Ive got a 454 bbc with a tunnel ram set up tall stack, and twin 660 carbs. I believe the heads are old 427? Compresion is about 155 to 160 on all cyl. Is this high compression? Do i need to be using only 91 or higher octane? When I got the boat it was idling about 1200 rpm. I toned it down to about 650 in my driveway hooked to a hose and seemed to run ok. Took it to the lake fired up idled great till i got the motor warmed up when I got bhack to the no wake I got off the throttle and it died. Then it seems like it loads up and floods itself? It back fired shot a flame out of my scoop, spit smoke exc.. I it cranked and cranked and acted flooded. I opened the throttle wide open to allow as much air in as possible still nothing. waited about 10 minutes then it back fired and fired up? Do I need to be running the motor at 1200 to burn the fuel through those carbs? I put 87 in it is that my prob? but it seems like it just keeps flooding itself.
Your compression is probably about 10:1 based on your cranking pressure. You should run 91 octane for sure. 650 is pretty low for idle. Mine idles at 800 rpms. The back fire indicates a lean condition. Try opening up the idle mixture screws some. What was the temp outside when you took to boat out. If it was colder than normal, this also leans the motor out some.
the temp was about 75. Ive got almost 1/2 to 3/4 tank of 87 should I get a couple of gal of race fuel? to up the octane?
Nah, just fill up and always use super unleaded.
check your plugs,you may have some trash in your needle and seat.This would cause your engine to flood.Plugs will tell you.
Did you just install the tunnel ram or has it always been there. Stack fire can also be caused by the timming being too retarded. And you shouldn't have the idle that low with twin carbs.......or a single for that matter.
Definately, the idle is too low. Tunnel rams are funky when it comes to low rpm operation. At 650 rpm the TR has too much volume and not enough velocity to keep the fuel suspended in the air. You get puddling, skipping, black smoke and just all around running like shit. A TR generally works pretty good on a jet, but that Idle has to be higher. If you are going too fast to dock safely, just drop the reverse bucket a little bit. 1100-1200 rpm sounds about right. Someone mentioned the needle and seat, Check this for sure, and the float levels.
fog
I was running 2 660s on a tunnel (BORED 440 TO 454 wedge). Had a lot of trouble with them getting plugged up from gas drying up in bowls (varnish scales). I had to clean them a lot to keep it running good. Finally changed to 2 600 edelbrocks, a lot less trouble and idles and runs great now.
I just got the boat and came with the tunnel ram. Carbs were just rebuilt. I think ill try to set them back at 1100 and see if that helps. I just replaced the plugs when I had the exhaust manifolds off....couldnt get the plugs out otherwise. But I did have back fire and black smoke exc...
my guess would be - check your float levels - ( in the water - cause your boat will have a different pitch in the water ) make sure you don't have the sticky float syndrom - check your needle and seat - also there are air bleed scews on the side of the metering block for adjustability !! 660's are great Preformace carbs -- but not an all around carb , from my personal experience 1
I would only run 91 octane in my boat - and i'd threw in octane boost , and some mystery oil / or lead additive every once in a while -- unless you run ss valves - and then i still would anyways
ohh and after the back fire - did you check your power valves ? other wise you will notice a flat spot /stutter
what is your timing set at ? what kind of cam ? solid - have you checked adjustment ? and also look for vacume leaks around gaskets -, carbs
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