cast iron intake vs aluminum high rise dyno test( round 2)
 

So i get a customer in seeking more power (long story short)
Lately since there has been threads in here that cast iron intake manifolds perform better than aluminum intakes in mild combos
Here is a appple to apple dyno test.

as arrived cast iron intake
http://img13.imageshack.us/img13/4543/xvvx.jpg

http://img543.imageshack.us/img543/5325/ls0d2.jpg

http://img853.imageshack.us/img853/3316/9eem.jpg

http://img35.imageshack.us/img35/918/x42z.jpg

19 RWHP GAIN @3700RPM

http://img560.imageshack.us/img560/5452/kgxk.jpg
22 RW TQ @2500 RPM


Sharing my testing here, if i get any smart a__ reply's back regarding the integrity of my dyno testing i am shutting this thread.

Harry, what's the aluminum manifold? Crosswind?

yes Rocky, its a copy cat of Crosswind.

Any other adjustments made to the tuning of the car? Is that a carb adapter on the iron intake? I'd be curious to see back to back runs with a spread bore carb.

I must be stupid, as I've been told, but which result is which?

The TQ curve shows an improved inhale across a broad RPM.

Personally, i'd like to see what a Q-JET does. ( should be same, right?)

Harry, I know you can't spend all day doing this but I notice that sometimes you get better numbers on the second pull just because(maybe because all the cr@p gets blown out on the first pull). I also wonder what a regular performer would do against the high rise? I ask because I'm thinking about going back to the regular Performer instead of the RPM but I don't want to if I'll be giving up that much.

the stock intake pull seen here was at its opimal tune,
the black thingee under the carb is 3/8 spread bore spacer with 4150 sealing gasket was used under the square bore Edelbrock carb as it arrived to me.

the red graph is iron intake and blue is aluminum intake.

noticible difference in power.

"Personally, i'd like to see what a Q-JET does."
would fry's go with that shake:D
its not equiped with Q-jet and i am not spending my dime on this one.

true if car is carboned up,unloading it wot on dyno you blow the carbon nicely away and the second pull will be miniscule higher.

"I also wonder what a regular performer would do against the high rise? I ask because I'm thinking about going back to the regular Performer instead of the RPM but I don't want to if I'll be giving up that much."
grab your performer intake & comon by and well do exactly what you want.

That looks great for street use. A lot of the other results extend the test out ot 600o rpm, and it does look like the lines begin to converge at higher rpms, and maybe the lines cross at some point, but for daily driving the extra torque from 2000-5000 rpms is enough to notice, at least on that cam/head combo. I know the edelbrock used to claim just about the difference your test shows between their aluminum and stock manifolds.

Based on the 350 max torque numbers, I assume this is close to a stock motor, with close to stock cam specs.

Harry, can you share combo details?

The results are pretty close to what we found using a square bore carb on a factory spread bore intake (unmodified) with an adapter/spacer. The spacer/adapter is a significant miss-match between the two parts. The last time I tested a deal like that it cost us just under 30hp on a pretty stout 455 making just over 500hp.

We did some dyno testing a few years ago with a pretty stout 428 engine and after finding the best tune for the carb and distributor, we swapped out 3 intakes back to back.

The first intake tested was a re-pop HO intake, then an Edelbrock RPM, then my own iron intake. All three intakes were gasket matched exactly to a stock Felpro blue gasket, and the HO and iron intakes were opened up under the carb to the same size/shape as the RPM. The runners on all three intakes were unported/as cast.

The HO intake made 487HP, the RPM made 491HP, the iron intake made 497HP. No spacers of any kind were used during the testing.....Cliff

While I don't doubt the aluminum intake has the ability to make more power, I can't help but wonder if the square bore carb adapted onto the spread bore iron intake may have hurt it's power to some extent?

As much as i know i will:
its a 400ci maybe 30over rebuild by local engine builder machine shop,no relation to me
it has 670 casting heads and 175psi cyl pressure i checked and its doing fine on our Ca. piss 91 octane, i dont know whats the pistons used in it (meaning SCR where it is) cam wise again i dont have details but it has 16to17" vacuum at idle and its 4spd manual car
the best part get this, its in a 1964 Chevrolet Impalla SS.

Irelevent mismatch or not, the test was here again apple to apple
1 more time remove cast iron intake & install aluminum intake with no other changes

The results are pretty close to what we found using a square bore carb on a factory spread bore intake (unmodified) with an adapter/spacer. The spacer/adapter is a significant miss-match between the two parts. The last time I tested a deal like that it cost us just under 30hp on a pretty stout 455 making just over 500hp.

I have seen the same Loss of power as Cliff did. On a Boss 351 engine and a Boss 302
with a Shelby 8V manifold when I installed open spacers on four hole manifolds.

Ken Maisano

Why should the results be surprising?

The charge has a much straighter shot with that aluminum high-rise. And the iron intake is going to have a lot of primary reversion with anything other than a q-jet.

great post thanks for sharing. also, even if the plots were a perfect overlay the aluminum is much lighter and that in itself is a performance gain. just wondering why you mark the horsepower points where you did and not at the peak position. again thanks for sharing.

Jim