Acceleration Hesitation

[Okie Boarder]

I'm having some hesitation with my acceleration. I have a 1989 Supra Sunsport with the 351w engine and Holley 4 barrel carb (4160 I believe). If I do a slow smooth increase in throttle, everything is fine. If I dump the throttle it will completely stall out. Somewhere in between and it will hesitate and start to stall until I back off the throttle a bit. I have already changed the fuel filter, plugs, cap/rotor/points, checked the timing and cleaned the carb. Do I need to do some adjustments or check something? Should I just take it to a mechanic?

[mapleleaf]

-I had the the same problem w/ my 351, only was after a near sinking , story in another thread!, So my electricals were all wet. I then had the marina look it over and there was a little water in the gas. Once removed I was back on track dump'in the throttle!
Not sure if that's you're problem though seening as how you changed out the fuel filter and prolly would have found the water then.....

[Pdowling1]

Accelerator pump. You aren't getting enough fuel when you hit the throttle. The rapid vacuum drop causes a sudden lean situation, the accelerator pump is supposed to compensate for it. A Holly jock can tell you how to fix/adjust it.

[Irish_Jack]

Agreed,
You will end up rebuilding the carb, cleaning the valve bodies, and probably replacing the power valve on it. If you get a complete rebuild kit the power valve diaphragm, gaskets, and valve body kits will be included. Idle mixture, power valve rocker arm tension, float levels, and vacuum pull-off specs usually are included in the kit as well.:cool:

[michael hunter]

Check for contaminated fuel if not rebuild the carb.

[csuggs]

Fuel and carb are both good places to start. I make a habit of putting fuel stabilizer in my gas, especially towards the end of the season towards layup. Another thing you might do is check the timing, especially since you just changed the points. An electronic iginition would have been a better choice since you changed them anyway! If you're interested, www.skidim has the electronic ignition to fit your boat (if you have a Prestolite distributor) for only $68 on clearance - that's less than half price.

[JUST-IN-TIME]

its the carb
i hate those POS holley's, 1 backfire and that thing needs o come off again because that stupid power valve stuff

i have the manual if you need for that carb

[Okie Boarder]

Hmmm, sounds like it might be good to consider a rebuild. The PO said he bought this carb new a few years ago and it hasn't been touched since. There is a guy in the area that does carbs that I talked to today. He's rebuilt a bunch of the 4160 Holleys and a few of them are the marine application. He said he has to buy a little different kit for them, that costs a little more than that of a car application. I may go that route. Not something I really want to mess with myself.

[Salty87]

okie

you might consider ditching the holley and getting an edelbrock. it will bolt up, just need to run a new fuel line usually. i got mine at summitt racing. runs great.

the power valve is easy to replace though. 3 or 4 screws and you're done.

[DKJBama92Mariah]

its the carb
i hate those POS holley's, 1 backfire and that thing needs o come off again because that stupid power valve stuff...

Holley put in a check ball to fix that problem in 1992 and the problem he has described is not symptomatic of a blown power valve. Personally, I would take a Holley 4160 or 4150 over a Quadrajet any day of the week. I bet we all can agree that a Marine Demon carb is better than both though.

[Okie Boarder]

I checked out a few things and tried a couple quick adjustments and no change. I'm pulling the carb sometime this week and taking it to the carb guy to have it rebuilt.

[JohnnyH]

sounds like a bad accelerator pump. Try a carb kit. Those holleys are easy.

[Okie Boarder]

I took the carb to the guy yesterday. He wanted to check a couple things with me there. First he pulled out the needle valve, then he pulled the primary bowl and metering block. There was definite evidence of build up and that the power valve was probably not functioning properly, that he explained to me. I left it with him to rebuild and we'll go from there. He should have it done Saturday. We'll see.

[Okie Boarder]

Got the carb back today and slapped it on. WOW! What a difference. It runs great! He said the major issues were a bad power valve (and the wrong one for the application, which is weird), and some general gunk build up. I can jam on the throttle and it just hums right along...very responsive! I'm looking forward to getting back out on the lake and see how she does.

[michael hunter]

I'm glad you got it fixed Okie.

[Salty87]

sweeet, gotta love it

[bellsons]

completely empty and flush your tank.
clean and lube the check valve on the top of your tank. make sure it works properly use a blow out tool for your air compressor.
while the hose is disconnected from both your tank and your carb, also blow out the line in both directions. filter pump and all in line.
put it all back togather, fill tank 1/2 or better with just high test and a whole bottle of seafoam system cleaner.
take your boat out and run the snott out of it.
After that. over night or the next trip it should run fine.
That is if you set your timing right and other stuff.

[bellsons]

sorry, i posted too late i guess.
The seafoam would have "un" gunked your carb.

[csuggs]

I'll second that - Seafoam works great on carbs. Another tip is to mix fuel stabilizer with the gas towards the end of the season. No muss no fuss in the spring!

[Okie Boarder]

I'll definitely be adding fuel stabilizer at the end of the season from here on out. I don't think the guy I bought it from ever did that.

[Okie Boarder]

Went to the lake Saturday afternoon for the firswt time since the carb rebuild. The boat runs GREAT! No hesitation and the power is wonderful. It nearly jumps out of the water onto plane. :)