Streetmaster to Airgap

[Bewy]

SM intake. What we are seeing is a history lesson from Edel....before they knew it was a history lesson.
If you compare the runners on an old school LD340 intake & a Perf intake, the Perf has smaller runners. Both were listed by Edel as 5500 rpm intakes. What you see here is a 20 yr technology gap where Edel learned [ slowly ] that bigger is not better because the Perf int has runners with a smaller CSA, & a trapezoidal shape in the runner bends.

This is what is being seen with the SM intake comparison. The small runners are not nearly as restrictive as they they were thought to be 'back in the day'. Hence the close HP #s.

I learned the hard way also. When I bought my 750 Honda m/cycle, I was given a spare cyl head with it. I immediately enlarged the ports because 'those small ports cannot possibly work'. The bike was slower everywhere with the bigger ports.

 

[Garrett Ellison]

The 318 SM looked like it had smaller port exits at the head flanges than a 318 SP2P I had in my possession a while back . I’m going to have to start working on the SM, I’m curious how much plenum volume all that extra aluminum occupies in it.

 

[rumblefish360]

If you've ever seen that manifold in person you would understand how small that runner opening really is. ...

Yes I have seen it in person.

I don’t know what to tell you guys. Well, only one thing, but it sounds rude, so here it is, out your engine on a dyno and re-do the magazine article. At least that camshaft is still available. Unlike a MP cam. The intake might be a PIA to find.

 

[RustyRatRod]

What intake is being bitched about having small ports? The Edelbrock Streetmaster? Of course it has small ports. They are 318 size ports.

 

[Garrett Ellison]

Not even that big at the head flanges. And even smaller at the runner entry inside the plenum.

 

[Garrett Ellison]

A strangulated checked to death design right out the box during the gas crisis.

 

[PRH]

I can only imagine how much more power my 475hp 340 would have made by swapping out the Victor that was on it for one of those tiny Streetmasters.
Then take the 850 carb off and replace it with an Ede 600.

Think of all that velocity!!

 

[318willrun]

I can only imagine how much more power my 475hp 340 would have made by swapping out the Victor that was on it for one of those tiny Streetmasters.
Then take the 850 carb off and replace it with an Ede 600.

Think of all that velocity!!

Wouldn't be complete unless you use the 302 heads with that streetmaster and 600 eddy

 

[PRH]

I guess it’s one of those things where people interpret the same info in different ways.

I read the article.......
One interpretation is that the modern AG intake was hardly any different than the old tiny SM on a 340.

My take away was.......if you take a 340, that has stock 1.88 heads on it, a small cam, a small carb, and stock log manifolds from a 318 on it along with the SM manifold...... and only upgrade the restriction that is the SM manifold....... you don’t see a big change in power.
Frankly....... no surprise there for me.

Seeing as how it was the first item they changed, I took that as a sign that they felt it needed to be swapped to not hold back the power that subsequent part changes could yield.

 

[Phreakish]

Seems this article is the rest of the story:
1970 340 High Performance Mill Dyno - Mopar Muscle Magazine

They went with additional changes including headers, valve springs, etc. Final pull was 392 hp (first pull was a near stock build at 291 hp).

Also, in what crazy *** world is 15 hp NOT a notable improvement? Plenty of folks spend big money on parts like heads to get that much gain. A 22hp difference at peak is also nothing to sneeze at. But take a look at the results from the article above, and it just goes to show that it takes the right COMBO to get big gains. Add more cam, headers, and a bigger carb and the engine went from good to great.

 

[Phreakish]

If you've ever seen that manifold in person you would understand how small that runner opening really is. If that tiny manifold only lost 15 hp @ 5600 how much would a larger opening lose? I guess my small port 302's aren't all that small and restrictive after all......

Your 302's that have the pushrod pinch tubed and removed? Sounds absolutely tiny...

15 hp is not a tiny amount of power. A 6% gain with a single part swap is notable. Change 3-4 things with 15hp each, you're at 60hp. Or would you rather it be 45hp just so your tombstone can read 'velocity'?

 

[Hysteric]

I can only imagine how much more power my 475hp 340 would have made by swapping out the Victor that was on it for one of those tiny Streetmasters.
Then take the 850 carb off and replace it with an Ede 600.

Think of all that velocity!!

But it wasn't was it. It was on a run of the mill basic 340 that most guys here would build for themselves. I can only imagine having to move the goal posts so as to make my point appear more intelligent than it actually is.

Guess that Edelbrock 600 or even a Holley 600 for that matter can't support 300 hp at the wheels now?

 

[Hysteric]

Your 302's that have the pushrod pinch tubed and removed? Sounds absolutely tiny...

15 hp is not a tiny amount of power. A 6% gain with a single part swap is notable. Change 3-4 things with 15hp each, you're at 60hp. Or would you rather it be 45hp just so your tombstone can read 'velocity'?

My 302's would be lucky to measure 140 cc's in total port volume. GTX Johns would probably be around 125 cc's and they don't have any problem making his 4000 pound station wagon run well into the 11's. He's doing far more with less.........All the more impressive considering he's using 3/8 valves too. Now consider he's limited to a stock cam lift.....Its a miracle that engine even runs its that restricted.

The difference between the port entrance of the Air Gap and the Street Master is HUGE. Yet the Difference in what the engine made at 5600 RPM wasn't. If the engine was airflow starved it would have picked up a lot more power in the swap but it didn't. That tiny port opening wasn't that much of restriction after all.

 

[Phreakish]

My 302's would be lucky to measure 140 cc's in total port volume. GTX Johns would probably be around 125 cc's and they don't have any problem making his 4000 pound station wagon run well into the 11's. He's doing far more with less.........All the more impressive considering he's using 3/8 valves too. Now consider he's limited to a stock cam lift.....Its a miracle that engine even runs its that restricted.

The difference between the port entrance of the Air Gap and the Street Master is HUGE. Yet the Difference in what the engine made at 5600 RPM wasn't. If the engine was airflow starved it would have picked up a lot more power in the swap but it didn't. That tiny port opening wasn't that much of restriction after all.

The O/SA record that was supposedly in the 11's is currently listed at 12.6x on the NHRA websites, so I'm not sure how accurate 11s is. That's also with a stock eliminator prepped car that bears exactly zero semblance to anything anyone drives on the street, other than the tires are rubber.

22hp is a decent difference for ONLY an intake swap on a stock motor. Keep the SM intake, and the engine would not respond to the rest of the mods they did in the same way - right?

Trying to say the intake isn't a big deal by looking at it in isolation is a joke.

 

[Hysteric]

The O/SA record that was supposedly in the 11's is currently listed at 12.6x on the NHRA websites, so I'm not sure how accurate 11s is. That's also with a stock eliminator prepped car that bears exactly zero semblance to anything anyone drives on the street, other than the tires are rubber.

22hp is a decent difference for ONLY an intake swap on a stock motor. Keep the SM intake, and the engine would not respond to the rest of the mods they did in the same way - right?

Trying to say the intake isn't a big deal by looking at it in isolation is a joke.

Do the heads have to flow enough air to make the power? Or do stock eliminator cars defy the laws of physics?

That 22 hp difference was at 3000 rpm where the airflow demands are less. The joke is your inability to accept that it just didn't need all that airflow you thought it did.

 

[Phreakish]

Do the heads have to flow enough air to make the power? Or do stock eliminator cars defy the laws of physics?

That 22 hp difference was at 3000 rpm where the airflow demands are less. The joke is your inability to accept that it just didn't need all that airflow you thought it did.

Stock eliminator cars aren't stock. Imagine that.

It obviously didn't have enough airflow to put out another 22hp. 22hp that would actually be felt and usable at an rpm that any reasonable enthusiast would reach. Or are you arguing that 22hp is actually 0 difference?

The engine obviously needed more airflow to make more power. Then they increased flow further with headers - and guess what? More power. Then they added a better carb, and gee whiz it made even more. Maybe they should have just given it a pep talk and told the motor that it didn't need all that airflow, and that it was a 10s engine all along, it just needed to believe in itself?

 

[Hysteric]

Stock eliminator cars aren't stock. Imagine that.

Irrelevant. Those tiny heads that you say can't make power are making power.........

So your saying an engines air demands are greater at 3000 RPM than they are at 5600?

The engine obviously needed more airflow to make more power.

And that tiny intake runner port that's incredibly small compared to the Air Gap had no problem meeting it.

Then they added a better carb, and gee whiz it made even more

That bigger carb made less power up to 3200 rpm and only made 12 more at peak.

 

[fishmens67]

The test was cheesy , who replaces an aftermarket intake as the first step on a stock engine.
It should have been one of the last steps, because that is what a greenhorn would have done thinking he already had an aftermarket intake.

 

[PRH]

Do the heads have to flow enough air to make the power? Or do stock eliminator cars defy the laws of physics?

My friends 350 Pontiac stocker has gone 10.80@123, at 3380lbs with small valve heads that flow right at 200cfm, at the max allowable lift of .420”.
Running the stock intake and Q-Jet of course.
(The Moroso slide rule puts it right at 7lbs/hp.
So, 482.8hp for 3380lbs)

How well does that flow line up with what the various ET calculators say the motor has to make for horsepower to reach that performance level?

Oh, and the 400 combo, with the bigger valve 220cfm heads has gone 10.37@127.

 

[Phreakish]

Irrelevant. Those tiny heads that you say can't make power are making power.........

No one says that. You hallucinate that people do, and then argue with the words you put in another's mouth.

So your saying an engines air demands are greater at 3000 RPM than they are at 5600?

See above. No one says that.

And that tiny intake runner port that's incredibly small compared to the Air Gap had no problem meeting it.

It didn't meet it, otherwise the AG would not have made more power. How is that not obvious.

That bigger carb made less power up to 3200 rpm and only made 12 more at peak.

12 is a reasonable gain, not 'only'.
The carb swap was 'phase ii' and shows a gain from 3k rpm on up. I see no data points below 3k. At 3k rpm, the power was already up 18hp. At 3400 rpm, the difference was 20hp. I'd be willing to pay for a new carb to get 20 more hp at 3400rpm on an otherwise stock engine! Peak was a 15hp difference, but peak moved up 4k to 4400. I guess the engine really didn't need more airflow. Being choked never results in a lowered peak HP rpm (this is sarcasm).


None of these are arguments. Nor do you ever explain what else would make more power. According to you, a stock engine in a stock car is capable of 11's, and changing any parts is seemingly a fools errand. I fail to see what you suggest anyone do to increase power. I mean, why did you port your heads if it didn't need more flow? Or do you think that since your port job failed, and you car slowed down, that it must be the excess air flow that slowed it?

 

[Phreakish]

My friends 350 Pontiac stocker has gone 10.80@123, at 3380lbs with small valve heads that flow right at 200cfm, at the max allowable lift of .420”.

How well does that flow line up with what the various ET calculators say the motor has to make for horsepower to reach that performance level?

Oh, and the 400 combo, with the bigger valve 220cfm heads has gone 10.37@127.

It's almost like stock racers play with a million tricks that all add a few hp each, and they all add up. I guess they didn't get the memo that 12hp is nothing, and shouldn't be pursued.

The tricks the stock guys come up with are always amazing to me..

 

[Phreakish]

The test was cheesy , who replaces an aftermarket intake as the first step on a stock engine.
It should have been one of the last steps, because that is what a greenhorn would have done thinking he already had an aftermarket intake.

It really only makes sense for the guy who's going from 2v to 4v. Of course, if you're going to do it, you want the 'best' for the 'future' upgrades that may or may not come. Maybe someone should tell them the 4bbl is just going to kill velocity and torque, and that all they need is to give their engine a pep talk.... but I digress.

If anything the article shows that you can go 'too big' and still be OK, and that future changes (assuming the tightwad makes them) will net even bigger gains. I honestly think the only place people tend to go 'too big, too soon' is the cam. Everything else can be made to work as good or better than 'lesser' parts when oversized on an in-progress buildup. That's what I take from it.

 

[Hysteric]

Your 302's that have the pushrod pinch tubed and removed? Sounds absolutely tiny...

So some how stock eliminator engines can make power with very little head flow small valves and little port csa but my 302 heads can't possible do that?

There's no magic in this they just use every bit of air that they get into the engine. If you cant understand that then you couldn't possibly understand that the HUGE difference in outright size between the minimum csa of an Air Gap and that of a Street master is perfect example of when tested on that engine that tiny intake runner area didn't make that much difference. If it didn't make that much difference its because that "area" in total wasn't that much of a restriction.

So which is it can a small port small valve 318 head make power on a 318/360 or not? A Yes or No answer will suffice.

 

[Hysteric]

My friends 350 Pontiac stocker has gone 10.80@123, at 3380lbs with small valve heads that flow right at 200cfm, at the max allowable lift of .420”.
Running the stock intake and Q-Jet of course.
(The Moroso slide rule puts it right at 7lbs/hp.
So, 482.8hp for 3380lbs)

How well does that flow line up with what the various ET calculators say the motor has to make for horsepower to reach that performance level?

Oh, and the 400 combo, with the bigger valve 220cfm heads has gone 10.37@127.

Thanks for agreeing with me.

 

[Phreakish]

So some how stock eliminator engines can make power with very little head flow small valves and little port csa but my 302 heads can't possible do that?

They're using multiple tricks to get more air into the engine. Duh. The most obvious is the camshaft, and lofting. Better flowing heads would make them faster in every instance.

There's no magic in this they just use every bit of air that they get into the engine. If you cant understand that then you couldn't possibly understand that the HUGE difference in outright size between the minimum csa of an Air Gap and that of a Street master is perfect example of when tested on that engine that tiny intake runner area didn't make that much difference. If it didn't make that much difference its because that "area" in total wasn't that much of a restriction.

Strange statement for someone that seems to think PFM is what makes power. Minimum CSA is not a linear relationship. If the CSA of the SM was large enough, it wouldn't have gained power. Simple as that. No amount of PFM is going to change that.

So which is it can a small port small valve 318 head make power on a 318/360 or not? A Yes or No answer will suffice.

You play word games. Invitation not accepted.