[Marty Mustang]

I have a 1965 Mustang with a 289 (I believe the engine is actually from a 1967). I a stock C4 transmission & but have an updated aftermarket dual exhaust (non header). I would like to open the motor by adding a 4B carb and manifold. On e-Bay I can see a KMJ Performance SBF dual plane aluminum intake manifold for about $150 (shipped). I am not sure which carb to use....guessing a Holley 600CFM? Can anyone tell me which model #? Is there any other solution you would recommend? Are there any other tips/tricks to use or traps to avoid? My first post ever to the forum...BIG thanks from the rookie!

 

[STERLING351]

Does it have stock heads?

 

[Marty Mustang]

Yes, the heads are stock. My dad bought the car new in 1965 and my brother drove the car in the '70's. He blew up the engine and replaced it with another (think it was a '67 because the valve covers were blue). I am also considering an electronic ignition. My plan is to keep the car as "stock" as possible while boosting the performance. I have kept all the origional parts in case I ever want to take it back to origional shape. Thanks!

 

[1968poney]

depends on what your looking for a 500 holey would be fine. there is a formula that you can use to determine the right carb. you can have a 1000cfm carb and it would act just like a 500cfm there is only so much gas you can get into the ports and valve and so much air fuel mixture you can get into the cylinders i just looked it up with a stock engine youd be fine at around 440cfm carb at 5000rpms if you go 6000rpms a 500cfm carb would do just fine once you get into bigger valves more displacent higher lift cam and blowers you put on a biger carb

a stock engine you arent going to see dramatic efects be sides it burns more fuel. you want more power change the heads and the cam. but for now a 500cfm woul do fine in my opinion.

Tom

 

[paul289]

If you plan on doing any serious mods, use a 550-600 cfm Holley. I know, my sig says I have a 750 cfm Edelbrock. Shut up. I was sixteen when I bought it and didn't know any better. A smaller carb will respond better than a larger one when properly tuned.

 

[Veronica]

If you plan on doing any serious mods, use a 550-600 cfm Holley. I know, my sig says I have a 750 cfm Edelbrock. Shut up. I was sixteen when I bought it and didn't know any better. A smaller carb will respond better than a larger one when properly tuned.

Hello. Don't feel bad. Many, many people think that a bigger carb is automatically better. I ran a little hands-on test on a K code that I used to have. I put a 600cfm Holley on it and drove it around, flogged it, etc... for a while, and then I put a 480cfm Autolite carb on it and didn't change anything else, and it ran better with the 480. I realize that 'runs better' is kind of vague, so, to dial that in a little better, the car was quicker off the line, more responsive, and got better gas mileage. It ran just fine with 600, but, it was almost like efi with the 480 as far as throttle response.

 

[Player]

Very interesting! Thanks for sharing the results of your test.

 

[67fstbk]

I agree with Veronica about the 480cfm Autolite. I replaced my stock iron 4-bbl intake with the aftermarket Cobra high rise and kept the 480 on it instead of changing over to the Holley. I actually had to lean the mixture because it was running too rich and it still has enough to feed a hipo cam. And I hear that you can actually get around 18-21 mpg with them if they are tuned right. That's if you don't kick in the secondaries too much :nono:. We all know how hard it is not to do that.

 

[ghjedi]

All, I have a similar question on changing out my original 2 bbl carb for a 4 bbl. I own a daily driver stock '66 coupe 289 w/ C4 automatic. It's got the original carb on it, but the carb is in need of some TLC. I've heard that upgrading to a 4 bbl would give me a little more off the line power and might actually save on mpg. Is that a myth? I'm less worried about higher mpg than I am about a little more power.

 

[65redcoupe]

the 2-4 bbl swap is a power upgrade for sure but not a gas saver ....i went from about 17 mpg with my stock 2 bbl down to the 11 or 12 range with the 600cfm....i wouldn't go much bigger then a 600 though my buddy has a 67 he slapped a 700cfm on it and it floods if u stomp on it...which i would believe is rather embarrassing if you were to flood it in public. i bought edelbrock i love the thing pulled it out of the box and only thing i ever did was turn the choke off in the summer except for that no work or maintance neccesary i think they are best out of the box

 

[MizzouMike76]

Pitfalls........I can think of only one which may occur, and is well documented here in previous posts: the oil pump driveshaft falling down into the pan when the distributor is removed. There is a search feature on these forums, it might be good to look up some of the older threads and see what folks have to say.

Since the engine was replaced some time ago this may or may not happen to you; I believe the more, um, "seasoned" engines are at a greater risk of this happening. Not the end of the world, as there are solutions to it. I must admit it has kept me from upgrading to that 4100 I have tucked away; my engine has never been apart and I just KNOW that driveshaft is waiting to fall...........

Michael

 

[andrewmp6]

Yeah too big of a carb is the most common mistake people make.The 429scj only had a 470 or 480cfm carb on it what does that tell you.

 

[ghjedi]

I'm thinking more and more about sticking with my original 2bbl carb. Thanks all for insights on a bigger carb.

 

[MizzouMike76]

Wait! Don't be discouraged. Like many mods and rebuilds, you won't believe how much better your car is and will love driving it that much more.

Everyone who has upgraded from 2V to 4V raves about their Mustang's new found spirit. I think you should definitely consider it.

There is a new Summit carb, Summit SUM-M08600VS - Summit Racing Street & Strip® Carburetors – SummitRacing.com
that has gotten very good reviews here and elsewhere. Is a modern copy of the venerable 4100 Autolite. Worth a look, as the cfm range is ideal (500cfm) and the price is right.

Michael

 

[hypostang]

I have 2 comments
1. Veronica's experience with the K motor, I did the exact same thing with the same results on a K motor also
2. In my 30 years of working on fords (small blocks in particular)only once has the oil pump driveshaft fallen


I say go for it but i would personally stay away from a Holley carb
I have had leakage issues with them after a few years .
My recommendation if you can is to go with the Autolite 4100

 

[65redcoupe]

haha that oil pump driveshaft thing is nothing 2 worry about....ive never heard of that happening before this thread....id definetely go with it...it took me nearly 10 hours cuz im a newb at this stuff and was worth every hour haha

 

[MizzouMike76]

Take a look at the search feature and you should find quite a bit on the subject.

Rare? Let's hope so.

In my experience with my own Mustang, anything that is fixed will always uncover between 2 and 5 other repairs that need to be done, and nothing, NOTHING is ever as simple as it seems. Perhaps I'm just becoming cynical?

It's almost as if my Mustang doesn't want to be restored at times :gringreen

At any rate, if you have the money and tools to do so, by all means upgrade that carb! That 'choked' sensation I feel when I step on the pedal of the '66 compared to the '90GT..............I never want a 4V more that at that moment!

Michael

 

[Joes72/65]

I just switched from a 600 CFM Edelbrock to a 480 CFM Autolite 4100 on my '65 with a 302. My experience is almost identical to Veronica's, and the engine actually seems to develop more power, faster. Haven't had it on long enough to tell if it's any more fuel-efficient, though. :bigthumbsup