305e Holley 500 swap question

[jerrspud]

Originally Posted by jbgroby

Because I had a '60, I had to create this linkage. Works perfect.

Originally Posted by jerrspud

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

[jerrspud]

Originally Posted by bigblockv6

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?

[James]

Originally Posted by jerrspud

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).

[bigblockv6]

Originally Posted by jerrspud

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

[quicksilver]

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.


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[jerrspud]

Originally Posted by quicksilver

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.

[jerrspud]

Originally Posted by bigblockv6

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

Originally Posted by James

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?

[jrmunn]

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

[jagarra]

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.

[bigblockv6]

Originally Posted by jerrspud

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.