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-   -   Jetting for Supercharged 502 (https://www.offshoreonly.com/forums/general-q/254246-jetting-supercharged-502-a.html)

bleek 05-23-2011 04:11 PM
Jetting for Supercharged 502
 
I have a 502 with a B&M 250 with dual Holley 750's. The carbs were set up by pro-systems, and are boost referenced. The jets are 74's all the way around with 5.5 power valves in both the primary and secondarys. The engine was a 500hp carb, but now has flat top pistons in it. I took the new engine out for a test ride yesterday, and the plugs were reading very lean. I have dual fuel pumps running to a manifold, and then to the carbs with 7.5lbs of pressure. Just wondering if anyone has an idea what I might jet these at? and do the power valves sound right? Was going to start with 78's all the way around to start with.

pachanga 05-23-2011 04:46 PM
Originally Posted by bleek (Post 3410640)
I have a 502 with a B&M 250 with dual Holley 750's. The carbs were set up by pro-systems, and are boost referenced. The jets are 74's all the way around with 5.5 power valves in both the primary and secondarys. The engine was a 500hp carb, but now has flat top pistons in it. I took the new engine out for a test ride yesterday, and the plugs were reading very lean. I have dual fuel pumps running to a manifold, and then to the carbs with 7.5lbs of pressure. Just wondering if anyone has an idea what I might jet these at? and do the power valves sound right? Was going to start with 78's all the way around to start with.
Apples and Oranges...but I have a procharged 454 running 9 lbs boost. I got rid of the plug fouling problems and low end torque when I cam down to 78's on the front....am running conservative and have 102's in the secondaries! I don't know what my power valve is. I know there is more left on the top but think I have my midrange within 90+% of potential and I should be safe!

PS Mine is a single 650.

lake speed 05-23-2011 07:54 PM
Originally Posted by bleek (Post 3410640)
I have a 502 with a B&M 250 with dual Holley 750's. The carbs were set up by pro-systems, and are boost referenced. The jets are 74's all the way around with 5.5 power valves in both the primary and secondarys. The engine was a 500hp carb, but now has flat top pistons in it. I took the new engine out for a test ride yesterday, and the plugs were reading very lean. I have dual fuel pumps running to a manifold, and then to the carbs with 7.5lbs of pressure. Just wondering if anyone has an idea what I might jet these at? and do the power valves sound right? Was going to start with 78's all the way around to start with.
Are you sure its a flat top piston? unless the combustion chambers are pretty big I would thnk that you would have too much compression with a flat top? that may be why the plugs showing lean.

Smitty 05-23-2011 08:36 PM
How much boost ??? When I had a similar setup, I ran 82 prim and 94 secondaries.

Smitty 05-23-2011 09:00 PM
Looks like we have a spammer !!!! ^^^^^^^^^

bleek 05-24-2011 12:47 AM
i'm running 6lbs of boost with this setup.

4bus 05-24-2011 06:22 AM
Originally Posted by Smitty (Post 3410940)
Looks like we have a spammer !!!! ^^^^^^^^^
Where? I read that as 80 primary and 92 secondary.....its just written in a secret tuner's code :lolhit:

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ezstriper 12-12-2011 06:17 AM
are you checking fuel pressure under hard run ? need to...if thats fine...read the plugs and tune from there..I have been running prosystems carbs for years(and still am) and they are usully real close out of the box...but close not always perfect...tune from there..

bajabob 12-12-2011 06:06 PM
put a a/f box on then you will have the reading on your a/f no guessing:drink:


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