I just found another carb at the house. It's a 4749-2. But I can't find any info on it, on the web.

 

You need to double check the number. The only 47X9 is a 4779 and it is a 750CFM.

 

I have a question on this. I hear everyone talking about 600cfm being all you need for a 390fe. I currently have a 750cfm, but it's a pieced together mess. I have the option to buy a 600cfm holley for $150 or a 3310 750cfm for $50. I don't know which one to pick? I have a stock 390 with headers, which one would you pick?

 

Your stock 390 wont require any more air/fuel than the 600 can provide.

 

I thought you figured needed cfm by 1.5 x hp
if his stock 390 with that mild port and polish with headers is up to 300hp then
1.5 x 300 = 450 cfm, so with formula he has enough carb.

 

Actually the chart can be found here that is used by Holley.

http://www.holley.com/TechService/Library.asp

Go to the second "selecting a carburator" and they have a chart or Ford uses the formula:

CFM= (RPM X CID) divided by 3456

This gives a rough number that will work. If you are real picky you can figure out the effeciency of your engine and factor that in, but the base formula will work for a street motor just fine.

Example;

6000 X 428 = 2568000 divided by 3456 = 743 and Ford used a 735 on their 428CJ.

 

Thanks Bear, Thats a good read. I just did my engine with 5000 x 393 = 1.965.000
Div. by 3456 = 568.58 I,m over carbed with a 600 lol Thanks again Bear

 

The vacuum secondaries will cover that without a problem. The 600s always worked well on the 390s. Whether they were GT motors or not.

 

Somone here noted that O-3310 has not changed through it's history. That statement is erroneous - - fancy word for wrong. The early/original 3310s were 4150 models with downleg boosters. As the got more popular - - and cheaper - - Holley decontented them. Later iterations went to less efficient straight leg boosters (hence the cfm reduction), and became 4160 non-metering block models. As each change and cheapening occurred a "-1, -2, -3" iteration was added to the base number. An early 780 cfm 3310 is a very good carb. A newer 3310 is OK, but not in the same league...

I worked at Holley for eight years. I have photocopies of several of the original hand written part number and airflow assignment book pages - but the part in the original question is not in my collection.

 

I never said the 3310 has never changed..

Here is what I said:
The 780 has remained virtually unchanged since it's 735/780 days...Now it's actually downgraded to a 750 cfm....they did not change a thing when they down rated it from the 3310 to the 3310-1/-2...it was smply a marketing ploy!!

You are right about it changing from a 4150 to a 4160...I always converted mine back to 4150's..

I meant virtually unchanged as in the venturi size and bores.


What I meant was that at one point they made a 3310-2 4160 that was then called a 780...Then all of a sudden it changed and was sold as a 750 with the same 3310-2 part number!

Now when you look up on their list, they dont even show a 3310-2 as a 780...they call it a 750!
I bought many many 3310-2 780's!!
They show the only 780 was a 4150...This is NOT TRUE...The original 3310-2 was a 780 4160!!

The first 750 3310 was introduced after the 3310-2..
That is what I meant by there no change marketing ploy!

 

How's this one look. This guy has two on ebay. One has the plastic vacuum housing and plastic man. choke linkage, and the other metal. What's the difference? The plastic one newer and made in Taiwan?

http://cgi.ebay.com/ebaymotors/ws/eB...3ARTQ%3AUS%3A1

Mike

 

The new carbs have the plastic because it is cheaper to make. Where they are made? I couldn't tell you, but the work the same. Some of the plastic ones have a quick change feature that let's you change the spring easier.

 

So this one would be a good one on the ol stocker 390? I think I'm gonna buy her... The only thing that si worrisome, is the fact the the plastic clamping for holding the man. choke cable.

Thank for the info.

 

The 0-3310 is, as far as I know, the only Holley carb to have retained it's list number despite a major cfm change and a model series change from a 4150 to a 4160. Normally a model change or a booster change calls for a new list number. Definitely a marketing ploy there. The -1, -2 is normally used to ID an engineering change - - which could be visual or functional - - like adding those plastic parts, or altering jetting.

(the "O-" numbers are referred to as list numbers, and are used for marketing and sales, the "R numbers stamped on the carbs and parts are engineering numbers. This two number system allows them to alter the part in the box without needing to change pricing or inventory systems).

The plastic stuff first appeared in around '90 or so. The plastic choke shafts blew apart so they went away from those in about 6 weeks. That plastic choke holder did break off easily if the cable got kinked or stiff - - it lasted a few years in production. Its easy to grind the nub down and retrofit a steel holder in it's place...