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SBC 350 zz4 carburetor question


Well-known member
That is the toughest thing to get right in a car motor boat. It just takes some accelerator pump linkage adjusting and maybe a bigger squirter! It's just in the primaries right!
If it is a Holley carb, I suggest installing a 50cc pump kit. With most manifolds, this requires adding a one inch spacer under the carb to keep the pump arm from hitting
the manifold. Buy a .037 nozzle or drill the old one to .037. Replace the pink pump
cam with the brown one that comes in the 50cc kit. Install the brown cam up side
down where the sharp side of the came is up. This will give you a hard shot on acceleration. Chuck
The curve kit will help but that's not the major problem but you should install one! Just install MR. Gasket spring kit Jeg's PN#720-929G and run the lightest springs in it (silver)! If you have a 2to1 ratio run 31 degrees of total timing if it's a 2.68 run 34 total timing! Be careful with those ZZ4 the aluminum heads are thin and don't hold head gaskets well! As for the pump you can adjust it out with the one you have but as Chuck stated the 50cc pump kit will make it easier to fix!
I did what Chuck and Waterthunder mentioned to my ZZ3 with a Holley 3310-4 750cfm vac secondary ,and spring kit for the distributor .

Now it launches!
Diamondback put the Holley 3310-4 750cfm vac secondary on my ZZ3

This carb has been on this engine for about 12 years. They are cheaper than a dbl pumper, get better fuel mileage but probably don't preform as well as the DP.

I was able to adjust the acc pump and squirter and advance curve and eliminated that problem.

It use to fall flat on it's face and almost stall.

You may have to experiment a little to see what your engine wants but it works!

I did what they suggested worked for me.
Do most auto parts stores carry the pump kits, can you buy them seperate or do you havr to buy the whole carb kit, I've been trying to adjust the accelerator pump on mine made it a little better after listening to thunder and chuck sounds like the kit is the way to go
Most speed shops will have all that stuff on the shelf ,you can get them from Jegs and summit also.

50cc pump --------- 20-11 about $44

121-37 pump squirter
121-40 pump squirter

the squirters are in pkg qt 2 and about $20

I have a #40 in mine
if you do a search you will see that NOT using the vacuum advance on the distributor is the best thing to do.......please do the search an you'll see which springs should be installed in the dist..........

make sure if you do try to adjust timing you use a good timing light-or you'll be needing a new motor along with the carb modifications you should have done in the first place. :wink:
duece was this a problem when you had a 2.09 and a 2 blade wide or was the responce better then?
sorry i re-read the original post.not every carb is going to act the same duece,remember 90% of the holley and edelbrock carbs are put together on an assembly line by mostly old ladies and gentleman that dont give a crap how it runs or works.
unfortunatly unless it is a marine carb it was made for street use,that carb in one of you jeeps would probably not need to be touched. but the imediate load of a prop on an airboat will lean your motor out if you stab it.i would guess but this is just a guess that almost 100% of airboat carbs out there have to be fine tuned not a bolt on and go.i understand beeing mad at paying a boat load of money and it have a quirk.but every small change will have an effect.such as a 2.09-1 to a 2.68-1 ,a 2 blade to a 3 blade, a wide to a superwide .load changes everthing, some can be noticed and some can go unoticed.an airboat engine has alot to overcome to be just right.
and by the way on the squirter the 30cc pump i believe is fine untill you get over a .035 nozzle then you need a 50cc.so you don't have to spend 50 bucks.you can bend the pump arm slightly to get a full shot but have to readjust the spring arm.and on the nozzle go to your local hardware store and you can buy wire size drill dits and drill out the nozzle.that is what i do cause i am cheap.
I'm sorry, I misunderstood what people want their boat to do. The stock carbs are
set up for stock cars. On a boat, it will work fine, just ease into the throttle like
you do with your car. It still has to be fine tuned in your car or your boat. Now if I want
my car to launch off the line, I will modify the carb and ignition to make it do so.
Some of us can fine tune your engine to work good the way it is. The suggestions for
the spring kit and pump kit are inexpensive mods to make it perform better. Thanks,
good job! sorry if i too was alittle raw-but when i first found this site i spent 2 weeks reading every old post there was here-before i asked one question-just about everything you can think of has been covered at least 3 times! :)
you have some easy mods to do, enjoy doing it, its supposed to be fun-if they work of course-then in a month when somebody else asks about a ZZ4 or for that matter a holley carb throttle response problem you'll jump up and repeat this process to them! good luck and be safe. :)
quest. you bought this boat new, have you made any mods to it at all?
or just routine maintenance ?
I have a ZZ4 engine too, I went to the Brown cam and it made a world of
I had some major hesitation before and now its gone :)
It's worth the $20 for the cam selection kit.
great! sure sounds like your going in the right direction, couple hundred more rpm's is definitely an improvement. and as long as you dont leave it pegged at wot than you'll be fine! keep going!