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Old 05-25-2012, 01:13 AM
Skylark
 

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Deburring the burrs off quadrajet?

I'm cnc operator for over four years that has strong habits to deburring everything I see. I'm seeing several burrs and chipped every where on my dummy quadrajet that I'm practicing with. I can't help but wondering why factory didn't deburr them? Are there reasons why burrs there? To distrbute the air/gas or it cost money to Burr them? I have all access to deburr tools, pin gages and precious drill bits. I'm thinking about deburring them without change measures. I even thought about Polishing internal. Bad move?

By the way, I do want join the club where they have lot of wild ideas for quadrajets like snake oils, screen gaskets, etc... Lmao

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Old 05-25-2012, 01:29 AM
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It comes down to cost.

Keith
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Old 05-25-2012, 02:53 AM
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Will deburring Burrs effect anything?
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Old 05-25-2012, 08:22 AM
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I assume you are talking about deburring the throats or barrels of the carb? Deburring won't hurt, but I doubt you are going to see any improvement. You have a lot more bottlenecks in an engine than a 750CFM carb.
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Old 05-25-2012, 08:37 AM
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Deburring it can help not only airflow but fuel delivery. If you do a thurough job you will need to alter the fuel metering to compensate, you'll likely have to lean it out as a smoother airflow should produce a stronger signal. If you do a super thurough job complete with filling in voids and thinning the shafts you could come close to a 100cfm gain with no significant increase in throttle size, in otherwords it'll work better at idle through redline.

A thurough job will take some time though, like 10-15 hours.
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Old 05-25-2012, 01:26 PM
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Quote:
Originally Posted by Silver Surfer
I assume you are talking about deburring the throats or barrels of the carb? Deburring won't hurt, but I doubt you are going to see any improvement. You have a lot more bottlenecks in an engine than a 750CFM carb.


Everywhere..... Throat of barrels, edges, booster rings, sides of internal and external, floor of bowls, edges.
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Old 05-25-2012, 01:30 PM
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Quote:
Originally Posted by ap72
Deburring it can help not only airflow but fuel delivery. If you do a thurough job you will need to alter the fuel metering to compensate, you'll likely have to lean it out as a smoother airflow should produce a stronger signal. If you do a super thurough job complete with filling in voids and thinning the shafts you could come close to a 100cfm gain with no significant increase in throttle size, in otherwords it'll work better at idle through redline.

A thurough job will take some time though, like 10-15 hours.

I'm practicing to rebuilding quadrajet for my 70 stock Buick 350. I don't think gain 100 cfm would be good for this engine. I just worry about deburr will effect poor performance.
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Old 05-25-2012, 01:59 PM
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Quote:
Originally Posted by Freddyfingaz83
I'm practicing to rebuilding quadrajet for my 70 stock Buick 350. I don't think gain 100 cfm would be good for this engine. I just worry about deburr will effect poor performance.
More cfm will not hurt ANYTHING it will make some things a lot better. Your signal will be a lot stronger which will allow you to have a more consistent tune.

Unlike swapping to a carb with a larger throttle bore (higher cfm rating) gaining cfm on the same size throttle bore will not have a negative impact at low speed.

A holley hp carb uses the same venturi and throttle dimensions as the standard line of carbs but they flow more and have stronger signal due to them being smoothed out a little.

As long as you retune your carb after working on it it will do everything better.

Btw if you think a quadrajet is bad my edelbrock 1406 has a very disrupted flow path, I've considered smoothing it but since its just a carb I slap on engines to break them in its not worth it.
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Old 05-25-2012, 02:20 PM
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Quote:
Originally Posted by ap72
More cfm will not hurt ANYTHING it will make some things a lot better. Your signal will be a lot stronger which will allow you to have a more consistent tune.

Unlike swapping to a carb with a larger throttle bore (higher cfm rating) gaining cfm on the same size throttle bore will not have a negative impact at low speed.

A holley hp carb uses the same venturi and throttle dimensions as the standard line of carbs but they flow more and have stronger signal due to them being smoothed out a little.

As long as you retune your carb after working on it it will do everything better.

Btw if you think a quadrajet is bad my edelbrock 1406 has a very disrupted flow path, I've considered smoothing it but since its just a carb I slap on engines to break them in its not worth it.
Is there step by step to do this? So, I can review to see if it's worth it.
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Old 05-25-2012, 02:36 PM
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There's a very good write up on a holley being done, I can't remeber the site right now though, google it.
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Old 05-25-2012, 02:49 PM
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Quote:
Originally Posted by ap72
There's a very good write up on a holley being done, I can't remeber the site right now though, google it.
Ok what's title do I use to Google it?
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Old 05-25-2012, 07:08 PM
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biggest problem with Q jets and poor performance is the throttle shafts wearing out the baseplate holes,, causing major vacuum leaks and poor tuning.
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Old 05-25-2012, 07:17 PM
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Quote:
Originally Posted by Jim Rockford
biggest problem with Q jets and poor performance is the throttle shafts wearing out the baseplate holes,, causing major vacuum leaks and poor tuning.
Yea I'm planning to order bronze bushing throttle kits for primary and secondary throttle when I'm ready to do real rebuild on original quadrajet.
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Old 05-25-2012, 08:07 PM
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Oh yea, I just remember that I might going convert my th350 to m21. My question is if I do that, do I have to make some changes on quadrajet for m21? Or will it be fine?
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Old 05-25-2012, 09:34 PM
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Quote:
Originally Posted by ap72
you'll likely have to lean it out as a smoother airflow should produce a stronger signal.
Don't you mean richen, since more airflow would need more gas?
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