Full throttle fall on its face

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   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??

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swoods1127 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: August-06-2020 Location: Indiana Status: Offline Points: 8	Post Options Post Reply Quote swoods1127 Report Post Thanks(0) Quote Reply Topic: Full throttle fall on its face 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??

TRBenj Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21186	Post Options Post Reply Quote TRBenj Report Post Thanks(0) Quote Reply 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.

swoods1127 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: August-06-2020 Location: Indiana Status: Offline Points: 8	Post Options Post Reply Quote swoods1127 Report Post Thanks(0) Quote Reply Posted: August-10-2020 at 12:33pm
	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

dgabler Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: June-12-2017 Location: Atascadero Status: Offline Points: 71	Post Options Post Reply Quote dgabler Report Post Thanks(0) Quote Reply 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.

Jonny Quest Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2978	Post Options Post Reply Quote Jonny Quest Report Post Thanks(0) Quote Reply Posted: August-10-2020 at 5:55pm
	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 JQ
	Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum

swoods1127 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: August-06-2020 Location: Indiana Status: Offline Points: 8	Post Options Post Reply Quote swoods1127 Report Post Thanks(0) Quote Reply Posted: August-10-2020 at 10:18pm
	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.

Jonny Quest Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2978	Post Options Post Reply Quote Jonny Quest Report Post Thanks(0) Quote Reply Posted: August-12-2020 at 12:15am
	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 JQ
	Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum

illiniball2000 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-27-2014 Location: Elgin,IL Status: Offline Points: 386	Post Options Post Reply Quote illiniball2000 Report Post Thanks(0) Quote Reply Posted: August-12-2020 at 2:50pm
	Does it run ok until a certain RPM?
	Beer is my friend 87 Dominique Had 67 Starflite

KENO Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11112	Post Options Post Reply Quote KENO Report Post Thanks(0) Quote Reply 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.

swoods1127 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: August-06-2020 Location: Indiana Status: Offline Points: 8	Post Options Post Reply Quote swoods1127 Report Post Thanks(0) Quote Reply Posted: August-13-2020 at 8:56am
	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

swoods1127 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: August-06-2020 Location: Indiana Status: Offline Points: 8	Post Options Post Reply Quote swoods1127 Report Post Thanks(0) Quote Reply Posted: August-13-2020 at 9:00am
	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

Full throttle fall on its face

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