backfire where to start doing what?

[sw33ttooth]

ok so my basic problem is over 4k rpm the engine will lose power and backfire then i have to return it to idle and its fine till i go over 4k rpm. i can run the motor at 3800-3900 all day long without issues.

engine, 1991, 5.8l, 351, cobra 430 hours and growing

replaced so far with in the last year,
plugs
wires
dist cap
rotor
fuel filter, twice
oil change/ oil filter
accelerator pump
reset timing, repair shop did this i not very familure on how to.
adjusted ESA, top cable only
lower unit gear lube
both belts
cleaned spark arestor
tank vent is clear, when i top tank off fuel comes out.

i just read a post with someone having a cracked dist cap and that solved there loss of power and backfire, so i just checked mine that is 2 months old and its fine the copper in it is also still shiny with minor burn marks where the rotor has made connections.

i know its not fuel feed issues, it may be the carb need rebuilding but most the time it starts up with out me primeing it. so i go to exhust or valves, i was looking in the bellows threw the slits for the flapper and found nothing i change props once a week or so between my 15 and 17 pitch and never seen anything in the housing.

i have not done a compression check and i have no clue where its at. to do so requires pulling the manafolds which i dont have a problem doing i'd just make sure i had the gaskets in hand when i do so i can close it all back up. also i dont want to waste a few hours of time and money to pull them for nothing.

i also noticed i lost WOT rpm last weekend, full tank of gas 1 person i push 4400 plus a little WOT with a 15x15 ss prop, i was doing 4200 with just me and a full tank same prop.

for the most part i dont need to go over 4k for anything more then hole shot but i may be selling to upgrade next spring and as a selling point kind of hard for me to tell them it backfires over 4k rpm but its still in top condition.

i work 3rd shift so i am on the boat least 2-3 times a week fooling around till i find a spot to fish or a beach to swim at.

 

[sw33ttooth]

Re: backfire where to start doing what?

the only differnce between my issue and yours is,
i can run WOT for probably 1/2 mile and then it startes popping [forgot that in first post] if i pull the heads do they have gaskets i have to replace? if so these would just be 91, 351, ford heads at local auto zone correct?

my mechancal background is with small engines weed eaters-lawn mowers-leaf blowers, ect... a lot of stuff still carries over like spark plugs and compression and piston and piston rings. i just need to know i can get all the parts before i start ripping into her.