3x1 vs 2V direct mount

[Javabean]

Hey all,

I think I've read just about every post written on the Offy and direct mounting of 2bbl, but am still trying to figure which is the best from a preformance standpoint. At one point I thought my direction was clear, 3x1 all the way, but now I'm not sure due to the success I've read about the direct mounting of a Holley 2300.

This is not a daily driver and strong overall performance is the goal. So considering all other mods to be equal here's my question:

On a tricked out '69 M-head, will a directly mounted Holley 2300 (500 cfm) flow as good and perform as well as a properly tuned offy 3x1 setup w/Autolite 1100s?

Thanks for any guidance you may provide,
Jay

 

[CobraSix]

If you don't plan to daily drive and want the most power out of the log, there are basically 2 options. Turbo/Supercharger with a direct mount 2V, or Offy. If you don't want forced air, the Offy has the best performance for the log head. I gives nice fuel distribution to all the cylinders that a direct mount 2V will still not give you.

Slade

 

[Javabean]

Thanks Slade!

You know I remember reading a post where you stated if your car wasn't a daily driver you'd keep the Offy. That statement has been stuck in the back of my mind as I started questioning my direction. But....the ease of the 2V is just so darn tempting and members are reporting good results with 'em. Do you guys with the 2V's feel your engine would benifit and perform a lot better with a 3x1 setup?


Thanks again,
Jay

 

[MIKE/ILLINOIS]

If you don't plan to daily drive and want the most power out of the log, there are basically 2 options. Turbo/Supercharger with a direct mount 2V, or Offy. If you don't want forced air, the Offy has the best performance for the log head. I gives nice fuel distribution to all the cylinders that a direct mount 2V will still not give you.

Slade

Slade I'm grappling with the same issues as javabean. Why is 3x1 not good for daily drivers? Frequent tuning, high maintenance? Thanks Mike.

 

[CobraSix]

It's all relative I should say.

The offy can be daily driven. There are a few around here who do with great success. I did it for a short while until I realized that there may be better ways for a daily driver, at least for me. I drive the crap out of my mustang. I put 10-15k miles a year on the 65. My wife also drives the car. I didn't want her to get faced with a complicated set up incase it broke down on her.

Compared to any 1 carb set up, multi carbureation is going to require more attention. It can run just as reliably and just and efficient, but it will require more work.

To give you relative performance, look here (a 2V, even direct mount to the log, I doubt will do better then the Offy in terms of power):

http://www.kastang.net/ozversusoffy.html

Those are basically the two standards for none forced air performance for the 6 (Argentinian being similiar to Aussie for arguments sake). In terms of shear HP, they are about the same according to a calibrated butt-o-meter. However, the Offy I was having to adjust about every weekend. But part of that is I'm extremely anal about keeping the car running very smooth. The Aussie with a 4V, I re tune probably once a month or when the idles sounds off a little, which ever comes first. It's usually only at extreme temperature changes. The Offy needed to have the linkage lubed every once in a while to keep it moving smoothly.

Please don't misconstrue my remarks about the Offy. It is an excellent upgrade. If I didn't drive my car 15k miles a year, I'd probably keep it as it was much better attention getter at shows then the Aussie is. Most people who don't know much think the Aussie is stock ("I had a 6 with a 4V just like that in 68").

Now what I think would rock, is an Offy with 3 1V projection TBI from Holley. 3 TBI fuel injection? That would rock!


Slade

 

[Soldmy66]

Why not do something different and get the best of both worlds (multi-carbs, direct mount, two barrels)? By macnining two flat spots on the log, you could mount two small two barrels, positioned right where you need them, and braze some type of block off plate in the original carb hole. This would effectively give you two separate manifolds, one off of each carb.

Thoughts or ideas?

 

[CobraSix]

SOmething like this:
http://inlinefever.homestead.com/RamAir.html

Slade

 

[Anonymous]

Geez, I'm looking forward to getting my six project going just so I have run a single barrel for a change! There's nothing more appealing to me right now that a 1 barrel carb, after all the 4+ barrel, and FI stuff I've been dealing with.

Jim

 

[Anonymous]

On a tricked out '69 M-head, will a directly mounted Holley 2300 (500 cfm) flow as good and perform as well as a properly tuned offy 3x1 setup w/Autolite 1100s?

Thanks for any guidance you may provide,
Jay

I think a direct mount Holley 2V will outperform the the 3x1 carb setup plus you have the added bonus of readily available Holley parts to tune your carb in for a specific application. Most if not all 1 Bbl parts (except for rebuild kits) are obsolete and hard to find.

Another plus is you wont have to worry about it flooding out or "bogging" off the line and you dont have to screw around with setting up the progressive linkage which everyone says is a PITA...I can remember Slade commenting on this several times when he was running his!

Later,

Doug

 

[Inline6Merc]

I was gonna run 3 carbs but then i figured out that that is too much carburation. I welded two flanges on the intake so it would take 2 1bbls. The places were i welded the flanges, distributes better fuel to all of the cylinders. It flows 370 cfm with both carbs.

Later,

Curtis

 

[MIKE/ILLINOIS]

Hey Curtis. Did you have a progressive linkage or both carbs working in unison? Mike.

 

[Inline6Merc]

both carbs are open no progressive linkage. I want to try proggresive tho to see if there is any major diffrences of getin of the line.

Later,

Curtis

 

[CobraSix]

Doug,

I don't know. I think pure all out WOT performance, the Offy will beat a direct mount 2V just due to better fuel distribution to the outer carbs. Even with a direct mount, you still have a hard turn to make to get the fuel to the outer cylinders.

How about an Offy with something like this:

http://www.holley.com/HiOctn/ProdLine/P ... 500-1.html

its a 1V that flows 300 CFM, but it's a TBI for EFI. Maybe direct mount 2 of those suckers with an ECM..you'll be smoking.

Slade

 

[Soldmy66]

I like Mustang Geezer's dual carb set up. MG - how did it work?

If the manifold were separated to yield (2) 3 cylinder manifolds, and small 2 barrels used, what type of results would it give?

 

[ski4evr]

I was thinking about 3 of the 300 cfm Holley 1bbl TBI's on the Offy intake. Does anyone know the bolt pattern on the Offy and possibly the Holley TBI's? Hood clearance issues as well? How close does the tri-carb setup with the Cobra Air Cleaner get to the hood of a 65 Mustang with a 200?

Also, after cutting the log head to accept the Offy intake, how does the Offy sit in/on the new holes? I've seen Slades page on installing it, but I still have questions. Does it just bolt only to the original carb spot? What does the underside of the Offy look like - straight tubes that come down from the carb holes and into the head? Do you have to use alot of Mr. Gasket to fill in gaps? I think a picture of the underside of the Offy tri-carb would answer most of my questions.


ski

 

[mustang6]

I ran the large-log Offy intake for awhile. Each end carb hole that you bore in the log is surrounded by four studs that you tap into the log. The intake bolts down tightly to the center carb mount, then you tighten down the eight ends nuts (4 on each end) just enough to squish the o-ring seals at each end. The underside of the manifold has a groove in it that circles each end carb hole, the o-rings sit in there and are squeezed against the head to form the seal for the ends of the intake. Sounds a little hokey I know, but I never had any sealing problems with the o-rings.

 

[ski4evr]

Thanks for the Offy intake description Mustang6.

 

[CobraSix]

Just FYI,

THere are 2 different kinds of Offy kits out there. I think Scott has one of the newer ones. I had an older model and it took something like this:

http://kastang.net/offenhausermod.html

Mine only had 2 studs per hole and used a metal bar to pull up on the log to put a nice seal on the o-rings. I only had issues after I had a major backfire. I solved it by putting sealant around the inside.

Slade

 

[hotrodbob]

I have run multi carb set ups for years. I do not understand the guys that always have to adjust them. These carbs were made to be run alone without frequent adjustments. Why do you think they need them now?

My last multi carb 6 was a non-Ford, but I ran it for 12 years as a weekend car and for a few years as a daily driver. Two stock carbs were adjusted twice in 12 years. Got 20+ mpg.

In high School I ran an offy set up on my 60 falcon and once set I only cleaned them(carbon buildup) evey few months and sync'ed them up every 6 months when I did a standard tune up.

I have a set to put on my Maverick now and I can't wait to set them and forget them. Start with a quality carb. I also never ran a progessive set up. They all opened at the same time. A little jet work and you are set. the only adjustment then is the idle mixture and idle rpm setting

I lost my fear of multi carbs when I raced and owned British sports cars. SU's are simple, but every month before a race they were cleaned and readjusted. Holleys and other stock carbs do not need that kind of attension. Set them and forget them. Hi RPM can lossen things, but adjusting? Set it right the first time and enjoy it.

Now, will these work on a 250 Maverick without cutting the hood?

 

[xctasy]

Front carb will be tight, but if a set of IDF's on a 300 I6 fits under the hood, then you won't have a problem. The later flat-top log may be taller than an early dog turd log. Check on the maverick froum the static height from between number one and two inlet tract. Then check against someone else with there's.

I'd say it'll waltz in with much more room than a low limbo.

Help out Hotrodbob, he's given a lot of great information here. That triple Weber 250 was quite an engine to behold!