Holley carb set-up Question(s); remove choke tower?

[wca_tim]

I've worked with holley carbs, but not for a good while, and haven't set one up for a boat. I'm sitting here at the bench in the garage trying to decide on a couple of things and know that at least a few of you have some real experience with this based on your posts.

Is there any reason not to remove the choke tower? I don't mind waiting a few for the boat to warm up - it doesn't run well until warmed up even with a choke, and if I'm out in it in cold weather it's just me playing so no worries on timing for warm-up, etc....

I have very little space above the engine and so am limited to a 3 1/2 inch tall flame arrestor, I can't believe that the choke tower won't interfere with airflow and know we used to mill them off and then blend it in. I could also buy an aftermarket body like a proform, but would prefer to spend the money on other things right now.

I've got a 4150 series carb (originally 4779 marine) with mechanical secondaries that I'm planning to put on my 383 with an airgap rpm intake and am currently thinking using the metering blocks for two corner idle. the engine is relatively mild, probably conservative estimate a bit over 400 horsepower with a peak at about 5500-5800 rpms

The other question is where to start for jetting and power valve (until I can put a vacuum gauge on it and see where it should be); start with jets at 74 / 82 and a 5.5 power valve on the primary side, no power valve on the secondary side.

Any advice or thoughts beyond the obvious, normal things very much appreciated... Thanks!

 

[winter]

I'm no expert on carbs, but i don't think the choke tower is constricting your airflow as much as you think. If you have a high strung motor and are worried the set up is restrictive, then you may want to shop for a more performance oriented carb.

 

[Old Navy]

If you're feeling frisky, take it off. The biggest concern is getting the carb clean after the milling/grinding whatever you are doing. My boat does not have a choke (Dominator) and is a little cold blooded at the ramp. My flame arrestor is only a 2x10 and testing has revealed no change in running with it on or off, so if your sole motivation is that you are concerned with airflow and a 3.5 in flame arrestor, I doubt you will make any performance gains by removing the cast in choke tower.

 

[wca_tim]

With the drop base flame arrestor, the choke tower is within an inch or inch and a half of the top of the flame arrestor inside - that's why it concerns me a good bit. I'm thinking that the flame arrestor will be fine, but that there's a lot less room for air to get into the primaries with the choke tower so close to the flame arrestor.

I'll probably do it on a mill to get it square and then blend in where needed with a die grinder and sanding. Your point about getting crap everywhere is well taken - I taped up all the holes and will clean it meticulously when done cutting.

If you're feeling frisky, take it off. The biggest concern is getting the carb clean after the milling/grinding whatever you are doing. My boat does not have a choke (Dominator) and is a little cold blooded at the ramp. My flame arrestor is only a 2x10 and testing has revealed no change in running with it on or off, so if your sole motivation is that you are concerned with airflow and a 3.5 in flame arrestor, I doubt you will make any performance gains by removing the cast in choke tower.

 

[happy]

As a mechanic, I have to strongly urge you not to remove your choke tower, if the carburator floods, you'll have a serious explosion issue. Its a fire hazard and if inspected by the local or federal law you'll recieve a citation. If a Marine mechanic ever works on the boat the carb will have to be repaired or replaced with a marine set up.

The legal responsibility is too great.

If you cant get a holly to idle it may be clogged up metering blocks, wrong jets ect.

 

[wca_tim]

it is a marine carb... a 750 cfm dp with mechanical secondaries (model 4779 marine) so the shafts are grooved and the jtubes would stay after taking the choke tower off. it's a fairly simple / standard modification.

The only reason or time I would be concerned that it might not idle well was when cold with no choke.

The carb is just like this one... except that it is a little older model

http://www.holley.com/0-80537.asp

 

[Big Red]

As a mechanic, I have to strongly urge you not to remove your choke tower, if the carburator floods, you'll have a serious explosion issue. Its a fire hazard and if inspected by the local or federal law you'll recieve a citation. If a Marine mechanic ever works on the boat the carb will have to be repaired or replaced with a marine set up.

The legal responsibility is too great.

If you cant get a holly to idle it may be clogged up metering blocks, wrong jets ect.

HP marine carbs don't run a choke tower, besides the j tubes direct the fuel down the carb when a float hangs. The choke tower filling up with fuel would only make for a bigger explosion and only reflects on the front barrels.

 

[Mr. Buss]

here's my 2 cents....

my boat has no choke on it, it was a heat activated choke quadrajet at one time..(another story) .... yes i have to warm it up at the dock until it idles right, but i warm everthing up before i run it. (old habit).... as i wish everyone would.

if you are palnning on milling off that choke tower, take it apart!! its not worth the hassle of your motor eatin that stuff, you wont tape off all the orfices... and when you put it back together you can make sure everything is clean..

 

[Mr. Buss]

As a mechanic, I have to strongly urge you not to remove your choke tower, if the carburator floods, you'll have a serious explosion issue. Its a fire hazard and if inspected by the local or federal law you'll recieve a citation. If a Marine mechanic ever works on the boat the carb will have to be repaired or replaced with a marine set up.

The legal responsibility is too great.

If you cant get a holly to idle it may be clogged up metering blocks, wrong jets ect.

HP marine carbs don't run a choke tower, besides the j tubes direct the fuel down the carb when a float hangs. The choke tower filling up with fuel would only make for a bigger explosion and only reflects on the front barrels.

I agree red..

here's a MARINE dominator pic, obviously its huge and not for your aplication by any means, but it is "legal" without a choke horn

 

[happy]

as long as the j tubes stay I guess you'll be ok, I have to look at it from the modified equipment law, (its in OSHA 1910) which basically says if I alter it, and you get hurt, I'm responsible. If the J tube gets whacked off or no longer functions, you won't be legal or safe. I have seen hollys puking fuel from both j tubes, and also watched boats catch fire because of this. Be careful, in a lot of cases this can do more damage than good. If you do make smooth, even radii. Also, if you have a slightly larger carb than you need or a fairly docile engine, you are generally served better to simply mill or cut the choke horn evenly to a level about even with the top of the air cleaner ridge. This tends to help midrange power at the expense of a little top end, if in doubt do the square top. In most cases, simply removing the choke plate and associated linkage will accomplish 80% of the increase you will gain with the rest of the top modifications. The main exception to this rule is in the case of clearance problems necessitating a low air cleaner lid- cutting down the choke horn will allow better entrance and a denser mixture. Also, after you finish your installation, do plug readings to determine if you are running lean, chances are you will.

 

[wca_tim]

Thanks for the input / replies.

I already cut it down this afternon before having to come back to work and have the cleaning up left to do with die grinder and sanding. carb is already completely disassembled and been tanked, etc.. I'm just working on the body. I plan to leave the cuts squared off adjacent to the air bleeds to keep from creating any unpredictable turbulence there and radius everything else carefully. It looks like it worked fine to tape over all the passages with painters tape.

Carb should be just about the right size and since I took a different one off, I'll be jetting / doing set up from scratch anyhow.

I'm swapping intakes and changing flame arrestors at the same time. The engine is your basic 383 with moderately ported, 200 cc intake runner aftermarket heads, 10:1 compression, mild enough cam to just be able to put into gear while running, and performance aftermarket exhaust, and routinely run at up to around 6000 rpms.

Thanks again. You guys are allright...

 

[ndaniels]

Hope it works out for ya.... I've always liked that diplomat of yours. When are you going to get some more running video of that thing?

 

[Big Red]

as long as the j tubes stay I guess you'll be ok, I have to look at it from the modified equipment law, (its in OSHA 1910) which basically says if I alter it, and you get hurt, I'm responsible. If the J tube gets whacked off or no longer functions, you won't be legal or safe. I have seen hollys puking fuel from both j tubes, and also watched boats catch fire because of this. Be careful, in a lot of cases this can do more damage than good. If you do make smooth, even radii. Also, if you have a slightly larger carb than you need or a fairly docile engine, you are generally served better to simply mill or cut the choke horn evenly to a level about even with the top of the air cleaner ridge. This tends to help midrange power at the expense of a little top end, if in doubt do the square top. In most cases, simply removing the choke plate and associated linkage will accomplish 80% of the increase you will gain with the rest of the top modifications. The main exception to this rule is in the case of clearance problems necessitating a low air cleaner lid- cutting down the choke horn will allow better entrance and a denser mixture. Also, after you finish your installation, do plug readings to determine if you are running lean, chances are you will.

90% of this advice was taken straight from a book instead of hands on experience.

 

[Big Red]

I probably would start with 70 to 74 jets or 72-76 a 82 rear sounds to strong, a stock 850 runs a 84 rear. I would run the stock power valve,, without looking I think is a 6.5 The only time I change my power valve is when I run a radical cam and the vacuum is off

But then again this ethanol in fuel has made me do some funky jetting lately

 

[wca_tim]

I probably would start with 70 to 74 jets or 72-76 a 82 rear sounds to strong, a stock 850 runs a 84 rear. I would run the stock power valve,, without looking I think is a 6.5 The only time I change my power valve is when I run a radical cam and the vacuum is off

But then again this ethanol in fuel has made me do some funky jetting lately

Thanks Red! I hoped you would weigh in, I know you've done a good bit with them. The only reason I was starting fat is to be sure I don't lean it out hard.... I'll try it and with the 6.5 power valve - the cam in there isn't too bad at all 270/286. I'm sure I've got one.

 

[happy]

90% of this advice was taken straight from a book instead of hands on experience.

Yup, had to go back to my notes, this was a common practice back in the 70's mostly done for hood clearance, and by the way, so you know that so little gain (if any) is accomplished by this its really not worth the effort, the probability of inducing turbulance is great unless you flow the carb contouring the venturi inlet, at which point you might as well bought the hp. The hp carb and what we are talking about match like a bumble bee and an ant. I have over 20 years in this field, I believe I've earned my respect, both in the shop and on the race course.

 

[Big Red]

As a mechanic, I have to strongly urge you not to remove your choke tower, if the carburator floods, you'll have a serious explosion issue. Its a fire hazard and if inspected by the local or federal law you'll recieve a citation. If a Marine mechanic ever works on the boat the carb will have to be repaired or replaced with a marine set up.

The legal responsibility is too great.

If you cant get a holly to idle it may be clogged up metering blocks, wrong jets ect.

Sorry Happy but this post really threw me for a loop . Being the choke tower has nothing to do with flood control, marine use, or federal regulations.

 

[ezstriper]

taking the choke horn off is the way to go, the flowed tops that come on the H/P holleys now is because what the racers were already been doing for years, so if you do not need a choke, remove it...good for airflow...Rob

 

[wca_tim]

Thanks a lot for the input fellas. I just decided to ship my heads off for (more) work and so it'll be a little while before I put things back together... Will let you know how it turns out once is all said and done.

 

[happy]

Sorry Happy but this post really threw me for a loop . Being the choke tower has nothing to do with flood control, marine use, or federal regulations.

Here ya go!! Read all the referenced cfr's, not alot of people read these, and mostly not enforced untill after a mishap.


Title 40: Protection of Environment
PART 1042—CONTROL OF EMISSIONS FROM NEW AND IN-USE MARINE COMPRESSION-IGNITION ENGINES AND VESSELS
Subpart G—Special Compliance Provisions


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§ 1042.605 Dressing engines already certified to other standards for nonroad or heavy-duty highway engines for marine use.
(a) General provisions. If you are an engine manufacturer (including someone who marinizes a land-based engine), this section allows you to introduce new marine engines into U.S. commerce if they are already certified to the requirements that apply to compression-ignition engines under 40 CFR parts 85 and 86 or 40 CFR part 89, 92, 1033, or 1039 for the appropriate model year. If you comply with all the provisions of this section, we consider the certificate issued under 40 CFR part 86, 89, 92, 1033, or 1039 for each engine to also be a valid certificate of conformity under this part 1042 for its model year, without a separate application for certification under the requirements of this part 1042.

(b) Vessel-manufacturer provisions. If you are not an engine manufacturer, you may install an engine certified for the appropriate model year under 40 CFR part 86, 89, 92, 1033, or 1039 in a marine vessel as long as you do not make any of the changes described in paragraph (d)(3) of this section and you meet the requirements of paragraph (e) of this section. If you modify the non-marine engine in any of the ways described in paragraph (d)(3) of this section, we will consider you a manufacturer of a new marine engine. Such engine modifications prevent you from using the provisions of this section.

(c) Liability. Engines for which you meet the requirements of this section are exempt from all the requirements and prohibitions of this part, except for those specified in this section. Engines exempted under this section must meet all the applicable requirements from 40 CFR parts 85 and 86 or 40 CFR part 89, 92, 1033, or 1039. This paragraph (c) applies to engine manufacturers, vessel manufacturers that use such an engine, and all other persons as if the engine were used in its originally intended application. The prohibited acts of 40 CFR 1068.101(a)(1) apply to these new engines and vessels; however, we consider the certificate issued under 40 CFR part 86, 89, 92, 1033, or 1039 for each engine to also be a valid certificate of conformity under this part 1042 for its model year. If we make a determination that these engines do not conform to the regulations during their useful life, we may require you to recall them under 40 CFR part 85, 89, 92, or 1068.

(d) Specific criteria and requirements. If you are an engine manufacturer and meet all the following criteria and requirements regarding your new marine engine, the engine is eligible for an exemption under this section:

(1) You must produce it by marinizing an engine covered by a valid certificate of conformity from one of the following programs:

(i) Heavy-duty highway engines (40 CFR part 86).

(ii) Land-based compression-ignition nonroad engines (40 CFR part 89 or 1039).

(iii) Locomotives (40 CFR part 92 or 1033). To be eligible for dressing under this section, the engine must be from a locomotive certified to standards that are at least as stringent as either the standards applicable to new marine engines or freshly manufactured locomotives in the model year that the engine is being dressed.

(2) The engine must have the label required under 40 CFR part 86, 89, 92, 1033, or 1039.

(3) You must not make any changes to the certified engine that could reasonably be expected to increase its emissions. For example, if you make any of the following changes to one of these engines, you do not qualify for the engine dressing exemption:

(i) Change any fuel system parameters from the certified configuration, or change, remove, or fail to properly install any other component, element of design, or calibration specified in the engine manufacturer's application for certification. This includes aftertreatment devices and all related components.

(ii) Replacing an original turbocharger, except that small-volume engine manufacturers may replace an original turbocharger on a recreational engine with one that matches the performance of the original turbocharger.

(iii) Modify or design the marine engine cooling or aftercooling system so that temperatures or heat rejection rates are outside the original engine manufacturer's specified ranges.