Need more speed

[rick1964]

Hey thanks for the reply, I set up the carb myself and the butterfly's are opening fully, I do have vacuum secondaries, they too are opening fully, as I had someone drive it full throttle whilst I checked, I even pushed on the secondary diaphragm linkage while running wide open to make sure they didn't open any further, its runnin full tilt. Im in San Diego near lakeside, I actually had to have the pump replaced with the same because the old one was so froze together they couldn't get the u joint off of the input shaft to get the thing apart. The work was done at JP marine in lakeside. I called him, he wants me to double check my rpms again and go from there. I have doubts about the tac that's in it, but my ear doesn't lie. There's no way that motor is turning anywhere near 4500 to 5000. I asked JP marine once before and he said they put a standard impeller in it. That doesn't tell me anything,,, I'm going to give them a call again. I had the motor rebuilt at Ricks machine in lakeside, they're good guys. The timing is at 32 degrees advanced throttled up. As high as it can go im told.. flame thrower coil, no ballast resistor, new plugs. 2 batteries so I can start it advanced. Should I always run premium in it? How much of a difference is it.... I don't think I had premium in it my last run first of november.

[shaun]

You need to find out what impeller is in it and what cut. The 12je pump is not the ideal pump for a performance deal but at the same time it doesn't sound like your cavitating the pump which means it's handling the HP no problem. I would get a new tach so you can be sure of your RPM. if you were running in the 4000's i'd say your cut is probably just too aggressive for the HP the engine is making. How much HP did the shop think your motor was putting out and at what RPM?

I wouldn't mess with the timing, it's not going to make that much of a difference. 32* all in on a naturally aspirated BBC is pretty normal/conservative, really it depends on the build.

Whether or not you should run premium again depends on the engine build. Running premium is not going to increase horsepower, in fact it does the opposite. You only need higher octane fuel if your engine's compression is higher and needs it to prevent detonation.

[rick1964]

Well i stand corrected... It seems i have a 12jg-a pump in my boat. Is that a good pump? Still not sure of the impeller size but I will call JP marine later...Maybe that's what the "a" means. Hey I just got a 50 dollar gas card for Christmas!! That's good for a 2 or 3 hour run! LOL

Also, Do you think a high rise intake manifold would make that much more power?

[shaun]

A 12JG pump is good, there are better pumps but you only need to go that route when making serious power. The A stands for the cut impeller that was originally in the pump. A is an aggressive cut and unless your making some good power your not going to be able to spin it very fast. In a stock application you would probably spin that impeller around 4000-4500 RPM. I'm spinning an aggressor A+ impeller 5400 RPM in my boat and i'm pushing close to 700 HP. You can have the impeller cut to match your application, there are advantages and disadvantages when doing that.

A high rise intake manifold will probably help make a little more power, but i don't think it's going to be noticeable.

Do you have any pictures of the boat? What are your goals with this boat?

[rick1964]

Yes I'll get a picture of the boat to ya... How do I upload one here? The chart is very helpful. Thanks, Are you in San Clemente? Thats not too far from me... Im in La Mesa...