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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old March 2nd, 2018, 10:31 PM
1965GMCK1502 1965GMCK1502 is offline
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Default Holley 500 conversion?

Hi All, was hoping to get some real life pros and cons of the 500. Current setup is the 305v6 with a Rochester 2G thatís working fine, especially after swapping in new Taylor wires and platinum plugs.....But always looking for a little more performance for the engine. Iíve heard nothing but great things about the Holley swap...but curious if anyone has had any negative outcomes?
Positive outcome info also very appreciated.
Thanks in advance!
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  #2  
Old March 2nd, 2018, 11:33 PM
bigblockv6 bigblockv6 is offline
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Default Re: Holley 500 conversion?

The Holley 500 will really wake up the 305 V6 though at times some 305's may run too rich and be a little over carbureted so a simple rejetting is all that's needed. To enhance this carburetor conversion I suggest a good flowing dual exhaust and an upgrade to electronic ignition
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Old March 3rd, 2018, 06:59 AM
1965GMCK1502 1965GMCK1502 is offline
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Default Re: Holley 500 conversion?

Quote:
Originally Posted by bigblockv6 View Post
The Holley 500 will really wake up the 305 V6 though at times some 305's may run too rich and be a little over carbureted so a simple rejetting is all that's needed. To enhance this carburetor conversion I suggest a good flowing dual exhaust and an upgrade to electronic ignition
Thanks, Peter. The HEI is in, and 2 1/4Ē dual exhaust going in next week. Holley carb on the way.
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Old June 18th, 2018, 08:50 PM
LoganKai LoganKai is offline
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Default Re: Holley 500 conversion?

Quote:
Originally Posted by bigblockv6 View Post
The Holley 500 will really wake up the 305 V6 though at times some 305's may run too rich and be a little over carbureted so a simple rejetting is all that's needed. To enhance this carburetor conversion I suggest a good flowing dual exhaust and an upgrade to electronic ignition
Have you had any success locating or building headers?
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Old June 19th, 2018, 03:46 AM
bigblockv6 bigblockv6 is offline
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Default Re: Holley 500 conversion?

I have not tried headers, though there are freer flowing manifolds used on bigger truck engines.
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Old June 19th, 2018, 02:35 PM
1965GMCK1502 1965GMCK1502 is offline
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Default Re: Holley 500 conversion?

[QUOTE=LoganKai;69353]Have you had any success locating or building headers

The headers are a major headache....there was some discussion about using Pontiac three-ports but they donít match up and require customization. Havenít tried....very happy with just the dual exhaust though.
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Old July 17th, 2018, 06:12 AM
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Default Re: Holley 500 conversion?

Dual exhaust with the stock manifolds will do the job just fine for ya. Headers would have to be custom made and the results would not be worth the effort(or money!) unless more work was done to the engine. The mentioned mods will make for a nice increase in power....and change the exhaust tone.
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Old August 5th, 2018, 12:26 PM
br-549 br-549 is offline
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Default Re: Holley 500 conversion?

I also have interest in swapping to a Holley but i have a 401. Anyone have an adapter or a "fix"? Thanks! ja
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Old May 13th, 2020, 03:24 AM
1965GMCK1502 1965GMCK1502 is offline
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Default Re: Holley 500 conversion?

Quote:
Originally Posted by TJ's GMC View Post
Dual exhaust with the stock manifolds will do the job just fine for ya. Headers would have to be custom made and the results would not be worth the effort(or money!) unless more work was done to the engine. The mentioned mods will make for a nice increase in power....and change the exhaust tone.
Finally got around to doing the Holley swap and very happy with the results.
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