I’d venture to say that in a comparison at the strip the AG would pull away from that one at least to mid track so much (if not entirely) to the point that any top end benefits of that LD4B would be negated. It would run out of track trying to overtake the AG’s jump and overall pull. Just spitballling
Streetmaster to Airgap
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Yeah, I think it’s more something for use on a 408 inch or bigger engine. I think it would probably be even a bit much for my soon to be installed 4.56 gears and L60-15s.
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Good observation. So its safe to say that the engine wasn't really handicapped by the tiny manifold runner that's way smaller than the 360 head port?
Your assertion. These 2 intakes are at opposites ends of the spectrum. Doesn't look like that engine needed all that much air flow to make 230 Hp at the wheels.
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What was 318WR's honest question?
I initially ran an opened up to 360 port window, deep ported, reworked and contoured plenum Weiand Action+ on my stroker and methodically tuned on things, knocked off et and gained mph ultimately removing the divider and seeing more gains to the point I ended up swapping to an AG and continued whittling away. Initially with just swapping to the AG (carb tuning required was minimal iirc) I knocked off about .15-.20 and gained 1-1.5 mph in the 1/8, I want to say about .20-.25 and 2 mph in the 1/4 over the ported Weiand. There was other testing and tuning with chassis so some of the et improvement was likely due to a few other things but the mph gains between the intake changes was definitely due to the AG. Only one way to find out what’s what! You never know until you try.
I ended up installing a fabricated divider back into the Weiand for my sons 360 powered 78 Magnum as we want maximum torque and lower range power to move that heft.
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About 175 CFM.
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So the engines not using all the airflow the heads are giving to it?
Just means the sum of all parts combined equates to the amount of air that can be moved.
Yep. On a combo that makes less than 240 whp, 15 hp more at peak is quite a bit IMO. More importantly, it makes at least 15 hp more at EVERY point on the dyno pull. 22 hp more at 3000 rpm. I would imagine that the SM would feel like a complete turd on the bottom end compared to the Air Gap.
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Professor Fate
Push the button, Max...
In this case max CFM at 5000 rpm. of course the air moved at 3000 will be lower.
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Then we agree that a 15 hp drop is not significant between a large port intake manifold 340/360 and a small port 273/318 manifold in total air flow demand on a 345 ci motor with 9.81 and 587 heads with 1.88 valves and a 340HP cam?
If the manifold runner size was the impediment we would have seen a greater difference in HP would we not?
Looks to me like a good gain for the manifold swap. I wouldn't expect 50 HP though.
It was actually only 15 Hp gain before all the other final add ons
I read it too. What were you expecting? 15HP by itself from an intake swap is a good improvement.
Mostly Correct. But correct.
Correct
The Edelbrock head had a totally different thought process behind it when it was designed.
Has anyone used that Edelbrock intake at the track into the 11’s? (Paraphrased)
The heads do not give the cfm. The heads cfm ratings are based on a machine with a 28” depression, which is what is getting the air to move. What is your vacuum reading @ WOT?
The heads ability to flow is a combination of the days air pressure (millibars) the vacuum generated by the engine, the size of the carb, the intake manifold & how well it flows all going past the head, which “Allows” only so much through it.
Bam!!!!
Even less once you understand that an engine doesn’t suck in the air and fuel at 28”’s of depression.
Not really, but as fishmen said, it is the some of parts.
The demand is higher because there is more rpm. Each revolution will have the engine digest a certain amount of air. Lets use 1oz. for each revolution. Now the engine idles at 740 rpm’s, that’s 740 oz’s. Cruising the Hwy @ 3200 rpm’s, that’s 3200 oz’s. Etc….
But now we have to look at the intakes. Let’s say the head will flow 200. The intakes once bolted to the head almost always hinder the heads ability to breath in the Air and fuel. The cfm drops because the head is now trying to move air and fuel, not just air like on the test bench.
The small port intake may flow 200 or even 250, but that was with dry air. Now add in fuel which requires more energy and since it is very heavy vs air, the fuel flows slower and also slows down the air.
Now the engine can only digest 175 cfm worth of air and fuel. By swapping to the rpm with its larger and better shaped ports for moving air, even though the lower ports have a harder time keeping up, there still moving more air and fuel due to the volume contained within the larger runner. Even if the RPM still slowed down the A&F to 175, there is just simply more available to squeeze in past the valve.
While 15 HP isn’t huge on its own, IMO, 15 hp is a huge amount on the swap of intakes on this low powered engine. Make the same swap on a well built street strip ride and it’ll be 50 or better.
Notice how the other parts only added a few hp? But in total, it all added up to nice package. They also help each other out. The whole engine gets better.
IMO, I actually think it was a good write up showing how an average guys without a lot of bucks can make a nice street ride. If someone had this type of a starter platform, and then paid the piper for the articles parts, there would only be 3 things to a hotter package.
Converter, gears and a better camshaft. Ok, maybe wheels and tires to. This is a good reason 5.9’s are popular? Even better with a forced induction. Look around FABO because there’s several that have done this.
I have eye-witnessed factory cast intakes with TQ's run 10's in all steel Demon. I have seen (and actually have a friend) that has run RPM's into mid 11's. AGAIN, has anyone even witnessed a streetmaster go .... 13's ?? OK, OK, OK.... 14's ???? Asking in sincerity.
This ^^^^^^ sums it up.
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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......
I have not, but I've seen a Holley Street Dominator (350 Chevy) go 10s. WAY different plenum than the chitmaster, though.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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This article , IMO, is not realistic nor representative of HotRodding, nor of our hobby.
For starters, everybody knows that if you have 318 logs on your 9.8Scr 340, THAT would be the first thing to get rid of. How is the AG supposed to overcome that dam. That it made any additional power at all is a testament to how bad the SM is. IDK, when looking at HRM stuff you gotta always be looking at their methodology.
In this case I see AG and headers together, over SM and 318 logs, is 42 hp; which seems reasonable. What if the headers on the SM only garnered 12 hp over logs, and then the AG WITH headers now on the engine, won another 30 over the SM/and headers? That sounds more realistic. To me it looks like somebody wanted to make headers look better than the actually are. In any case I feel the headers shoudda been first up, or the SM never tested.
But what do I know; I'm the guy with TTIs and dual full length 3" cannons on his stock Smoggerteen, cuz yakno, I don't care what anybody says, a little backpressure is NOT good a good thing, lol.
For starters, everybody knows that if you have 318 logs on your 9.8Scr 340, THAT would be the first thing to get rid of. How is the AG supposed to overcome that dam. That it made any additional power at all is a testament to how bad the SM is. IDK, when looking at HRM stuff you gotta always be looking at their methodology.
In this case I see AG and headers together, over SM and 318 logs, is 42 hp; which seems reasonable. What if the headers on the SM only garnered 12 hp over logs, and then the AG WITH headers now on the engine, won another 30 over the SM/and headers? That sounds more realistic. To me it looks like somebody wanted to make headers look better than the actually are. In any case I feel the headers shoudda been first up, or the SM never tested.
But what do I know; I'm the guy with TTIs and dual full length 3" cannons on his stock Smoggerteen, cuz yakno, I don't care what anybody says, a little backpressure is NOT good a good thing, lol.
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It was a cheesy comparison. imo
I don't believe the Air Gap would have gained 15 HP over a factory 340 manifold.
But it was their test.
Maybe not the 71 only intake. I think it would be substantial over the 70 and prior intakes. I call anything over 10HP substantial for "just" an intake change. The 71 only TQ intake has to be one of the best ever flowing stock iron single 4 barrel intakes ever made.
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