Question about Holley carb sizes

[Striper Blues]

I have a 1989 OMC I/O with a new 460 Ford Long Block. The old carb is a Holley 4160 600cfm (0-80318-01). Is there any reason I shouldn't replace with a 750cfm (0-9015-1)Holley ? They're 100 bucks cheaper. Just a cost issue? <br /><br />thanks...

 

[rbezdon]

Re: Question about Holley carb sizes

I dont know any reason why not if it bolts on and you can hook the throttle linkage up. In fact, if you calculate the max CFM for your engine, 600 is a little on the small side. You may pick up a bit of preformance with the 750.

 

[rbezdon]

Re: Question about Holley carb sizes

see the following post, it may help<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=005904#000001 <br /><br />or buy this book<br /><br /> http://www.amazon.com/exec/obidos/t...002-5845285-5540800?v=glance&s=books&n=507846

 

[f_inscreenname]

Re: Question about Holley carb sizes

Go with the 750.

 

[ron7000]

Re: Question about Holley carb sizes

what's the reason you have a 600cfm carb, and now a new 460 engine?<br /><br />was the previous engine/carb combo a 460 block with a 600cfm holley?<br /><br />a 460 engine should defintely have a 750cfm carb. The 600 will work, and probably give you excellent throttle response, and great performace 3000 rpm and under, if it is set up right. You will lose top end power and torque all around due to the lower airflow capability. Depending on the boat and how you use it, you may not be significant and worth buying a new carb. If you run the thing wide open all the time or hammer the throttle and need the power and acceleration then buying a 750cfm carb is worth it. If your doing something like a complete repower, at $2000+, then the right way to go is the 750cfm carb for a few hundred.<br /><br />vatter posted a good link, worth buying if it's still available.<br /><br />coincidently, some carb size reading for those who are interested:<br /> http://chevyhiperformance.com/techarticles/148_0403_choose/

 

[Striper Blues]

Re: Question about Holley carb sizes

Ron,<br />The boat came with a 460 ford omc i/o setup that came stock with a 600 cfm holley 4160. But the new long block does not reach 4400 to 4800 rpm even with a smaller pitched prop. I have had the same problem show up with two different 600 cfm carbs where in after getting hot the engine sucks the front fuel bowl dry at higher cruise rpms, say 3200. Its not related to any other part of the fuel system as it is all new and recenty checked/cleaned several times.

 

[rbezdon]

Re: Question about Holley carb sizes

If you are right and the problem has been sucking the front bowl dry, going to the 750 cfm carb will not likely solve the problem. The problem is then fuel delivery. The engine, at a given 3200 rpm, is passing a specific CFM of air. Since this is well below the WOT CFM of either carb, the amount of fuel being consumed (assuming the same air to fuel mixture) would be constant and the fuel system would not keep up with either carb. In fact if this is true you would have more issues at WOT with the 750 cfm as your engine will pull all of the 600 cfm through it so then engine is limited by the carb. In the case of the 750cfm the engine will pass more cfm of air causing more gas to need to be mixed with that higher than 600 cfm of air, actually demanding more fuel from the system. You need to find out why your fuel system can not keep up the front bowl level before changing carbs. All this is assuming your diagnosis is right about the front bowl level. <br /><br />It is also true that the 600 cfm carb is limiting your engine from producing its max hp. If this is all your problem is from and the fuel system is truely funbctioning normally, I think you'll be pleased with the improvements that can be had fom better sizing the carb to the engine.