618HAWK

iTrader: (361)

Which would be better for a forced induction setup.

Going to go with AFR heads!! Undecided on which to go with either 205,s 66cc or 225,s 62cc-72cc?

I plan on dropping in a set of forged pistons and rods at the same time. I understand that I need to lower my stock comp-ratio as well, for F/I.

Will also be installing a new cam as well GT2-3 571/578-118.5 (have and ready to install)

Would it be better to go with the larger CC or smaller piston?

Which head is more suited for F/I. I am leaning towards the 225,s.

Lets hear some thought on this please.

HEY TONY@AFR you out there......Fill me in.

Wnts2Go10O

iTrader: (12)

72's with flat tops and the runner size depends on power goal gl man

618HAWK

iTrader: (361)

As for power goal currently @ 540hp & 533tq. Would like to make more, which we all want. " The more the better" But I want to keep the the torque up thers as well.

Wnts2Go10O

iTrader: (12)

well do the rod and forged piston swap, but i say flat tops because theres simply more material to stand up the the pressures. and since ull prolly be keeping it stock cubes, the 72cc heads will give u roughly 9:1. ull be set. as for the runners, the 225's will also let u make more later if u wnted w/o takeing too much down low.

618HAWK

iTrader: (361)

Thanks for the good info, keep it coming. Giving me good points to ponder.
So flat tops with lager cc........??? SO I take it 205,s would be to restrictive for F/I.

Tony Mamo @ AFR

iTrader: (13)

My response will be similar to other threads debating the 205/225 situation. This is aimed at stock displacement engines (not strokers...)

For a killer street piece still capable of 600 RWHP or so (and loads of low/midrange grunt), the 205's are the ticket.

For a higher HP race oriented set-up with lots of boost, the 225's will certainly shine....they also come with a larger chamber which might help you dial in the right compression ratio based on various piston choice.

Can't go wrong with either, but my advice is to really think about what you want and where your priorities lie. Really its a matter of how aggressive a build you are looking for....

Tony M.

PS....Once you cross the 400 CID mark, unless you were looking for tractor like low RPM torque, the 225's would be the head of choice in both street and strip applications.

618HAWK

iTrader: (361)

Thanks Tony.

Well I am not after a race oriented setup. Would like to be well over 600 hp some where close on the torque as well. Like you say "low and mid range grunt", is what I am after. With a good streetable driver.

So I take it the 205,s would put me there and if I were to go with 225,s would be even better. But put me more into a race oriented set up with the option to make more if needed. And give me lots of low end grunt. And still be a good streetable driver.

I cant see pushing more than 12-13 psi of boost. So would the 225 be to better for this condition? And give me the option for more if needed down the road.

Chris

Wnts2Go10O

iTrader: (12)

the thing is 12-13 psi on the 225's is gonna be different because well.. ur gonna be pushing more air in those runners to reach that psi.

618HAWK

iTrader: (361)

That is what I am trying to find out. Will the 225s be to much due to larger runners, with more boost needed. To make good power and tq. Or would the 205 be just as good for more power down low with just a bit more boost to compinsate for slightly larger runner, from my current 9psi ? And still be able to make just as good power.

Chris

JZ'sTA

iTrader: (23)

i would do the 205's with a -15cc piston and .045 gasket.

Cary@Perf-Induction

iTrader: (1)

I would reccommend the 225's you may lose actual boost pressure, but flowing the same amount of air. anytime you can flow the same amount of air at a lower psi, the result will be more horsepower. you have less drag on the crankshaft, less load on the internals of the blower, resulting in lower intake air temps. a 225 cc runner is not a "big" port. Good Luck!!

DavidNJ

Tony,

Did you do back to back comparisons of the 205 vs. 225 on street and track cars to form your opinion? I can understand why the 205 would give crisper response, but neither seems over the top in flow for any LS1 displacement. And both seem like they would be challenged in really big (say over 441) engines.

David

Ragtop 99

iTrader: (7)

That's my theory too. Boost is like a measure of backpressure on the system and the 205s could increase that if you are running enough pressure to hit over 500 rwhp. Seems like the only reason to stay with the 205s would be if you don't make boost below 4000 rpm and want better torque for a street driver. On boost you're feeding the engine as much or more air than a 400" NA motor. That's how that 346 will make the same or more HP as 408.

John02SS

iTrader: (47)

We did a car at the shop that was an 02 Z06, forged short block, AFR 205 right out of the box, 224/228 cam, ls6 intake, A&A P1SC setup, 8 lbs of boost, with 160 miles on the motor that did 644 rwhp and a VERY conservative tune! The car has power everywhere and I think the 205 head is Awesome! He is in Kuwait right now, but when he gets home we are retuning on 10.5 lbs and a much more aggressive tune! Gonna have some killer AFR 205 numbers posted up!

Tony Mamo @ AFR

iTrader: (13)

John,

Those are killer numbers and your right about the 205 being a very effective piece. Certainly with a blower (and considering the request to "grow" down the road), I would advise a 225 in this particular application but don't dismiss a 205 if you are wanting a more rounded street package still capable of laying down a number. A centifugal style blower doesn't make a lot of boost or move alot of air at lower RPM's, hence my comment about possibly going with 205's if you were searching for "big block" type torque lower in the power band. The 225 will obviously offer slightly more horsepower potential and on a larger displacement build makes the choice a no brainer, especially if that laregr displacement includes a 4" or greater bore diameter (where the 225 head really shines).

I don't have any blown A-B tests regarding both 205's and 225's but I will be sharing some results on a naturally aspirated 383 in the following few weeks...

Thanks,
Tony M.