Engine potential

carboy · 01-02-2009, 11:47 PM

After rebuilding my engine I cannot get over 5k RPM, it starts missing badly. Before the overhaul I could get over 7k with no cutting out. I'm running 12 degrees advance. I've replaced my stock fual pump with a Holley blue electric pump. Any one got any Ideas on why I can't get any higher on my RPM.
Also this is only under a load, because I can sit in the driveway and rev it over 7 k and it doesn't cut out at all,,,just when I try to run it hard down the road.

jim2f · 01-08-2009, 04:07 PM

Are you sure it is ignition? Was it doing this before the pump replacement?

talaposa · 02-27-2010, 01:16 AM

Does it backfire through the carburetor? If so it may be jetted lean.
Or it could be related to too large of a carburetor. When you hammer it on the road the engine sees a large volume of air and if there is not strong enough a signal it may run lean until rpm catches up.

bored · 03-05-2010, 09:42 PM

I would take a look at the accelerator pump to make sure its working correctly

goodyear1984 · 04-18-2010, 02:18 PM

well i wouldnt blame it on the ign system cuz it will work in the driveway.i wouldnt blame it on the carb being to big because that would be more of a problem in the lower rpm rather then the higher rpm and as far as accelorator pump that would be a problem with throttle response because it only pumps fuel when you press down on the gas and doesnt do anything if your just wide open in a gear.now it does sound like its running outta fuel by the way u explaned other then the missing it would have to be pretty lean to miss.i would go thu the bassics and check your float levels make sure theres no vaccum leaks.one thing you can do is get a vaccum gauge and plug it into manifold vaccum, tape the gauge to the windsheild and see where the vaccum level is when its breaking up that will tell you if its running lean or rich

01-02-2009, 11:47 PM	#1
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	Engine potential After rebuilding my engine I cannot get over 5k RPM, it starts missing badly. Before the overhaul I could get over 7k with no cutting out. I'm running 12 degrees advance. I've replaced my stock fual pump with a Holley blue electric pump. Any one got any Ideas on why I can't get any higher on my RPM. Also this is only under a load, because I can sit in the driveway and rev it over 7 k and it doesn't cut out at all,,,just when I try to run it hard down the road. __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

01-08-2009, 04:07 PM	#2
jim2f 65 coupe Join Date: Nov 2005 Location: missouri Posts: 11	Re: Engine potential Are you sure it is ignition? Was it doing this before the pump replacement?

02-27-2010, 01:16 AM	#3
talaposa Registered Member Join Date: Feb 2010 Location: California Posts: 2	Re: Engine potential Does it backfire through the carburetor? If so it may be jetted lean. Or it could be related to too large of a carburetor. When you hammer it on the road the engine sees a large volume of air and if there is not strong enough a signal it may run lean until rpm catches up.

03-05-2010, 09:42 PM	#4
bored bored Join Date: Mar 2010 Location: cookstown ontario Posts: 3	Re: Engine potential I would take a look at the accelerator pump to make sure its working correctly

04-18-2010, 02:18 PM	#5
goodyear1984 Registered Member Join Date: Dec 2006 Location: new york Posts: 482	Re: Engine potential well i wouldnt blame it on the ign system cuz it will work in the driveway.i wouldnt blame it on the carb being to big because that would be more of a problem in the lower rpm rather then the higher rpm and as far as accelorator pump that would be a problem with throttle response because it only pumps fuel when you press down on the gas and doesnt do anything if your just wide open in a gear.now it does sound like its running outta fuel by the way u explaned other then the missing it would have to be pretty lean to miss.i would go thu the bassics and check your float levels make sure theres no vaccum leaks.one thing you can do is get a vaccum gauge and plug it into manifold vaccum, tape the gauge to the windsheild and see where the vaccum level is when its breaking up that will tell you if its running lean or rich __________________ 347 stroker all forged,arp everything,stud mains w/girdle,7qt pan,full roller, custom cam, aluminum heads swirl valves 5 angle valve job.quick fuel 750,areomotive pump,cobras w/nitto drags,and m/t et drags for the track, ford racing 373 gears,centerforce clutch,tko500,underdrive pulleys,bassani x-pipe,flowmasters ^best et so far 11.6 1.61 60ft coming soon 9sec et's 1992 mustang gt 2001 gmc 1500 4x4 78 century boat 92 skidoo

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