Anyone run an Offy 6x2 or 8x2 log style intake manifold? Rather it be on a Hemi, Nailhead, Cad, whatever.... Like this: Four questions: 1) Did you have interferance with your ditributor? 2) Did you open up the balance tube ports a little to get better flow or any other modifications in that department? 3) What did you run for hoses for the balance tubes? 4) If you needed a vacuum supply, where did you drill and tap? Thanks for any help. These are just some questions that have been weighing on my mind lately. Looks like I may have to notch for the dizzy a little and was thinking about opening up the cross port bungs just a bit to allow a better flow balance and maybe even welding in larger bungs all together for larger hoses. I'm especially interested in that. Maybe it would actually hamper my performance!? Not sure of the science behind the design and the atomization that is taking place. As a rule of thumb I usually like to leave engineered things alone, but always wondered about this characteristic of the manifold. Just curious what some (or ANY) of you have done. Cheers! Scooter
Hello..The cross overs, balance tubes are just to regulate the air/fuel flow..There isn't any per say air/fuel going through them..You can like you mentioned bore them out a little larger, I don't think it will make any difference.. I would use any good rubber hose, like radiator.. The real thing is to index the ports on the intake to match the heads..Also no sharp edges, leaving the intake or entering the heads.. I would run two vacuum lines, one off each back end of the intake. Also, if you have any welding skills you can make your own water crossover.. Hope this helps Duane.
Hey scooter, is that an early 331 block with later heads on it?? As for the room for the dizzy, I've got an old crower u-fab 6x2 on my 354 and I changed to a vertex mag. perfect fit. With the stock dizzy I would have had to cut into the tube and curved it a bit to leave room. You car looks like a lot of fun, keep us posted.
Not concerned about water crossover. Got that all handled. Always thought that would be cool though! Maybe someday... I figured knew there would be any large amount of fule mix going through there, but when I like at this manifold and I look at the Weiand Dragstar and the Edelbrock version (ES6/8, whatever it's called) one has HUGE balance tubes and the other has three blance tubes. All are still larger than the two that I have supplying quite a bit more volume for balance. HOWEVER... the OFFY has little teeth in it for baffles to help with air-fuel mix. Maybe the balance tubes aren't a big deal. Just seems like if they went through all the touble to cast it this way with the small balance tubes there must be a reason... I just don't know what that reason is...
YES! That's a '53 331 block with the long bell. It has later 331 car heads on it. I think they're '56 331 heads. This manifold will be going on a different Hemi though. Here's the interference I was talking about. It's VERY close! If I switch to a Mag I think it's going to actually interfere completely.
The dist. clearance is strange. Are you sure that is the proper dist.? My friend rocks and edelbrock 6x2, all carbs work w adj jets to lean out the fuel some. He is also rocking a vertex mag and has no clearance issues.....
I had the same problem with my crower u-fab. The vertex clears just fine, but a mag isn't for everyone on the street. I just thought you might like to know how I solved my problem, and know the new vertex look a like dizzies are the same outer dimentions as the original mags, as far as they told me anyway. That being said, it probably wouldn't hurt to "shave" a little off that one end. I to would think the casting is fairly thick there.
If you do clearance the corner a little you will take some risk of creating a slight air leak at that spot. The risk is minimal though. The manifold is probably a sand casting rather than a die casting. On die castings the thin layer on the outside and inside are what seals. 97% of the inside of the walls are quite porus and if the thin layers of "skin" are broken an leak will result in about 30% of the time.
Sorry - not much further with the motor at this point - we run Vertex mags in our other cars (BBC/Flathead); but will probably just stick with a stock dist. for this car. It fits - but very close between the intake and firewall. The 94's are coming off in favor of '97's. Using a stock 392-style water crossover. John R.
Here's a 6x2 Edelbrock for a Nailhead just for comparison. The three cross tubes appear quite a bit larger (2 3/8 OD hose) It is set up to run only the two center carbs (my version of bogus induction). After installed it at the beginning of a four day car show a year ago just for looks and getting absolutely no comments ( not even a "nice car, kid" from the judges) I just gave up on it. That Edelbrock four barrel that I run sure beats trying to keep a bunch of leaky 97's tuned and running.
This picture is EXACTLY the reason why I wonder if I should make some modifications and open them up. Does the Edelbrock manifold have little baffles inside too? Just curious...
So, if I round a corner off and it breaks through, would there be any problems welding on this manifold???
Here's a shot of the underside of that Nailhead intake. I felt around on the inside of the casting and there are no baffles of any kind, just a big hollow chamber with three large cross tubes. There's a lot of theory that goes with intake design so it might just be Edelbrock vs Offy in-house theory or street application vs top end racing theory with a couple of other variables thrown in. Wish I knew more but I don't.
I was wondering what to do to make a remote thermostat work using these offenhauser logs and early 331 heads. thanks for the help.
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