[Will]

Originally Posted by 78w72

...

to answer your question, no a stock HO or repro HO does not flow as goood as an RPM, but stock intakes are much better than non rpm performers & will probably support 12's in stock form, or you can do the notch trick on the plenum divider & do a hand gasket match to the E-head intake ports to improve it a bit. ....

I would even go out on a limb and say a factory intake absolutely will support 12s or better without a lot of work. Hell, I was running mid 12s on street tires with a Performer. Only mods were a notch in the plenum divider between the secondaries, and a gasket match a the port openings. A stock intake with the same mods, or probably just the gasket match should easily equal that.

[Formulajones]

Originally Posted by Will

I would even go out on a limb and say a factory intake absolutely will support 12s or better without a lot of work.

They absolutely will, without any work. I've done it and I know many others out there have. You don't even need to touch the factory intakes to go 12's.

[Cliff R]

It's a lot more about how the car is set up that puts you into the 12's, or even quicker with this sort of thing.

The intake manifold is actually a small part of a big plan. You aren't going to see big differences with any of these parts back to back testing once you have the car set up to make good power and effectively use it.

Countless times I've back to back tested many parts, just like Jim Hand used to do. My car hooks solid and leaves hard. Even parts to hurt power some still ran very well and even with the very worst parts in place I'd typically only see a few hundred's of a second difference and maybe .5 to 1.5 mph on top end.

This simply happens because of how hard the car leaves and that it is heavily loaded across a broad RPM range. So "average" power is the key to making the car ET well once it hooks solid. As long as it pulls hard down the track after the launch it really takes a LOT of power loss to kill ET and MPH.

Case in point. I can shift at 5000rpms, 5500rpms and even clear up at 5800rpms and the can only picks up about .02-.03 seconds. The engine is outfitted with custom CNC ported 298cfm heads from Dave at SD, and a 298/308, 236/245, 112LSA cam with .381" lobes and Crower 1.65 rockers on it. The compression ratio is 11.3 to 1. Changing a single part, like an intake, or testing a spacer, or even putting a different carburetor in place with less cfm really doesn't have a big impact on ET.

I can't ever remember testing any part related to the intake tract, whether it be a carb, spacer, intake or different combinations of them that lost over a tenth and no more than 2mph.

As it relates to this topic the WORST carb I ever tested far as ET/MPH loss was an Edelbrock 800 Thunder Series carb.

The WORST intake was a Torker 1.

The WORST spacer was a 4 hole and a fully open was a close second.

The following parts worked so poorly I had to abort testing. The Edelbrock Performer intake (HUGE stumble/hesitation/bog on the launch that would NOT tune out). The Edelbrock Performer Series AFB clones for the same reason. I also tried the K & N Xtreme lid and got a similar result.

My combination hates certain parts for unknown reasons as I seem some folks run OK with them. I suspect it has something to do with the CID/power level and excellent power to weight ratio. The engine is full of lightweight internals and spins up with a little 283 Chevy, so anything that effects that deal seems to KILL it during "transition" from idle to WOT for some reason........FWIW.

Some additional information although not directly related to the intake is carburetor testing. On several private track rentals I've taken as many as 9 carburetors to the track for testing and ran them on two different vehicles. Both cars run solidly into the 11's and mine runs nearly into the 10's in full street trim. On BOTH vehicles the Edelbrock 800 netted the worst ET and slowest MPH. My engine ran quickest ET and MPH with my 1977 Pontiac Q-jet, the other vehicle ran the fastest with a big Holley carb in MPH but quickest in ET with my Q-jet. So when you are changing out carburetors for example, and looking for BIG gains in performance, they will only be there if the carb you are replacing is WAY off the mark someplace. Even at my power level going from a big Holley 850 DP carb clear back to a 1969 Ram Air 750 Q-jet only kills off about half a tenth and 1.5 MPH or so.

I suspect folks making 100-150 less HP would see much of anything between them..........Cliff

[steve25]

A big key part to any cars ultimate performance is how fast the motor gains rpm under load!

In a true street strip car that can not max out its compression ratio to help achieve maximum VE part of the way to get around that is to get the highest level of port velocity to happen in the rpm range that best suits the way the motor and the car is set up.