6066 (1960-1966) GMC Truck Club Bitcoin now accepted here! 
Pay Dues
Pay Dues or become a Site Supporter
 



Go Back   6066 (1960-1966) GMC Truck Club > 6066 GMC Truck Club Forum > GMC V6 and V12 Engines


GMC V6 and V12 Engines Engine repair and rebuilding

Reply
 
Thread Tools
  #11  
Old May 14th, 2019, 04:13 PM
jerrspud jerrspud is offline
Junior Member
 
Join Date: Apr 2019
Location: Boise Idaho
Truck: 1963 1500 custom cab
Age: 44
Posts: 14
Rep Power: 6
jerrspud is on a distinguished road
Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by jbgroby View Post
Because I had a '60, I had to create this linkage. Works perfect.

Quote:
Originally Posted by jerrspud View Post
what's the number for that spring bracket? I don't know what it's called.
I found the number

https://www.holley.com/products/fuel...age/parts/9678
THROTTLE RETURN SPRING KIT
Fits Holley
PART# 9678
__________________
Jerr
1963 305 V6 1500

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #12  
Old May 14th, 2019, 04:15 PM
jerrspud jerrspud is offline
Junior Member
 
Join Date: Apr 2019
Location: Boise Idaho
Truck: 1963 1500 custom cab
Age: 44
Posts: 14
Rep Power: 6
jerrspud is on a distinguished road
Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by bigblockv6 View Post
You're right the 305 V6 may run rich with the Holley 500 but it's an easy fix by just installing leaner jets.
did you do that? how many numbers you go down?

Also does everyone just bolt it on and forget it, or do you modify the intake at all so it flows better?
__________________
Jerr
1963 305 V6 1500

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #13  
Old May 15th, 2019, 01:08 AM
James James is offline
Tinkering on old trucks.
 
Join Date: Jun 2013
Location: Greer, SC
Truck: 1964 GMC 1500 2wd
Age: 64
Posts: 176
Rep Power: 85
James is on a distinguished road
Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by jerrspud View Post
did you do that? how many numbers you go down?

Also does everyone just bolt it on and forget it, or do you modify the intake at all so it flows better?
Personally I would make the everything (adapter and manifold) opening the same side as the carburetor throttle bores. I would also radius the lower edge of the manifold as it make the turn toward the runners. This is what I am planning on doing when I get around to do it (to many chores getting in my way).
Reply With Quote
  #14  
Old May 15th, 2019, 04:09 AM
bigblockv6 bigblockv6 is offline
-= Dues Paid =-
 
Join Date: Jan 2013
Location: Rohnert Park, ca.
Truck: 1968 KM2500
Posts: 1,278
Rep Power: 368
bigblockv6 will become famous soon enough
Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by jerrspud View Post
did you do that? how many numbers you go down?

Also does everyone just bolt it on and forget it, or do you modify the intake at all so it flows better?
Yes when I had the 305 in my 68 I opened up the intake at the base to match the larger throttle bore of the Holley 500
Reply With Quote
  #15  
Old May 15th, 2019, 04:28 PM
quicksilver quicksilver is offline
Junior Member
 
Join Date: May 2019
Location: ocqueoc, michigan
Truck: 1960 gmc stepside
Posts: 4
Rep Power: 0
quicksilver is on a distinguished road
Default Re: 305e Holley 500 swap question

Any idea of what headers to use with a 400sbc in my 60 gmc? Huggers headers? It has rams horn oem manifolds and straight spark plugs. Thanks, Joe.


Sent from my SM-T560NU using Tapatalk
Reply With Quote
  #16  
Old May 15th, 2019, 08:17 PM
jerrspud jerrspud is offline
Junior Member
 
Join Date: Apr 2019
Location: Boise Idaho
Truck: 1963 1500 custom cab
Age: 44
Posts: 14
Rep Power: 6
jerrspud is on a distinguished road
Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by quicksilver View Post
Any idea of what headers to use with a 400sbc in my 60 gmc? Huggers headers? It has rams horn oem manifolds and straight spark plugs. Thanks, Joe.
this is the V6/V12 section of the site.
__________________
Jerr
1963 305 V6 1500

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #17  
Old May 16th, 2019, 03:02 PM
jerrspud jerrspud is offline
Junior Member
 
Join Date: Apr 2019
Location: Boise Idaho
Truck: 1963 1500 custom cab
Age: 44
Posts: 14
Rep Power: 6
jerrspud is on a distinguished road
Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by bigblockv6 View Post
Yes when I had the 305 in my 68 I opened up the intake at the base to match the larger throttle bore of the Holley 500
Quote:
Originally Posted by James View Post
Personally I would make the everything (adapter and manifold) opening the same side as the carburetor throttle bores. I would also radius the lower edge of the manifold as it make the turn toward the runners. This is what I am planning on doing when I get around to do it (to many chores getting in my way).
So what would happen if I left it? I really don't like the idea of destroying the manifold because one day I may want to put the original carb back one. Would it just be less efficient or have running problems?
__________________
Jerr
1963 305 V6 1500

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #18  
Old May 16th, 2019, 04:35 PM
jrmunn jrmunn is offline
Senior Member
 
Join Date: Feb 2013
Location: Davis, California
Truck: 1964 1500
Posts: 125
Rep Power: 72
jrmunn is on a distinguished road
Default Re: 305e Holley 500 swap question

I didn't make any changes to the manifold. Seemed like I needed to rebuild the original carburetor (again), so it was a good time to try the Holley 500. I just bolted it over the adapter. Truck runs fine (better), just a little rich. I have smaller jets, but haven't installed them yet. Except for choke, conversion on my '64 305E was easier than a rebuild. The truck starts easier, which is good for the starter and battery, runs rough until it warms up (probably an adjustment issue), then runs better and with more power - especially at the top end. My main concern is potential to over rev the engine while trying to keep up with freeway traffic, which I have mostly solved with taller tires and 3.54 rear end - and trying to keep in mind that these trucks were not designed to go or stop as fast as modern vehicles. One thing to watch out for is that a backfire can pop off the vacuum port plug at the rear of the carburetor. This causes truck to die at idle and run only at higher rpms.

JRMunn
Reply With Quote
  #19  
Old May 16th, 2019, 07:12 PM
jagarra jagarra is offline
-= Dues Paid =-
 
Join Date: Apr 2014
Location: Reno, NV
Truck: 1962 Custom Wideside SB
Age: 73
Posts: 200
Rep Power: 86
jagarra is on a distinguished road
Default Re: 305e Holley 500 swap question

When I did my swap, I just bolted the adapter on and installed the carburetor. made the linkage work, moved the choke to the right side and I was off. Truck starts easier, runs smoother and best of all the carb is jettable if need be. I went from 1 size smaller jet, back to stock as my mileage went down after going smaller.
+1 on the vacuum port plugs, seems most issues I have had with swap deal with the port plugs disintegrating and allowing air into process. If your mileage or performance takes a sudden dump check them first.
Reply With Quote
  #20  
Old May 17th, 2019, 04:28 AM
bigblockv6 bigblockv6 is offline
-= Dues Paid =-
 
Join Date: Jan 2013
Location: Rohnert Park, ca.
Truck: 1968 KM2500
Posts: 1,278
Rep Power: 368
bigblockv6 will become famous soon enough
Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by jerrspud View Post
So what would happen if I left it? I really don't like the idea of destroying the manifold because one day I may want to put the original carb back one. Would it just be less efficient or have running problems?
Don't think you'll have any problems at, for instance the Magnum Trapezoid base manifolds have a considerably larger opening than the WWC carbs throttle bores.
Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Re: [6066 GMC] 305E & New Holley 500 problem. Archiver Previous Forum Posts 0 August 11th, 2008 10:08 AM
305E & New Holley 500 problem. Archiver Previous Forum Posts 0 August 11th, 2008 02:57 AM
Holley 350 or 500 cfm on 305E Archiver Previous Forum Posts 0 August 21st, 2006 01:32 AM
Holley 500 on a 305E? Archiver Previous Forum Posts 0 July 18th, 2005 02:07 PM
Re: [6066 GMC] Holley 500 on a 305E? Archiver Previous Forum Posts 0 July 18th, 2005 01:23 AM


All times are GMT +1. The time now is 01:29 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2013, Jelsoft Enterprises Ltd 113|0
Feedback Buttons provided by Advanced Post Thanks / Like (Lite) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.