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Old 05-22-2020, 01:38 AM
topfuel67 topfuel67 is offline
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Default End carb base issues

I am in the process of restoring my carbs for my 66 GTO. Both of my end carb bases are pitted pretty bad where the throttle blades seat. I have used dag 213 on previous end carbs, but they weren't pitted. I am also missing the throttle blades. Are there slightly larger blades and can I bore the bases out a bit? Or will the correct size allow a slightly larger bore? Also the throttle shaft levers have a tiny bit of play where they're pressed onto the shafts. I tried tapping on the center where its pressed but its not helping and feels like I'm going to end up breaking the mushroomed part thats holding it. Is that play okay? I'm not sure if these bases are worth continuing with if I need shafts and blades. Or just cheaper to find another pair.

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Old 05-22-2020, 02:10 AM
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Old Man Taylor Old Man Taylor is offline
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You can buy new ones. That's what I did.

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Old 05-22-2020, 08:48 AM
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Dick Boneske Dick Boneske is offline
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What you describe is fairly common in carb throttle bodies from some parts of the world. I have never seen cast iron bases that could not be restored for acceptable performance. Yes, sometimes it is necessary to replace the throttle plates, but only if the edges are pitted and/or the flat surface is very badly corroded. But, with DAG 213 and some judicious polishing, the throttle bodies can be made whole again.

Regarding the throttle levers being loos, this too can usually be fixed with red Locktite and the right sized punch and hammer. This is, however, risky until you have done a few and know exactly how to set up the pieces so they are not damaged by re-swaging the end of the shaft. If the end of the throttle shaft is damaged, a 8-32 screw and drilling/tapping the end of the shaft can nearly always remedy the problem.

If you want, I'd be happy to restore the bases for you. PM if you want to pursue that.

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Old 05-22-2020, 12:06 PM
topfuel67 topfuel67 is offline
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I will try boring them out a little more. I don't have any of the thick blades though. Will the stock size still work if I bore out? Are there over sized blades. I guess I need to bore it and then measure. I will try re-swagging them and drill/tap if that doesn't work.
Thank you for the replies.

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Old 05-22-2020, 06:25 PM
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Dick Boneske Dick Boneske is offline
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I've not seen oversized throttle plates. Ames sells standard end carb throttle plates for $29 a pair. For $58, you've got bot end carbs covered.

You cannot use thin plates because of the slot width in the end carb throttle shafts.

Remember, all that matters is the perimeter of the plate. Pits in the surface have no effect on performance. A little careful fitting and DAG213, and you'll be set!

Here are a few of the 21 carbs I did last week.
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Old 05-22-2020, 09:55 PM
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We made a couple of dozen oversize plates many years ago for our own use. I never needed DAG-213, ESPECIALLY after a few conversations with John Sawruk.

Not at all difficult for a good machine shop to fabricate the oversize plates. But not worth the effort for only 1 or 2 pair. We made them 0.005 and 0.010 oversize.

No, don't have any left.

Jon.

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Old 05-22-2020, 11:24 PM
topfuel67 topfuel67 is offline
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So I got one of the bases honed out nice. The blades fit with plenty more room to go. The second one is pitted pretty bad. I used a brake cyl hone on a drill press. I'll try a coarser stone. Thanks again for the tips and reassurance.

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Old 05-23-2020, 11:38 AM
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This thread reminds me of the change made in 1964, when the end carb throttle plates had the .028" holes added. Rochester engineers had a reason for doing this. Since those people are not available to answer questions today, we can only guess the reason for the questions we have about Tri-Power carbs.

With no holes in the throttle plates, under normal driving conditions, the end carb throttle plates are closed, resulting in zero gasoline flow out of the fuel bowl. Every time you shut down the engine, some of that gasoline evaporates through the air horn vent--about a 3/16" hole. If the end carbs are not opened, and as gas evaporates, the non-volatile ingredients (varnish) become more concentrated and eventually form a gummy residue inside the carburetor.

With the .028" holes, there is some gasoline drawn by vacuum through the holes into the engine. The holes are small enough so that this flow is insignificant and has little effect on operation of the engine. That flow does, however, provide a minute amount of gasoline flow into and out of the float bow., ensuring that little or no varnish collects in the end carbs.

I think the above explains why, beginning in 1957 Pontiac Tri-Powers, Olds' J2, '58 and up Chevrolet triple carbs, and '58-'60 Cadillac three carb setups got a bad reputation. Most of the owners of three carb GM cars were older people, especially with Olds' and Cadillac. After a few months of daily use, where these drivers seldom, if ever opened the end carbs, they became badly gummed up, eventually causing a visit to the dealer because the car didn't run well--or at all. After a few of these experiences, many of these owners said "Take that thing off my car and put a four barrel on it!" I also believe that's why three carb setups were so plentiful in the late '50
s and '60's.

Today, however, most of us regularly "exercise" our end carbs, so the above "gumming up" is not an issue.

That's just my theory. Tell me what you think. I've been adding those /028" holes to all the Tri-Power end carbs I restore.

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Old 05-23-2020, 03:31 PM
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I think they added the holes to pull fumes wich would otherwise gum the blades.
Also, i have found Pontiac changed the throttle body gasket from being vented to a closed gasket at the same time the .028" appeared.
With closed gaskets the fumes did not escape like with the vented gasket and to get the fumes off of the blades holes were drilled in the blades.
With vented gaskets dirt might have entered the venturi, better with holes in the blades? No dirt and still get rid of the fumes!
I donīt think the tiny .028" holes will pull any fuel from the main circuit i the end carbs.
Think about the larger holes in the A/T center carbs, how much fuel wouldnīt those pull? None that iīm aware of.

JMHO

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Old 05-23-2020, 03:48 PM
topfuel67 topfuel67 is offline
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That makes sense. I have been using a single strand from a wire to clean those holes out.
I found an extra set of thick blades and I have another base I previously restored. So I just need to order some dag213 and I'll have my tripower finally on my car.
That just reminded me of a post I read in this section a while back recommending copper crush washers for the fuel inlets. I need to get those too.

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