302 to 306 and carb

ericnhu · Sep 26, 2011

we just bought this car. owner said it was a 302 and he turned it into a 306. Can anyone tell me what may have been done to it to make it a 306?

All I can say is it has a mild/wildish cam...

The idle is sky high and it has a holley 500cfm double pumper on it. He threw in a holley 1100cfm double pumper too....said it was too much for the car.

wondering, with a 306ci, what is the best carb route you guys have used that worked out best....?

thanks in advance.

eric

robbz28 · Sep 26, 2011

306 is just a bored out 302 (.030) nothing fancy. Need to know more about the internals of the car to really suggest a carb...but an 1100 is definately WAAAAY to much. The 500 is probably a good carb for it, but being a mechanical secondary, double pumper its probably not the best for fuel consumption.....see if you can get some cam/pistion/compression ratio information. Also what kind of heads/intake/exhaust is on the car.

Can you get a number off of the choke tower of the carb? 500 is a funny sounding carb....it may be a 600 dp carb. Also are you certain its a double pumper and not just a standard 4 barrel carb...more people than one would guess don't know the difference.

I am becoming a big fan of good ol autolite carburetors (ford factory) they are very no-nonsense easy to configure carbs. Holley's are great if you have time (and a phd in the theory of carburetion) to get them set up. I have never owned an edelbrock, but have heard good things about their street manners.

2+2GT · Sep 26, 2011

we just bought this car. owner said it was a 302 and he turned it into a 306. Can anyone tell me what may have been done to it to make it a 306?

Yep. An ordinary rebuild. No one does this to get the one or two hp that result.

All I can say is it has a mild/wildish cam...

Which is it?

The idle is sky high and it has a holley 500cfm double pumper on it. He threw in a holley 1100cfm double pumper too....said it was too much for the car.

A double-pumper is overkill if it has an auto trans. An 1100 cfm carb is total insanity on anything this side of mega-dragsters.

wondering, with a 306ci, what is the best carb route you guys have used that worked out best....?

If the cam is stock-ish, use a 500 vacuum secondary. If it's pretty stout, use a 600 cfm vacuum secondary. If you are racing the car, use a 600 or 650 double pumper.

ericnhu · Sep 27, 2011

a little update

as we are tearing into this project, and calling the guy that had the engine done, its one brick wall after another.

He said he had no build sheet on the engine, and I will end up looking at the carb myself tonight.

The cam is lumpy, but far from crazy.

Headers 3" to what looks like 2 1/2" pipe... H pipe... dual to 2 flowmasters. They are way short and sound mean as all hell...

Going to turn main focus to dropping the trans tonight. Put it in reverse and lost 100% of the fluid in seconds. Looks like the bulk of the leak is coming from the area of shift linkage. Shocking to see such a bad leak at that location.

Will become a big part of this forum and will share pics along this project.

can't seem to upload pics to my garage or profile no matter how small I make them... ????

Thanks for the reply guys... I'll try to sharpen my ford skills and ask questions when I have the right details.

ericnhu · Sep 28, 2011

more details

it is a 500cmf Holley...not a double pumper.
the trans came out last night. it's a C4,,,,NOT a C6.
looking into this trans issue, I hear that a C6 isn't the best idea for a 302/306

C4 being med duty and C6 being heavy duty.... As a chevy guy, I would assume the C6 would be like putting a TH400 behind my 355ci to better handle the power....

Anyone think a C6 is too much for the 306?

Slobin3d · Sep 28, 2011

About your pics, what format are they? if they are Bitmap nomater how small you make them they will be too large .KB to fit. If you run windows, microsoft offers a free image reducer that you can spec XxY dimentions and total KB for posting

JonK · Sep 28, 2011

Dbl. post.

JonK · Sep 28, 2011

C6 isn't too much for a sbf, just heavier, more rotating wt. robbing some power before it gets to the rear wheels. The BB cars came C6 if they were auto.
The exh. sounds fine, most with a sb go 2 1/4"-2 1/2", 2 1/2" is more common as it will be there if you add other upgrades -carb., intake, alum. heads, etc.
Put a vacuum gauge to the intake port and see what vacuum it pulls at idle, that may give us an idea of how radical the cam is.

I would suggest getting a pic hosting site like photobucket, flickr, etc. they are free and make sorting, storing and posting pics so much easier.
Jon

2+2GT · Sep 29, 2011

ericnhu said:
Anyone think a C6 is too much for the 306?

The C6 was used on the 351C 4V engines, but the FMX was used on the 351C 2V. The C6 has, IIRC, 30-50% more parasitic drag than the C4. Unless your 302 is a racing monster, it would be a pure waste of money to install a C6. The C4 has proved to be extremely versatile and upgradeable, capable of handling more power than your engine can produce.

robbz28 · Sep 29, 2011

I'm still hung up on that carburetor, i have never seen/heard of a 500 cfm 4 barrel holley....they make a 500cfm 2bbl....id bet a shiney new penny you have a 600 cfm 4160 (the most common holley 4bbl ever made) on top of your engine there. Anyway, 500 or 600, its still a vaccum secondary and still a good carburetor for your engine (if tuned properly). The exhaust sounds adequate. If he gave you an 1100 cfm carb, that should be a dominator series and you ought to be able to fetch a pretty penny for that on ebay or craigslist....just a thought. Get us some pics when you can!

2+2GT · Sep 29, 2011

This is a D0PF-U Ford Service Replacement carb, 450 cfm.

This is a new 465 cfm Holley.

302 to 306 and carb

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