460 losing power - Pirate4x4.Com : 4x4 and Off-Road Forum

bogger37 · 06-12-2003, 09:06 PM

i recently installed a rebuilt 460 in to my bronco. i ran great and had lots of power. then the needle and seat started messing up on it, so i installed a rebuilt carb of the same model. its a holley carb made for motorcraft. the carb is from a 87 ford with a 460. now i don't have nearly the power i had before. the truck runs great and every thing but it just dosent have the power i had before. what gives

D'sYJ · 06-13-2003, 08:37 AM

mmmmmmm. Might be that Ford emblem on the front

But for real, what did you have on there before for a carb? was it bigger, possibly giving more go juice to that power house?

SilverZuk · 06-13-2003, 09:53 AM

The carb is probably smaller than your previous if everything is functioning properly.

My Dad di the same thing on purpose to help his gas mileage.
He had a 750 CFM that would get it, but he replaced it with a 600 CFM to help on gas. It helped but you could really tell it was under carburated

Proeliator · 06-13-2003, 09:56 AM

And even if you put on the same cfm carb, it could be jetted entirely differently, have a different power valve, etc. First make sure you have the correct cfm for your engine, then start experimenting with jets, mixture setting, etc. Holleys are the best imo, but you can't just bolt them on and expect maximum performance.

bogger37 · 06-13-2003, 09:55 PM

the carb i replaced was the same model holley that is on my motor now. i checked the jets and the powervalve between the two carbs and they are the same ones. i even swapped the jets out of my old carb to see if it helped. i was thinkin maybe my secondaries are not opening all the way. how can i tell if they are opening all the way. they are vaccum secondaries and im told that there has to be a load on the motor for then to open.

Proeliator · 06-13-2003, 10:23 PM

Well, if everthing else is equal, try putting a lighter spring on your secondaries and see if that was it. They do need load to open so I don't think you'll be able to check it in your garage, other than visually inspecting the linkage and making sure there isn't a tear or leak in the diaphram. Or you can do what I do and run a dominator and not worry about vacuum secondaries

SR5Dave · 06-15-2003, 05:23 PM

The carb may have been purposely made to produce lower performance AND lower emissions because of the year.
What was the year of the last carb?

Dave

06-12-2003, 09:06 PM	#1 (permalink)
bogger37 Registered User Join Date: Apr 2003 Member # 18467 Location: canada Posts: 24	460 losing power i recently installed a rebuilt 460 in to my bronco. i ran great and had lots of power. then the needle and seat started messing up on it, so i installed a rebuilt carb of the same model. its a holley carb made for motorcraft. the carb is from a 87 ford with a 460. now i don't have nearly the power i had before. the truck runs great and every thing but it just dosent have the power i had before. what gives __________________ 78 bronco frame with 75 regular cab. 38" boggers and 460. 4.56 gears with spool in rear.

06-13-2003, 08:37 AM	#2 (permalink)
D'sYJ Registered User Join Date: Jun 2003 Member # 20224 Location: Springfield, Or Posts: 102	mmmmmmm. Might be that Ford emblem on the front But for real, what did you have on there before for a carb? was it bigger, possibly giving more go juice to that power house? __________________ Timbercrawler 89 YJ on 36's, 2.5L, Atlas4.3, D44 FR & RR, ARB and Detriot

06-13-2003, 09:53 AM	#3 (permalink)
SilverZuk Hillbilly Houndsman Join Date: Aug 2002 Member # 13420 Location: Kenna, West Virginia Posts: 6,868	The carb is probably smaller than your previous if everything is functioning properly. My Dad di the same thing on purpose to help his gas mileage. He had a 750 CFM that would get it, but he replaced it with a 600 CFM to help on gas. It helped but you could really tell it was under carburated __________________ The penalty for punching someone in the mouth is way too high in our society. www.MountaineerOffroad.com

06-13-2003, 09:56 AM	#4 (permalink)
Proeliator Registered User Join Date: May 2002 Member # 12042 Location: a den of iniquity Posts: 7,069	And even if you put on the same cfm carb, it could be jetted entirely differently, have a different power valve, etc. First make sure you have the correct cfm for your engine, then start experimenting with jets, mixture setting, etc. Holleys are the best imo, but you can't just bolt them on and expect maximum performance. __________________ [QUOTE=94stepsideford;7266691]Seth is scarier than you though. He looks like he would kill and eat a baby with his bare hands.[/QUOTE] '73 F250, 533 on N2o, 35spln chromo Superior/CTM D60/D70, twinsticked 205, hydro-assist, f&r lockers, HAD drivelines, 46" Titan R1s. Vid: [url]http://youtu.be/KaL-IsCWrrI[/url] [url]http://youtu.be/l9cuRoEfCn0[/url]

06-13-2003, 09:55 PM	#5 (permalink)
bogger37 Registered User Join Date: Apr 2003 Member # 18467 Location: canada Posts: 24	the carb i replaced was the same model holley that is on my motor now. i checked the jets and the powervalve between the two carbs and they are the same ones. i even swapped the jets out of my old carb to see if it helped. i was thinkin maybe my secondaries are not opening all the way. how can i tell if they are opening all the way. they are vaccum secondaries and im told that there has to be a load on the motor for then to open. __________________ 78 bronco frame with 75 regular cab. 38" boggers and 460. 4.56 gears with spool in rear.

06-13-2003, 10:23 PM	#6 (permalink)
Proeliator Registered User Join Date: May 2002 Member # 12042 Location: a den of iniquity Posts: 7,069	Well, if everthing else is equal, try putting a lighter spring on your secondaries and see if that was it. They do need load to open so I don't think you'll be able to check it in your garage, other than visually inspecting the linkage and making sure there isn't a tear or leak in the diaphram. Or you can do what I do and run a dominator and not worry about vacuum secondaries __________________ [QUOTE=94stepsideford;7266691]Seth is scarier than you though. He looks like he would kill and eat a baby with his bare hands.[/QUOTE] '73 F250, 533 on N2o, 35spln chromo Superior/CTM D60/D70, twinsticked 205, hydro-assist, f&r lockers, HAD drivelines, 46" Titan R1s. Vid: [url]http://youtu.be/KaL-IsCWrrI[/url] [url]http://youtu.be/l9cuRoEfCn0[/url]

06-15-2003, 05:23 PM	#7 (permalink)
SR5Dave Registered User Join Date: Dec 2002 Member # 15697 Posts: 2,862	The carb may have been purposely made to produce lower performance AND lower emissions because of the year. What was the year of the last carb? Dave __________________ Wait, what?

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode