[Alizar]

I just installed a Holley Sniper (550-510) with square bore flange on my 1966 Bonneville with a stock 421. The spread bore mounting flange on my intake manifold doesn't quite match up to the ports on the Sniper and as a result I'm getting a vacuum leak. I called Holley tech support and they recommended part 520-2 (sealing plate) but I'm not sure that will work since it appears to be 4 holes of the same size, and my front holes are 1/8" smaller. I would just give it a shot, but there isn't much sealing surface on the stock intake manifold. I have found adapters for quadrajet manifolds, but I don't think those will work either since those hole sizes appear to be different too.

Has anyone mounted a Holley Sniper to a Stock 66 intake manifold? If so what adapter did you use?

[steve25]

Transdapt makes a 1/2” adapter # 2062 that sounds like it will work for you.

[tom s]

might look into a factory AFB intake,they go VERY cheap,used on 65-66 and big car 67s.Tom

[steve25]

This is the iron intake he already has, no?

[Alizar]

Originally Posted by steve25

Transdapt makes a 1/2” adapter # 2062 that sounds like it will work for you.

Thanks. I'm not sure the 2062 is correct for me, but they have a really good chart. I'm just not sure if my intake manifold falls under the "Quadrajet" or the "AFB/Large Rochester" category. It's for a Carter AFB, so I'm guessing that's it, but the primary and secondary ports are different size like the Quadrajet. They just don't seem to be as big of a difference as the quadrajet.

[Alizar]

Originally Posted by tom s

might look into a factory AFB intake,they go VERY cheap,used on 65-66 and big car 67s.Tom

I already have this one, just trying to figure out how to mount the sniper to it. The flanges bolt up, I just can't get it to seal because the sealing face on the manifold is so small.

I have been thinking about going to an aluminum intake manifold at a later date. I'd consider doing that now, but the Edelbrocks all seem to be out of stock. Also not sure they are worth it on a street car (cruiser).

[steve25]

The secondary bores on a Q-jet intake are near 2.250” in diameter.

[tom s]

they make simple AFB to holley adapters.QJ intakes just dont adapt well to square bore intakes.JMHO,Tom

[tom s]

The factory AFB intake has smaller primary opening.The QJ has WAY small primary and huge secondary.I actually have the AFB intake in my cabinet.Tom

[tom s]

this is the one you need if you have a AFB intake.Tom
https://www.ebay.com/itm/Carb-Carbur...-/391429722314

[Alizar]

Originally Posted by tom s

this is the one you need if you have a AFB intake.Tom
https://www.ebay.com/itm/Carb-Carbur...-/391429722314

Thanks. That one looks close. I actually got it working, but I know what I did isn't preferred. I made my own spacer by stacking three gaskets and it seems to be running fine and the throttle valves now open 100%.

In case it helps anyone else, here are the port measurements I got:
Manifold: Primary - 1 9/16" / Secondary - 1 11/16"
The stock AFB carb I removed was: Primary - 1 3/8" / Secondary - 1 5/8"
The Holley Sniper was 1 11/16" on the primary and secondary.

With just one gasket, the Sniper was too close to the manifold and the throttle valves would only go to 95%. I now think the sealing plate the Holley recommended would work. The size difference on the primaries is so minor, I'm not sure it matters for a street cruiser other than it doesn't give much sealing surface for the gasket. I may just run it this way until I rebuild the engine and then decide if I want to go with a different manifold.

This is my first time swapping carburetors. I always thought they were relatively universal, but now I know better. Thanks for the tips.

The Sniper was a PITA to install, but throttle response is dramatically better. Top end feels about the same, but out of the box the car drives better than it did on the carb.

[NeighborsComplaint]

I thought the sniper needed a single, open plenum under all 4 venturis?

[Formulajones]

They have made the steel plate to adapt a square bore holley to Q-jet manifolds for decades. I used to run them for many years on stock performer Q-jet manifolds when switching back and forth to a Holley square bore as far back as the mid 80's that I can remember.

It's just a simple steel plate with a small kick out to seal the back of the manifold where the Holley doesn't cover that well, and a pair of gaskets on either side. Very simple deal and cheap. I have them hanging on the wall out in the shop.

Here is just one example....made by many companies. I think the old ones I have are Moroso.

https://www.holley.com/products/engi...ies/parts/9006

[NeighborsComplaint]

Is this the intake you're using?

[68WarDog]

Originally Posted by NeighborsComplaint

I thought the sniper needed a single, open plenum under all 4 venturis?

That's exactly what we were told, and I'm going with the Holley 1250 stealth super sniper. I have eliminated the 1" 4 hole Wilson taper spacer on the single plane Torker 2.

[Formulajones]

We are running 2 snipers, on a 600hp and 700hp engine.

The 600hp setup is an rpm air gap dual plan intake and the 700 setup is a single plane Victor with a 4 hole super sucker taper spacer.

The Sniper works perfectly fine on both.

[68WarDog]

Originally Posted by Formulajones

We are running 2 snipers, on a 600hp and 700hp engine.

The 600hp setup is an rpm air gap dual plan intake and the 700 setup is a single plane Victor with a 4 hole super sucker taper spacer.

The Sniper works perfectly fine on both.

FJ, I think when we go to the dyno, I will try the sniper with and without the 1" Wilson 4 hole taper spacer to see what if any difference .

[Formulajones]

Originally Posted by 68WarDog

FJ, I think when we go to the dyno, I will try the sniper with and without the 1" Wilson 4 hole taper spacer to see what if any difference .

I honestly don't know how the Wilson spacer, if at all, affects the Sniper but engines with single plane intakes sure seem to like that particular spacer. Those 4 hole Wilson taper spacers rock. When dad's engine was dyno'd with a carb, it was worth something like 20 or 22 hp. I'd have to go back and look at the dyno sheets but it was a significant improvement for a 2 minute bolt on.

So when he switched over to a Holley Sniper Stealth setup, of course he didn't want to remove that spacer. The Sniper has been fine with it.

I run the RPM air gap intake on my engine and the Sniper works really nice on that deal too.

There may be guys out there that complain about dual planes with these throttle body EFI setups, but I just haven't experienced any issues myself, on 2 different engines that make pretty good HP.