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View Full Version : Changing Holly Carbs on twin 454s to what?



Donzigo
01-20-2002, 09:06 PM
My new/old boat, 1989 Z-33, of 2 monthes ago, came to me with twin Hollys. They are running very rich, won't idle well. So, I'm thinking of switching to new carbs. These are probably 8 or 10 years old. A freind told me that purchasing new ones would save much more money than a re-build of these. I'd appreciate any comments or advice. Thanks.
Richard

Jamesbon
01-20-2002, 10:03 PM
Hi Richard,
Pinellas Carburator will re-build them to better than new specs for about $150.00. I had'em do one for me and it was flawless.

Or you can have Nickerson Performance re-build and tune them on their flow bench. You'll have flawless carbs that are matched to your specific application if you go this route. I believe it's around $250.00 per carb., but again, then flow benched to your specific engine. Let me know if you need the #. Personally this is the route I'd go.

Nate

turbo2256
01-21-2002, 10:40 AM
New Holley's are about 400+ each. Due to there old equipment the last one I bought was a real dissapointment. Rebuild what you have. If its the power valves you can turn in the idle mixture screws all the way and the engine will keep running. Often the gaskets will pucker up and block off passages too.

BigGrizzly
01-21-2002, 06:54 PM
Rebuild the old ones its a piece of cake. Replace the power valve with the same size even if there Ok. Then call summet racing for a anti blowout kit for the power valve.On thoes motors spending money for tweeked carbs is a waste of cash.

Randy

Donzigo
01-21-2002, 08:18 PM
Thanks for the replys. Seems like I'm going to be rebuilding or, Jamesbon, having Pinellas do it; but if it's as easy as Grizzly says, I'll just bring it up to the shop and away we go. thought I would check the screen for debri first. It just idles for a while and then, goes dead, just like you shut it off. reallt strange. then, other times it will idle fine, but eventually it loads up as it sits there. Scot, I'll get the numbers. Thanks for the reply. I have tickets to Miami boat show. Hope to see you there. I'll look for Grizzly at the Stainless booth close to Tomahawk.

Rootsy
01-21-2002, 08:27 PM
I have to agree with BigGrizzly on this one... i've rebuilt somewhere in the neighborhood of 100 holleys and as long as you get them SPOTLESSLY CLEAN inside and out, use the correct gaskets so everything seals, get it all back together correctly and get the float height right you're good to go... it really is simple... there are some good books out there and some good instructions that help you step by step... all the tuning is done already (jets, power valve size, accelerator pump cam and discharge nozzles, secondaries....) just need to get it all working correctly and clean... and the anti power valve blowout protection is worth the time and teh few dollars you spend... i wouldn't suggest turning the idle needles in against the seats to cure the problem it is just a bandaide that will be erratic and likely you'll still be very rich if it is a power valve gone bad. first things first... set the float heights, if it is too high it'll make you extremely rich to the point where fuel will spew out the vents into the venturi's if they are TOO high, set the fuel level even with the bottom of the sight plug with the boat in the water idling. get a set of clear float bowl plugs so you can see your fuel level while you are adjusting the floats... if it isn't the floats it's likely an internally leaking metering block gasket, leaking needle and seat or a bad power valve... Get a vacuum gauge and hook it to a vacuum port on the carburator base or put a fitting in the intake runner to hook it to.. turn your idle needles in til they lightly seat.. back out 1 1/2 turns and start motor... turn in or out slowly until you achieve your hightest vacuum reading.. this is the optimum set point for your idle circut but a tad rich so turn the needles in 1/8 turn, this'll help keep it from loading up.

turbo2256
01-22-2002, 08:57 AM
Didnt mean for him to run around with his idle mixture screws in all the way its just a way of diagnosing the problem.

Jay Robertson
01-24-2002, 10:23 PM
I would go to fuel injection. Carbs only have two to three fuel metering positions. It depends if you have a 2 step or 3 step metering rod. Hollys have 2. The engine only gets the correct fuel mixture at two throttle positions. Other than idle of course. Fuel injection is constantly tuned by the computer.

BigGrizzly
01-24-2002, 11:37 PM
He doesn’t want to reinvent the wheel just fix his boat. Replacing what he has in this boat with thoes engines with an injection systen would not get him anything that he doesn't already have. To set up an injection sistem with a o2 sensor wouldn't work for long- it gets wet. If he uses a complete merc setup he would have reprogram the ECM and do more work and spend a large amount of money. If he uses a Holley bolt on system on that motor he will waste at least $2000 and not gain anything over the correct carb and settings

Randy

Rick
01-25-2002, 10:20 AM
The beauty of your carbs is that you have two! Get the kits rebuild one at a time. Take your time, if you get confused look at the other one for reference. This is how I did mine and they worked beautifully. Just be patient and meticulous! Good luck Rick

Donzigo
01-25-2002, 10:25 AM
Thanks to all. It's tommorrow morning's project. I'll give a report after I give it a whirl.

Rootsy
01-25-2002, 11:26 AM
If they are really dirty... varnish inside, rust from water in the bowls etc etc etc or just long use.. even if you see nothing the small passages may be dirty or have foreign material in em. I disassemble and let mine soak in chem dip carb cleaner for a few days. This also makes it very easy to get the gasket residue off of the aluminum and cleans em up spic and span. There is a raised sealing bead on most aluminum part gasket surfaces and if you nick or gouge it appreciably you can increase the risk of developing an internal leak. Another good suggestion is to spend the extra few dollars and purchase the non stick gaskets. They are worth the money especially if you have to take the carb back apart in the future or if you want to tune, etc etc. The non stick ones are blue but i've also seen them in red. They also tend to seal better than the regular gaskets you get in the rebuild kit. Also keep note of the gaskets as you take the carb apart. The new kit will likely contain 2 or 3 of the same gaskets but with small differences. Keep as much of the old ones intact if you can so you can match them up and make sure you use the correct ones. this pertains to the gaskets between the metering blocks and main housing on both primary and secondary side and also the gasket between the throttle shaft housing and main body. using the wrong one especially between the main body and the primary metering block will cause you to have the same problem you are fighting now, it'll run good when you get it revved up but it'll run like crap below 3000 rpm and billow black smoke... and watch for those check balls... make sure you get the correct ones back in the correct holes eh... Most rebuilt holleys fail to perform because they are dirty inside or they develop internal vacuum or fuel leaks... happy rebuilding...