carb replacement 71 mustang

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micali

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Jun 12, 2011
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rogers
My Car
1971 mustang mach 1
My father in law has a 71 mustang and the old autolite 4300 has given up.  He doesn't have any intentions of replacing the stock intake.  He wants to keep it as original as possible.  The car only has 52,000 miles on it and for the most part is factory.  We would like to know what would be the best replacement carb that would give him stock performance.  I've read about a few carbs like the summit sum-mo8600vs. It sounds like a great carb but I read I will need a carb spacer to make it fit.  So if it needs a spacer, will the stock breather still fit?  Do I need a kick down adapter? I really don't know much about FORDs so any help will be greatly appreciated.

We really want a bolt on and go option if that is possible.  What about the autolite 4100?

 
There is a guy in NY called KP Carbs that rebuilds the 4300's back to stock original like new. If you google KP Carbs you will find him. He was recommended by my local builder here and one of our European members recently sent a carb to him to have rebuilt. Just an idea if you want to keep it original. Plus I think he only charges in the $250 range for a 4300 or less.

 
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Just as a suggestion. I can't comment on the Summit carb, never seen one, but as the 4300 is a 4 barrel, I would get either a Holley Street Avenger 670 or 770 or a Quick Fuel 750, not sure of the exact model you'd need, but these are very good carbs and will pretty much run right out of the box, with minor adjustments. If your engine does not have ram-air, you can use a spacer without issue. I run a 1" fiber spacer without any clearance issues on my 351C 4V with the stock air cleaner. You would need to change your fuel line to the carb and that could be rubber Hose or better yet a solid tube connection, but that takes some extra know-how. If you use rubber hose, make sure it is high pressure fuel injector hose as it will be ethanol resistant and PLEASE don't use gear clamps!!. Buy proper fuel line hose clamps. VERY important on both counts IMO! Used carbs are out there pretty cheap, but that's what you get and you'll likely end up spending almost as much just getting it running, a waste of money unless you are able to find one that is known to run correctly.

If originality is important, yes, get the Autolite rebuilt professionally, but in the mean time a Holley or QF will give great performance at reasonable cost.

 
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The Summit carburetor comes with a Ford kickdown and will not need an adapter. The 4300D intake manifold, which is a spread bore, would need an adapter.

 
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The Summit carburetor comes with a Ford kickdown and will not need an adapter. The 4300D, which is a spread bore, would need an adapter.
He has a 4300 not a 4300D. Different animal as you know.

Edit: OK I just realized what you were referring to....... IF he got a 4300D he would need an adaptor, kick down and base.

 
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I edited it, actually I meant if his intake manifold were for a 4300D he would need an adapter for the Summit carburetor.
Okay, I see what you meant to say now. I think he said it was a 71. If so it would be a square bore. 72-73's are spread bore. Oh well, he'll sort it out.

 
OK, thanks for the info. I say I have a 4300 but could it be a 4300D? The motor is the Cleveland.

 
OK, thanks for the info.  I say I have a 4300 but could it be a 4300D?  The motor is the Cleveland.
 It is easy to tell. a 4300 has all 4 bores equal in diameter for a 71, a "square bore". a 4300D is a spread bore, secondary's larger then the primaries and was the 71 Boss carb if I'm not mistaken, but could also have been used on the 72-73's. Those are not my years of familiarity. No doubt someone will set me straight!

 
Mike's Carbs online has rebuild kits for pretty much every carb on the planet. If he wants to stay stock, rebuild the original, its not that hard at all!
 Good to know where to get those parts. You are right it is not that hard to rebuild a 4300 as long as you follow the instructions........... well at least I'm hoping. I plan on rebuilding my original 4300 at some point just to have it, but not necessarily to use it.

Good info.

 
Mike's Carbs online has rebuild kits for pretty much every carb on the planet. If he wants to stay stock, rebuild the original, its not that hard at all!
 Good to know where to get those parts. You are right it is not that hard to rebuild a 4300 as long as you follow the instructions........... well at least I'm hoping. I plan on rebuilding my original 4300 at some point just to have it, but not necessarily to use it.

Good info.
I was told that some bushings were out on some rod and it would need to be sent off to be fixed and that its expensive. I have a guy that can rebuild it for $100 but he doesn't have what's needed to fix thosenparts.

 
So has anyone used the Summit carb? Other than the gas line what would I need to fit the Summit on the 71'? What about the choke? On the factory carb there is a hard line going to it. What do I need to do for the choke.

 
Anyone heard of the Tomco 3-379 carb? Oriellys has this as a replacement for my FNL car.

 
Ok, so If I choose a holley what all do I need to put it on the car? Thanks

 
Ok, so If I choose a holley what all do I need to put it on the car? Thanks
 Which Holley Carb? a Street Avenger is a good start, at least a 670 #80670.

 Not much. At least a 1/4" insulator for sure to stop heat transfer and maybe top and bottom gaskets if required. There is a Fel-Pro base gasket with a metal insert you will need on a 71 as it has a heat transfer passage and you will need block this off or it will burn the base of your brand new carb. Re-route the fuel line to the right side. You can use good rubber for now till you get it set up. Use Fuel injector line as it is ethanol resistant and buy proper fuel line clamps, "T" clamps, not freakin gear clamps that everybody uses!! NO glass fuel filter either. Just make sure everything is tight and rechecked before putting gas to it. Electric choke needs keyed power source, been talked about before.

If I forgot anything others will add I sure.

Good luck as keep us up on progress.

 
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