 cfm. Edelbrock and Holley both say 600 cfm. I am thinking way ahead, in terms of many years of running this same boat. I am not looking to break even in 1 or 2 years but many more years of running. If I could gain 1/2 mpg over my 1 1/2 mpg that I get now it would mean a pretty good savings in the long run. Who knows what gas will do in the future. The more gas costs the bigger the savings will be to me once I reach the break even point. Holley has always been a big name for speed but not for economy and staying in tune. I used to run a Holley and only Holley when I raced a Chevy powered jeep but the Edelbrock on the 302 boat was trouble free for more then 6 yrs. Thanks for your replies. I hope to keep getting some input on this.

Re: Holley jetting questions
 

I don't think you are not going to gain much impovement, as motor efficency in boats is such a small factor in the economy. On a car, different story. You would see better (actual) gains per dollar by installing trim tabs to help plane at lower speeds (read; reducing load on motor), investing in a good stainless prop, and keeping the hull clean.

I personally think that you are not going to gain anywhere near 1/2 MPG by changing the carb, etc. All things equal, I doubt you'd notice any difference.

Re: Holley jetting questions
 

Your time would be better spent taking weight out of the boat, clean hull... which would make a bigger impact on MPG rather than increasing your engine efficiency. I think at this point your splitting hairs. Yes your charge velocity and vacuum signal would increase with the smaller carb, but I cant imagine you would increase eff. that much...maybe better throttle response.

Re: Holley jetting questions
 

Your looking for a 33% improvement. That's a HUGE amount, especially for a motor that is running good now.

Re: Holley jetting questions
 

Crazy,

You said that you have plenty of power out of the hole......

Try over-drive, i.e. go up 2 pitches from 17 to 19 or 19 to 21 or 21 to 23 on your Rev4.

BBlades has a test program and can provide you with a 25p Rev4 if you need it.

Cheapest, easiest, cleanest thing you can do to change / enhance performance/driveabliity is prop change.

2 cents

Re: Holley jetting questions
 

I tried a 23p 3 blade, the 19p rev 4 is much better. My prop came from bblades and Brett is very knowlegable. I do have hyd trim tabs with indicators and a nav man fuel flow indicator that shows around 2900 rpm to be the most efficient. The boat is trailered so the bottom is clean. It sounds like im wanting to gain something that is near impossible. Thanks for any replies.

Re: Holley jetting questions
 

You could not load the boat with other people and coolers plus drive at 2500-3000rpm at partial throttle, but that would be no fun at all and not worth it.

Unless the motor tune is way out, there is not going to be a good jump in mileage by getting it 'spot on.' Maybe just a little tiny bit.

Drag / weight / how you drive / how much you drive is what makes/breaks fuel useage/mileage.

If economy is a real 'concern' for anyone I would suggest getting a fuel flow meter (as Crazycat has)so you can see what changes do what to fuel mileage, giving you knowledge on what rpm, trim, throttle setting, weight, etc,etc gives you the most acceptable fuel usage.

I personally just cut down on the length of my trips. I go out just as often, but picked closer spots to hang out for the day.

Fuel prices stink bad - definatley influencing things fore 99% of us.

Re: Holley jetting questions
 

CrazyCat57,

You’re not asking for the impossible, but improbable is going to be the best wording. Picture what you’d have to do to take your streetcar from 20 MPG to 30 MPG. This is what you’re asking for, and it’s not going to be very cost effective with where you are. Now that’s not to say you can’t make the engine more efficient. There are plenty of upgrades that can be done to help the engine, cam profile, cylinder heads, different coatings, etc. however you’d be better off making these changes as the engine is in need of rebuild/upgrade.
To do what you want to do there is a better approach:
Start by getting a fuel flow meter so you can see how much fuel is going into your engine while you are running the boat. Once this is done, you can run the boat at different speeds to see what RPM, Drive, Tab, settings run most efficiently. Then you can try different props to see what gives you exactly what you’re looking for. Most likely a newer prop with more blades will help your low speed efficiency.

Re: Holley jetting questions
 

Rumrunner thanks for your reply. Would you re read my earlier posts if you have time, as far as my trim tabs,feul flow meter, props,etc. I have tried 4 different props, a 3 blade 19p, a 3 blade 23p, a four blade 20p, and a 4 blade 19p. All were stainless. The rev 4 from bblades is by far the best. Thanks for your replies.

Re: Holley jetting questions
 

CrazyCat57,

How are you meassuring your MPG? Are you actually using a flow meter or going by tank loads?

Re: Holley jetting questions
 

I would like to knoe when your power valve opens. I have the same carb and it came with a 10.5 power valve. Turns out it was open all the darn time and according to Holley it uses 25%-40% more gas witht the power valve open. I changed mine to a 3.5 and now it only opens when I really need it. Just a thought.
Ty

Re: Holley jetting questions
 

There are a few items needed to really fine tune for economy.

1) Engine RPM
2) MPH
3) TPS
4) MAP
5) Lambda
6) Fuel flow

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.

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.

Re: Holley jetting questions
 

Edelbrock carbs are built by weber just like the mercury ones!

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.

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.

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

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.

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. :D

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.

Re: Holley jetting questions
 

Power Valves:

A Power Valve is a vacuum operated switch. When the vacuum is higher than the rating on the Valve it remains closed, when the vacuum drops below the rating on the valve it opens. i.e. if you have a 6.5 Power Valve it will be open when the engine vacuum is less than 6.5” Hg, and will be closed when the vacuum is greater than 6.5” Hg. When the Power Valve opens it adds additional fuel to the main circuit of the carburetor. This would be equivalent to going up between 6 and 10 sizes on your main jets (depending on how the carburetor was built).

The purpose of a Power Valve: The Power Valve serves a few purposes. First, since the idle circuit gets all of its fuel from the main metering circuit running a slightly leaner main circuit will have a minor affect on the engines idle quality. Second, and main purpose is enrichment under engine load. The Power Valve system will lean the engine out under light load cruising increasing your fuel economy, but once the engine load increases and vacuum decreases the additional fuel is added.

Power Valve tuning: The number on the Power Valve controls when it opens, and closes. You can change the Power Valve to open later, and close sooner by going to a lower number Power Valve. The opposite is also true going to a higher number Power Valve will get the valve to open sooner and stay open longer richening the circuitry. i.e. If you have 12” Hg at cruise, when you accelerate the engine vacuum will decrease requiring more fuel. A 9.5 Power Valve will open sooner, and remain open longer than a lower numbered Power Valve (2.5, 3.5, 4.5, etc.). You can tune with the valve to give you optimal drivability, and performance.

Power Valve Fuel Flow: The rating or number on the Power Valve has nothing to do with the fuel flow, only the timing when the fuel is added to the engine. The fuel volume is controlled by the P.V.C.R. (Power Valve Channel Restrictors), which are the two holes behind the Power Valve in the metering block. Changing the size of these holes will control the fuel volume.


Vacuum Secondary Operation:

The Vacuum Secondary Butterflies open based on the air velocity traveling past a hole in the primary venturi, as the air passes this hole it creates a pressure differential or vacuum in the vacuum pod. Based on the amount of vacuum in the pod, and the rate of the spring it controls the opening rate of the secondary butterflies. So engine RPM, and load will vary the secondary opening rate. What does this mean? If you’re running at a specific engine RPM, but have more load on the engine (due to trim, sea conditions, weight, etc.) it will change how far your secondary butterflies are open at that point.

Changing the spring rate controls when the secondary butterflies will start to open, and at what RPM they will fully open. Having the secondary butterflies open later than optimal can increase fuel economy, but can hinder top end performance, and acceleration while having them open too soon can cause a bog or hesitation.

Re: Holley jetting questions
 

What he said. The 10.5 power valve was open almost all the time and was burning a ton of fuel. Change it to a 3.5 so it opens only when needed and my milage increase accordingly. Took a while to find the right one but now it's waiting in the wings at cruise just step on it a little and opens. Good luck, Ty

Re: Holley jetting questions
 

WOW I am sure learning a bunch here. I went to my dealer here this morning and all he could come up with from his books was, both primary and secondary should have 2.5 power valves, his book did not list spring color or jet sizes in the factory specs. He did have the cam lift specs, intake .2343 and exhaust .2530. Thanks again for all your replies.

Re: Holley jetting questions
 

Hmmm.
.398", .430" lift cam ? On a big block ? Never seen that.
Not that this applies to this thread, but just in case anyone wants to know, this is what I have listed for the Merc BBC w/oval heads and hydraulic flat tappet cam:


Standard Flat Tappet (oval heads)

.004” 287*, 302
.006” 278*, 289
.050” 214*, 218*
.200” 111*, 119*
Valve lift with 1.7 .460” , .480”
ICL 110 ATDC
ECL 118 BTDC
114 LSA

Re: Holley jetting questions
 

I dont think that I have ever mentioned this but it is one of those dreaded omc king cobras.

Re: Holley jetting questions
 

I finally got the boat out. I found 2 air bleeds plugged and cleaned them. Its running 10 in of vacuum and the secondary butterflys start to open at a little over 2700 rpm, that seems way to low to me. Most all of my running is around 3000 rpm. The boat is a 1992 so I have to decide what to do, repair or replace the carb. Just to open a carb that old will probably require new gsks, power valves, secondary diaphragm, secondary opening spring set to re calibrate, accelerator pump and whatever else I might encounter. I have been thinking that instead of opening my holley to look inside this late in the Minnesota boating season I might take the money I would have spent on the holley and put some more with it and try a new #1409 600 cfm Edelbrock. Edelbrock recommends it for economy. They also say it will improve low and mid range power but probably loose 2 or 3 mph on the high end. The #1409 Edelbrock does have smaller primaries similar to the holley spread bore. I would like to hear some suggestions of what you think I should do. Thanks for your time.

Re: Holley jetting questions
 

10" of vacuum means you have an engine or ign timing issue. 10" (on a healthy motor) would be typical of a fairly large cam with a good amt of overlap.

Check your ignition timing and then let's look for vacuum leaks and do compression test.

2700rpm is normal range for vac secondaries to 'start' opening.

I really feel tuning a '1409' and then using it will not be worth it.

Re: Holley jetting questions
 

If you feel that a new carb is in order.

RumRunner wouldn't promote his products :drink: , but I would suggest you look at a Sea Demon by Barry Grant, good quality carb and RumRunner could spec the exact model that should work best for you. USCG type approval also. You would need a spread bore adapter, but the right one may help your torque a little.

Jegs has good prices.

Re: Holley jetting questions
 

It may be that the boat is overpropped. By putting a large load on the boat, you are required to open the throttle more to maintain speed. Large throttle load means secondaries open sooner and power valve opens sooner. I would try to prop the boat to spin 4600.

Re: Holley jetting questions
 

If you want to have better fuel economy and still decent performance with a 330 I would suggest a 750 CFM Q-jet. The small primaries are very good at cruising RPM and idle. Also I think you are propped a little heavy. I would WOT prop at about 4600 minimum. I would not mess with Holleys or Edelbrocks on a stock 330, go with the Q-jet.