Re: 305e Holley 500 swap question
 

https://6066gmcclub.com/attachment.p...9&d=1557493862
I found the number

https://www.holley.com/products/fuel...age/parts/9678
THROTTLE RETURN SPRING KIT
Fits Holley
PART# 9678

Re: 305e Holley 500 swap question
 

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?

Re: 305e Holley 500 swap question
 

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).

Re: 305e Holley 500 swap question
 

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:thumbsup:

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.
https://uploads.tapatalk-cdn.com/201...ecaa8dcba2.jpg

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Re: 305e Holley 500 swap question
 

this is the V6/V12 section of the site. :thumbsup:

Re: 305e Holley 500 swap question
 

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?

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

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.

Re: 305e Holley 500 swap question
 

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.