Carburetor Jetting and Lifter question??

« **on:** July 03, 2013, 09:36:52 PM »

Hey guys,

I have a hardin marine 454 that has been bored out, has radical camshaft and 049 large oval heads. Just bought the boat, rebuilt the carb, took it out and opened it up a few times. The secondaries weren't open (vacuum diaphragm has leak). I checked the plugs after and they were all white. and I was getting popping at 4,000 rpms. Do you guys think the lean condition is from the secondaries not opening or does it need bigger jets? Its a 750 holley with the stock # 72 jets. Also, it has a light popping out through the exhaust from the #6 cylinder. I checked the rockers and none are loose so im assuming its not a flat cam lobe, but possibly a collapsed lifter (they are hydraulic). Anyone no how to be sure if one is collapsed? Also if there anything else you guys think might be causing the slight popping/ clacking noise? Thanks!

« **Reply #1 on:** July 03, 2013, 10:01:20 PM »

Quote from: Ckaz21 on July 03, 2013, 09:36:52 PM

Hey guys,

I have a hardin marine 454 that has been bored out, has radical camshaft and 049 large oval heads. Just bought the boat, rebuilt the carb, took it out and opened it up a few times. The secondaries weren't open (vacuum diaphragm has leak). I checked the plugs after and they were all white. and I was getting popping at 4,000 rpms. Do you guys think the lean condition is from the secondaries not opening or does it need bigger jets? Its a 750 holley with the stock # 72 jets. Also, it has a light popping out through the exhaust from the #6 cylinder. I checked the rockers and none are loose so im assuming its not a flat cam lobe, but possibly a collapsed lifter (they are hydraulic). Anyone no how to be sure if one is collapsed? Also if there anything else you guys think might be causing the slight popping/ clacking noise? Thanks!

In short a vacuum secondary set up is not ideal for a jet.

That being said, you aren't going to be able to troubleshoot anything unless the carburetor is working properly. You sound as though you have a lean condition, but to change anything without replacing the $13 diaphragm would be steering you in the wrong direction.

Good luck

« **Reply #2 on:** July 03, 2013, 10:21:01 PM »

Thanks,

yea im going to do that this weekend. Didnt me to post this in For Sale section

Ckaz21

Carburetor Jetting and Lifter question??

GT Jets

Re: Carburetor Jetting and Lifter question??

Ckaz21

Re: Carburetor Jetting and Lifter question??