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The 'real' performance differences between a stock 350ci engine with open air cleaner or dual snorkel air cleaner are minor, I'm sure. But Chevy Engineering experimented with the 'snorkel' type air cleaners and promoted that the snorkel type did a better job of getting outside air flowing better to the air cleaner. Tests have been done on the dual snorkel cleaner on the '63 C2 (the 'ping-pong' ball inlet cleaner) and open air cleaner, with the dual snorkel winning out...even though there was a rather small area open to engine compartment air.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I think BKbroiler has tried both stock cai and open air element at the dragstrip. I believe he does quicker passes with the the hot air, open element. Why? Because he can get more air into the engine than going through a stock, restricted, ducted, cai. More air, more power, which more than compensates for a stock cai. That said, if one decides on cai, don't go with a stock, restrictive cai. Do it another way such as Jebby's. Remember, at 70 mph, it only takes about 60 hp. So adding a cai don't make any difference. At 6500 rpm it helps, if not stock.
I think BKbroiler has tried both stock cai and open air element at the dragstrip. I believe he does quicker passes with the the hot air, open element. Why? Because he can get more air into the engine than going through a stock, restricted, ducted, cai. More air, more power, which more than compensates for a stock cai. That said, if one decides on cai, don't go with a stock, restrictive cai. Do it another way such as Jebby's. Remember, at 70 mph, it only takes about 60 hp. So adding a cai don't make any difference. At 6500 rpm it helps, if not stock.
That's why you take vacuum measurements inside the air cleaner to establish how much vacuum is seen there. If it's more than 1.5" of water in vacuum then you do not have sufficient cubic area in the intake tract to supply the engine without restriction. I did take these tests and the stock 77 single snorkel is a restriction to a non-stock engine. So more intake area has to be added.
The reason BK has better times with open air cleaner is due to the restriction that a stock SINGLE snorkel (stock 77 L-48) presents for a non-stock motor at higher RPMs. If he were to actually provide sufficient air from a cold air source then his performance would be even better.
I know you understand the science behind cold air vs hot air.
I also know your running an open element, to each his own, it's just not optimal running an open element.
resdoggie and REELAV8R - You guys have good memories. Just to summarize my findings, on the drag strip: I made several, back to back passes using my stock L48, SINGLE snorkel air cleaner with all ducting and the pickup on top of the radiator in place and then with a 14 x 3 drop base open element air cleaner. My car ran a full 3 tenths quicker with the open element (12.7 vs 12.4) than with the stock set up. But, as you guys both understand, this had to be due to the flow restriction, in my case, of the single snorkel air cleaner.
I am sure my car would run quicker with a cold air intake setup in place. I don't just don't like the looks or the complexity of it.
Two other tidbits on this subject: I have made back to back runs with my open element air cleaner and then with the element removed but the base still installed. This resulted in a few hundredths improvement in ET and less than 1 mph increase in top end.
I also have tried running my car with the hood unlatched vs latched and I don't see any difference there.
Forum member PAULDANA designed, built and sold numerous fiberglass CAIs that were well designed and looked fantastic.
I know he was still manufacturing them a couple of years ago.
I plan to look him up in the future to see if he is still producing them but need to wait until I get my engine in and can check hood clearance before I pull the plug on one.
Here is a photo of his design.
Last edited by OldCarBum; Jan 17, 2021 at 01:05 PM.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Originally Posted by BKbroiler
resdoggie and REELAV8R - You guys have good memories. Just to summarize my findings, on the drag strip: I made several, back to back passes using my stock L48, SINGLE snorkel air cleaner with all ducting and the pickup on top of the radiator in place and then with a 14 x 3 drop base open element air cleaner. My car ran a full 3 tenths quicker with the open element (12.7 vs 12.4) than with the stock set up. But, as you guys both understand, this had to be due to the flow restriction, in my case, of the single snorkel air cleaner.
I am sure my car would run quicker with a cold air intake setup in place. I don't just don't like the looks or the complexity of it.
Two other tidbits on this subject: I have made back to back runs with my open element air cleaner and then with the element removed but the base still installed. This resulted in a few hundredths improvement in ET and less than 1 mph increase in top end.
I also have tried running my car with the hood unlatched vs latched and I don't see any difference there.
Do you think that you could knock off more than 3/10 of a second just by switching to a dual snorkel stock cai?
Do you think that you could knock off more than 3/10 of a second just by switching to a dual snorkel stock cai?
I would like to try it, if I had all the hardware. But right now, I have an Edelbrock air gap intake installed which requires an adapter to fit a Qjet since its a square bore manifold. They don't make a spread bore air gap to use with Vortec heads. That adapter is about 3/4 inch thick which means I have to use a drop base air cleaner with it.
Although everyone seems to agree that colder intake air makes more power, how much more is it? I think I read something about 1% HP increase for every 10 deg F drop in temp. So if I lowered intake air by 50 deg, that would be a 5% increase in HP. Lets say I have 400 HP, so 5% additional would be 20 HP. That won't make 3 tenths improvement. Maybe not even 1 tenth.
Many factors to consider.
What is the ambient temp vs underhood temp?
are you doing hot laps or cooling between laps? and is the hood up to allow cooling between laps?
are the headers ( I’m assuming headers) coated or uncoated?
how and when did you jet the carb? If you tuned it in 70* temps and underhood temps are 160* then you have a seriously mistuned mixture.
if ambient temp is 80* while racing and under hood temp rises to 160* that’s 8% power loss using the figure mentioned.
8% of 400? 32hp lost just due to temp, not counting the now mistuned fuel mixture which will substantially add to that loss due to excessively rich mixture.
you can’t ONLY factor in loss of air density. Tune or lack thereof adds to that loss .
Last edited by REELAV8R; Jan 17, 2021 at 03:17 PM.
Great link, I think the best I saw. There was one reply in there which made a comment that given equal amounts of air colder is better (I assume he meant equal volume in which case colder would be more mass), but then went on to say but when there is insufficient air it all falls apart. True enough. But, if the implication is is that the snorkels cause a restriction which an open air filter won't have, that ignores the other two other restrictions. The first is the filter itself since whatever air is coming in has to pass through the paper. Second is the throttle body. If the snorkel cross sections are larger than the throttle body bore cross sections, then the throttle body is the restriction. And the fact is that the total cross sections of the 2 snorkels are at least 18 sq. in. The throttle body of a Q-jet is about 11 sq. in.
If the snorkel cross sections are larger than the throttle body bore cross sections, then the throttle body is the restriction.
As logical as this sounds I am fairly certian airflow doesnt rely on this alone and the flow could still be negatively effected.. for the same reasons that some smaller ported heads flow better than larger ones.
Great link, I think the best I saw. There was one reply in there which made a comment that given equal amounts of air colder is better (I assume he meant equal volume in which case colder would be more mass), but then went on to say but when there is insufficient air it all falls apart. True enough. But, if the implication is is that the snorkels cause a restriction which an open air filter won't have, that ignores the other two other restrictions. The first is the filter itself since whatever air is coming in has to pass through the paper. Second is the throttle body. If the snorkel cross sections are larger than the throttle body bore cross sections, then the throttle body is the restriction. And the fact is that the total cross sections of the 2 snorkels are at least 18 sq. in. The throttle body of a Q-jet is about 11 sq. in.
He said one snorkle caused a restriction......not two.
Read BKbroilers post then read mine above.....
As logical as this sounds I am fairly certian airflow doesnt rely on this alone and the flow could still be negatively effected.. for the same reasons that some smaller ported heads flow better than larger ones.
I agree, it's not area alone, but I get the sense that a lot of folks figure if they compare some 14" diameter 3" high air filter they have some 131" of area for the air to come through (note, I'm not considering the pleats which obviously add a lot of area) vs. the smaller area of a snorkel which, by the way, I did not notice anyone actually determining the size of (apologies if I missed it). However, my point was primarily that the throttle body itself is more of a restriction than the dual snorkels. As for what's going on inside the passages of the duct work, yes every bend will cause further resistance to flow, but these are large sweeping bends for the most part. And the ducts have the advantage of air being directed into them as the car speed increases so it is flowing in the direction it is needed. I suspect air around an open filter is moving in random directions and thus counting solely on vacuum to pull it in. Further, once past the filter, there are significant twists and turns for the air as it attempts to make 90 degree turns to go through throttle body and down into the manifold, banging into venturies and other obstacles along the way. Given all that, I doubt that the snorkels are restricting airflow more than the carb itself - note snorkels in bold to emphasize that in prep for next response.
He said one snorkle caused a restriction......not two.
Read BKbroilers post then read mine above.....
Jebby
I'm not sure if you thought my reply in which I noted another posters claim that if there isn't enough airflow it doesn't matter about temperature was pointed at BK. If so, it wasn't. It was referencing another thread. And in any case, I did say, "true enough" about the comment. A couple points on BK's post, first it is excellent, nothing like actual testing. Second, being an L48 and seeing such a difference implies an L82 would be even more impacted using a single snorkel given that its torque and hp curves are bumped up about a 1000 rpm over an L48. All else being equal, i.e. things like displacement and volumetric efficiency, that 20% higher RPM (and power, e.g. in 1980 a 190 hp for an L48 vs 230 for an L82) would need to flow 20% more air. So, if the L48 was restricted with one duct, it would be quite a loss on an L82. Lastly, I liked BK's note on the pulling the filter element out and seeing negligible change in performance. Good to know that the filter, at least what he used was not a factor.
Loaded a few pics of the mods made to my 77 L-48 in order to get sufficient air to the engine without presenting a restriction to power all the way up to 6700 RPM.
the first iteration of this system was with one additional intake on the passenger side, and that was good enough for the DART SHP heads that were on there at the time making abput 406 HP. No more than 1 1/2" of water column vacuum present inside the air cleaner assembly during operation.
Then I put on AFR 180 heads. Suddenly I did not have enough air for the engine. Jumped up to something over 7" of water vacuum. I did not have it calibrated higher than that. The water was just sucked into the air cleaner assembly and consumed. AFR's are producing about 440HP. Also had to drill the float main orfice larger to provide enough fuel for the carb/engine as it was running out of fuel at the top of second gear.
Goes to show how much better the AFR's flowed vs the DART SHP's. I added the second intake tube on the drivers side and once again dropped the vacuum inside the air cleaner assembly to 1 1/2" or less of water.
Those are 2" exhaust pipe sections I used to weld onto the air cleaner can and also attached to the wall into the wiper tray area.
I don't know how much square area is required for a certain CFM carb and I'm not sure it's even a linear relationship. I do know how to measure the vacuum present inside the air cleaner assembly though. And modify the system until it meets the demand of the engine.
There is also a flapper valve inside the snorkel of the 77 L-48 that is vacuum actuated via water temps. That was removed completely. Then the stove pipe hole on the bottom that sucked hot air during warm up was plugged.
I think at one time I measured the square area of the snorkel and it was around 7"square IIRC. So I have effectively added 6.28 square inches to that number. People that look under the hood don't even comment on the mod. I assume they think it's stock.
Additionally by collecting air at the wiper tray it is somewhat pressurized at speed as that is a high pressure area.
Last edited by REELAV8R; Jan 17, 2021 at 07:50 PM.
The first is the filter itself since whatever air is coming in has to pass through the paper.
Yes! I tested this too and found that the paper filter was a significant restriction vs the K&N filter.
When I did a dyno a couple times I tested with air cleaner lid on and removed, there was no difference in HP or torque. Proving that the mods I added were working and providing sufficient air to the engine.
Also proving that the K&N filter was not a restriction.
Loaded a few pics of the mods made to my 77 L-48 in order to get sufficient air to the engine without presenting a restriction to power all the way up to 6700 RPM.
Nice post. Question, you mentioned the heads and I can see the headers. Did you mod anything internally? I'm still debating new engine or just upgrade the top of the L82.
Nice post. Question, you mentioned the heads and I can see the headers. Did you mod anything internally? I'm still debating new engine or just upgrade the top of the L82.
Yes, extensively modified. The only thing original is the oil pump, although ported for additional flow,
the bore of the engine is still stock as is the deck height,
and the Q-jet is original, but extensively modified as wel, via Cliff Ruggles' book.
Scat crank 3.48" and 5.7" con rods. So it's still a 350 CI engine.
11.5 cc Kieth black hyper pistons,
Heads have been angle milled to 55.5 cc's giving me 10.6:1 CR.
Cam is a roller cam, 270/270 on a 108 LSA with .549" lift at the valve. Full roller rockers 1.6 ratio.
Edelbrock performer intake that has been significantly ported to provide adequate flow to the heads.
An L82 will take to just a top end modification far better than an L-48 with stock internals. You got forged internals and flat top pistons to work with.
Last edited by REELAV8R; Jan 17, 2021 at 08:55 PM.
