4150 problems

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4150 problems

Post by JF74chevelle on Mon Mar 26, 2018 7:15 pm

Hey guys, my engine is a 357 brodix heads comp cam xe274 14in of vacuum. Some problems, first when braking the engine tries to die out but I blip the throttle and it comes back. Second, when I’m in third and punch it, it bogs and pops. Could this be because of my 2.73 rear gears and my m20 ratios? Or tuning issue. Also it just tries to die when going slow and trying to pull into a drive way
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Re: 4150 problems

Post by Joe73 on Mon Mar 26, 2018 7:52 pm

Mechanical secondaries, correct? Probably dumping too much fuel at too low of an rpm. That coupled with it wanting to die when braking sounds like carb tuning is required. Did you set up all 4 of your idle screws with a vacuum gauge to get you close? What cfm is the carb?
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Re: 4150 problems

Post by JF74chevelle on Mon Mar 26, 2018 8:12 pm

Joe73 wrote:Mechanical secondaries, correct?  Probably dumping too much fuel at too low of an rpm.  That coupled with it wanting to die when braking sounds like carb tuning is required.  Did you set up all 4 of your idle screws with a vacuum gauge to get you close?  What cfm is the carb?

Yes it’s a DP, 650 cfm. I have been tuning the carb with a vacuum gauge on all four corners with the hi of 13-14 Hg with VA connected to full manifold vacuum
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Re: 4150 problems

Post by Joe73 on Mon Mar 26, 2018 8:28 pm

Carb size is good but I think you would always bog when jumping on it at a low rpm. The rear gear ratio is not helping the matter. I prefer a vacuum secondary for the street. But guys also love mechanical on the street. I sold my 650 dp in exchange for a 750 vacuum thats going on my new motor.

Anyway. how's the timing?? Do you have it set at a total of 32-36 when all in? How much timing is the vacuum advance giving you? Whats your initial timing? Did you play with the weights to it all in ? At what rpm?
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Re: 4150 problems

Post by JF74chevelle on Mon Mar 26, 2018 9:16 pm

Joe73 wrote:Carb size is good but I think you would always bog when jumping on it at a low rpm.  The rear gear ratio is not helping the matter.  I prefer a vacuum secondary for the street.  But guys also love mechanical on the street.  I sold my 650 dp in exchange for a 750 vacuum thats going on my new motor.

Anyway.  how's the timing??  Do you have it set at a total of 32-36 when all in?  How much timing is the vacuum advance giving you?  Whats your initial timing?  Did you play with the weights to it all in ?  At what rpm?  

I got the dying when braking figured out, but the big is still there in third, it doesn’t happen when I’m power shifting though. So it could be that the ratio is jut too low but I’m changing to 3.73s real soon
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Re: 4150 problems

Post by JF74chevelle on Mon Mar 26, 2018 9:19 pm

Joe73 wrote:Carb size is good but I think you would always bog when jumping on it at a low rpm.  The rear gear ratio is not helping the matter.  I prefer a vacuum secondary for the street.  But guys also love mechanical on the street.  I sold my 650 dp in exchange for a 750 vacuum thats going on my new motor.

Anyway.  how's the timing??  Do you have it set at a total of 32-36 when all in?  How much timing is the vacuum advance giving you?  Whats your initial timing?  Did you play with the weights to it all in ?  At what rpm?  
Also, timing is 18 initial w/o VA hooked up, then 36 all in at 2700 with VA hooked up. I have one lighter spring and one heavier spring on the distributor weights.
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Re: 4150 problems

Post by Joe73 on Mon Mar 26, 2018 9:29 pm

Ok, your timing is where it should be. While power shifting your rpms are high so you wont have much of a problem. I think its your rear axle ratio hurting you.
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Re: 4150 problems

Post by JF74chevelle on Mon Mar 26, 2018 9:42 pm

Joe73 wrote:Ok,  your timing is where it should be.  While power shifting your rpms are high so you wont have much of a problem.  I think its your rear axle ratio hurting you.  

That’s what I was thinking too, thanks joe. Happy tuning!
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Re: 4150 problems

Post by JF74chevelle on Tue Mar 27, 2018 1:01 am

Turns out nothing was fixed went and drove it again and it still tries to die when I’m coming to a stop, not sure if it’s the brake booster causing a vacuum leak or something with the carb
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Re: 4150 problems

Post by JF74chevelle on Tue Mar 27, 2018 1:04 am

Also it tries to die when I’m leaving in first and I really have to ride th clutch to keep it alive
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Re: 4150 problems

Post by bracketchev1221 on Tue Mar 27, 2018 7:26 am

JF74chevelle wrote:
Joe73 wrote:Carb size is good but I think you would always bog when jumping on it at a low rpm.  The rear gear ratio is not helping the matter.  I prefer a vacuum secondary for the street.  But guys also love mechanical on the street.  I sold my 650 dp in exchange for a 750 vacuum thats going on my new motor.

Anyway.  how's the timing??  Do you have it set at a total of 32-36 when all in?  How much timing is the vacuum advance giving you?  Whats your initial timing?  Did you play with the weights to it all in ?  At what rpm?  
Also, timing is 18 initial w/o VA hooked up, then 36 all in at 2700 with VA hooked up. I have one lighter spring and one heavier spring on the distributor weights.

Timing should be 36 WITHOUT the vacuum advance hooked up.
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Re: 4150 problems

Post by Sinister on Sun Apr 15, 2018 7:54 pm

http://www.allcarbs.com

These guys are awesome.
Bought a number of rebuilt carbs from them.
They look pristine out of the box.
Work of art.
They are flow tested and dyno tuned on an engine before being shipped.
Bolt them on and go.
You can send them your carb for rebuilding,if you want to keep it 100% original.
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Re: 4150 problems

Post by Sinister on Sun Apr 15, 2018 7:57 pm

Float settings too high can cause fuel to spill into bowl at stops and stall out.
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Re: 4150 problems

Post by JF74chevelle on Sun Apr 15, 2018 7:59 pm

Sinister wrote:http://www.allcarbs.com

These guys are awesome.
Bought a number of rebuilt carbs from them.
They look pristine out of the box.
Work of art.
They are flow tested and dyno tuned on an engine before being shipped.
Bolt them on and go.
You can send them your carb for rebuilding,if you want to keep it 100% original.

I got it figured out, doesn’t stall anymore thanks though. I did adjust the floats and connected the vent tubes
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Re: 4150 problems

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