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Topic: Carburetor Question?, Help< Next Oldest | Next Newest >
miller19jMale Offline
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Post Icon Posted: Mar. 29 2003,1:10 pm Post # 1 see this member send this member a private message  quote this post in reply
My old carb is leaking all over the place and I think one of the floats has a problem. It is a Automotive carb and I had thought about replacing it with a marine carb for some time now. With the covered engine I would like to have a marine carb just for peace of mind. I think now would be a good time before I start a fire.  

Currently it is a 750dp and I thought I would replace it with a marine 750dp but now I have a choice between mechanical and vacuum secondaries. I think that I have vacuum secondaries currently but am not sure. What are the pros and cons between the two. I really need help deciding as I have no clue.

The other question is how hard are they to adjust out of the box? Do I just bolt it on and go or is their a lengthy adjustment procedure?

Any help would be greatly appreciated.

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Post Icon Posted: Mar. 29 2003,3:58 pm Post # 2 see this member send this member a private message  quote this post in reply
IMO Mechanical secondaries use more fuel and for pleasure boating vacuum secondaries are the way to go. Also for pleasure boating the carbs are set close enough, I'm sure if ya tweak on them you can pick up some hp and driveability but but you can do that later or never.
Which carb ya looking at? I like the shiny Edelbrock or Holley but I don't think they are marine carbs.  I saw some reman Edelbrock marine carbs in the Jegs website.
Had a crappy day working on mine today it was Murphy's Law with everything I touched. Gona take a break and watch the UofA in the NCAA Tourney and knock back a few Ultra's  :) Then give her hell tomorrow.

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Post Icon Posted: Mar. 29 2003,8:07 pm Post # 3 see this member send this member a private message  quote this post in reply
I agree with KC. I run vacuum secondaries but one thing I don't care for is they don't always kick in when you want them to.  :angry  It's a minor prob. that I will live with it's not worth going out and buying a new carb.

BR

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Post Icon Posted: Mar. 30 2003,12:01 am Post # 4 see this member send this member a private message  quote this post in reply
Quote (Knuckle head @ Mar. 29 2003,9:07 pm)
I run vacuum secondaries but one thing I don't care for is they don't always kick in when you want them to.  

The beauty of the vacuum secondary is the adjustment is all in the spring.  You can buy different springs and swap them out in the vacuum pod to control when they open.  Other than that, they are pretty much set up to run right out of the box.

Everyone is a tough guy, until you meet one.  
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Post Icon Posted: Mar. 30 2003,6:33 am Post # 5 see this member send this member a private message  quote this post in reply
Quote (miller19j @ Mar. 29 2003,1:10 pm)
My old carb is leaking all over the place and I think one of the floats has a problem. It is a Automotive carb and I had thought about replacing it with a marine carb for some time now. With the covered engine I would like to have a marine carb just for peace of mind. I think now would be a good time before I start a fire.  

Currently it is a 750dp and I thought I would replace it with a marine 750dp but now I have a choice between mechanical and vacuum secondaries. I think that I have vacuum secondaries currently but am not sure. What are the pros and cons between the two. I really need help deciding as I have no clue.

The other question is how hard are they to adjust out of the box? Do I just bolt it on and go or is their a lengthy adjustment procedure?

Any help would be greatly appreciated.

Since you don't have a race application here, I would highly suggest losing the double pumper, it has no value. All you're doing is using more gas for nothing. With the vacuum secondaries, they only open as you need them and operation is a lot smoother. Tuning them is very simple, if it even needs to be messed with. An appropriate size carb is set close from the factory. Most of the time, the shooters are they only thing you may have to enlarge if you get a stumble on take off. The secondaries are just a matter of changing springs. You can get a kit with assorted springs also you can get a quick change cover to make changing springs a snap, no more undoing the diaphram. The best way to do it is to take it out of the box, make sure everything is tight, bolt it on and try it as is, you may be supprised how well it may work right out of the box, then go from there. BTW, if you have an engine cover, do get a marine carb, for venting purposes. I's not so much the fire, it's that "KABOOM" that will kick you in the ass!... Hope this helps!...  :)
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miller19jMale Offline
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Post Icon Posted: Mar. 30 2003,12:23 pm Post # 6 see this member send this member a private message  quote this post in reply
I did a little reading last night and found that my carb is not a dp and it does have vacuum secondaries. All of my books agree with what you guys are saying and I am going to go with a vacuum secondary carb. I will definitely get a marine carb as well the whole boom idea makes me a little nervous.

Thanks for your help! :)

Brad

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GoFastRacerMale Offline
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Post Icon Posted: Mar. 30 2003,5:32 pm Post # 7 see this member send this member a private message  quote this post in reply
Anytime Brad, if you have questions, just holler!. ;)  BTW, what's the list number on that carb?, I may be interested in it if you want to part with it after you get your marine carb!.. :D
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miller19jMale Offline
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Post Icon Posted: Mar. 31 2003,8:30 am Post # 8 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ Mar. 30 2003,5:32 pm)
Anytime Brad, if you have questions, just holler!. ;)  BTW, what's the list number on that carb?, I may be interested in it if you want to part with it after you get your marine carb!.. :D

I will check tonight. I have no use for it after I get a new one.

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Post Icon Posted: Mar. 31 2003,8:36 am Post # 9 see this member send this member a private message  quote this post in reply
Aint nothing finer than a brand new carb, put it on set the idle and drive it.

If quizzes are quizzical, what are tests???
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GoFastRacerMale Offline
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Post Icon Posted: Mar. 31 2003,11:29 am Post # 10 see this member send this member a private message  quote this post in reply
Quote (miller19j @ Mar. 31 2003,8:30 am)
Quote (GoFastRacer @ Mar. 30 2003,5:32 pm)
Anytime Brad, if you have questions, just holler!. ;)  BTW, what's the list number on that carb?, I may be interested in it if you want to part with it after you get your marine carb!.. :D

I will check tonight. I have no use for it after I get a new one.

Cool!..  :)
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Post Icon Posted: Mar. 31 2003,11:30 am Post # 11 see this member send this member a private message  quote this post in reply
Quote (blown 472 @ Mar. 31 2003,8:36 am)
Aint nothing finer than a brand new carb, put it on set the idle and drive it.

Yeah, if you're lucky!.  :laugh
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miller19jMale Offline
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Post Icon Posted: Mar. 31 2003,6:06 pm Post # 12 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ Mar. 30 2003,5:32 pm)
Anytime Brad, if you have questions, just holler!. ;)  BTW, what's the list number on that carb?, I may be interested in it if you want to part with it after you get your marine carb!.. :D

I know nothing about carburetors so I don’t know if this is the correct stuff, but these are all the numbers that I could find.

Choke tower
3310-4
0616

Looking down into air horn
6R 6931

Main fuel bowl side
10569

Butterflies
172

Side
P-80

I may have some of the terminology wrong but you will get the idea.

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Post Icon Posted: Mar. 31 2003,6:19 pm Post # 13 see this member send this member a private message  quote this post in reply
Thanks, 3310 is the List no!, it's a 780, that's all I need to know, let me know what you want for it when you're ready to dump it, I may buy it!.    :)
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miller19jMale Offline
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Post Icon Posted: Mar. 31 2003,6:25 pm Post # 14 see this member send this member a private message  quote this post in reply
What’s a 780? Is a 750 smaller?

I think I am ready to get rid of it right now.  I don’t know what a fair price is. I was just going to put it on ebay and see what happens. What is it worth to you? I am not looking for high dollar here I just have no clue what is fair.

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Post Icon Posted: Mar. 31 2003,7:22 pm Post # 15 see this member send this member a private message  quote this post in reply
Actually now it is a 750, the 3310 used to be rated at 780, don't know why they changed it?, that carb has been around for ages!.  :eek As far as what ther'e worth, that's hard to answer, the swap meets are full of them, I see them from $10 to $75 depending on the shape they are in. What you get for them depends a lot on the person buying it, if he can't rebuild it himself then he'll pay more if it looks in good shape?, what kind of shape is yours in?.. :rolleys
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miller19jMale Offline
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Post Icon Posted: April 01 2003,8:20 am Post # 16 see this member send this member a private message  quote this post in reply
What kind of shape is mine in? Its like brand new! Why am I replacing it? Well I just feel like it.  :D

Seriously I know very little about carburetors as you know so I am probably not the best judge. But I can tell you what I know is wrong with it. It leaks fuel out of what I think are the secondaries jets. They are on the secondary side I am just not sure Jet is the correct term. They are the cylindrical pieces that are mounted into the center of the venturi (sp).

At 2k the primary side has a nice mist of fuel coming out of them and the butterflies are opened. But the secondary side has a constant drip coming out and the butterflies are closed.

I ran the carb all last season and did not notice any problems with it. This seems to have started after the carb was sitting on a shelf for several months during my engine rebuild. I don’t know how serious this problem is. But it was a good reason for me to buy a marine carb.

If you are interested I can take a few pictures of it tonight for you.

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Post Icon Posted: April 01 2003,8:33 am Post # 17 see this member send this member a private message  quote this post in reply
Sounds like an internal leak. The part you're talking about are called booster venturis. A pic would be cool!.. ;)
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Post Icon Posted: April 01 2003,10:35 pm Post # 18 see this member send this member a private message  quote this post in reply
The new HP model carbs from Holley work really well, right out of the box.  They are dp's, but they use progressive linkage on the secondaries.  I think these are well worth the money.

I ran a single 950 HP Holley on my blown sbc the first time it was built.  It ran awesome!  I am now running dual 4150 750 DP's (I got them for free) but I think the single 950 ran better most of the time.  It was trouble free - and looked cool.  The HP's almost look like the Demon's - except half the price and little tuning needed.
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Post Icon Posted: April 02 2003,7:26 am Post # 19 see this member send this member a private message  quote this post in reply
The HP carbs are cool right out of the box, a friend of mine put one on his and he likes it. Since they are a DP, they work best on a single plane manifold. On a non high performance ski boat with a dual plane manifold, a vacuum secondary carb would be smoother and easier on gas since you're running most of the time at part throttle. This way, the secondaries will open only if the motor needs it. Don't remember, does the HP series come in a marine configuration??.

Your 950 ran better because it was about the right size carb for your application. A pair of 750's is 1500 cfm, that's a lot for a small block unless it's a mega buck Pro Stock type deal..

Here I go shooting my big mouth off again!...  :rolleys  :rolleys
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Post Icon Posted: April 02 2003,7:40 am Post # 20 see this member send this member a private message  quote this post in reply
Yes, the 950 was the right set up for my sbc in the first blower build.  It made about 550 HP - ran 4 lbs of boost - redline of 7000.

Now, it makes 750+ HP.  Runs 12 lbs of boost.  (Currently changing the cam so redline will be 6500).  Theoretically, the motor requires ~1300 CFM.  So, the dual 750's are on the big side, but have been tuned in on the dyno.  They are a set of Gary Williams.  I do get a better hole shot at 3/4 throttle vs. wide open.
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Post Icon Posted: April 02 2003,7:42 am Post # 21 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ April 02 2003,7:26 am)
The HP carbs are cool right out of the box, a friend of mine put one on his and he likes it. Since they are a DP, they work best on a single plane manifold. On a non high performance ski boat with a dual plane manifold, a vacuum secondary carb would be smoother and easier on gas since you're running most of the time at part throttle. This way, the secondaries will open only if the motor needs it. Don't remember, does the HP series come in a marine configuration??.

Your 950 ran better because it was about the right size carb for your application. A pair of 750's is 1500 cfm, that's a lot for a small block unless it's a mega buck Pro Stock type deal..

Here I go shooting my big mouth off again!...  :rolleys  :rolleys

I have seen small block blown motors with two 1050's, blown motors like an unrestriced inlet.  Unlike my ex. :laugh

If quizzes are quizzical, what are tests???
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Post Icon Posted: April 02 2003,7:52 am Post # 22 see this member send this member a private message  quote this post in reply
Quote (HolyMoly @ April 02 2003,7:40 am)
Yes, the 950 was the right set up for my sbc in the first blower build.  It made about 550 HP - ran 4 lbs of boost - redline of 7000.

Now, it makes 750+ HP.  Runs 12 lbs of boost.  (Currently changing the cam so redline will be 6500).  Theoretically, the motor requires ~1300 CFM.  So, the dual 750's are on the big side, but have been tuned in on the dyno.  They are a set of Gary Williams.  I do get a better hole shot at 3/4 throttle vs. wide open.

LOL, funny you should mention 3/4 throttle, back in the 80's a buddy and I ran a 23 T altered car in the high 8's. All it had was a 427, it was an L88 except for the cam, we decided to try a 1050 dominator, the car slowed down at full throttle so we put a stop at 3/4 throttle and it picked up almost a tenth, about the same as it did with an 850. Then we put injectors on, needless to say, all carbs were shitcanned!...  :laugh
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Post Icon Posted: April 02 2003,7:53 am Post # 23 see this member send this member a private message  quote this post in reply
Quote (blown 472 @ April 02 2003,7:42 am)
Quote (GoFastRacer @ April 02 2003,7:26 am)
The HP carbs are cool right out of the box, a friend of mine put one on his and he likes it. Since they are a DP, they work best on a single plane manifold. On a non high performance ski boat with a dual plane manifold, a vacuum secondary carb would be smoother and easier on gas since you're running most of the time at part throttle. This way, the secondaries will open only if the motor needs it. Don't remember, does the HP series come in a marine configuration??.

Your 950 ran better because it was about the right size carb for your application. A pair of 750's is 1500 cfm, that's a lot for a small block unless it's a mega buck Pro Stock type deal..

Here I go shooting my big mouth off again!...  :rolleys  :rolleys

I have seen small block blown motors with two 1050's, blown motors like an unrestriced inlet.  Unlike my ex. :laugh

That's funny!.. :laugh
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Post Icon Posted: April 02 2003,8:11 am Post # 24 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ April 02 2003,7:52 am)
Quote (HolyMoly @ April 02 2003,7:40 am)
Yes, the 950 was the right set up for my sbc in the first blower build.  It made about 550 HP - ran 4 lbs of boost - redline of 7000.

Now, it makes 750+ HP.  Runs 12 lbs of boost.  (Currently changing the cam so redline will be 6500).  Theoretically, the motor requires ~1300 CFM.  So, the dual 750's are on the big side, but have been tuned in on the dyno.  They are a set of Gary Williams.  I do get a better hole shot at 3/4 throttle vs. wide open.

LOL, funny you should mention 3/4 throttle, back in the 80's a buddy and I ran a 23 T altered car in the high 8's. All it had was a 427, it was an L88 except for the cam, we decided to try a 1050 dominator, the car slowed down at full throttle so we put a stop at 3/4 throttle and it picked up almost a tenth, about the same as it did with an 850. Then we put injectors on, needless to say, all carbs were shitcanned!...  :laugh

Ah, injected motors, I am planning a long term project, flatie with an injected small block on 50 to 60 percent nitro.

If quizzes are quizzical, what are tests???
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Post Icon Posted: April 02 2003,8:30 am Post # 25 see this member send this member a private message  quote this post in reply
Quote (blown 472 @ April 02 2003,7:42 am)
like an unrestriced inlet.  Unlike my ex. :laugh

LMAO :rotflmao  :rotflmao  :rotflmao

Knuckle Heads
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