Full throttle fall on its face
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=49057
Printed Date: May-30-2024 at 9:57pm
Topic: Full throttle fall on its face
Posted By: swoods1127
Subject: Full throttle fall on its face
Date Posted: August-10-2020 at 11:29am
| I have a 1992 Supra 351w HO Pro Boss with the GT40’s. Low hours. It ran great a couple years the it started falling on its face coming out of the hole at WOT. First I bought a new 4150 Holley carb. New fuel lines, fuel pump. Still continued. I did the DUI conversion. New plugs and wires. Set the timing. Still fall on its face before dying or taking off. Now I’m looking at the Excelerator pump adjustment and cams... I’m running out of ideas. Does anyone have any suggestions?? |
Replies:
Posted By: TRBenj
Date Posted: August-10-2020 at 12:13pm
| Timing set where? Idle mixture and level set appropriately? Then move to transition circuit (accel pump adjustment). Doubtful you’ll need a cam change, start with the basics. |
Posted By: swoods1127
Date Posted: August-10-2020 at 12:33pm
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I have the timing set at 12 degrees btdc. I thought I read that somewhere. Is that the correct timing? After work I Will checked the float levels. I haven’t done that. I’ll start there first. Then turn my mixture screws back in and out 1-1/2 And hook the vacuum gauge up and try to readjust it. I watched a couple videos on it. Soo we’ll see. I’ll let you know. Thank you |
Posted By: dgabler
Date Posted: August-10-2020 at 5:50pm
| When I had a similar issue the problem was because the person who rebuilt the carb (PO) did not connect the accelerator pump arm correctly. |
Posted By: Jonny Quest
Date Posted: August-10-2020 at 5:55pm
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Timing and accelerator pump circuit is where I’d start. There is a good YouTube video by Summit Racing on tuning he accelerator circuit. Might be worth your while to check it out. https://www.youtube.com/watch?v=tMKxD_OFuCA" rel="nofollow - https://www.youtube.com/watch?v=tMKxD_OFuCA JQ
------------- Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
Posted By: swoods1127
Date Posted: August-10-2020 at 10:18pm
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I had to replace my solenoid before checking my float levels. The old one quit. I was bumping it trying to fill my bowls. After doing this a few times the starter stopped engaging. It spins but won’t engage. Any suggestions? Also how exactly do you check the leve on the front bowl? The motor is at a hell of an angle in the boat. |
Posted By: Jonny Quest
Date Posted: August-12-2020 at 12:15am
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You may need a carb wedge spacer. https://www.hardin-marine.com/p-12376-12-spacer-wedge-plate-for-square-bore-carburetor-bolt-pattern.aspx" rel="nofollow - https://www.hardin-marine.com/p-12376-12-spacer-wedge-plate-for-square-bore-carburetor-bolt-pattern.aspx JQ ------------- Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
Posted By: illiniball2000
Date Posted: August-12-2020 at 2:50pm
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Does it run ok until a certain RPM? ------------- Beer is my friend 87 Dominique Had 67 Starflite |
Posted By: KENO
Date Posted: August-13-2020 at 8:39am
 Here's a picture of a Holley front bowl with the float level adjusted a little lower that what Holley would call normal.
This helps compensate for the angle of the engine Keep in mind that the bowl is upside down in this picture The rear float can be adjusted level so that the top of the float is parallel to the top of the bowl. Also keep in mind that you should have no need for an angled spacer since it used to run just fine without one from the factory  Like TRB said...............start with the accelerator pump adjustment and don't screw with the pump cam. |
Posted By: swoods1127
Date Posted: August-13-2020 at 8:56am
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Thank you. I’ll adjust my float as close to that as I can. It seems to run fine. It’s just from idle to wide open throttle it falls on its face. I adjusted the accelerator pumps and mixture screws and I have it really close now. I think after the float adj it’s a timing issue. But now my starter spins and won’t engage when it’s warm. Fml |
Posted By: swoods1127
Date Posted: August-13-2020 at 9:00am
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It runs good. And starts good. It just falls an it’s face from idle to wide open throttle. I adjusted my accelerator pumps and mixture screws. I think I have it really close now. Having starter issues so I haven’t had a chance to fine tune it from there. Starter spins but won’t engage Thanks |