Marine Quadra jet secondary rod question?

[stevea661]

My boat is a 1986, 268 with a 5.7 OMC. This question would apply to any 5.7 with a q-jet does anyone know what size secondary rods they are running. the rebuilt I got has DP (.0678) rods. The old carb has CM (.0397) rods. I need to go some where in between. I have 2 other pairs to play with. BA (.0567) and DA (.0440). The smaller the size, the richer it runs. If any one knows what they have on their carb or has played with these to dial them in any info would be appreciated. I am currently chasing a lean condition at about 4000rpm and wot.
Thanks

Steve

 

[stevea661]

someone knows but isn't sharing:smt100

 

[Jersey Mike]

Are you sure the secondary air door is opening enough? you know the spring tension is adjustable? you can also adjust the height of the needles in the jets... you could also reduce the size of the secondary air bleeds that would create more fuel draw. Just some thoughts. Good Luck, Mike

 

[stevea661]

Mike,
I've been to a bunch of sites and all the adjustments you wrote of were also written on them. I just figured that rods would be easiest. I contacted the guy that rebuilt the carb and he has offerd me a new one, but I don't think it's a carb problem, I think it's just not dialed in for my engine. He said they either use dp(0687) rods or ch(0567) rods. The ch rods are richer. The carb guy I got extra rods from thought that ba(0567) should work well, they are a little richer throughout their range than the ch rod but at wot are the same. I will try fine tunning when I get close, but I don't think I'm close enough with the dp rods. I was able to smooth it out by putting my hand over the secondary barrels once it started to lean out.

 

[Tail Chaser 661]

Your questions are much to difficult steve.
CSR needs questions like.... My boats engine wont crank. Reply... Did you turn your battery selector on. Reply... Thanks, that fixed it. :grin::smt043

 

[Brian Weatherbee]

I just dynoed two 5.7 and they made the most power with CK's .527dia (about 3hp over CH's.567dia.) secondary rods. So your BA's should be very close. My engines have GLM manifolds and performer rpm Q-jet intake, comp cams ex256 cam. Made 328hp at 5100. The flame arrestor makes a big difference. The stock one is way too small and won't make use of the richer rods, at least 8" by 3" is needed. Also there was a alot in how far the secondary air flap opens, not quite all the way open way picked up 10hp. Better to be a little rich than a little lean.

 

[Brian Weatherbee]

...

 

[stevea661]

I just dynoed two 5.7 and they made the most power with CK's .527dia (about 3hp over CH's.567dia.) secondary rods. So your BA's should be very close. My engines have GLM manifolds and performer rpm Q-jet intake, comp cams ex256 cam. Made 328hp at 5100. The flame arrestor makes a big difference. The stock one is way too small and won't make use of the richer rods, at least 8" by 3" is needed. Also there was a alot in how far the secondary air flap opens, not quite all the way open way picked up 10hp. Better to be a little rich than a little lean.

Thanks Brian:thumbsup: I'm still playing with it, but I've been out in the ocean and haven't had the opertunity for any wot. It ran great up to about 4200, since then I had a rocker nut back off and went back to the builder. I pulled the covers and he installed all new rocker nuts and adjusted so I don't think I'm floating a valve, which I thought might be happening. It did seem to run better out in the ocean. Last time I had it up to 3800 rpm and 28mph with about 2" of throttle left, which is more than before the valves were adjusted and no issues with rpm hunting which didn't happen anyway until about 4200.