Offenhauser 3x1 Build Thread

[1strodeo]

Acquired an Offy 5205 Intake with linkage and 3 Motorcraft carbs. I took a 200 cylinder head to my machine shop for a rebuild and they basically said they would not mill the intake log to accomodate the Offy because it "wasn't their cup of tea" So my plan is to modify my existing 170 head to mount the Offy while getting the 200 head redone (my 170 bottom end has good compression).

I already had 2 rebuilt carbs and another from the 200 (with auto choke), but I can't understand why the Motorcraft carbs look so much larger than them? (See first pic)

So I may use the Motorcrafts down the road, but for now it makes more sense to use the 3 carbs i already had. Can I just remove the automatic choke from the one? My understanding is that only one carb needs a choke for cold start.

 

[Skiddy]

I have no idea but that is going to be sweet

 

[NC_Pinz]

Completely different vehicle, but I've owned three other vehicles that had multiple carbs. They had two single barrel carbs. Manual choke and I believe the cable hit both carbs.

Try choking just one. I'd think you'd need to hit all three but I don't know.

Good luck and get yourself a synchronizer to get all the carbs balanced.

 

[Broncobowsher]

Typical multi-carb applications the outer carbs have no choke and no idle screws. They are like the secondaries on a 4-barrel carb. Now a 4-barrel carb can be mechanical or vacuum secondaries.

The linkage you have is mechanical. In fact I don't even see the linkages as being progressive. It looks like a linear linkage. In progressive the center carb operates alone until ~½ throttle at which point the outers open up at a quick rate so at full throttle all three carbs are fully open. My experience with linear linkage multi-carb applications is a boat motor. It is a double carb engine, Dearborn marine V8. The engine was sold as 135HP in a single carb application and 150 HP as a double carb application. The only change for the engine was adding the second carb instead of the blockoff plate. Both carbs have a working choke and idle screws. This might also apply for a three carb setup with a linear linkage as well, but I don't know.

If you felt like getting creative you might go looking for a load-o-matic carb for the center carb and use the venture vacuum to pull the throttles open on the outer carbs. Probably going to be the hardest to make this work but will probably be the most drivable if you can ever get it all figured out. Probably shouldn't try this one.

 

[Pa PITT]

Man it's been a long time since I've seen a set up like that. But man that'd be cool on a rat rod. But Back in the 60's I had 2 4's on a 327..
& I had a friend that had 3 DEUCES on his 55 chevy. As I recall his center carb had the choke .. Then his linkage was Progressive . I'm meaning the next 2 carb opened up as would the back 2 barrels on a 4 barrel .So you drove around on say the 1st 1/3 of the center carb. For your gas mileage so to speak. But then when when you nailed it you opened up all the carbs wide open.
... Hope that makes since.

 

[1strodeo]

Yes PA Pitt makes perfect sense as that's how I've always understood them to operate, basically starting/idling/low-rpm driving on the center carb.

Thanks for the info on the linkage bowsher, I haven't set it up in a way to try and understand exactly how the linkage works, just took a photo for when i revisit after cleaning everything up. I did know the middle carb was supposed to have a head start on the others though.

Wouldn't the spark control valves on the two smaller carbs pictured indicate they are load-a-matic carbs?

**Actually I just noticed you can't see the SCV's in the pic, but they both have them**

 

[ntsqd]

A friend had that set-up on a 200 in a 64.5 Mustang Coupe with a T-10 and a 4.11 geared & Detroited 8" rear. The car would scoot! Surprised a lot of near stock V8's.

He always had trouble with the o-rings that seal the outer carb to the intake. I suspect that by buying those o-rings in Viton instead of the much less expensive and much more common Buna-N that this problem would go away.

The linkage is progressive, but when the center carb is at WOT the end two carbs are not also at WOT. Note at each of the outer carbs that the horizontal bar in the linkage has a stop block with a slotted head set screw on it. At idle (roughly how pictured above) those blocks are not in contact with the bell-cranks for the outer carbs. Where they are set on the bar determines how much the center carb opens before the end carbs start working.

 

[1strodeo]

Informed by machine shop the 200 head is cracked in the usual place (between 3/4 exhaust ports I think) so not quite so eager to go cutting on my 170 head any more...but I'm still gonna do it!

 

[1strodeo]

I've got my chassis and drivetrain for at least the rest of the week, thinking of trying to mount this bad boy!!! Maybe installing the 3/4 exhaust port divider while I'm at it. I've got nothing to lose really...it's a 170 after all.

 

[1strodeo]

Removed the head, cleaned up the mess I found, 'machined' the head for the Offy adapter, ran out of time so capped off the outer carb holes, returning chassis tomorrow hopefully tub will be back from blaster soon, and I'm headed to the beach for a week

 

[ledslinger29]

That's a pretty picture


Sent from my iPhone using Tapatalk

 

[Yeller]

That motivates me to tinker on my 6cyl

It just happens to not be a ford