Go Back  Offshoreonly.com > Technical > Do It Yourself, Boating on a Budget
blown 350 wont pull over 4000rpm >

blown 350 wont pull over 4000rpm

Notices

blown 350 wont pull over 4000rpm

Thread Tools
 
Old 09-20-2012 | 06:32 AM
  #11  
Thread Starter
Registered
 
Joined: Dec 2011
Posts: 49
Likes: 0
From: evansville indiana
Default

Originally Posted by articfriends
Prop pitch/drive ratio? The hyperpistons dont make the best blower pistons, I have broke the Gm zz4 ones in a non blown 350 small block so watch the boost, timing and don't torque load it (which is what you might be doing right now), Smittty
15dia 22 pitch 4 blade /1:50 but it will do the same with a 13.750 23 3 blade.
michaelb63 is offline  
Reply
Old 09-20-2012 | 12:28 PM
  #12  
Registered
10 Year Member
 
Joined: Jun 2011
Posts: 1,211
Likes: 145
Default

15" diameter is a lot to swing for a small block, even with a blower. I'd try a 21" or smaller 3 blade or a 20" or smaller 4 blade.
Trash is offline  
Reply
Old 09-20-2012 | 12:36 PM
  #13  
Griff's Avatar
Charter Member # 55
25 Year Member
Charter Member
Super Moderators
 
Joined: Oct 2000
Posts: 20,271
Likes: 2,512
From: Omaha/LOTO
Default

Originally Posted by michaelb63
bought engine as is runs extremly rich with 90 in secondary,5 psi boost,cant find any info on cam. probly pull it out and go with a lt4 hot cam.
Having #80 jets squared with no PV in the secondaries makes no sense. If its rich with 90's in the secondaries, then the primaries must be rich with 80's.
You probably need something more like 74's and 84's.

With todays clean burning fuels, the porcelain on the plugs should be almost completely white. Too read the plugs, you need to look at the base circle coloring.
Griff is offline  
Reply
Old 09-20-2012 | 04:32 PM
  #14  
Thread Starter
Registered
 
Joined: Dec 2011
Posts: 49
Likes: 0
From: evansville indiana
Default

Originally Posted by Griff
Having #80 jets squared with no PV in the secondaries makes no sense. If its rich with 90's in the secondaries, then the primaries must be rich with 80's.
You probably need something more like 74's and 84's.

With todays clean burning fuels, the porcelain on the plugs should be almost completely white. Too read the plugs, you need to look at the base circle coloring.
thanks griff ill give that a try this weekend and see what happens
michaelb63 is offline  
Reply
Old 09-20-2012 | 04:59 PM
  #15  
Registered
20 Year Member
 
Joined: Nov 2003
Posts: 2,296
Likes: 3
From: Lake Travis ,Texas
Default

I wouldnt run any supercharged boat without a wideband a/f and a fuel pressure gauge,, otherwise you are playing russian roulette with your engine
HTRDLNCN is offline  
Reply
Old 09-23-2012 | 01:17 AM
  #16  
Registered
 
Joined: Aug 2005
Posts: 6,306
Likes: 1
From: Between A Womans Leggs in IL
Default fixx

Originally Posted by michaelb63
no detonation,pops or backfires starts great ,idels great,runs great, just wont go past 4000
does not matter what the plugs look like,,the boost will blow the spark out after a certain amount of rpm,,i have seen this before,,the boat will still run but it wont have enough spark to ignite all the fuel and will smell rich when it blows all the unburned fuel out the exhaust..4000 rpm is usually the magic #..
FIXX is offline  
Reply
Old 09-23-2012 | 08:23 PM
  #17  
Registered
 
Joined: Jul 2009
Posts: 8,527
Likes: 706
From: Taunton Ma
Default

Good point, what ignition system? Plug gap?
Unlimited jd is offline  
Reply
Old 09-23-2012 | 09:17 PM
  #18  
Registered
 
Joined: Aug 2005
Posts: 6,306
Likes: 1
From: Between A Womans Leggs in IL
Default fixx

Originally Posted by lil red
Good point, what ignition system? Plug gap?
dont know if its the same gut i talked to a few weeks ago but he said he had the plugs at .040..
FIXX is offline  
Reply
Old 09-24-2012 | 05:46 AM
  #19  
Registered
15 Year Member
 
Joined: Apr 2007
Posts: 113
Likes: 0
From: AZ
Default

What Ignition? Stock HEI? Might need an ignition upgrade, cam appears on the small side, which would explain a lot, but definately throw a WB O2 on 'er, and keep that thing rich or you're going to be melting pistons...

How does she act when the power falls off? Any breaking up or misfiring? Or just feels soft when the power builds? Could be spark or fuel, double check both before changing anything internal...

I agree with staying Hyd Roller, but not sure if the hot cam is the best choice with boost.... If everything else checks out (spark, air, fuel) add more cam...

Good luck...
Bowtiepower00 is offline  
Reply
Old 09-24-2012 | 05:16 PM
  #20  
Thread Starter
Registered
 
Joined: Dec 2011
Posts: 49
Likes: 0
From: evansville indiana
Default

Originally Posted by lil red
Good point, what ignition system? Plug gap?
thunderbolt IV ignition plugs gaped at 035
michaelb63 is offline  
Reply


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.