Jet Size increase for ma3 on o300 with High Comp Pistons.

[abushey123]

Hello all,
Working on an experimental o300 engine. I am planning on dropping in a set of combustion technologies 9.5-1 pistons along with a port and polish. Curious if anyone has experience with that size the main jet on the ma3 would need to be drilled to accommodate this? The other option is replace the ma3 with an ma4 and make an adapter plate. Reading online however it seems the ventures on the ma3 and ma4 are the same which begs the question, does the ma4 actually flow more air due to the smallest cross section in the bore being the same as the smaller carb in general?

[canav8]

Although this is not a usual topic for these forum pages, I would say there are resources that can probably answer your questions here. So curious minds. I have long studied this topic. I even produce an exhaust system to aid in the O-300 series. I have ran dyno data on an O-300 and I can probably answer your question, if you had provided more information. Just because you increase the compression ratio, you have not offered the other variables that are necessary to protect the engine from detonation. Are you working with someone on this or are you DIY? Doug

[Bruce Fenstermacher]

Doug! In this case, I have ported the cylinders, intake tubes and sump as well as pull timing back a bit until I get a better base line. I corrected issues with baffling to help with cooling and will be trying some different spark plugs. I am running strictly 100ll at this point and may experiment with opening up the jet on the ma3 if I loose leaning authority. This is a DIY project.

Webmaster note. The above original post by abushey123 was lost due to admin software failure and is being manually entered here, unedited in its entirety, as it was not included in our latest backup.

[n2582d]

CC Pocock at Bush-Air could probably answer your question.