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Swapping holley carbs and questions

"Junk the Holleys and get 2&#4

"Junk the Holleys and get 2(Twins??) Edelbrock 600cfm marine carbs. No runs,drips,errors..Good economy ez maintenace."
 
".."spray them down with s

".."spray them down with some non stick cooking spray[PAM], it will make future removal a lot easier."

Slick idea (no pun intended). I'll try that.

Thanks.

Jeff"
 
"no need to junk the holleys ,

"no need to junk the holleys ,just normal tuning and they will get great economy.With simple jet changes they're adjustable to most any application.Most later models have a built in back fire valve to help cut down on power valve problems.Edelbrocks have to have jet and needle changes to correct fuel adjustments most times. Just a matter of preference [ and cash]. TURBOMAN ROLLTIDE 11-0"
 
"everett, I'm still lookin

"everett, I'm still looking for some specifics on tuning the holley for efficiency in 2800-3200 rpm range. Do I change jet sizes?
steve"
 
Better leave the jets alone--g

Better leave the jets alone--gas is cheaper than pistons--but you CAN }block the secondaries from opening. That will help a bunch IF they are opening at your cruising speed.

Jeff
 
"That is a real concern Jeff,

"That is a real concern Jeff, I can't afford that. I'm still on the fence to switching to the edelbrock 1409 since it gets such rave reviews for economy, but crusader must have paired up the holley with the intake for a reason."
 
"Steve:

here's a link t

"Steve:

here's a link to one of Holley's tuning documents. You can find a wealth of info there.

http://holley.com/data/TechService/Technical/Carburetor%20Tech%20Info.pdf

If you are careful and methodical, you can change the tuning of your carb without fear. That said, if you don't verify each change then don't start. The big difference in the marine world is the load the engine sees - there really isn't a 'cruise' mode like with a car.

The big driver for the change to holley's was probably purely business driven. there aren't too many carb makers left. Out of those, holley probably cut them the better deal."
 
"From the scuttlebutt going ar

"From the scuttlebutt going around, I hear that Holleys are not famous for gas mileage. That said, you CAN tune a carb to improve gas mileage at ONE specific rpm and not damage anything IF you use the following precaution:

1. Pre-select your "sweet spot", a cruising speed you can live with most of the time.

2. Run the engines at this point for at least 10 minutes, then shut them down as fast as you dare and drop the hook. Excess idling at this point will defeat you purposes, so make it quick as possible.

3. Pull at least 2 plugs (the easiest location) and read the colors: A light tan tip is what you're after. If the plugs are brand new, then you'll need to "age" them for a few hours before trying this.

4. Now, if the plugs come out a medium brown, then you can drop the primary jet size one step leaner. But if the plugs are already a light tan you're already there. (On my boat, with a new Edelbrock 1409, I had to go one step RICHER since the plugs came out stark white, and that is not good.)

A lot of work and burnt fingers, but worth it IF your plugs are running a dark brown.

Jeff"
 
"I think one will find three &

"I think one will find three "subsystems" within the carb where you can make metering changes on all current (popular) carbs: primary, power, and secondary. For economy, you need to worry about the first two. The rochesters and the edelbrocks have more 'tuning points' than the holley's -> that why, if you take the time, you can find the sweet spot. If you are willing to spend time tweaking the air bleeds, you really can control the A/F ratio over a large part of the operating range."
 
"Jeff, thanks for the procedur

"Jeff, thanks for the procedure. I have been thinking about changing the jets on my Rochester 4 barrell. I have been running at 1200 RPM for a while. I took 4 plugs out a few weeks ago and they were dry but black. Not much build up of carbon, just black. How much time, running at higher RPM, do you think would be necessary to turn them brown?

Chuck Hanson
[email protected]"
 
"Chuck:

Unless you know the

"Chuck:

Unless you know the primary system is rich, you may want to start with a change of primary rods, especially if you operate around 1200 rpm most of the time."
 
"Chuck.....
I run Crusader 35

"Chuck.....
I run Crusader 350s and I had the same problem and I also run at about 12-1300RPM. My engine guru and I talked about it and we decided to change the thermostat to 160 degrees, put in hotter plugs and redid the carbs. Worked well but like you I still found a bit of black carbon , even when I ran at about 2-2500 rpm for 15 minutes every 2 hours.

I have Rochester QJets and will be installing new jets next spring. Got some .062 and.064s and will see what works best. Personally I think the photos of Gibsons rocketing through the water are very misleading. I cruise at about 6-6.5 kts and find I can save alot of gas at low power settings....probably not as good for the engines but I can live with it and will keep tinkering.

regards."
 
"Don: Is that an old Convair?

"Don: Is that an old Convair? Rode on a bunch of them.

You need to change jets, not rods, on a Q-jet used on a boat since there's not a lot of vacuum at even slow cruising speed.

To wit: The rods lift to open up the jets when the throttle is advanced. When you back off the throttle (which is not the case in a boat), the rods drop to lean out the mixture. Since a boat is always "going uphill" there's rarely enough vacuum to 'drop the rods', so you need to put in smaller jets (IF it won't hurt the motor--you MUST check).

Jeff"
 
"Hi Jeff,
yeh, that is a Cana

"Hi Jeff,
yeh, that is a Canadian Military Convair, (CV580 called a "Cosmo") and was designated as Smoky 02, the personal aircraft of the Deputy Commander of NORAD. I was fortunate enough to spend 3 great years in Colorado Springs as Commander of that aircraft.

Re Rochester Q-Jets. Do you feel that new Q jets, (rebuilt), set up properly are just as good as the Edlebrocks??

I have only had q jets and at times, because we spend so much time tweaking them, I was wondering if I should change?"
 
"Under 1500 rpm, there should

"Under 1500 rpm, there should be enough vacuum to keep the rods down in the primary jets, even on a 4-cylinder. Best thing to do is to document your present baseline of where the rods are along with the vacuum in the manifold, as a function of RPM. Then you can tailor things to meet the needs of the specific application. The prop and the gear will factor in much more than the speed.

Don: what do you have in the carb now? I've never seen 0.062" primary jets (none smaller than 0.066"). If you really have 0.062" jets, and put them in, make sure your insurance is paid and covers the engines as I'd bet you'll see what Jeff described as the "fried piston" syndrome."
 
Makomark....

Good points re

Makomark....

Good points re-primary jets. I do not know what we have but will ensure the "engine guru" lets me know and will discuss the "fried piston syndrome" with him as well. The change is supposed to be done in the Spring.
 
"A good Q-Jet, properly set up

"A good Q-Jet, properly set up, is the best fuel economy carb out there. This presupposed that the secondaries remain closed during cruising mode. If not, they are a pig!

Jeff"
 
"smallest I've ever seen,

"smallest I've ever seen, factory installed, were 0.068's; 0.062's would be a reduction of 17% from them and that's a radical change"
 
"Steve ,sorry it took so long

"Steve ,sorry it took so long to get back to you, had to put my mother in the hospital. To get back to your holleys, try using a vacuum gauge to check your reading at your sweet spot. In doing this,you can possibly go with a different power valve to match it's opening point to go along with the upper point of your cruise speed. Some of the best advice is what mako suggested.It's hard to tune a carb over the forum,over the phone,ect. ,you need to be there to be able to see and check various things.But ,the hollys can make good fuel milage properly tuned,so check out the site as suggested by MAKO ,and I still can't get in touch with the address you gave me. Leave a phone # ,I'll call .thanks. TURBOMAN ROLL TIDE 12-0 GEORGIA bound."
 
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