Streetmaster to Airgap

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I've got one of those old streetmasters. It's surprisingly heavy with all the extra aluminum in it. I've been wondering forever what it would do if someone milled the plenum open and cut the runner dividers back to a knife edge about an inch past the plenum just to see what it could do. It has nicely swept runners and no bolt pinch at the ports. Modified like that with the addition of a 1 inch open spacer I suspect it would be like a downsized version of an Offy Port-O-Sonic or a Weiand Xcelllerator. It would almost certainly have to be better than the Edelbrock TM5 or Torker 340 intakes that were available at the same time.
 
Me too. Its was down 22 hp at 3K but around 15 as the RPM's increased where you would have thought the bigger difference would have been. You would expect a big difference in airflow between the 2 but some how the engine doesn't see it. Funny that.
 
Hysteric said:
Mopar Performance Parts - '71 Satellite 340 Small-Block Bolt-Ons - Hot Rod Magazine

What increase would you expect when going from a streetmaster intake that looks really restrictive to an airgap that's meant to be the best dual plane currently available.

Doesn't look like that little intake manifold was really choking down the performance of that engine.
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Depends on what engine you're putting it on...
The article you posted said they netted a 22hp gain- not surprising on a 340. The Streetmaster 318 uses the small 318-sized ports, and as Garrett noted, a plenum choked down so small that a Briggs couldn't breathe through it... Remember, this manifold was from the gas-shortage era of the mid-late 70s and it and it's sibling the SP2P were attempts to make an "economy" manifold with lot of torque but no top end, using a 500-600 cfm squarebore carb, or a small-primary Thermoquad/QJet/Holley spreadbore in the case of the SP2P. Horsepower was not the prime concern here.
I wouldn't even consider a SM for anything over a stock 318, much less a high-revving deep breathing 340..
That said, I am thinking of using one on a future 273 build, lightly modded similar to what Garrett laid out... :rolleyes: The small runners and plenum may actually be a benefit if I cam it just right...
 
Hysteric said:
Me too. Its was down 22 hp at 3K but around 15 as the RPM's increased where you would have thought the bigger difference would have been. You would expect a big difference in airflow between the 2 but some how the engine doesn't see it. Funny that.
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You won't see huge improvements for the AG at higher rpms until you ditch the Eddy 600 that they ran the initial comparison with- you need more carb to realize the AG's better flow at higher rpms; whereas a bigger carb on the stock SM would be more or less worthless, or even a hinderance.

Edit: Note how the addition of an Eddy 800 late in the test bumped their total from 291@5200 to 302@5000... Granted, they had performed other mods at that point; but it just shows what uncorking the intake side to take advantage of your flow improvements will do.
 
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So a streetmaster manifold that uses 318 ports tiny runners and a tiny plenum only saw a 16 hp difference at 5600 RPM on a 340 head.......Funny that.
 
Has anyone seen a street car like a Duster, with a streetmaster intake, run 11's or 12's ?? (on all throttle). Not being sarcastic, it's an honest question. I don't have to ask the same for the air gap.
 
I’ve heard of 13s, but I would have to see it in person!
 
Hysteric said:
So a streetmaster manifold that uses 318 ports tiny runners and a tiny plenum only saw a 16 hp difference at 5600 RPM on a 340 head.......Funny that.
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Huh?
"The Air-Gap lived up to expectations here, raising the entire power curve right from the bottom of our test rpm range with a gain of 22 hp at 3,000 rpm and holding a similar gain right up to the top of our test at 5,500 rpm. "
I had to double check the date on the article when they talked about installing a PAW cam... 2009- I thought they'd been gone longer than that. Oh, the memories... they got a lot of my money back in the day.
 
Professor Fate said:
Huh?
"The Air-Gap lived up to expectations here, raising the entire power curve right from the bottom of our test rpm range with a gain of 22 hp at 3,000 rpm and holding a similar gain right up to the top of our test at 5,500 rpm. "
I had to double check the date on the article when they talked about installing a PAW cam... 2009- I thought they'd been gone longer than that. Oh, the memories... they got a lot of my money back in the day.
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Did it really? Go back and look at each measured interval and compare the difference. Please stop quoting the article because its clouding your ability to see the real differences. It wasn't 22 hp all the way through the range.
 
Stuff a couple dollars down in the plenum and throw it away just so you can say you lost something.....318 streetmaster sux.... kind of like keeping on spinning your tires expecting different results without any changes....had one on a 318 in a duster in 1989 and it was getting smoked by stock 5.0 automatics...went to LD4B and actually won a few
 
Who here is actually running a Streetmaster? Or a Torker? Can’t say I’ve ever seen any more current builds or postings mentioning its use. Akin to Splitfire plugs, Slick 50....ultimately a “why bother” deal at this point. You see those two intakes at swap meets or on EBay, certainly not on engines being posted about here.
 
The way it looks to me: the SM is pathetic on the top end and REALLY pathetic on the bottom.The Air Gap stomped all over it and I'm sure a stock 340 or 360 intake would have as well. This test just reinforced what I already believed; that a SM is probably good for nothing. Mayyybeee.....fuel economy? As Garrett mentioned above, it would be interesting to see one tested with all the plenum crap carved out of it.
 
12many said:
Who here is actually running a Streetmaster? Or a Torker? Can’t say I’ve ever seen any more current builds or postings mentioning its use. Akin to Splitfire plugs, Slick 50....ultimately a “why bother” deal at this point. You see those two intakes at swap meets or on EBay, certainly not on engines being posted about here.
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I ultimately would have to agree with that philosophy. One reason I’ve not tried all that work on a streetmaster is because an unmodified Holley Street Dominator with a one inch open spacer and a spread bore carburetor works so well with one of the smaller cube engines and low gears. And I am sure the old pre Xcellerator Weiand 8510 (same manifold without the name and an even deeper plenum) that I used to have and still kick myself for getting rid of would be even better providing enough gearing and camshaft.
 
I guess I don't understand. You put your duck in the pond and it lost the race across. End of story ? Did I miss something?
 
Garrett Ellison said:
I ultimately would have to agree with that philosophy. One reason I’ve not tried all that work on a streetmaster is because an unmodified Holley Street Dominator with a one inch open spacer and a spread bore carburetor works so well with one of the smaller cube engines and low gears. And I am sure the old pre Xcellerator Weiand 8510 (same manifold without the name and an even deeper plenum) that I used to have and still kick myself for getting rid of would be even better providing enough gearing and camshaft.
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The real question is how "didn't" that manifold cause a greater difference in power. Look at the photo and tell me you only expected a 16 hp difference at 5600?

This differences are huge but the performance wasn't. Why?
 
Hysteric said:
The real question is how "didn't" that manifold cause a greater difference in power. Look at the photo and tell me you only expected a 16 hp difference at 5600?

This differences are huge but the performance wasn't. Why?
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There isn’t enough information in that article to make a clear assessment of what happened. At the track that street master intake would be .3 slower than an OE intake.
 
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I’m curious what this manifold would do head to head against a stock air gap. It’s an LD4B that’s been ported out like a super stock LD340. It’s at the machine shop now getting cleaned up, a crack welded, and the flanges trued up.
 
Rat Bastid said:
There isn’t enough information in that article to make a clear assessment of what happened. At the track that street master intake would be .3 slower than an OE intake.
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Think about the difference in the plenum and how small that runner entry is on the street master and the biggest difference was only 16 hp at 5600
 
I'd say for the same reason 5.2 magnum has only 15 hp less than a 5.9 magnum. You'd think 42 cubes would be worth more than 15 hp.
Hysteric said:
The real question is how "didn't" that manifold cause a greater difference in power. Look at the photo and tell me you only expected a 16 hp difference at 5600?

This differences are huge but the performance wasn't. Why?
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I believe some members here in the past more schooled on these matters have mentioned, or brought up the fact that with any of these intake manifold swaps (single planes dual planes etc) there has to be jetting changes to compliment or else it’s a worthless endeavor. The point being that you can’t just yank and plop. You gotta tune for each.
 
Hysteric said:
Think about the difference in the plenum and how small that runner entry is on the street master and the biggest difference was only 16 hp at 5600
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Once again, not enough information on the dyno pulls to say for sure, but what I know is that is the slowest intake manifold you can run on a small block. That article was done by a car magazine. That says it all right there.
 
Hysteric said:
So a streetmaster manifold that uses 318 ports tiny runners and a tiny plenum only saw a 16 hp difference at 5600 RPM on a 340 head.......Funny that.
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Hysteric said:
The real question is how "didn't" that manifold cause a greater difference in power. Look at the photo and tell me you only expected a 16 hp difference at 5600?

This differences are huge but the performance wasn't. Why?
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Because the engine didn’t demand or couldn’t move more air at the time it was done. Your scoff at the RPM VS the lower restrictive intake because there’s no great leap in power on a low demand engine is funny as hell.

318WR’s honest question was completely valid.
I’ve seen and read here RPM’s into the 11’s and a few low in that 11 range.

Oh! If I ever was so bored to port that Edel SM intake, I would not cut back the runner walls way under the open plenum area that would need to be cut out. That would actually be the first thing I’d do is to lay a gasket on top and cut straight down to form the basic plenum area and then address the roof down to the floor.

Cutting the runner dividers back shortens then runners. This is a high RPM attempt that doesn’t always work out so well.

I also see a TorkerII take a beating here a lot. There a bit rough on the street with the big plenum and stubby runners. They NEED a high stall and gear to work right and then you’ll see there not really a slouch.
 
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Excellent observation on the runner length. But yes, cutting the plenum all the way open to the carburetor flange was the idea. I’ve not even been bored enough to attempt to measure the divider width at the point where it would terminate into the plenum, but it looks like it would thin out enough at that point enough to not have to grind without end to knife edge the divider. My disdain for the excessive aluminum causes my butchery to know no bounds. My plan was going to find a hole saw with same radius as each corner of the carb flange, chuck the whole mess up into the mighty King Feng Shu drill press, and get rid of the four corners of the plenum funnel first. I believe the recip saw and the cut off wheel could get the rest. That should minimize the die grinding time… So what if I tear it up? It’s not like it has a whole lot of use as it is!
:rofl:
 
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