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6066 (1960-1966) GMC Truck Club (https://6066gmcclub.com/index.php)
-   GMC V6 and V12 Engines (https://6066gmcclub.com/forumdisplay.php?f=9)
-   -   Holley 500 conversion? (https://6066gmcclub.com/showthread.php?t=50307)

1965GMCK1502 March 2nd, 2018 10:31 PM
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 that’s working fine, especially after swapping in new Taylor wires and platinum plugs.....But always looking for a little more performance for the engine. I’ve 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!

bigblockv6 March 2nd, 2018 11:33 PM
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:ok:

1965GMCK1502 March 3rd, 2018 06:59 AM
Re: Holley 500 conversion?
 
Quote:
Originally Posted by bigblockv6 (Post 68857)
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:ok:
Thanks, Peter. The HEI is in, and 2 1/4” dual exhaust going in next week. Holley carb on the way.

LoganKai June 18th, 2018 08:50 PM
Re: Holley 500 conversion?
 
Quote:
Originally Posted by bigblockv6 (Post 68857)
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:ok:
Have you had any success locating or building headers?

bigblockv6 June 19th, 2018 03:46 AM
Re: Holley 500 conversion?
 
I have not tried headers, though there are freer flowing manifolds used on bigger truck engines.

1965GMCK1502 June 19th, 2018 02:35 PM
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 don’t match up and require customization. Haven’t tried....very happy with just the dual exhaust though.

TJ's GMC July 17th, 2018 06:12 AM
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. :thumbsup:

br-549 August 5th, 2018 12:26 PM
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

1965GMCK1502 May 13th, 2020 03:24 AM
Re: Holley 500 conversion?
 
1 Attachment(s)
Quote:
Originally Posted by TJ's GMC (Post 69431)
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. :thumbsup:
Finally got around to doing the Holley swap and very happy with the results.

steve in MI August 22nd, 2020 06:04 PM
Re: Holley 500 conversion?
 
Any suggestion on what jets work best?


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