Tunning my 780 holley - Team Camaro Tech
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post #1 of 8 (permalink) Old May 24th, 02, 02:36 AM Thread Starter
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I bought a 780 holley 4150 vaccum secondary carb (3310-1) at a swap meet last weekend. I was looking for something smaller to put on my small block but that one was in good shape and it's only 30cfm more than a 750.

The only performance part that is on now is an Holley aluminium intake on a small block bored to 355. I plan on adding more horses in the future.

I'm I looking for trouble?

Can I tune this carb up or is this a waste of time and money?

It curently has 69 primary jet and 72 secondary.
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post #2 of 8 (permalink) Old May 24th, 02, 05:04 AM
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The fact that it's a vacuum secondary carb is going to help you alot. You can change the secondary springs. A heavier one now will keep it from bogging out and a lighter one later after some changes will wake it up. Also it has a secondary jet plate which makes tuning easier. The primary accelerator pump is also tuneable as well as the power valve. I think you did all right.

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post #3 of 8 (permalink) Old May 24th, 02, 05:12 AM
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Ben,

That 780 is most likely a bit more carb than you need. The good thing is it's very forgiving because of the vacuum secondaries.

Get a rebuild kit, stock jets and accelerator pump cam and squirter and rebuild it back to Holley spec's. Also get a quick change spring kit for the secondaries. Once you have it back to factory spec's it will be very easy to tune for your application... For refrence you might want to weed through www.holley.com and find their FAQ anf Tech Reference pages...



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post #4 of 8 (permalink) Old May 24th, 02, 06:10 AM
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The above replies from 1 2RUN and DjD are excellent and will get you off to a good start with this carb. I would also add to carefully check the throttle shafts for wear and looseness, this is common in these older carbs and can lead to idle and other problems. The bores can be bushed (and seals added if wanted)to original size and the shafts are easy to replace if necessary, or you can get a complete replacement base assembly. You can purchase Manual, Electric, Manifold ('stove heated') and Divorced type chokes to fit these carbs.
These are great carbs and are easy to tune to meet your needs as you increase the mods on your engine. I still run one I bought new in 1969.
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post #5 of 8 (permalink) Old May 24th, 02, 06:10 AM
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Also do a 'search' using the word Holley in this section and you will find excellent posts on tuning a carb. Read them all. Ive copied and pasted the best ones to my 'notepad' and printed them so they are next to me when I overhaul my Holley soon.
There are some real experts in here with great ideas.
click

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post #6 of 8 (permalink) Old May 24th, 02, 06:11 AM
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Sorry Click - great idea too! We posted at the same time.
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post #7 of 8 (permalink) Old May 24th, 02, 06:30 AM
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post #8 of 8 (permalink) Old May 24th, 02, 08:14 AM Thread Starter
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Thanks for the info, I'll look into the links.

So It's not the best carb for my application but it will work fine once it's tuned-up.

I ordered the gasket renew kit this afternoon.
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