Slant Six Forum
https://slantsix.org/forum/

Offenhauser 4 Barrel Intake to Weber 2 Barrel Adapter
https://slantsix.org/forum/viewtopic.php?t=62391		 Page 1 of 1
Author:  Leaning Dusty [ Wed May 23, 2018 1:20 pm ]
Post subject:  Offenhauser 4 Barrel Intake to Weber 2 Barrel Adapter
Good afternoon Fellow Slanters,

So according to the shop my less-than-1,000-mile Edelbrock 500 4-barrel carb crapped-out on me, but since I still don't have the bigger valves, larger bore, or cam in my car, I decided to get a Weber 38/38 2-barrel to play around with. Apparently there are several 4-barrel to 2-barrel adapters out there, however I'm still waiting on the carb to arrive, and now I'm not sure the adapter I got will work for me.

I have a Mr Gasket 1933 adapter, anybody have luck with one of these and a Weber DGES 38/38, or do you know where I can get one that will work for my application? I read several people running adapter plates with their setups, but nobody posts what adapter they are running.

Additionally, the Offy 4-barrel has 4 ports on the top plenum and mounting plate, does anybody know if I would have to machine the center part out to run the Weber 38/38, or if it's enough to replace the mounting plate with an adapter that creates a little extra space under the Weber before going through the 4 holes on the plenum?

I made the mistake of calling Clifford Performance to ask them about their adapter for their 6=8 manifold, and their tech was just blanketly telling me how much better their manifold is compared to the Offy which is why their intake creates "an extra 50 horsepower" :roll:... anyway, since they did not want to confirm their bolt pattern, anybody here who actually has one of their intakes have any input on the bolt pattern, their Weber adapter, and or any other Weber 2 barrel adapter?

Thank you to anybody with input, as always!
Author:  Leaning Dusty [ Fri Jun 01, 2018 8:05 pm ]
Post subject:  Re: Offenhauser 4 Barrel Intake to Weber 2 Barrel Adapter
In case anybody cares, I was able to adapt the Weber DGES 38/38 to my car with the use of 2 adapter kits, but still working on the linkage for the throttle and kick down (since my shop managed to pull apart my Lokar cable kits and left half in the car and the other on the old carb... instead of just unbolting them).

The Offy intake is designed for a single 4-barrel carb and has the 4-hole center plenum which would block flow from the Weber if it was bolted down directly on top of that (with the 2 ports opening directly over the center divider of the 4 ports on the manifold... which was the argument Clifford tried to make), so the issue is that you need more open space to atomize the air/fuel properly without half the port area being essentially blocked-off by a built-in restrictor plate. I was able to get around this by using a 2-barrel to 4-barrel adapter which has a single open port/spacer, then using another kit to convert the bolt pattern from Edelbrock/Holley to Weber... except instead of going from 2 barrel to 4-barrel, I went the other way.

I debated modifying the 2-barrel to 4-barrel adapter to use it by itself, but unfortunately the 2-barrel part of the adapter was too wide at the base and would not clear the linkages on the Weber DGES without some serious grinding, and then you would still have the problem of the adapter not having the correct bolt pattern for the Weber (it's designed for a Holley).

This is where another adapter kit was used to convert from a 2-barrel Holley to a 2-barrel Weber bolt pattern.

The kits in question are:
- Mr Gasket #1933
and
- Omix-Ada 17704.03 <- Typically used on Jeeps

To bolt the Omix-Ada kit on the Mr Gasket kit I had to get longer carb bolts (about 1/4" longer if I remember correctly) attached with nuts at the bottom and plenty of red thread locker. It's a 2-piece adapter, where the bottom piece has the Holley bolt pattern and the top piece has the Weber bolt pattern (compatible with 32/36 and 38/38 carbs).

To mount the Mr Gasket adapter onto the manifold I had to get completely differently-threaded (from "fine" to "coarse") bolts and nuts which were way shorter than what came in the Mr Gasket kit to keep them from bottoming-out. I used the washers that came in the kit.

I should have this thing up and running by early next week, so let me know if anybody wants to see pictures of the setup.

I wanted to do it this way so that I could have the option of going back to 4-barrel carb or TBI once the rest of the engine is built-up more, and I've had enough trouble with leaky intake/header gaskets to not want to make my current non-leaky gasket leak again.

With all parts required this costs around $100 with gasket material and thread locker included, but also several hours fiddling with it and liquid gaskets (the paper ones I had were not port-matched very well, so my OCD kicked-in :oops:)... you could probably do it for cheaper and with less time wasted, but I'm just sharing.

If anybody has a better/cheaper setup, let me know!

Why not just run a Holley and be done with it using one adapter plate?! <- Is the smart question... my answer is that I got a great deal on my Weber (I want to say it was about $145), and it seems to be perfectly matched for my mostly stock motor. The other benefit is that now there is equivalent of roughly a 4" spacer under the carb which should maybe do something, while still fitting under the hood of my '72 Duster.

*fingers crossed*
Author:  DusterIdiot [ Fri Jun 01, 2018 8:59 pm ]
Post subject:  Re: Offenhauser 4 Barrel Intake to Weber 2 Barrel Adapter
Quote:
If anybody has a better/cheaper setup, let me know!
Ford Pinto and Mustang II 4 cylinder engines and some of the 1979-very early 80's Mustangs also had a similar setup.

Ford was somewhat forward thinking as this 2 barrel manifold had a Holley 2300 mounting pad (which allows the
old iron duke to be used in certain class races)...

For street these manifolds came with a bolt on adaptor/spacer that goes from Holley 2300 to Weber, and comes with
the much needed 3/8" PCV nipple.

Should be a junkyard part for no more than $5....
Quote:
The other benefit is that now there is equivalent of roughly a 4" spacer under the carb which should maybe do something,
Because the added time for the fuel to atomize before it hits the plenum floor, you will get a little seat of the pants boost in torque.


That being said, it's a weber...make sure to get the weber carb book as they have more adjustments and tuning than the holley has...
One of our local slanters a long-long time back added that much spacer to his manifold in his truck....
Author:  emsvitil [ Fri Jun 01, 2018 9:18 pm ]
Post subject:  Re: Offenhauser 4 Barrel Intake to Weber 2 Barrel Adapter
Go about 1/4 way down on this page:

http://garage.grumpysperformance.com/in ... tion.1038/

Anyway to get a spacer like that for good airflow into the 4 holes of the manifold ?
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/