Hi! I recently purchased a 77 cheetah boat with a harmin marine built 460 which had sat for many years. 120psi compression pretty well all the way across.Single point "marine" distributor which i cannot seem to locate a rotor and cap. Coil, plugs wires have been replaced.Carb Rebuilt. Numbers 5 and 7 are not producing.Firing order has been checked. Engine runs but will not open up and is missin on these two cylinders. I have cleaned the fuel tanks and added fresh fuel yet motor still runs erratically and backfires when punched. What would be my next step? What would u recomend for a replacement distributer?
Are you absolutely certain that the rebuilt carburetor is functioning properly? Fuel delivery must be deemed to be in perfect operating order before adjusting electrical (and visa-versa).
if your motor sat for a while it most likely hav some surface rust on a couple of valve seats, this is probably why it misses and if an intake valve seat has rust on it and wont seal perfectly you will get a backfire thru the intake and it wont rev well due to the contaminated intake charge. try a cylinder leak down test. you will hear air coming up thru the carb if an intake valve is leaking. i get this all the time with motors i import from usa.
have you checked for timing chain slop? usually once the chain is so worn that you jump a tooth, it will jump enough to not even start at all. try mercruiser for the rotor etc. cheers
Thanx! The timing chain did jump a cog.....i have replaced it and still am having problems.The whole right side is not firing properly and upon further inspection i noticed bent push rods on that side. So now im going to remove the head and inspect for valve damage.Now for my question.....I have a set of d3ve heads on it currently. This motor is built exclusively for harman marine.I have aquired a set of d0ve heads and am wanting to replace my d3ve heads with the d0ve heads. Would the water jackets be smaller in the d3 marine (Im guessing they would be marine?)heads be smaller than the d0ves?Would this be an issue?
I will also be removing the camshaft for inspection to make sure there is no scarring of the lobes.I am un sure of the pistons, what style etc.. and will post more when i get the heads off and know what i have.Any recomendations as where i should go now as per say the type of camshaft to go with if the dove heads are used? Should i go with the Doves or stay with my original d3s?What type of modifications would you recommend i do to the heads b4 i install them. This will strictly be a go fast boat .I may not be able to have the nicest boat on the lake, but i would like the fastest.......!
Thanx!
D3VE heads and D0VE heads will fit any 429/460 block
If you have the cast 24cc dished pistons, the the c/r is about 7.9:1 with the D3VE heads. Switching to D0VE heads will bump c/r to about 9.2:1
If you have the flat top pistons, the the c/r is about 9.25:1 with the D3VE heads. Switching to D0VE heads will bup c/r to about 11.2:1
D3VE's and D0VE's use different valve trains (not interchangable) and so you will need a roller rocker upgrade with the D0VE heads (unless you can find the 1968-1970 valve train). Such an upgrade will require hardened pushrods, guideplates, rocker studs, roller rockers and polylocks
Either set of heads benefit from port work, particularly porting the exhaust side (remove the "smog bump" in the roof of the exhaust port).
if you want the fastest boat, go the dove heads. as paul quoted 11.2:1, much nicer than 7.9 or 9.2 !! get ready to spend some tine removing those smog bumps, ! they are more like mountains! we'd need to know more specs and figures about the boat and jet before suggesting a cam to you. Paul, out of interest, can you still get the early rocker gear new in usa. i used to be able to get them here in australia through the sealed power dealer but have not seen them for years? cheers
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Re: Pre 76 460 jet boat
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