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Old 12-16-2008, 08:53 AM
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proper carb size Ford 302

I have a 93 roller motor, that was switched to a carb setup. I have an Edelbrock RPM Performer intake on it, and the rest is basically stock. After looking around, I don't think there a whole lot that I do plan on doing with the motor. Its now in an 88 Mazda pickup, so the weight is a little over 3000 lbs with a C6 auto trans.

So, would I be best running a 500 or a 600 CFm carb on it?

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Old 12-16-2008, 09:56 AM
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Go low....the 500 should work well.
But you could still go lower as long as you dont plan on hittin a lot of RPMs
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Old 12-16-2008, 09:59 AM
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600's are a dime a dozen & will work fine on your combo. If you have the $$ a holley 390 cfm would be perfect.
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Old 12-16-2008, 10:02 AM
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look in the "Knowledge Base" link at the top of this page under "engine" then "fuel delivery" for articles like this one:

http://holley.com/data/TechService/T...Carburetor.pdf

the stock cam rpms range (500-4500) is a mismatch for street rpms TQ with the RPM intake rpms operating range (1500-6000) for A/F velocities due to more total intake cubic inches...

go find a used Performer intake (500-5000) and use that with a 500cfm carb with the stock cam for a bit more mid range for now????

"ALL" the parts designed rpms operating ranges have to match to make more power...
EX: Edelbrock "Top End Kit",,,RPM intake/RPM cam/and higher rpms heads....

the stock cam and heads and RPM intake will "run"...
but likely make less HP and TQ than a stock motor driving normal...
(need more gas pedal for equal to stock acceleration)
the carb needs 1.0 to 1.5Hg at WOT to operate so the smaller 500cfm may(?) help with the large cubic area RPM intake diluting the Hg signal that reaches the carb base....
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Old 12-16-2008, 10:11 AM
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second link from the Knowledge Base to confirm the above posts

cubes versus CFM versus RPMS chart on page #1:

http://www.arnolt.com/Bitmaps/Articl...rafbtuning.pdf
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Old 12-16-2008, 05:34 PM
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Heres a huge surprise, I named the wrong intake, not the first time I used the wrong name. Anyways, I meant to say the I have the Performer 289, not the RPM. That one is the stock replacement. So a 500 would probably run the best with that?
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Old 12-16-2008, 06:27 PM
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A stock 5.0 HO cam is fine for power upto 5700 rpm.
The FI engine rating is limited by the low rpm intake configuration.
3300 pound Mustangs with stick shift ran low 13s in the quarter with totally stock engines...... if everything else was right.

Many 5.0 HO engines have been equipped with Performer RPM intakes, Edelbrock 600s, and perform very well throughout the rpm range, pulling well past 5500.

Several dyno tests have been published about stock cam 5.0 HOs with upper end upgrades with carbs that tickled 400 hp..... with the stock puny cam.

If yours happens to be the SE headed cast flat top piston engine from a CrownVic (etc) with its sad cam, they still run pretty well with the RPM/600 set up, as we have several on the street now. Cam upgrades on these usually require piston notches for valve clearance.

If you don't know which engine you have, the cam firing order will tell you if you have an HO or not.

Last edited by ScoTFrenzel; 12-16-2008 at 06:33 PM.
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Old 12-16-2008, 07:13 PM
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I do know for sure its the HO, I removed the FI manifolds and still have the nameplate on my toolbox. They are flat top pistons, and its just the Performer 289 intake, not the RPM like I previously stated. I was told it was from the T-bird, but it has the double sump oil pan, and only found a single for the T-bird and double sump for the Mustang.
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Old 12-16-2008, 07:33 PM
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Quote:
Originally Posted by Scotto
I do know for sure its the HO, I removed the FI manifolds and still have the nameplate on my toolbox.

They are flat top pistons,

and its just the Performer 289 intake, not the RPM like I previously stated. I was told it was from the T-bird, but it has the double sump oil pan, and only found a single for the T-bird and double sump for the Mustang.
The 86 Mustang 5.0 HO with SFI is the first year for SFI and the only engine to have flat top pistons from the factory because it used the old style heads.
It was a one year only engine.

I suggest you check your head casting numbers if you want to figure out what you have.
There is a stamped in number on the block at the rear top. This can help.
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Old 12-17-2008, 03:37 PM
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Scot,

different years HO cams are different durations....

like always, with Ford you have to find the specific's to know what you are dealing with....
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