Performer RPM II too much for stock engine?

Aftrbrnr · May 17, 2007

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 · May 17, 2007

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 · May 17, 2007

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 · May 17, 2007

whtpny said:
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 · May 17, 2007

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 · May 17, 2007

whtpny said:
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 · May 17, 2007

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 · May 18, 2007

Bullitt347 said:
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 · May 18, 2007

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 · May 18, 2007

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 · May 18, 2007

whtpny said:
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 · May 18, 2007

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

90_Red_LX · May 18, 2007

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 · May 18, 2007

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

Performer RPM II too much for stock engine?

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