Performer RPM II too much for stock engine?

[Aftrbrnr]

I'm planning to go get some AFR 185 heads and they (AFR) say that the RPM II is good match for the heads (though there is most likely better). However, I don't have the money right now for the heads but I do have the money for the intake. However, even my own intuition tells me that installing the RPM II on a stock engine will probably cause a few performance woes including a large loss of low-end, etc. Anyone else have anything to say?

 

[whtpny]

If it part of a complete HCI matched for it then it is fine. I would however not use the 185s unless you are stroking it or going forced induction.

 

[modusmortis]

waaay too much intake for the stock motor. with my smaller cobra intake on the stock heads I gained 11hp at the peaks (5200rpm), but lost power everywhere below 4000rpm. More importantly, I lost average power. With that larger intake things will be less than optimal.

 

[Aftrbrnr]

If it part of a complete HCI matched for it then it is fine. I would however not use the 185s unless you are stroking it or going forced induction.

Why would you say that? What would be the downsides of the 185s?

 

[whtpny]

You would lose a lot of port velocity. I would go with the 165s they will be a better match for a 302 and will keep that low end torque.

 

[Bullitt347]

You would lose a lot of port velocity. I would go with the 165s they will be a better match for a 302 and will keep that low end torque.

Yes, IF the rest of the engine stays stock! If any other mods are planned I personally would go for the 185's. I mean if your going to pop for the aluminum heads go for something you can grow with. Hell I have built plenty of 5.0's with the 205's even and still have good streetability. It is all about making everything work together. And like I said, if your staying stock then you would get a good extra punch in performance with those "little" 165 heads. This is of course MY opinion. Your results may vary!

 

[Aftrbrnr]

My plan is to pretty much go with the 185s and the RPM II to match. After that, I'll try to find a cam that is fits a street/strip profile maybe to go with the above two.

 

[5spd GT]

Yes, IF the rest of the engine stays stock! If any other mods are planned I personally would go for the 185's. I mean if your going to pop for the aluminum heads go for something you can grow with. Hell I have built plenty of 5.0's with the 205's even and still have good streetability. It is all about making everything work together. And like I said, if your staying stock then you would get a good extra punch in performance with those "little" 165 heads. This is of course MY opinion. Your results may vary!

I would let him know if he gets the 185's that the pistons will have to change (rebuild).

And what combos have you did with 302 cubic inches and AFR 205's???? I bet your revving 7-7500rpm. Not a street engine.

AFR 165's can flow very well, you could get 400rwhp out of them N/A with a stroked bottomend.

 

[Maryland Stang]

An RPM II trying to flow through a set of stock heads is like you trying to breath through a straw. It can be done but it's no where near optimal. The RPM II ports are way bigger then the ports on the E-7s and the air moving through the ports will be severely disrupted by the mis-match. The result will probably be poor performance, throttle response and loss of low end.

 

[whtpny]

I have seen some great motors on the 185s but the reason I suggested the 165s was the stock motor. As long as the whole HCI and supporting mods are done with the 185s it would be a great motor but I would not do them as just an intake and head deal.
Aftrbrnr - what are the rest of your mods? 5spd? or Auto? What do a set of 185s run Canadian?

 

[Aftrbrnr]

I have seen some great motors on the 185s but the reason I suggested the 165s was the stock motor. As long as the whole HCI and supporting mods are done with the 185s it would be a great motor but I would not do them as just an intake and head deal.
Aftrbrnr - what are the rest of your mods? 5spd? or Auto? What do a set of 185s run Canadian?

I have an AOD car which I plan to put a high-stall converter in. However, I don't plan on building the tranny up because I intend to make it a T-5 car (or maybe even T-56) one day so I don't want to throw money in that will go to waste eventually. 185s run about a little under $1,800 CDN.

This thread pretty much reinforced what a lot of people have told me, if you're going to do HCI, do at all at once instead of one component at a time.

 

[Aftrbrnr]

Oh, one more question, the RPM II doesn't clear the stock hood or any strut tower braces, right?

 

[90_Red_LX]

The old rpm intake gained me 3 tenths and 2mph in the quarter, and 2 tenths and 2mph in the 1/8th with stock heads, and cam. Only mods were full exhaust, t/b, maf, cai, and gears. However, I believe the rpm II is a bigger intake than the old one though I believe. Someone with more knowledge would have to compare em.

 

[whtpny]

I was expecting more in Canadian. That's not too bad. Got any pics of the car?