Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

[Gerard F.]

Well,I'm getting down to the assembly, and I figured I'd start with the throttle body and point out a few differences between original and reproduction parts.

Here's my assembly setup:



Geez, have I got enough parts and manuals. The parts on the table are only about half of my cache of Holley parts. It is also very helpful to have an assembled carb sitting in front of you to get the correct orientation of the parts during assembly.

But the primary manual for this assembly of a 67 carb is this tattered 67 Chassis Overhaul Manual:



This manual came with the car when I got it in 68, it was ordered by the original owner from the card in the owners manual. It sat in the jack compartment for many years, as you can probably tell.

However, this 67 Overhaul Manual vs the Service Manual, is the only many that I have found that describes the overhaul procedure particular to the 67 carbs with the non-externally adjustable floats in the fuel bowls. It also has lots of pictures and assembly diagrams of a 67 3810 from which you can tell the original configuration of the carb. Here's on diagram from the Chassis Overhaul Manual:



In preparing for this project I ordered a lot of reproduction parts for parts that I might need. I found that a lot of new reproduction parts are a lot different from the original parts. Here's an example:



If you will notice the three Secondary Throttle Stop screws in the center of the picture, one is a reproduction, one is a screw I made, and one is from an original 65-66 throttle body. On this 67 3810 throttle body I couldn't get the set screw out of the body for the life of me, so I had to drill it out. So I ordered what I thought was a correct replacement.

The replacement came as a #10 X3/8" set screw whereas the original was a #8. ( I guess they figured that once you drill them out, you would retap the hole to a #10).

But the threads were still good on mine, so I made a stop screw from a hardware store slotted set screw (#8 X 3/8") by just deepening the slot and rounding the opposite end. But then I found another vintage base plate with a #8 stop screw which came out easily. So that's the one I used.

(continued next post)

[Gerard F.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

There are also a few other parts that are quite different from current reproduction parts, here's some other examples:



In the top of the picture is an accellerator pump lever adjustment screw, on the left is a repro, on the right is an original. I used the original.

In the lower part of the picture are two accellerator lever studs. The one on the right is a current production with the groove for the C clip on the outside. The one to the left is the original for this base plate, with the groove for the C clip on the inner tang of the lever. I used the original.

Quite a difference in the primary to secondary throttle links:



The one on the bottom is a current reproduction of the link. The one on the top is the link original to this 67 throttle body.

I first tried the reproduction on the throttle body and was wondering why the secondary throttle plates had about a 10 degree movement with the primary throttle closed (and even when I had the secondary stop screw adjusted to 1/2 turn out beyond touching the secondary throttle lever and the the primary idle screw 1 1/2 turns out). I guess the movement could be resolved by bending the link a bit, but I couldn't find any documented adjustment procedure in any of the manuals for this link.

So I used the original and it fit just right with no movement of the secondary throttle plates with the primaries fully closed. Here's the fit of the original:



Here's something to think about. You hear all these complaints about how tough it is to get 3810's and other carbs to idle slowly. Maybe it is the overlooked adjustment of this link, that is the root of these complaints.

On a 3810 with four corner idling, and a .020 pinhole in each barrel below the transfer slot, it would probably be impossible at high vacuum to get the idle down, with a floppy secondary throttle shaft and plates.

Just a thought, I might be all wet.

Here's the assembled throttle body:



Has anyone used gasket compound between the throttle body and the gasket to the main body?

Having fun,

[Erik S.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Jerry - I enjoy reading your post. Although I have another Holley set up (3x2) I have now gained confidence to start the work myself. Very good and detailed pictures are very helpful - thanks!

Erik

[Timothy B.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Jerry,

Everything looks great, I can't wait to hear if this carburetor runs any different than the 3810 on your car at present..

Most base gaskets measure approx .030 +- and I really don't think there is any need for a sealing compound here. With the surfaces flat, the thinner the better for the base gasket. Just make sure the boss for the choke pull off does not hit the main body keeping it from seating flat..

Also, about the red accelerator pump cam color. I think the original of the same cam # is that off white color.. What are you thoughts on this? Seems like the red color is on the replacement throttle shafts..

The screw adjustment for the secondary throttle stop is a great way to admit more air and keep the ideal primary throttle position. We will not get into this except to say on my 3810 I adjusted the secondary stop screw to just touching and 1/8 turn so no sticking. The primarys can then be opened more allowing more slot exposure. At 600-650 idle RPM it's still a horse race.

[Clem Z.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

here are all the holley pump cams with their color,part # and the CCs of fuel for 10 strokes of the pump

[Jack H.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Erik, those who do tri-power restoration services professionally say the number one issue they see is with mating surface warpage. That doesn't mean you can't do the job yourself, it's just a 'heads up' warning that you could buy/install overhaul kit components only to find the carbs act 'flakey'...

If I remember correctly, Jerry Luck told me about 50% of the tri-power restoration work he does is on carb(s) that somebody else attempted to overhaul/rebuild... If true, the warppage issue could be the result of the packing density of a tri-power setup (vs. single 4-Bbl) relative to effective heat dissipation.

[Jim T.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

There are also a few other parts that are quite different from current reproduction parts, here's some other examples:



In the top of the picture is an accellerator pump lever adjustment screw, on the left is a repro, on the right is an original. I used the original.

In the lower part of the picture are two accellerator lever studs. The one on the right is a current production with the groove for the C clip on the outside. The one to the left is the original for this base plate, with the groove for the C clip on the inner tang of the lever. I used the original.

Quite a difference in the primary to secondary throttle links:



The one on the bottom is a current reproduction of the link. The one on the top is the link original to this 67 throttle body.

I first tried the reproduction on the throttle body and was wondering why the secondary throttle plates had about a 10 degree movement with the primary throttle closed (and even when I had the secondary stop screw adjusted to 1/2 turn out beyond touching the secondary throttle lever and the the primary idle screw 1 1/2 turns out). I guess the movement could be resolved by bending the link a bit, but I couldn't find any documented adjustment procedure in any of the manuals for this link.

So I used the original and it fit just right with no movement of the secondary throttle plates with the primaries fully closed. Here's the fit of the original:



Here's something to think about. You hear all these complaints about how tough it is to get 3810's and other carbs to idle slowly. Maybe it is the overlooked adjustment of this link, that is the root of these complaints.

On a 3810 with four corner idling, and a .020 pinhole in each barrel below the transfer slot, it would probably be impossible at high vacuum to get the idle down, with a floppy secondary throttle shaft and plates.

Just a thought, I might be all wet.

Here's the assembled throttle body:



Has anyone used gasket compound between the throttle body and the gasket to the main body?

Having fun,

I have maintained 2 Holley's since 1974 and have not used any gasket compound between the throttle body and the main body. Have you?

[Gene M.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Jerry,
Nice work as always. I just had a small (part) question. The cotter pin securing the secondary link, Is the yellow dichromate finish correct? Natural?

I'm not trying to be picky just never payed much attention to it. Most all replacement cotter pins I noted were not plated as such. I do have some small brass cotter pins in my collection.

[Gerard F.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Jerry, .................................................. ........................................

Also, about the red accelerator pump cam color. I think the original of the same cam # is that off white color.. What are you thoughts on this? Seems like the red color is on the replacement throttle shafts..
.................................................. ....................................

Tim,

The primary shaft I took off this original throttle plate from 3810 751 had a pump cam which was red. Doesn't mean it wasn't changed at one time, but the Holley Parts Catalog I have from just a few years ago indicates the 240 pump cam (which is the red cam in Clems chart) as correct for a 3810.

Could be they have changed for the later replacements(which also have red pump cams), but all evidence points to the red cam being used on originals.

Does anyone out there have an unmolested 3810 with a white pump cam?
Inquiring minds would like to know.

Thanks for the pump cam chart, Clem.

[Gerard F.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Jerry,
Nice work as always. I just had a small (part) question. The cotter pin securing the secondary link, Is the yellow dichromate finish correct? Natural?

I'm not trying to be picky just never payed much attention to it. Most all replacement cotter pins I noted were not plated as such. I do have some small brass cotter pins in my collection.

Gene,

You caught me The cotter pin I finally used was a brass one from a Holley small parts kit. Also notice the brass washer below the cotter pin (also from a Holley small parts kit), that you usually don't see on replacement throttle bodies. But a washer was on the 67 Overhaul Manual Assembly drawing, so I used it.

If you notice photos 1 & 2, from the second of my posts above, you will see two bent up cotter pins in the photo. The crudy one on the left was the one on this original thottle body when I disassembled it, it goes with the original link I used. It is zinc dichromate.

However, I have one replacement cotter pin (in the envelope in the photo) for a 64-72 which is natural or dull zinc plated. But then again, I have another replacement from a correct carb kit labelled 64-67 which is zinc dichromate.

So who knows which is correct. I think I'll replace the brass one with the 64-67 zinc dichromate one.

Isn't it funny how we get interested in all these small details
You NCRS guys did this to me.

But having fun,

[Clem Z.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Quite a difference in the primary to secondary throttle links:



The one on the bottom is a current reproduction of the link. The one on the top is the link original to this 67 throttle body.

I first tried the reproduction on the throttle body and was wondering why the secondary throttle plates had about a 10 degree movement with the primary throttle closed (and even when I had the secondary stop screw adjusted to 1/2 turn out beyond touching the secondary throttle lever and the the primary idle screw 1 1/2 turns out). I guess the movement could be resolved by bending the link a bit, but I couldn't find any documented adjustment procedure in any of the manuals for this link.

So I used the original and it fit just right with no movement of the secondary throttle plates with the primaries fully closed. Here's the fit of the original:

.



there are 3 different length pri to sec links,4160/4010,4175/4011 and 4150 carbs

[John M.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Jerry,
When I bought my 67 it had a replacement carb on it and the owner, first owner, had saved the original carb. It has a white cam for the accelerator pump. I think its very unlikely that he would have changed it before he changed the carb.
It's not really white, kind of yellowish like original windshield washer tanks look.
John

[John M.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Eric, Re the Tripower.
I have a fixture that I attach the carb to that allows me to hold it in a milling machine so that I can true up the surfaces removing the absolute minimum amount of material. I don't know what would constitute to much warpage to do this but I have had good luck on two center carbs with this simple fixture.
You could easily make one of them.

[Clem Z.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

carb aluminum throttle base plate can be straighten by using a proper clamping fixture and putting them into a oven. this is the way aluminum heads with the camshaft in the head are straighten if they are bowed because just milling them will not solve the problem as the cam bore will still be out of alignment

[John M.]

Re: Holley Carb Restoration-Part 11-Throttle Body Assembly-Part2

Clem, The fixture I'm talking about is for the main body where the metering block mates up. I see your point re the base plate.
John