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Hey guys, I've got a 68' mustang with a bone stock straight 6, and I was wondering if I could put a 2 barel carb adapter plate on to the stock intake to use a 350 or 500 cfm Holley carb. Would this be possible to do?
 

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The 1 barrel to 2 barrel plate works but you loose a lot. It would be best to put a 2 barrel intake on it. Another great upgrade is the split header. These engines also need a better distributor. If you want to continue, you can get an Australian head and run a better cam. The difference would be astounding compared to the original engine. The better engine to start with would be the 250 though unless that is what you already have.
 

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Start with igniton first, the stock dizzy on these kind of suck.

The adapter for the 2bbl is fine, but it's best to have the head milled to get the full potential of the new carburetor.

A 350 CFM is probably plenty.


We're currently building an i6 200 with an Aussie head, 500 CFM 2bbl and a comp cam for a '65 coupe.

...oh and we're adding a turbo charger:)
 

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Ditto on what everyone else has already said. There is an adapter plate you can use to put a 2bbl carb on the inline, but it's much better to get the head modified (the opening is enlarged to take advantage of the 2bbl).

The original distributor is a real weak point for these engines. One of the biggest gains I noticed was going to an HEI style distributor. The next biggest gain (so far) was installing a header.

I'm currently working on a project to switch to a tri-carb setup (I have a current thread about the head swap). The same fellow who built my new head also sells heads modified to run the 2bbl carb. Here's a link to another listing he has (his number is in the listing, and you can just call him and ask if he would modify your head for a 2bbl carb- I've seen him list such heads before): Ford 170 200 Ford Mustang Bronco Falcon Offenhauser Tri Power 3x1 Cylinder Head | eBay
 

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My suggestion is to sit back for a little while and follow Varilux's thread. IMO the best way to save the I6's induction is exactly what he is doing. The stock log manifold has such poor distribution in stock form I really wonder how much power the two end cylinders make? I think it's running like a 4 cylinder. Even putting on a 2 barrel carb I'm sure would help but I think the 2 end cylinders aren't really do much. Putting on the two end carbs improves distribution significantly and all the cylinders are making power.
 

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Best 2 bbl for a stock 200 engine is the pinto carb. A 350 is too big for a stock engine 500 way too much. I have blocked off one side of a 500 making it a 250 (i think) it worked grate. I have also used both a 2305 350 and 500 progressive 2 bbls (no longer in production). On a stockish 200 the 350 2305 worked best with the secondary only opening half way.
I you look atthe calculations for a 200 possibly turning 5500 rpm a 250 cfm carb has been the best. As long as you dont have a VacUmatic dizzy is ok shouldnt have one on a 68
 

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Biggest issue with poor distribution is the throttle plate opening arrangement. If it opens towards the cylinder head it flows into the center ports if it opens away from the cylinder head flow is quite even as the throttle blade helps to block intake charge from the carb directly into the center ports.

The 1 to 2 bbl adapter can help with this issue also as the throttle plate is way away from the intake log/ports. I also spend some time with my head porting equipment to smooth out inside the adapter and if the heads off with adapter installed open the manifold adapter transition. Also do the same with the 3 1 bbl adapter mostly on the end carbs mating to the log.
 

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The 1 barrel to 2 barrel plate works but you loose a lot. It would be best to put a 2 barrel intake on it. Another great upgrade is the split header. These engines also need a better distributor. If you want to continue, you can get an Australian head and run a better cam. The difference would be astounding compared to the original engine. The better engine to start with would be the 250 though unless that is what you already have.
That is pretty much the exact route I went with my first mustang. When the 200 was tired I swapped in a 250, tossed on an Australian head and a weber 38 DGES carb, and a clifford 3-1 header set. The difference was absolutely astonishing. You would be surprised how strong one of those little 6's can be when you get them to breathe.

The integral log manifold is a serious choke point on those motors. So while a carb upgrade will help "I did that route first" you still get limited by the log itself. If I was to do it again I would be tempted to machine off the log and find a way to make my own manifold/runners. The Aussie heads have become hard to come by and it's kind of a whole deal getting one in the states. I got lucky back in the day as the guys on fordsix.com had some sources for them. But that was nearly 16 years ago now.
 

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OVER 50 years ago went the Alk mILLER ROUTE AND installed 4 Honda 750 carbs. Car long gone traded in on my new 69 GT350. Kinda chuckled when he stated my 67 Sprint was a girly car. It would wip most SBFs back then being in the low 13s
 

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OVER 50 years ago went the Alk mILLER ROUTE AND installed 4 Honda 750 carbs. Car long gone traded in on my new 69 GT350. Kinda chuckled when he stated my 67 Sprint was a girly car. It would wip most SBFs back then being in the low 13s
Ak Miller - theres a blast from the past! Turbocharged Pintos brochure I have from c. 1973:


Paul
 

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Back in about 66 started drag racing a 65 mustang. Parents then traded it for a new one in 67. Then is when I started realy going crazy with performance and handling.
 

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meh, who needs em' I just like dreaming up ideas to make the 6'es run well. I still have a later large valve 250 head somewhere in storage at my mom's house. I might just pick it up next time I am home and make it a fabrication project to see if I could make a bolt on manifold setup work.
 
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I love my 6 bangers . . for utilitarian use. I have a couple. But in no way do they excite me to try and make power from them. To me, why not go about it with a better power making format ?? What I do want and will modify then for . . . . is MPGs. That is what makes me smile with a 6 banger.
 

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Done the MPG thing with one decades ago. got 45 MPG city and 35 MPG in town. Also set it up to handle using a lot of the Trans Am mods. Many could out run me but never out cornered. Except in a real high speed curve top end was around 90 95
 

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Since the inline six (classic inlines) website is not monitored anymore, does anyone know where I can buy the adapter plate he sold on there. I ordered one from Summit but it doesn't allow for the off-angle bolt pattern on the log.
 
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