Holley model 4160, series 3310 carbs

[patrickt]

Originally Posted by dcdoug

I was told that it was probably enough to do it annually and is on my list to do soon. My vacuum does seem quite low though. Thought non-emissions engines should be at 10 inches at least.

The "once a year" only applies after you've adjusted them for the first time, say around 1500 miles. Your valve are probably a good bit out of adjustment, but after you adjust them you can then do them once a year or maybe even less often than that. But there's a big difference between zero to 1500 miles and 1500 to 3500 miles when it comes to your engine breaking itself in.

[dcdoug]

Originally Posted by patrickt

The "once a year" only applies after you've adjusted them for the first time, say around 1500 miles. Your valve are probably a good bit out of adjustment, but after you adjust them you can then do them once a year or maybe even less often than that. But there's a big difference between zero to 1500 miles and 1500 to 3500 miles when it comes to your engine breaking itself in.

Sounds like a rookie move to me.

[patrickt]

Originally Posted by dcdoug

Sounds like a rookie move to me.

Adjust the valves, adjust the idle mixture screws, double check the timing, and your car will be perfectumundo.

[dcdoug]

On lash adjustment - hot or cold? I know that most say hot, but I have also heard that you can do it cold.

[patrickt]

Originally Posted by dcdoug

On lash adjustment - hot or cold? I know that most say hot, but I have also heard that you can do it cold.

Your engine builder should have provided you with the valve lash specs and whether or not they are at HOT or COLD. Guys do them both way, but the lash will be different on hot than cold, even on the same engine. Personally, I adjust my valves COLD to .018 -- that's with an iron block and aluminum heads. The iron/iron, iron/aluminum, aluminum/aluminum all have different variations in the hot to cold lash relationship. If you don't have the specs from your builder, give him a ring and ask him what you should set your valves to and whether that number is hot or cold.

[dcdoug]

Originally Posted by patrickt

Your engine builder should have provided you with the valve lash specs and whether or not they are at HOT or COLD. Guys do them both way, but the lash will be different on hot than cold, even on the same engine. Personally, I adjust my valves COLD to .018 -- that's with an iron block and aluminum heads. The iron/iron, iron/aluminum, aluminum/aluminum all have different variations in the hot to cold lash relationship. If you don't have the specs from your builder, give him a ring and ask him what you should set your valves to and whether that number is hot or cold.

He said you can do it cold and told me to give him a call when I was going to do it, so I'll do that.

[StanJ]

::: Commenting on various points in this thread...no particular order :::

Yes, the original #3310 carbs were rated at 780cfm. They had a metering block on the rear (although still a "two corner idle" carb) and were equipped with down-leg boosters. As with all #3310's, the diameter of the primary venturii was/is 1.375", while the secondary venturii measure 1.437", the throttle bore diameter of both the primary and secondary is 1.687".

As Patrick pointed out, when Detroit stopped using the #3310 and it's variants for OEM applications, Holley found it necessary to reduce production costs in order to justify keeping the #3310 in their product line at a time when nearly everyone with a race car was convinced they needed a mechanical-secondary double pumper. Also, from a simple marketing standpoint, Holley didn't really want customers who did actually need a mechanical secondary carb getting stuck on the idea that the additional 30cfm of airflow capacity of the then-780cfm #3310 over the more competition oriented #8156 double pumper trumped all other factors. The change to the more restrictive straight-leg style booster -- and the attending loss in airflow capacity -- was made for this reason. Aside from some cosmetic changes...and one major retooling of the production casting dies made in 1992...the #3310 has remained largely unchanged since then.

Unless specifically prohibited by class rules, we use a metering block on the rear of every vacuum-secondary carburetor we build for several reasons. Ease of tuning due to removable jets (and idle feed restrictions if the metering block is machined for them) is the obvious first, but also:

Compared to the current "metering plate", a metering block's ability to efficiently emulsify main-circuit fuel before it is discharged into the venturii is far better -- the average diameter of the discharged fuel droplet on the rear of a #3310 equipped with a metering block is roughly one quarter of that on a "stock" #3310.

The use of a metering block also make possible the use of a power valve in the secondary side of the carburetor. In all but the hardest-leaving drag race applications, this is a very good thing as it allows much more control of the air/fuel ratio during part throttle conditions. It is important to note here that the main bodies of "new style" (1992 and beyond) #3310's do not have a cavity in the rear metering face for the head of a power valve to reside in, and therefore require additional machining to accept this addition.

Finally, use of the proper-style metering block allows the carb to be set up as a "four corner idle" unit, with each venturi/throttle bore having it's own separate curb idle fuel circuit rather than the rear venturi having to "rob" fuel from the primary venturi idle circuits through a much-tortured (read: slow to respond) route. This is extremely important from a throttle response standpoint when you get into moderate-and-beyond performance applications, since absent a rear accelerator pump as a means of momentarily introducing additional fuel into the airstream as the secondary throttle blades open, the rate of secondary throttle opening cannot be allowed to outrun the idle/transition circuits ability to respond without causing a lean "bog". As an added benefit, this type of curb idle fuel circuitry makes it much easier to calibrate for bog-free operation that is also "sniffer friendly" at emissions test time. For me personally, 4ci on a Holley four-barrel carb is kind of like American Express -- don't leave home without it.

When properly built and calibrated, a #3310 carb makes an extremely strong and responsive carb for serious street applications.

Stan Justus
Stallion Racing Components