afr 205's on stock 302

dmc919 · Mar 12, 2009

i know they are a little big but i can get a set for $800 from a freind of a freind. how bad will they be on the stock 302, or should i start building a 351 for these heads. the price is awesome, i cant pass this up

95Vert383AOD · Mar 12, 2009

Do it!!! If the valves are a little to big you can calm the heads down with less cam lift. If you ever go 351+ stroker you'll have a head that will feel comfortable from everything 351-408.

What you will notice is that your car will make a ton of power at lower RPMs because of the very high flow numbers at low lift. On a 302 those heads will NEVER run out of air.

2000xp8 · Mar 12, 2009

Buy them and sell them on ebay, then get the proper sized set.
They will be horrible on a 302. It will take alot of rpm to get the car going. Nobody in their right mind would use them on a stock shortblock, unless they wanted a car that ran like crap.

If the 351(or 347) is in your near future, keep them for that, but if the 351 isn't a realistic goal for you anytime soon, they are just a waste of money.
A deal is only a deal if you can use or profit from what you are buying.

bubba-dough · Mar 12, 2009

Those heads will drown a stock 302.....

clement · Mar 12, 2009

i dont know the exact minimum cross section of those heads, but the average cross section is 2.5^sq inches. so you could estimate the MCS is between 2.3 and 2.4^sq inches.

so on a stock shortblock that head would probably hit target airspeed somewhere between 6400 and 6900 with a really, really mild cam depending on which number you use for target airspeed and what the MCS actually is. obviously the more aggressive the cam the higher the powerband will be. the above numbers i estimated are pretty much the basement.

dmc919 · Mar 12, 2009

ok, my next question is what kind of rpms can the stock bottem end handle? and/or would those heads be to small for a 408 for future plans?

7upstang91 · Mar 12, 2009

Buy Them! 408 with those heads easy 600rwhp. I think.

5spd GT · Mar 13, 2009

Mean (aka. average) cross section does not mean much to an engine. A minimum cross section can not be based on a mean cross section as well. It has virtually nothing to do with it.

Stock block (pistons) with a 2.08" intake valve and a cylinder head like that on a ~37.7 inch ^3 cylinder is not the best way to attack this type of combination.

A large cylinder head may like a delayed intake opening (or atleast slow beginning ramp) so when the piston speed approaches its peak speed, the draw on the intake runner (head + intake) is greater (open valve later), which increases the air speed (some call it velocity) and brings inertia with it.

clement · Mar 13, 2009

5spd GT said:
Mean (aka. average) cross section does not mean much to an engine.

like ive said before, ACSA is a tool. it has its uses. a port isnt developed solely on MCSA. they both have their place.

A minimum cross section can not be based on a mean cross section as well. It has virtually nothing to do with it.

so you are saying the MCSA of the AFR 205 falls outside my estimated window? then what is it? i guess i could email Jason at AFR and find out. are we taking bets?

Stock block (pistons) with a 2.08" intake valve and a cylinder head like that on a ~37.7 inch ^3 cylinder is not the best way to attack this type of combination.

so how would you calculate a window for target airspeed if you dont use MCSA and cylinder volume? (in this case only estimated) no one is saying the head isnt to big cross sectionally. i was just giving the poster a vague basement range to start with. once he has the information he can better make up his mind based on what he wants to do. fwiw, i dont think their is a best way to attack any combination. their are just a number of physics calculations you can make, put the numbers on paper and choose the one that best fits the application.

LarsD · Mar 13, 2009

Can heads with those size valves even fit a stock bore 302?

Rick 91GT · Mar 13, 2009

2000xp8 said:
Buy them and sell them on ebay, then get the proper sized set.
They will be horrible on a 302. It will take alot of rpm to get the car going. Nobody in their right mind would use them on a stock shortblock, unless they wanted a car that ran like crap.

If the 351(or 347) is in your near future, keep them for that, but if the 351 isn't a realistic goal for you anytime soon, they are just a waste of money.
A deal is only a deal if you can use or profit from what you are buying.

I agree, if you are planning on a build down the road buy them and put them on a shelf. They are way to big to be effective on a stock style combo, and you would need to notch the pistons to clear the large intake valve.

The heads are perfect for a healthy 331, 347, or 408 combo. Camming a motor to make a large head work when it is not needed has other effects.

clement · Mar 13, 2009

LarsD said:
Can heads with those size valves even fit a stock bore 302?

its not ideal. whether they will clear the pistons or not depends on the cam. id check them for sure.

clement · Mar 13, 2009

dmc919 said:
ok, my next question is what kind of rpms can the stock bottem end handle?

according to fords factory rev limer, 6250. above that its luck and a just a matter of time.

Touring23 · Mar 13, 2009

I would love to try AFR205's on a 302!. Just think 32V Cobra.

The trick will be the cam, as Clement all ready said.

One other issue: Does the 205 require special headers and/or intake manifolds?

KamiKaziDK · Mar 13, 2009

I'd say they're a good investment but to save them for a deserving engine like a stroker or 351. You could put them on a 302, but your power will come in late and it'll take a lot of pedal to get there. Now....if you were building a high compression 302 with a wicked cam, h-beams and a forged crank for a high rpm screamer....that could be a lot of fun!

FastDriver · Mar 13, 2009

Revving a stock block above 7000 is wreckless. Back in the day, guys with the best forged, balanced, girdled assemblies couldn't prevent crank-walk at those engine speeds. With a 50oz imbalance, I absolutely wouldn't go past 6500.

Depending on what you're trying to do, I don't think it's a terrible idea. Obviously, 205s would be far from optimum on a 302, but I wonder how they'd compare to a non-top-of-the-line 302 cylinder head. For example, how would the numbers with a 205 combination compare to say a GT40X headed combo, which you could probably purchase for around the same amount of money?

You would certainly suffer on the low-end with the 205s, but you'd make a lot of that back up top. Stick with a high RPM intake and cam to take advantage of the extra flow the cylinder heads offer. You'd definitely pick up some serious power, and you should highly consider stroking the block out to a 347 to help the motor draw the air necessary to really take advantage of them.

Word to the wise: take a very very close look at everything on the head. Ask if they've been milled. What work has been done? Test the seal on the valves and ensure that the bolt holes aren't stripped etc... You usually get what you pay for, and $800 is extremely cheap for these heads even though they're used.

Good luck,

Chris

Rick 91GT · Mar 13, 2009

Touring23 said:
I would love to try AFR205's on a 302!. Just think 32V Cobra.

The trick will be the cam, as Clement all ready said.

One other issue: Does the 205 require special headers and/or intake manifolds?

They will take a stock style header along with the wider bolt pattern (they are drilled for both), any of the aftermarket intakes will bolt up.

The large valves even with a very small cam will hit on the very edge of the outside eyebrows, the stock piston reliefs do not have the required radial clearance.

Clement is right at 6250 the stock computer shuts off fuel...

95Vert383AOD · Mar 13, 2009

Hey i have a 383 with 210 Pro Comp heads. Problem is they flow like 185's (277CFM @ .600 lift.)
With my motor untuned they made 500lbs tq @ 2000rpm and 265hp @4000rpm. I bet they would actually flow some decent numbers on a 302 but they choke my motor. Anyways im looking for AFR 205's or 225's and would like to avoid "new" prices.

If you can't use these heads....i sure can!!! Let me know.

Rick 91GT · Mar 13, 2009

95Vert383AOD said:
Hey i have a 383 with 210 Pro Comp heads. Problem is they flow like 185's (277CFM @ .600 lift.)
With my motor untuned they made 500lbs tq @ 2000rpm and 265hp @4000rpm. I bet they would actually flow some decent numbers on a 302 but they choke my motor. Anyways im looking for AFR 205's or 225's and would like to avoid "new" prices.

If you can't use these heads....i sure can!!! Let me know.

I took a set of the Procomp 210's off a customers 414ci motor, swapped over to a AFR205 and picked up 65RWHP.....you get what you pay for. You would see major gains by swapping to a better head.

95Vert383AOD · Mar 13, 2009

Rick 91GT said:
I took a set of the Procomp 210's off a customers 414ci motor, swapped over to a AFR205 and picked up 65RWHP.....you get what you pay for. You would see major gains by swapping to a better head.

Yeah im just torn between getting a 205 or 225 on a 383ci motor

afr 205's on stock 302

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