Edelbrock perforner rpm vs air gap

-
D

Dillon Crowell

Active Member
Joined
Jan 7, 2022
Messages
33
Reaction score
3
Location
Georgia
How much hp is an out of the box performer rpm capable of supporting vs an air gap? Building a 416 stroker and buying trickflow heads. Wondering if intake will need work in order to not restrict the ootb cnc head flow.
 
Probably the same airflow just at different temps
 
Dillon Crowell said:
Wondering if intake will need work in order to not restrict the ootb cnc head flow.
Click to expand...
A gasket match at the very least.
To take full advantage of the cylinder head, porting the intake is required.
A cylinder head is only as good as to what the intake will flow.
 
You will choke the **** out of those heads with an unported intake of almost any intake. A well ported rpm is around 260 ish cfm. You want more? Single plane or tunnel ram if it suits the rest of your combination and car (plus intended purpose). A dual plane manifold needs a big carburetor as half the cfm feeds 4 cylinders.
 
Once the engine is fully heart soaked the difference will be small.
 
I have noticed though that on my air gap the temp directly below the carb remains significantly cooler than the rest of the engine due to the cooling effect of the fuel vaporization. A non-air gap will completely cancel this out.
 
remytherat said:
I have noticed though that on my air gap the temp directly below the carb remains significantly cooler than the rest of the engine due to the cooling effect of the fuel vaporization. A non-air gap will completely cancel this out.
Click to expand...
Coating the inside and outside (after porting of course) with a thermal heat barrier coating will significantly reduce running temperatures.
 
I would say that getting good power gains from porting a dual plane could be difficult. Too many areas are inaccessible. I'm posting a link showing the before and after results of porting three different intakes ( small block shivies ), one of which is a Air Gap RPM. Flow bench and dyno test. At 6000 rpm and below, the ported Air Gap made less power than the OOTB version. https://www.motortrend.com/how-to/hrdp-0802-chevy-intake-manifold-porting/
 
Head over to Moparts and do a search and you'll find some guys running good numbers with the Air Gap on 400 cubers.
 
Only reason I’m considering the performer rpm is because it’s what I already have and would be one less part I need to buy. What brand and model would you suggest if I bought a different one.
 
We built a 408 with a gasket matched Air Gap and it made 497/519 and was a fun hot rod engine but I'm sure we left power on the table by using that intake (that's what I had also). We are building a 416 now with ported W2 heads and will be going with a Mopar M1 single plane intake. With a little work to the intake and a solid roller lifter cam, we are hoping to make close to 600hp with this one.

As I understand it, dual plane intakes are designed to boost low RPM torque. The 4" arm provides plenty of that, but needs more air flow at higher RPMs. A ported single plain would be my choice. The two intake choices you posted above would sell quickly here and pay for your new intake.
 
Hood clearance with a stock hood, and these different intakes comes to mind. What hood are you running ?
 
Dillon Crowell said:
Only reason I’m considering the performer rpm is because it’s what I already have and would be one less part I need to buy. What brand and model would you suggest if I bought a different one.
Click to expand...
Then run it. I be damned if I would buy another one. You'll need to port "whatever" intake for optimal performance anyway, so use what you have.
 
Dillon Crowell said:
I am just running factory hood for 74 valiant.
Click to expand...
The RPM and the Air Gap have the same carb pad height 5.35". So they are doable under the stock hood, usually with a drop base air-cleaner. The single plane intakes usually are taller, which will give you diffucties, with a stock hood.
Both intakes are rated at 1500-6500 rpm's.The Air Gap runs cooler. Since you have the RPM, it would be tough not to run it.
 
Last edited:
Is it even worth getting trickflow heads if my cam only has .560 lift, or would I just be better off porting the speedmaster heads I already have?
 
I've run both, Air-gap is good for racing conditions where you can keep it consistently cool but in street driving around town it'll get heat soaked which defeats the purpose. Cruising at higher speeds with more throttle will keep the manifold cooler but the gist of it is the tune will never be quite right since the intake temp is always changing. I chose a non-air-gap RPM for my current 360 since it spends the vast majority of its time on the street; it might be down a bit on HP in ideal conditions but at least the tune stays consistent and it's not as temperamental in colder weather. There were times my carb would ice over driving on the freeway in the winter with an Air-gap manifold on a fully warm engine, not fun!

If I was building any kind of 4" stroke SBM it would get a single-plane, hands-down. Heck my 360 is only a "moderate" build (400-450 HP) but I might switch to a single-plane after I swap this 904 with loose 2600-rpm converter and 2.94 gears for a TKX 5-speed and 3.55s.
 
You must log in or register to reply here.
-

Back
Top