Carb Question

Bigbearcl · 09-14-2006, 07:45 PM

I have a 66 mustang with a 289 that has been worked on and has a really crazy camshaft with a 600cfm carb on it. This should have plenty of power to bust the back tires loose but whenever I go to do so it just gives me a huge lag and acts like it is going to die on me. It also chugs while in all the gears when I'm not stepping on the gas pedal. I've had it looked at by a guy at an auto shop and he tune the carb and changed out the power valve but it still does the same thing. Any suggestions on where to go next? Please help me out

Gearhead999 · 09-16-2006, 05:36 AM

Sounds like the accelerator pump isn't working properly. Also, check your timing.

Bigbearcl · 09-19-2006, 05:51 PM

Ok, I took it to an auto preformance shop and now the guy tells me that it could be the ratio in the rear end is too big for the 289
(bored .03 over with a comp cam). I have a 428 shelby rear end in it. However, when I look at the carb it has been carboning up(this is after the guy who tuned it up worked on it). I took it into the preformance shop yesterday and I really am trying to avoid getting screwed...are there any suggestions out there? Is the rear end possibly whats doing all this? Please help me out.

Is there an equation or something that would help me out in figuring out what rear end and tranny I could put on it to get the most torque and horsepower out of it?

bmxmon · 09-19-2006, 11:38 PM

I would highly doubt it. If the gears in the back are to high your engine will be revving high at relatively low speed, opposite if your gears are too low. Do you mean its a 9 inch rear end? Pretty rare in 66 (like you said shelby only i believe), plus they didnt have 428's yet. (at least in the stang) Might be that crazy cam isnt the best thing for your little 289. Does it idle nicely, or is it real rough until it gets into the higher RMP's? Manual or auto transmission? Reason im thinking that is maybe its slipping and your not getting all the power to the rear wheels, though if your engine sounds like crap its probably that. Does it spin in gravel, if not then i would guess your trans is a bit messed up. Check for vaccum leaks too, they can suck. How old is the carb, might be time for a rebuild or just a new one.

Bigbearcl · 09-19-2006, 11:48 PM

spins in the gravel. Doesn't run too rough with the cam in it. I'm not sure what size the rear end is but I know its out of a shelby from a different year. Carb is brand new...only about 400 miles on it. Definitely runs better when it gets up to a decent speed though. It is a four speed. Thanks for the help so far. Hopefully I'll hear what the guy at the shop thinks it is tomorrow. Let me know if you can think of anything else.
Drive train is 289 bored out with a wild cam....302/351 wide ratio tranny...and a 428 rear end.

bmxmon · 09-19-2006, 11:57 PM

65 and 66 were the only years of that size rear end, it grew after 66. So either its from 65, 66, or narrowed. Check inital timing, and again vaccum leaks around the carb/intake. I had a problem before that there was another vaccum hook up on my carb and i didnt notice it, so check that out. Intakes seem to like to leak out the back where you cant see them very well, so look that over. When you time it make sure you block all your vaccum lines off. Also, when you adjust your carb keep leaning it out until it starts stumbling, then turn up the idle. Its possible your dumping too much fuel in there. Good luck, hope ya get it figured out.

Bigbearcl · 09-20-2006, 07:25 PM

Thankyou much. I'll let ya know how I come out!

Bigbearcl · 09-30-2006, 10:44 AM

Alrighty, I took it to the shop and they helped time it out, put an electronic timing system in and a new vaccuum advance on it and set it to a high idle on the carb. Runs pretty smooth but is still pretty hard to start in first without having quite a bit of shimmy. The only way I can get it to start smooth is if I lay on the gas and let the clutch up really slowly....and I know that is going to kill my clutch really quick. I looked at the rearend to see if there was a ratio tag on it but the only numbers I could find were 4K2 stamped on the differential. other that the shimmy she runs wonderful:-)...but I would still like to figure out the shimmy so I can drive it without tearing up my clutch.

09-14-2006, 07:45 PM	#1
Bigbearcl Registered Member Join Date: Jun 2006 Posts: 13	Carb Question I have a 66 mustang with a 289 that has been worked on and has a really crazy camshaft with a 600cfm carb on it. This should have plenty of power to bust the back tires loose but whenever I go to do so it just gives me a huge lag and acts like it is going to die on me. It also chugs while in all the gears when I'm not stepping on the gas pedal. I've had it looked at by a guy at an auto shop and he tune the carb and changed out the power valve but it still does the same thing. Any suggestions on where to go next? Please help me out

09-16-2006, 05:36 AM	#2
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	Re: Carb Question Sounds like the accelerator pump isn't working properly. Also, check your timing. __________________ "Support our Troops" Dave 1968 Cougar 2004 Thunderbird 2007 F150 Harley-Davidson, SuperCrew 1986 LTD 1997 Ranger 1992 Honda Civic

09-19-2006, 05:51 PM	#3
Bigbearcl Registered Member Join Date: Jun 2006 Posts: 13	Re: Carb Question Ok, I took it to an auto preformance shop and now the guy tells me that it could be the ratio in the rear end is too big for the 289 (bored .03 over with a comp cam). I have a 428 shelby rear end in it. However, when I look at the carb it has been carboning up(this is after the guy who tuned it up worked on it). I took it into the preformance shop yesterday and I really am trying to avoid getting screwed...are there any suggestions out there? Is the rear end possibly whats doing all this? Please help me out. Is there an equation or something that would help me out in figuring out what rear end and tranny I could put on it to get the most torque and horsepower out of it?

09-19-2006, 11:38 PM	#4
bmxmon Registered Member Join Date: Mar 2004 Location: Minnesota Posts: 950	Re: Carb Question I would highly doubt it. If the gears in the back are to high your engine will be revving high at relatively low speed, opposite if your gears are too low. Do you mean its a 9 inch rear end? Pretty rare in 66 (like you said shelby only i believe), plus they didnt have 428's yet. (at least in the stang) Might be that crazy cam isnt the best thing for your little 289. Does it idle nicely, or is it real rough until it gets into the higher RMP's? Manual or auto transmission? Reason im thinking that is maybe its slipping and your not getting all the power to the rear wheels, though if your engine sounds like crap its probably that. Does it spin in gravel, if not then i would guess your trans is a bit messed up. Check for vaccum leaks too, they can suck. How old is the carb, might be time for a rebuild or just a new one. __________________ Alex

09-19-2006, 11:48 PM	#5
Bigbearcl Registered Member Join Date: Jun 2006 Posts: 13	Re: Carb Question spins in the gravel. Doesn't run too rough with the cam in it. I'm not sure what size the rear end is but I know its out of a shelby from a different year. Carb is brand new...only about 400 miles on it. Definitely runs better when it gets up to a decent speed though. It is a four speed. Thanks for the help so far. Hopefully I'll hear what the guy at the shop thinks it is tomorrow. Let me know if you can think of anything else. Drive train is 289 bored out with a wild cam....302/351 wide ratio tranny...and a 428 rear end.

09-19-2006, 11:57 PM	#6
bmxmon Registered Member Join Date: Mar 2004 Location: Minnesota Posts: 950	Re: Carb Question 65 and 66 were the only years of that size rear end, it grew after 66. So either its from 65, 66, or narrowed. Check inital timing, and again vaccum leaks around the carb/intake. I had a problem before that there was another vaccum hook up on my carb and i didnt notice it, so check that out. Intakes seem to like to leak out the back where you cant see them very well, so look that over. When you time it make sure you block all your vaccum lines off. Also, when you adjust your carb keep leaning it out until it starts stumbling, then turn up the idle. Its possible your dumping too much fuel in there. Good luck, hope ya get it figured out. __________________ Alex

09-20-2006, 07:25 PM	#7
Bigbearcl Registered Member Join Date: Jun 2006 Posts: 13	Re: Carb Question Thankyou much. I'll let ya know how I come out!

09-30-2006, 10:44 AM	#8
Bigbearcl Registered Member Join Date: Jun 2006 Posts: 13	Re: Carb Question Alrighty, I took it to the shop and they helped time it out, put an electronic timing system in and a new vaccuum advance on it and set it to a high idle on the carb. Runs pretty smooth but is still pretty hard to start in first without having quite a bit of shimmy. The only way I can get it to start smooth is if I lay on the gas and let the clutch up really slowly....and I know that is going to kill my clutch really quick. I looked at the rearend to see if there was a ratio tag on it but the only numbers I could find were 4K2 stamped on the differential. other that the shimmy she runs wonderful:-)...but I would still like to figure out the shimmy so I can drive it without tearing up my clutch.

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