Airfilter restriction cure

[Hog]

Hi,
my name is Hans, writing from Sweden.
My car is a - Corvette 454 with a 468 with some tuning and a modified QJ with parts from Cliff´s. I have been strugeling with different things to get the engine response I am looking for and when I removed the air cleaner there was a huge difference.
As you all knows, there is not a lot of room under the hood in a C3 Corvette and I don´t want to kill the performance with a low intake manifold so I am using a two plane intake manifold and a L88 stock height hood. This means a low profile air cleaner which it doesn´t like at all.
I am looking for ideas on this one?

Br
Hans

[Cliff Ruggles]

Why would a low profile intake hurt performance?  Despite what all the guru's and self proclaimed resident experts on all these Forums tell you they factory intakes are very capable parts.   

I help Pure Stock and FAST Class customers frequently with the Q-jets they use on their engines, and they are required to use the low-rise factory intakes.

A couple of years ago an engine "builder" who was doing a 454 (stroked to 496cid) for one of my customers called up here complaining that the "low rise" intake was a "turd" and the POS Q-jet I built "would not feed his engine". 

Dyno day came and for sure he called up again with the "I told you so" crap that the 496 he built was only making 425h, done making power at 4500rpm's, and it should have been closer to 575-600hp up near 6000rpm's.  I had him try a few things and nothing improved.  The entire time I'm taking chit from him about how bad those carbs and intakes are. 

I didn't get my panties all wadded up, stayed focused and moved forward.  Finally I asked him about the distributor and he blurted out that he "recurved" it and put a Pertronix in it to replace the points. 

I asked him to remove the Pertronix and put the points back in it.  He was NOT liking that idea and assured me that the distributor he set-up was NOT part of the issue. 

In any case he did what I asked, then called back later in the day and told me that the engine cranked out 565hp and 587ft lbs torque!  The entire time the Pertronix was shutting it down like a rev-limiter just past 4500rpm's.

That's not the first time we've had engine "builders" tell us that the factory intakes and carbs are NOT up to par for big power levels. 

Another FAST customer doing almost exactly the same thing was getting laughed at as he unloaded his LS5 454 for dyno testing.  Everyone at the dyno shop right down to the guy who takes out the trash scoffed at him and told him that the Quadrajunk and stock iron intake were door stops and that he needed to replace them if he wanted to make any power at their facility.

My customer said very little, they bolted down the engine, did a quick "run in" set the timing and made a pull-on it.  He called me and told me that they were dialing 911 and heading for the exit doors......the completely "stock" looking LS5 engine made just under 600hp and over 600ft lbs torque!

So tell me that a stock low rise intake isn't up to par for this application?

From the testing I've done you will loose a LOT more power moving the air cleaner lid too close to the carb trying to use a high rise intake vs just leaving the stock one in place and using an air cleaner that'll get more air into the engine........FWIW......

[novadude]

Interesting story about the low-rise manifolds.  I have tried two different Pertronix products... points eliminator kit (the original one) and stand-alone rev-limiter.  This was two different vehicles.  All turned out to be crap.  I will never use anything from that brand again. 

Good 'Blue Streak' breaker points or '990' GM modules (if you have an HEI) seem to be the most reliable ignition systems available, IMO.  The factory knew what they were doing.... 

[Handyman57]

I believe my new Pertronix has went as well. A lot of junk out there these days.

[Cliff Ruggles]

Not a fan of Pertronix.  There parts have caused me a LOT of grief over the years with customers calling up here with "carb issues" that were related to those parts instead.

+2 on Blue Streak points and 990 factory modules.  I will only use 990 modules in my HEI's, and to date have never had a single issue with one.

When it comes to intakes, folks need to realize that about all you get more times that not from the money spent is taking 27 pounds off the engine. 

Bigger runners do NOT guarantee more power, especially if the existing intake isn't restrictive or the runners are big enough to feed the engine under it.

Matter of fact, I dyno tested my Pontiac iron intake, a Pontiac HO (reproduction) intake, and an Edelbrock RPM on the same engine back to back at the dyno.

The engine was 440cid, 260cfm aluminum heads, 10.6 to 1 compression, 236/242 @ .050" roller cam and 4 tube Hedman headers. 

The Edelbrock RPM intake cranked out 491hp, the iron intake 497hp, and the HO intake 487hp.  No other changes were done between pulls.

No imagine for a minute how many much smaller CID engines get high-rise aluminum intakes and they have less head flow, smaller cams and more restrictive exhaust and the folks installing them are expecting a power increase........no likely.......IMHO

[Cliff Ruggles]

While I'm on a roll here the WORST places to spend money in this hobby to improve engine power and vehicle performance are intake manifolds, carb spacers, fancy air filters, bug zapping ignition systems, and roller rocker arms.......

[ks_skyhawk]

Cliff,  When you mentioned GM HEI modules, does the "990" you quoted in this thread refer to the last 3 digits of this GM part number?  GM 1875990.  Is this the module?

[novadude]

Not a fan of Pertronix.  There parts have caused me a LOT of grief over the years with customers calling up here with "carb issues" that were related to those parts instead.

+2 on Blue Streak points and 990 factory modules.  I will only use 990 modules in my HEI's, and to date have never had a single issue with one.

This ^^^ !!!

I have had terrible luck with Pertronix point conversion kits.  Unreliable junk.

Standard Ignition Blue Streak still makes quality points, and the electronics in the newer HEI modules seem to be much different than the old '990' that always seems to work best!