Offshoreonly.com - What Intake for a 502ci Carburated?

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Re: What Intake for a 502ci Carburated?

A carb that is too large for an engine will need to be jetted with bigger jets to compensate for a weaker signal to the carb.

Re: What Intake for a 502ci Carburated?

Hey Guys how about this, I have already offered a GM performance parts large oval port CNC dual plane intake manifold that is a proven winner (used on the ZZ502, 502 HP-565 lbs. torque crate motor). To help out in getting this guy closer to a more "completed" combination, I have a brand new 850 #4150 Holley carb, straight from the ZZ502 kit. Already jetted (OK, it is close but could be fine tuned for marine purposes). Send it off to Nickerson to get the J marine vents installed and you are ready to rock and roll. Set the distributor for 36 degree's of total advance and go do some testing. http://www.gmgoodwrench.com/perfpart...f/12496962.pdf

The real missing link is the cam numbers. He wrote "mild cam". Don't know what that means? The ZZ502 has a 224 intake and 234 exhaust at .50, set a 110 degree's.

I am trusting that your motor has the large oval ports and not the small "peanut" oval ports. Aluminum or cast iron?

Re: What Intake for a 502ci Carburated?

Quote:

Originally Posted by SB

Do we know what is happening ? I still don't get the 'flooding the intake" and 'velocity' thing.

I don't think a box stock 950cfm Holley is too much cfm for any 502, however, it's possible the calibration is not the best choice. These are typically used on pretty 'hot cammed' engines. I'm not just speaking about jetting when mentioning calibration. Boosters, bleeds, channels, etc,etc are not the same from one carb to another.

I could swear I remember Rumrunner (Doug at BG) mention their 850 flows more (wet) than Holley's 950. Don't totally hold me too that.

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We need to get this boat tuned in all aspects - carb, ignition, prop, etc,etc,etc in a correct fashin. Guessing usually leads to dismal performance unless extrememly lucky. Don't count on it.

I do need to put my finger on the problem, I just wish I was more knowledgeable in these areas and could better explain what all is going on so you guys would have a better idea where to start but that is tough for me to do. I know that I the engine is not running to it's max performance and the downside is that in my area there is not any performance marine mechanics available to check it out and run the boat at WOT and feel it out. That is why I have been asking so many questions to you guys so I can provide info to the regular mechanic I have that only has experience with bone stock products.

Thank you all for the input and ideas, I really appreciate it.

Re: What Intake for a 502ci Carburated?

Quote:

Originally Posted by wieland77

I was told that the best performance, also depending on weight and prop, that this engine should run in the low 5,000 rpm at WOT. The 950 that is on the engine was just put on before I purchased the boat and is brand new, so with this carb can I jet it to 800 or 850 and replace the intake after I see how it performs?

ROTAX454, I am definitely interested in your intake. I will let you know... Thanks again guys, MIKE

Mike, I just had a OSO member PM on purchasing my manifold. Told him you had first right of purchase on it. What's your decision?