Engine stumble at High RPM
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=49242
Printed Date: November-23-2024 at 11:14am
Topic: Engine stumble at High RPM
Posted By: AlfaDon
Subject: Engine stumble at High RPM
Date Posted: September-18-2020 at 1:38am
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On the lake today trying out a spare prop I’ve had for a while. Trying to find top speed/rpm. It’s a older 3 blade OJ 14 x 16. Plus the 422 was singing so I decided to give it a try. Flat lake, 5000’ elevation. I’m running the RPMs up and up. When I get to about 5700, it stumbles and I back off the throttle. It felt like an electronic cut out only because it was quick and sharp. Either the stern came up a bit or the nose dropped slightly. 48 mph on the GPS. I just confirmed the tach reading with a cheap laser. Any ideas? I always thought the end of the power band would just stop accelerating. Was it a prop issue? It was pretty rough running. I’m going to put the 422 back on tomorrow and see what the numbers are. |
Replies:
Posted By: GottaSki
Date Posted: September-18-2020 at 5:53am
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5700, it's Valve float likely ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: KENO
Date Posted: September-18-2020 at 6:56am
Maybe a little bit of info on the engine and what's inside it and bolted onto it would be helpful 
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Posted By: AlfaDon
Date Posted: September-18-2020 at 10:39am
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Thanks. I should add this to my diary Stock crank and rods. New pistons, Ported Aluminum heads w/ 2.02/160 valves running 10.5/1 compression, Hyd roller cam and lifters .550 lift, about 230 duration both I & E. New Comp springs to match. Edelbrock Performer Intake manifold 650 CFM Quickfuel Carb, DUI Dizzy |
Posted By: TRBenj
Date Posted: September-18-2020 at 11:02am
| 5700rpm and 48mph with that prop don’t make any sense... some of your numbers are wrong or your prop should’ve been retired a long time ago. |
Posted By: AlfaDon
Date Posted: September-18-2020 at 11:11am
| Yep. It’s a prop I got cheap as a backup. It’s officially been determined that it’s junk. I now have a Nibral candle holder or wall ornament. |
Posted By: GottaSki
Date Posted: September-18-2020 at 11:21am
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heh, hot motor..forgot that ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |