We use a 1st gen 13b engine with racing beat air intake and 4-barrel holley marine carb. Exhaust are 2 harly muffler 2" which we removed temporary to see if back pressure might be a problem
Engine starts up easy and revs up to 3500 RPM smooth - thereafter only under full throttle open reaches 4000 RPM with spikes into 4300 range - thats it.
Now my big question is is the RPM gauge wrong or do we have a engine problem ( gauge is stock livorsi marine rpm gauge set on 4 cylinder reading off ground of 1 coil) or should we use different setting on RPM gauge?
Any help highly appreciated
Michael

 

is that 4bbl feeding the motor enough air? keep in mind in piston terms this is a 2.4L (around 140cid) engine... i have no experiance with marine carb flow rates.. is yours greater than 400cfm?

make sure the secondaries are opening on the 4bbl (if theyre vac-ack!)
(when the secondaries dont open on the stock unit, redline seems to be around 4k)

jets jets jets!

your tach should be correct, as a four cyl generates 2 sparks per rotation, just like a 2 rotor.

also inspect ignition timing, and ignition timing advance... somewhat important.


..oh yeah.. marine carb? Hog mufflers? you are a homebrew champion - and i salute you!