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Rod
04-26-2001, 09:31 AM
I have a 22ft 9ftwide flatbottom handbuilt boat. It has berkeley jet AA impeller and 350 chevy all rebuilt . Moter has flattops 78cc heads and comp cams XM 262 marine dur 218I 224E .460I .477E lift. The moter runs goods but stops pulling at 4000rpm. I would like to see 4500rpm. Thinking of putting 64cc heads to rising compresstion .

skeepwerkzaz
04-26-2001, 09:44 AM
Hi there,
Sounds to me like a cam is the key to your happiness. Yours sounds a little small, might want to lolok into a cam/lifter change rather than pulling the heads. You can get a kit for around 100 bucks. Do you have a four barrel, headers, good ignition? I would tune these before a head swap. You also want to be able to burn 92.
hope this helps,
SKEEP

spectras only
04-26-2001, 10:16 AM
Rod, besides you have a relatively good cam [if duration given at 0.050 lift], you should change your impeller to an "A" or "AB" to get the RPM where a 350 makes the most HP.
[This message has been edited by spectras only (edited April 26, 2001).]

Jetmugg
04-26-2001, 01:33 PM
Rod:
The problem is not in your engine!!! It's in the pump!!!! An "AA" impeller is very much too large for any naturally aspirated small block. I have been there before, with a small block Olds and an "A" impeller. Jet pumps take large amounts of torque and HP to turn at higer rpms. My best recommendation is to have the impeller re-cut to a "B" size, and see how it runs at that level. You probably want to spin that small block to around 5000 rpm in order to hit the HP peak, if not higher. A "B/C" cut may even be needed, but the "B" is a good place to start with a small block. If in doubt, call one of the professional shops (MPD, Walts, or GS Marine are all great places to deal with), and listen to their recommendations.
SteveM.

spectras only
04-26-2001, 01:48 PM
Rod , I've cut a lot of impellers down to a "C", but before you do that,try an "AB".You can always go lower but not the other way around!

LIQUID ASSETS
04-26-2001, 05:16 PM
Big Block It!!!

mister460
04-27-2001, 11:30 AM
This just proves what I always say "When in doubt, BIG BLOCK IT!!!" Seriously though, if you really want some performance, go a size or two up in cam, go with the smaller heads, PORT THEM! Then make sure you have a carb that will flow enough as well as a good intake. If you don't want to yank the heads, then I agree with the others. Go with just a bigger cam and smaller impeller. Just remember though, your motor's only as good as it's weakest link. And I mean the heads. A big cam won't do anything unless to ports can handle the increased flow. Good luck!