Holley 3810 Vacuum Secondary Diaphragm

[Michael M.]

[Patrick B.]

Re: Holley 3810 Vacuum Secondary Diaphragm

I think the diaphram is the same for all Holley 4bbls including the common 3310. Chicago Corvette supply has a lot of real Holley components, but the Summit ones should also work.

[Joe L.]

Re: Holley 3810 Vacuum Secondary Diaphragm

Can anyone tell me which replacement vacuum secondary diaphragm is correct for a Holley List 3810 or if one is even available? I’ve checked out the Holley and Summit websites and none of the replacement applications list the 3810.

I guess my next step is to pull the old one out and measure the rod. I assume the measurement is taken from the diaphragm base to the center of the hole?

Thanks in advance for your help.

Michael------

These should be easily available from suppliers carrying Holley SERVICE parts. The original Holley part number, which may or may not still be in use, is 35R-235A.

If you want an original GM piece (which was, of course, Holley manufactured), here it is:

http://www.ebay.com/itm/64-72-Chevrolet-Holley-Carburetor-Diaphragm-NOS-3852474-/221294031916?hash=item338626f42c&vxp=mtr

[Michael M.]

Re: Holley 3810 Vacuum Secondary Diaphragm

Joe – thanks for the info but it looks like Holley part number 35R-235A is no longer in use. I would also be reluctant to use a 40+ year old NOS rubber carburetor part in a car I drive quite a bit.

My dilemma is there appears to be at least 3 current Holley part numbers available for 4BBL carburetors, but nothing specified for the List 3810. The diaphragms appear to be the same, just different rod lengths.

Holley # 135-2, rod length 2.047”
Holley # 135-3, rod length 1.97”
Holley # 135-4, rod length 2.054”

As you can see the range in length is .084” with two only .007” apart. Since my first post, I have measured my old diaphragm rod with calipers (from the base to center of hole) and I believe the # 135-2 would be the best fit. I also have an inquiry into Holley but haven’t heard back yet.

I was just hoping someone might have run into the same issue?

[Gerard F.]

Re: Holley 3810 Vacuum Secondary Diaphragm

Mike,

You should contact Chicago Corvette for the part;

Located here:

https://chicagocorvette.net/

You can download the C2 catalog, order the part or call them. In the past, I have found the best way to order a part is to call them and give them the part number from their catalog.

The part you are looking for is their part number B1541. listed at about $20.
The diaphragm is the same for all 64-67 4160 Holleys

[Gerard F.]

Re: Holley 3810 Vacuum Secondary Diaphragm

Also Mike, Chicago's Super Carb Kit includes the secondary diaphragm

[Joe L.]

Re: Holley 3810 Vacuum Secondary Diaphragm

I would also be reluctant to use a 40+ year old NOS rubber carburetor part in a car I drive quite a bit.

Michael-------


I agree. However, some folks just want NOS regardless. In the vast majority of cases, it's the best choice. In cases like this, though, it might not be. Nevertheless, I really think you would be surprised at just how supple the elastomer of this old part would be. By the way, it's not necessarily 40 years old as this part was available in GM SERVICE for quite some time. I've got one in the collection [not for sale]. When I get a chance I'll dig it out and see what it looks like.

[Michael M.]

[Joe L.]

Re: Holley 3810 Vacuum Secondary Diaphragm

Here's an NOS GM #3852474 I dug out [not for sale]. The elastomer component is still very supple with no signs, at all, of any deterioration. I don't know how old this one is, though.

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