only 4000 rpm 21 open bow help!

[Natedog]

i just got this boat with a 454 all stock and a 12je with I believe a 'a' pump but i put a hei,edleblock performer and holly 750 with vac sec on it.Something doesn't seem right i was running 4200 at elsinore with the stock intake and dual point dist and a 750 that was in bad shape replaced everything and went to silverwood which is a lot higher in elavation and only ran 4000 but at 48mph.The motor is a fresh rebuild with only about 20 hours.Just looking for some advice don't know if i have a bad tach or boat is just to heavy or motor problems.Set the timing at about 12 and have the lightest springs in the dist and runs great just looking for more topend.I bought the carb used and don't know what jets are in it or what i should be running.thanks

[flat broke]

i just got this boat with a 454 all stock and a 12je with I believe a 'a' pump but i put a hei,edleblock performer and holly 750 with vac sec on it.Something doesn't seem right i was running 4200 at elsinore with the stock intake and dual point dist and a 750 that was in bad shape replaced everything and went to silverwood which is a lot higher in elavation and only ran 4000 but at 48mph.The motor is a fresh rebuild with only about 20 hours.Just looking for some advice don't know if i have a bad tach or boat is just to heavy or motor problems.Set the timing at about 12 and have the lightest springs in the dist and runs great just looking for more topend.I bought the carb used and don't know what jets are in it or what i should be running.thanks
Nate, for reference our family's old 21' open bow with a Hardin 454 pulled 4500RPM or so on a stock A impeller. Honestly, the carb and manifold change might not net you enough HP to see any more RPM. You need to check your full advance timing to see if you're getting too much/not enough for starters. As far as the drop in RPM from Elsinore to Silverwood, the elevation change will cause you to run fatter which can pull your RPM down. Any time you're doing "before and after" comparsions, its good to keep as many of the test variables apples to apples. I wouldn't be surprised that after verifying your timing with all of the advance in, and running the boat at Elsinore, you find that your back to your 4200.
Good luck,
Chris

[Floored]

You may need to adjust the secondary spring on the carb. the stock one opens way late and you may want to get a quick change secondary cover and the spring assortment( about 20 bucks for both) and start going lighter until you feel the secondaries open, then put in the next heavier spring and your set. do this at elsinore to get data against your base line runs before the changes. check your plug color also.

[Natedog]

all right that gives me som more places to look into just want about another 500-700 rpm and should be able to by fine tuning i think thanks.

[Squirtin Thunder]

One thing that you might want to try besides what Chris (Flatbroke) stated is wires. You should step up to spiral core if you haven't already. Now some of the stock type HEI ignition modules limit the performance. You may want to upgrade to a performance one that you can get from your GM Performance Dealer. I have found 200 - 600 rpm in those modules in the past.

[Natedog]

yea i just put a accell hei and new 8.8 msd wires the one problem i have is the timing gun wont read thru the thick wires so i have to swap number one out with a old wire anybody had this problem.and how do you check full advance on the lake in neutral or some else driving?

[BrendellaJet]

if you can get your advance in soon enough you should be able to check total advance on the trailer and keep the noise down too. You'll see better throttle response too.

[Commander21]

Hey NateDog,
Were you at Rex Marine about two weeks ago buying cables for your diverter?
You told me to look into purchasing an Edelbrock manifold? Just wondering.

[Natedog]

i was there about 2 weeks ago but i didn't talk to anybody about a manifold.

[Flip]

Hey NateDog,
Were you at Rex Marine about two weeks ago buying cables for your diverter?
You told me to look into purchasing an Edelbrock manifold? Just wondering.
That was me.