Offenhauser 3x1 Build Thread

1strodeo

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Supporter 2019
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.
 

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Nice work.

Someone makes an aluminum ring w/ a set screw to go from ford to the common chevy size air cleaner mouth, it's a lot nicer than the plastic ring adapters or otherwise if you need to find 3 that match


l37Aev.jpg
 
Howdy 1st Rodeo:

Good get on the adapter. They are very cool. FYI- on the machinist I'd be looking for another. If you can look for a new machinist with a little gray in his thinning hair and a willingness to appreciate your project. If you can find one that gets a little gleam in his eyes at the thought of a tri-carb project.

Your adapter is for the early style, smaller log heads from 1960 to some '69 heads. You didn't say which castings you are working with. you'll find the casting numbers on top of the log just behind the carb hole. Anything C9xx and earlier will work with this adaptor.

On the carbs you have, I think the top three are Service Replacement Holley #1940s. It looks like the fuel lines are made to match these carbs. Check to make sure they all have the same inner venturi size. I can't tell for sure from the photo but they appear to be NON-SCV carbs.

In general, you will only need a choke system on the middle carb. What distributor are you using.

The polishing is really brings out the bling on this project. My preference on carbs for this setup are a team of glass bowled Holley #1904s. So Cool!

Keep it coming.

Adios, David
 
:shock: I will second the find another "machinist".Your current one seems to be rather closed minded.
Good luck.Have fun.Be safe.
Leo
 
Hey thanks everyone, both heads I have are '66, so the intake will work with either one. Think i'll take your advice (x4!!) and call around to other machine shops. I've used 3 shops in the Dayton area for various projects...I'm sure one will show a willingness to assist.

As for the carbs, I used my telescoping gauges and measured the narrowest part of the venturis (I believe that's where you measure) and 2 of the three Motorcraft carbs measured 1.2 (didn't measure the third) and one of the smaller carbs is even 1.2. The other smaller carb with the auto choke, which came off a 66 Mustang, measures 1.1.

Just thinking out loud, it seems that you wouldn't necessarily want the higher cfm carbs when spread across the cylinders? Just crossed my mind.

I'm still wanting to modify my existing 170 head for the Offy...if nothing else to get the setup functional and ready for the new head, assuming it's rebuildable.
 
...by the way the three Motorcraft carbs are indeed non SCV, and I'm running a Duraspark ignition system, graciously donated by a '78 Fairmont or two.
 
Howdy Back:

FYI- 1.1" venturi gives approximately 150 cfm. 1.2" = approximately 185 cfm. Many have used a center carb with a choke

Getting matching carbs will facilitate linkage. The Offy progressive linkage was designed with Holley #1904 in mind. The #1904 were used on 144 engines with a cfm of130. The 170 Holleys were rated at 150 cfm. Three carbs with 150 cfm will give you a thrill when all three are at full throttle and 450 cfm are roaring through that screaming 170.

What exhaust are you planning to use?

The DuraSpark is a great ignition system but you will have to experiment with which vacuum advance works best for your situation. Are you planning on using the stock cam?

The Autolite 1100 with the electric choke will likely not fit with three-in-a-row due to space.

Adios, David
 
Basically, the 1.10 Venturi(150 CFM) is ex 170 ThriftPower Six, 1.4375 Throttle,105 or 101 hp gross, and then on some then derated 67- 68-69 200's
The 1.20 Venturi(185 CFM) is normal 200 and some 250 Six, 1.4375 Throttle, downgraded from 120 to 115 gross some years.
The 1.29 venturi is 210 CFM 240 and some 250 sixes,1.6875 throttle, 145 to 155 gross.

Now its imperitive that igntion timing is pegged first, and that lifter preload, cam chain and cam degreeing are correct. The wide open throttle settings need to be varified. Sometimes the results of this swap are disapointing if thriple 1100's are used. datac had some issues a few years back, we think it was lifter preload and maybee peakthrottle opening, as he changed to a 1970 Mustang and Lokar cable set up.

viewtopic.php?f=101&t=70151&p=538337#p538337
Anyway,

5 articles blended answer your carb questions.

1. Horsing Around with the Mustang Six -
http://www.cometcentral.com/tech/hm6/index.html
http://www.cometcentral.com/tech/hm6/page2.html
http://www.cometcentral.com/tech/hm6/page3.html
http://www.cometcentral.com/tech/hm6/page4.html
http://www.cometcentral.com/tech/h2/index.html

2. Jan 1970 Hot Rods PDF. http://wildaboutcarsonline.com/members/ ... Up_1-3.pdf
3. The 1970 Hot Rod Yearbook artical above posted by unklechop
4. The board member Invectivus 1989 reposts of Jay Storers articals

HRM's mustang magazine number 3
http://www.invectivus.com/hrm_mustang3/Cover.jpg
http://www.invectivus.com/hrm_mustang3/Page 90 copy.jpg
http://www.invectivus.com/hrm_mustang3/Page 91 copy.jpg
http://www.invectivus.com/hrm_mustang3/Page 92 copy.jpg
http://www.invectivus.com/hrm_mustang3/Page 93 copy.jpg
http://www.invectivus.com/hrm_mustang3/Page 94 copy.jpg

5. Que unklechop's three piece Ak Millers article from HAMB's jalopy journal...
http://www.jalopyjournal.com/forum/thre ... 452/page-2



These articles offer two center carb choices by Replacement Carb number, not exactly the Original year part number code...it was a reorder number.

Choice A.The approx 193 to 200 cfm Carter YFA DOZZ 9510-F (They state 156cfm for the 200 and 146cfm for the 170 with there YFA's for 1970)
Choice B.The 200 tripower was listed with the D0TF 9510-G or F Autolite 1101 in the middle. Similar result from the 210 CFM carb.
A potential Choice C. C7AZ-9510-AA, the 240 cubic inch six cylinder Ford engine. This carburetor gave us a throttle bore diameter of 1.687 with a venturi of 1.290. The standard 1967 200 California Thermocator unit was the Autolite 1100 with a throttle bore of 1.437 and a venturi of 1.100.

The outers have Original Part numbers of those tiny little C2DZ 9510-A, what I think was an 1909 which were actually 170 Falcon carbs with 1" holes under them on the log

From other sources, the small early 1904/1908/1909 Holleys that were on the small sixes kinda sucked.
130,
150
or 170cfm for the 1904,

135
or 150cfm for the 1908,

125
or 150cfm for the other 1909's,

One kind of 1962 Holley 1909 is rated at 170 CFM and I think that was C2DZ 9510-4.

FalconSedanDelivery (Faron) got 14.39's with the 1909 outer and Autolite 1100 (not 1101) inner set up. His cam duration was about the same as Aks Mavi GT 250, and his lift figures on his Crane Solid Cam were 460 thou inlet and 480 thou exhaust.

FalconSedanDelivery":14uytdsu said:
.......250 .040, 1100 center, Little Holleys on ends , Crane Solid Cam .460int, .480exh Duraspark ign with GM 4 pin Module , 12-1 compression ( head was milled .120 , Deck .100 , Clifford Headers twin outlet ( open exh Drag car only ) car is a 1965 Mustang 3.50 gears C-4 with 10 inch converter ,( out of my 68 Blown 390 car ) 26.5 Slicks , Moroso Electric Water pump drive , adjustable Rockers , port divider in head , shift at 5000 , 4300 thru the traps.....


The he got a 14.39 sec for the 1/4 mile...

Ak used a stock aftermarket Hydraulic cam no smaller than 260 degrees as per his 1967 Hot Rod article on Classic Inlines, (Article 1 above)


and ( from Article 5 above) no bigger than 290 degrees, with no less than 430 thou and no more than 470 thou lift at the valve, 48 to 70 degrees overlap and used 9.7:1 compression with a 170 head with its stock 51.5 cc.

This was more than Ed Iskys 260° duration, .408 lift, 42° overlap, in-take opens 21° BTDC, intake opens 21° ATDC, exhaust opens 59° BBDC, exhaust closes 21° ATDC cam listed in that 1967 artical.

On the 250, its stock 59.4 cc chamber could take Jahns pop tops on that bigger cam without interferance. That's about 9.5:1, seeing as the 250 has the 103 thou or more short fall.

The 2 door 250 would have weighed in at 2600 pounds with its TopLoader and heavier six, and to pass 15's, it would need a Ford SedanDelivery Faron Rhoads style cam.
 
I use three Autolite 1100s on my set-up, which seems to work well. A previous poster was correct- there is no room for the choke housing when all three carbs are installed. I originally planned to install a manual choke, but have never hooked it up (because rarely gets all that cold in Dallas- and I don't drive it on those days anyway).

One suggestion- switch to a cable throttle! I think the most time I spent on my 3x1 setup was fiddling with the stupid linkages. At least on my car there was just no way to get that accelerator rod to work (at least not with my header in the way). The cable throttle was an easy install and has made all the difference in getting the linkages to work.

I documented the conversion on my tumblr site (link in my sig). Good luck!
 
I'm not surprised the machinist declined the Offy mod on the head. Finding a capable machinist with an interest and enough time away from more typical work is a challenge.

Does the early Offy' TriPower use the same carb port size for each carb and C-clamps around intake log to secure intake runner ?, later Offy' triples use the larger center port for higher cfm 1Bbl's and four studs into top of runner.

. .

The Offy linkage can be set (and re-set), from synchronous operation of the three carbs variable to having the Outer carbs open at any degree of primary-Center carb. The outers' throttle opening rate also can change from gradual to snap-open at any point. (enabling hours and hours of tuning fun). A 'kick in the pants' secondaries open @ 2/3 throttle for street and full synchro' carbs at the track can be done.


My simple Tri-Power 'start-up' is to get engine running great with center carb only and outers' blocked off. Once engine runs great, then Tri-Power tuning fun starts. I swap each outer carb on center position and get each carb to work well alone before trying to get to work together. Each carb (especially vintage) has different characteristics to blend into Tri-Power optimization. I don't mess with any chokes as I never drive it in crappy weather and a few Tri- carb accel pumps' and it's plenty rich/primed.

$.02: IF you can, test all those carbs and use best running for center and nexts' for outer even if don't match. Pretty good running rebuilt early carbs often still have worn shafts with minor vacuum leaks that can make for unsolvable idle problems when needing to 'shut' outer tri-carbs. Cable throttle allows swapping different carbs fairly easily.


have fun


.
 
I fiddled around with mine for hours of fun as POWERBAND has mentioned can happen. A wideband AFR gage really helped with tuning. Once you get it right it's N-I-C-E. Not to mention anytime the hood is up, people just flock around it to look.
 
Wow! Thanks for all the input, a lot to digest.

First and foremost I probably should've mentioned this is going in a 66 Bronco, not a car. But I love the six and I want to make it the best (and coolest) six I can.

To answer some of the questions posted, I have a dual outlet header from VI, but it needs a slight modification on the front-3 outlet for the connecting pipe to clear the frame. In my past experiences with headers I could've just rotated the flange, but these flanges are welded in place. I haven't decided on mufflers yet...how do the Flowmasters sound? My pipes will exit either in front of or behind the rear wheels, not straight out the back (if that matters).

Because my current 1100 carb is SCV, I have the vacuum plugged off at the distributor and carb as my understanding is that the Duraspark doesn't work with SCV (loadamatic) carbs. Also being a Bronco it already has a cable throttle and a cable (manual) choke, the latter which I was planning to keep connected to the middle carb.

My plan was in fact to mount each carb individually and tune first, and I figured the third 1100 that I have will not fit with the electric choke, that's why I asked if I could just remove the choke mechanism, or better off just finding another 1100?

I will use the stock cam for now, but when I install the 200 head I will likely upgrade the cam at that time.

Looking forward to reading your build thread Varilux, but cant go to that link at work :nono: I guess I should be grateful I can get on Fordsix!

Thanks again,
Jeff
 
powerband I'm not sure about the port size on the intake, but now that you mention it the center port did appear larger to me over the weekend...I guess I should've measured that too. Will do tonight.

Jeff
 
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!
 
Some expierenced w/'forge welding' have done a more than adiquite job of saving.
The better jobs on the 200/250 have chosen specific heads and added materiel B4
machining 4 direct mounts.
The middle carb is "the master' carb (start, run, idle) while the other 2 R more 2ndary
(pour it on when giving it more peddle).
 
Here is the crack between 3-4 exhaust on the 200 head...can this be fixed? Would welding in the Clifford wedge fix (part of) the crack at the same time? Of course this same machine shop said "we don't fix cracks" :!:
 

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That crack will close up when it's hot. I know that's not what you want, but it's still true.
 
Here is the crack between 3-4 exhaust on the 200 head...can this be fixed? Would welding in the Clifford wedge fix (part of) the crack at the same time? Of course this same machine shop said "we don't fix cracks" :!:

... interesting idea but doubtful to undo-able


Try to look around a little and find another head locally, they aren't that rare yet thankfully. Depending on your location, regional CL's often post 'Mustang' sixes swapped for V8's . Car cruise or show discussions can be helpful for swap parts.

Here in rust belt NE my Small Block Ford Six projects are mostly sourced from Mavericks'. The Maverick bodies seem even less survivable than the early cars. I use the engines, drivetrain, suspension from three dissolved Maverick's in '61 and 63' Falcon/Comets.

have fun
 
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