regalman4925

i have had my boat on the water a bit this summer and i have noticed that the moi have the more the motor is popping and picnging and sometimes back firing when i am geting on plane. i originally had the timing set at 10 degrees and than backed it back to 8 thinking this would correct it but the boat seemed to run like crap when i did that so i bumped it back up to 10. the motor started out as a gen 6 "L98" 330hp 454, it now has a crane 731 cam, gil hp500 exhaust, dual plane edelbrock air gap, holley 750 with no choke, thunderbolt ignition.... it starts great, it runs to 5000 rpm which i think is too low since the original gen 4 330hp motor witht he exact prop should have been at 5000 rpm also...... we are guessing that i am at 450hp give or take the way i sit right now so i would have expected some more rpms out of the combo. i am wondering if i need to bump up to a 800cfm carb? the 750 has a fresh holley rebuild kit in it as of 3 months ago also. could a weak coil be causing this? it starts great and seems to have plenty of top end power, its just getting on plane i have that popping and pinging going on. also i am running 91 octane fuel, i originally thought that may have been part of the issue because i had been running 89... any input would be great! thanks in advance!

fireboatpilot

I had somewhat of a similar issue without the pinging. 700hp 540's but anyway they would start right up, idle great and rev fine out of gear. Would spit thru the carbs until it got up on plane and then run great at upper rpm's to over 6K. All MSD ign system with 37* total advance. I installed the lightest advance set of springs and the problem went away. I think your expectations for reving over 5K are high. possibly 5200 but not much more. Stick with the carb for now, once you get rid of the popping issue se if it runs out of fuel at WOT. No expert here just my 2cts worth.

Knot 4 Me

What CC accelerator pump you running?

regalman4925

i honestly am not surte on that one, it came with the carb hit i think? that may very well be part of my issue... are they numbered?

dslbrnr

Maybe the float level?

fireboatpilot

Accel pump are either 30cc or 50cc you can tell by the size of the pump cover. 30cc is about 1/8" and 50cc is about 1/4". Just look under the carb bowls. I'm still thinking timing and advance rate with the pinging but what do I know?

PatriYacht

Sounds like you need someone skilled in carb tuning to work on this. Maybe send it to Nickerson or Pro Systems. Installing a larger cam and intake will usually reduce the amount of signal the carb gets at lower speeds. You're probably running lean getting on plane.

Knot 4 Me

Had a buddy run into the same proplem after Baker built a set of 465 HP 454's based off of stock 330HP mills. Nickerson worked his carbs and he added a full MSD ignition setup (dist., coils, wires) and finally cured it. Needed more fuel and all the timing coming in sooner.

regalman4925

as far as tuning goes i had my friend tune it out but not on the water, he has a 125mph chris cat and tunes his out... i have a crane igntion box that i may try throwing on, maybe that will cure it, as far as the msd stuff i have read too many negatives things to go that route, no offense to anyone that runs them. that crane box is also made to work with the thunderbolt setup. the plugs, wires, cap and rotor are all new as of this spring and maybe have 10 hours at most on them. i am not sure what accel pump i have but iremember matching it to what came out of it...

Griff

It is pretty much impossible to tune a carb accurately without it being in the water and putting a load on the engine.