[tjs72lemans]

I restored my 72 Lemans vert and the original 400 engine was rebuilt mostly stock, except a 701 Voodoo cam and hei ignition. The dyno came in at 308 hp and 400 max ft lbs torque. I also put stock exhaust on. It has a 400 turbo auto. The real issue for me is it seems sluggish. I was expecting power similar to my 350 in my Camaro. Most of my present and past hot rods have sported open element air cleaners, because they seem to breathe better and less restricted. I'm considering either using my dual snorkel for car shows only and replacing with an open element or flipping the lid like in the old days to allow more air all around the dual snorkel. Would you agree the dual snorkel is a restricted type of filter? Anyone test any of this?

[ta man]

Either air cleaner will not make a huge difference in power. Stock exhaust will eat up horsepower. What is your gearing and carb?

[Matt Meaney]

back in the day, i took the log manifolds and stock exhaust off my '72. replaced it with headers and 3" pipes. picked up a full second and almost 5 mph with no other changes. including leaving the dual snorkel air cleaner on. went from 13.8's to 12.7's.

[SRR]

Any head work? HEI re-curved?

[b-man]

You’ll see a big difference replacing the stock exhaust with a 2-1/2” mandrel bent exhaust and whatever free flowing mufflers you prefer.

The dual snorkel air cleaner isn’t restricting your engine’s breathing it’s your exhaust. The stock exhaust is always the first thing you upgrade from, even if you’re keeping the log manifolds.

Your Le Mans likely has a 2.78 rear gear which isn’t really going to help that 400 move a car that weighs close to 4000 pounds, convertibles are heavy.

[Schurkey]

NASCAR teams figured out that hot underhood air was detrimental to performance in the late '50s if not before.

Never understood why folks would put an open-element air cleaner on a vehicle, when the Treasure Yards are full of air cleaner housings already set-up for cold air intake from the radiator support, or nearby.

[tjs72lemans]

Since I did absolutely everything in my garage on this frame off, I didn't want to drive open exhaust downtown to a garage to do that. So, I wanted something that I knew would fit and have no interference (had no exhaust to go by when purchased in parts). Therefore I just bought a stock system with stock mufflers and installed myself on my back. It sounds quiet and the tips out the side have the sound I want. I figured if stock configuration was 250 hp and I'm now at 308 hp, there's not much difference to worry about with exhaust. Maybe I'm wrong.

No recurve to hei. Rear end is stock 3:23. Stock 4 bbl rebuilt by Cliff that runs and performs great. The motor was bored out .03 and stock rebuilt heads with no work and roller tip rockers. The sad point is the stock 8.2 compression ratio was whistled on the dyno at 7.8. I also have stock manifolds.

If I thought it would really make a difference, I would take it down to the local shop now and ask to replace with bigger tube exhaust. Not sure if that would also mean getting different mufflers than the stock style too. ?

[b-man]

The stock restrictive exhaust is the biggest thing hindering performance. New free flowing mufflers are needed along with it, my favorite for quiet and low restriction is the Walker Dynomax 17749 20” long muffler.

A recurve of the distributor would also be a big help.

You’d be surprised what having a more performance oriented ignition curve can do, coupled with a good exhaust it should feel like a different car.

[NeighborsComplaint]

I run a Stock dual snorkel and my butt dunk says I lose 10 + hp compared to no air cleaner or an open element air cleaner. I’ve tried a low restriction element and also no element in the dual snorkel and they run the same so it’s the dual snorkel housing that’s the restriction. With the dual snorkel, it spins the tires about 50’ from a 20 mph roll. With an open element or no air cleaner. It spins the tires as long as I’m on the throttle. Or hit the redline. I’ve found replacing the lid with a standard 14” lid works as well as an open element and keeps the OEM look

[ZeGermanHam]

Engine Masters season 2, episode 27 tested nineteen different filter combinations on a 760hp BBC. A factory style dual snorkel came out at 15th worst, killing 53hp compared to baseline. They estimated it would be suitable to run on something making up to around 390hp. An open 14x3" K&N filter with drop base killed 12.7hp compared to baseline. An open 14x3" paper filter with standard (i.e., non-drop) base killed 10.1hp relative to baseline.

A dyno cell is not the same thing as an engine bay, so it's not always apples to apples, but there are differences for sure. The Engine Masters episode is definitely worth a watch. There are some surprises in there.

[242177P]

Originally Posted by tjs72lemans

... or flipping the lid like in the old days ...

Flipping the lid gave quiet cars a fun *BWAAAH* noise, but I've never associated it with anything that could perform. Good for a day's worth of amusement, like hockey cards in bicycle spokes. Exhaust first, helps mpg too. After that, if you still feel the intake can use some help, slip a K&N inside the air cleaner.

[GTOLou]

Originally Posted by ZeGermanHam

Engine Masters season 2, episode 27 tested nineteen different filter combinations on a 760hp BBC. A factory style dual snorkel came out at 15th worst, killing 53hp compared to baseline. They estimated it would be suitable to run on something making up to around 390hp. An open 14x3" K&N filter with drop base killed 12.7hp compared to baseline. An open 14x3" paper filter with standard (i.e., non-drop) base killed 10.1hp relative to baseline.

A dyno cell is not the same thing as an engine bay, so it's not always apples to apples, but there are differences for sure. The Engine Masters episode is definitely worth a watch. There are some surprises in there.

They also flipped the top on the dual snorkle and it came out far better. Easy way is to run that dual snorkle w/ a taller filter element and it'll work out fine.

[GTOLou]

snorkel* lol.

[Matt Meaney]

access to a chassis dyno could make short work of dialing in the dist. and carb.

another part that can have a dramatic effect on how the car performs, is the torque convertor. having one that best works with where the engine makes power, how much the car weights, rear gear, etc. can be very different than any old one picked off the shelf. cliff works with tri shield on custom convertors, might be worth contacting him.

[Formulajones]

On my stock RA III when I upgraded from the stock Gardner transverse exhaust to a 2 1/2" mandrell bent transverse kit it went from 14.10 at 99 mph to 13.70's at 102 mph with no other changes.

A long time trick done in pure stock where original air cleaners must stay in place is to run a slightly taller filter that raises the lid about a 1/2". This also gets the base of the lid away from the top of the carb air horn which is a big improvement. A lot of those factory snorkel air cleaners have that lid nearly right on top of the air horn with a stock height filter

[Murf]

Originally Posted by ZeGermanHam

Engine Masters season 2, episode 27 tested nineteen different filter combinations on a 760hp BBC. A factory style dual snorkel came out at 15th worst, killing 53hp compared to baseline. They estimated it would be suitable to run on something making up to around 390hp. An open 14x3" K&N filter with drop base killed 12.7hp compared to baseline. An open 14x3" paper filter with standard (i.e., non-drop) base killed 10.1hp relative to baseline.

A dyno cell is not the same thing as an engine bay, so it's not always apples to apples, but there are differences for sure. The Engine Masters episode is definitely worth a watch. There are some surprises in there.

Yeah but, He probably don’t have room for the salad bowl! ��

Anyway, I wonder how similar dyno rooms are to engine compartments. Not very would be my guess.

I love the show but sometimes I think it’s hard to apply what they find to the real world.

Cold air intake would be the winner in my mind but it’s sometimes hard to implement.

Murf

[25stevem]

Let’s for now leave peak hp and the needed air flow for that out of the picture for now.

If the OP is talking about off idle sluggish throttle response below 3500 to 4000 rpm with that still kinda small cam then my guess is that the cam is in retarted and or the vacuum advance and or dizzy timing is not right yet.

The motors cranking compression really needs to be checked to truly start the process of eliminating what the root problem is.

[Formulajones]

Originally Posted by Murf

Yeah but, He probably don’t have room for the salad bowl! ��

Anyway, I wonder how similar dyno rooms are to engine compartments. Not very would be my guess.

I love the show but sometimes I think it’s hard to apply what they find to the real world.

Cold air intake would be the winner in my mind but it’s sometimes hard to implement.

Murf

Track testing That's where I have the most fun anyway

Changing air cleaners around is eye opening. I did a bunch of that at the track on a few different cars until I settled on something that worked best. Each car was a bit different. I've seen interesting stuff on chassis dynos too, like the car making more power with the air cleaner in place vs removing it. Even makes a difference if you just put the base on and leave the lid and filter off.

[ZeGermanHam]

Originally Posted by Murf

Yeah but, He probably don’t have room for the salad bowl! ��

Anyway, I wonder how similar dyno rooms are to engine compartments. Not very would be my guess.

I love the show but sometimes I think it’s hard to apply what they find to the real world.

Cold air intake would be the winner in my mind but it’s sometimes hard to implement.

Murf

The salad bowl is king!

I don't disagree about the difference between a dyno cell and an engine bay. I do however still think there is valuable info in that episode regarding airflow. IMO, a dual snorkel is still sucking in hot air from the top side of the engine compartment, and they are much more restrictive than an open filter in terms of airflow. A true cold air intake is the best option.

Back to OP's report of sluggishness, I'd probably flip the lid on the dual snorkel he has and just run that. The Engine Masters episode showed that flipping the lid improved airflow a good amount, and it should flow more than enough CFM for OP's current power level.

My hunch is that the sluggishness that OP is experiencing will remain regardless of the air filter combo, and I agree with the others above regarding the ideas of exhaust, timing, converter, etc.

[Murf]

+ 1 to all the above!