SP2P Intake

[optomatt]

I've read or heard there is an issue with the SP2P, maybe it could still be worth something? I bought a 17059504 listed as a 79 305 carb, I want to maximize torque on a 79 305 that I am rebuilding and wonder if there might be some suggestions to tune in the 17059504 to an SP2P?

[optomatt]

I should have added, stock compression with a SUM-1101 cam.

[Cliff Ruggles]

The SP2P intake isn't worth two squirts of duck poop.  A smaller intake isn't going to help anything anyplace, same as installing a larger intake than what is needed.

The engineers did an excellent job with the stock factory manifolds on the SBC engines, I would use one of those instead.......Cliff

[optomatt]

Well, I guess we will just change jets until we don't see any carbon on the plugs. But then, we could always go back to the 2 barrel it came with if the 4 on the sp2p doesn't work out. Got a 350 goodwrench from the 75 nova this 305 from a 78 Nova is going into., we were thinking of doing a 383 with that goodwrench and following all your recommendations in your quadrajet book. But we wanted to try this one for max mileage per gallon for the wife's daily driver. We'll see how it works out.

[old cars]

You have a 350 Goodwrench? When it comes to torque there is no replacement for cubic inches.

[Cliff Ruggles]

Installing an intake with smaller runners does nothing to improve engine efficiency anyplace, hence why the SP2P intakes are not popular.  Matter of fact you can experience issues running an intake that doesn't have enough plenum volume for the engine, so I'd recommend obtaining a factory intake instead.  Plus an iron intake (preferred) improves thermal efficiency if you are looking for improved MPG's.  The added heat allows you to effectively burn a leaner mixture.  Keep in mind that it is a wet-flow system and we are trying to induce a cool/cold intake charge to the carburetor, mix fuel with it, then very quickly raise the temperature by compressing/heating it up so that it will burn effectively. 

Nothing has change in that arena since the very first internal combustion engines were introduced.  A heated intake is a LOT more effective than a cold one in a wet-flow system, despite what you hear on various Forums from "guru's" and other resident experts who really know little if nothing about this topic.

The manufactures even took steps to heat the carburetor to make things even better, hence the "hot-slot" intakes used thru the late 1960's.  Excellent idea in theory, and effective at improving economy and reducing pollutants, but fuel boils at a relatively low temperature so those systems often cause issues in the hot summer months, or if you get stuck in traffic idling for long periods of time, etc......

[Cliff Ruggles]

"Well, I guess we will just change jets until we don't see any carbon on the plugs."

That is NOT how we tune a Q-jet for improvements at light engine load and for fuel economy.  Get a set of my full taper primary metering rods so you will have full control of part throttle A/F from rich to lean via the APT system.

Teamed with the correct jet size there will be no need to remove plugs to look at them, you can tune for best results instead.......

[novadude]

Nothing has change in that arena since the very first internal combustion engines were introduced.  A heated intake is a LOT more effective than a cold one in a wet-flow system, despite what you hear on various Forums from "guru's" and other resident experts who really know little if nothing about this topic.

THIS!!!!  I have no idea why you see so many basic 300hp 350 chevy engines at car cruises, etc with "air-gap" intakes.

[old cars]

Although the factory Small Block Chevy intake design was good at the time, port runner shape has evolved since then so much that you could spend 30 ( experienced )  hours porting to gain 20 hp on a motor starting with some 300 HP.
You can look at 20-30 hp gain on a 350 / 325hp range engine swapping out to a current dual plane Weiand , Professional Products, Holley, or Edelbrock. On a 383 SBC the increase will be better.
These performance increases are well documented independently.
I am not saying a 305 sbc will see this.

[Cliff Ruggles]

"I have no idea why you see so many basic 300hp 350 chevy engines at car cruises, etc with "air-gap" intakes."

IF you are going to market a part, carb, intake, distributor, camshaft, etc you MUST tell the target audience that it works better everyplace than what you are currently using.  In most cases, at the power levels of the engines these high rise aluminum intakes are installed on, about the only true statement is that you took 27 pounds of the front of the vehicle swapping out your iron intake for an aluminum aftermarket intake.

I for one do NOT buy into the BS that all of these intake make more power than what you just removed.

What Old Cars says may be true in some cases as some of these intakes are very well designed with larger runners, so they can show more top end power with some engine builds.  So I'm not telling anyone reading this to toss theirs in the trash and put the stock one back in place. 

I will say however, that with a lot of engine builds you aren't making more power (torque), giving up some throttle response, low speed power and often average power in the loaded RPM range.

A few years back we were on the dyno with a 428 Pontiac engine.  It was bore to 440CID, aftermarket 260cfm aluminum heads, 10.6 to 1 compression, and custom ground 236/242 @ .050 hydraulic roller camshaft. 

We dyno'd it at 497hp/540tq with a factory cast iron intake.  The intake was slightly "modified" so for sure it gave naysayers a reason to cry foul.  Even so, we were asked to test an Edelbrock Performer RPM intake against it, so I did.  With no other changes the very next pull netted 491hp/535tq.

Yes, to everyone's surprise it made LESS power at every RPM.  With that in mind and thinking about the engine combo, how many folks have you seen install Edelbrock Performer RPM intakes on 350 Chevy builds with 882 heads, 8 to 1 compression, a Comp XE262 cam, and think they are making more power anyplace?  To make matters worse, more times than not the taller intake requires a drop base air cleaner moving the air cleaner lid closer to the carb.  I've dyno tested those drop base air cleaners and found that they can know upwards of 30hp right out of the engine if/when you move the lid too close to the carburetor.......some food for thought on this topic.......

[77cruiser]

I put a RPM on a 305 that had a mild cam & headers, it felt better than with a Performer. It came with a 2 barrel, so I can't compare to that.

[old cars]

I have no reason to doubt your pontiac tests. It would seem they were better designed (factory)than the chevys.

SBC after market intakes come in many designs and you need to match what you choose to your  build /use.
Of the basic 2 plane intakes I was referring to the the port shapes / corners play a big role in the improvements over the factory intake.

[Cliff Ruggles]

I build and dyno SBC engines as well, or did until retiring from all that a few years ago.  The stock SBC intake is excellent.  Thru at least 1hp/CID it's a complete waste of time/funds to go aftermarket.  You may see a little more upper mid-range and top end power but almost always with a loss of low end and average power in the useable RPM range.

I'd like to have a nickel for every SBC engine powering a 4 x 4 Chevy truck that's been brought to the shop still sporting it's dished pistons, 882 heads topped with an Edelbrock Performer or even the RPM, and they owner is wondering why it's such a gutless "turd".  I refuse to get involved with those projects as there is no where to go.

I do a LOT of factory appearing work.  Even those flat Big Block Chevy intakes EVERYONE tossed aside for a aftermarket high rise intake are a LOT better than you'd think.

Recently I was helping an engine builder with a Factory Appearing Street Tire big block application, 1970 Chevelle 454 stroked to 496.  All correct factory parts used, my contribution to the project was the carburetor.  The engine builder also owned a dyno, and told me right from the beginning that the "Quadrajunk" and this POS flat iron intake would NOT feed his engine.  Dyno day came and it topped out at 424hp (he was expecting around 560-580hp.

Of course all the bad mouthing came, and the "I told you so stuff".  I went over a few things and he said it was DONE at 4500rpm's.  I asked him about the distributor and he said he built and curved it himself and "upgraded" to a Pertronix.  I asked him to remove it and go back to points/condenser.  He reluctantly did so, then called me back an hour later.........it made 567hp an nearly 600 ft lbs torque!

Not the first time I've seen one of those Pertronix act like a rev-limiter and I will not use them here........

[Cliff Ruggles]

"I have no reason to doubt your pontiac tests. It would seem they were better designed (factory)than the chevys."

Keep in mind that the Pontiac iron intake is still considerably smaller than the RPM, over 1" shorter, etc and it made MORE power on a 440cid engine making right at 500hp.  There is a lesson to be learned in there someplace.  I swapped out the RPM on my 455 (makes over 550/600tq) for a ported factory HO intake and picked up some short times and quicker thru the 1/8th mile but not quite as much MPH.  So added top end charge at the expense of low end and average power does NOT automatically improve vehicle performance.......as we are often led to believe........FWIW....