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Caress of Steel
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Discussion Starter #1
So about those air cleaners...this style:
https://www.summitracing.com/parts/sum-g282/overview/

Last drive of the season last year my motor all of a sudden starts popping and spitting. Thought I had lost the cam gear again or dizzy and timing had gotten mucked up. Had the car taken home but between work and other obligations never really dug into it all winter. Noticed the air cleaner top was turned around and looked odd, so I was worried might have happened.

Now it's confirmed. Was getting OK compression all the way around, but one cylinder was 120 where the rest were at 135-140. It was clearly running pig rich and plug 3 was wet. Pulled valve covers and spun it again and noticed #3 exhaust rocker wasn't moving at all. Pushrod was still there though and wasn't spinning loose or bent. At this point I pulled the motor and tore it down, confirming that at least one of the screws that holds the top and bottom center piece had worked its way loose and went into the motor. Damage could have been much worse. All it really did was very light scraping of the piston top and wreck the exhaust lifter. No damage to head, though the valve may be very slightly bent. Then, of course, the wrecked lifter wrecked the cam.

Could replace those parts, slap some new main bearings and a new cam in and be fine, but, this block has been through 5 rebuilds, 3 since I've had it, so I'm retiring it from active duty. Time for a Dart 427!
 

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So what of the damage is attributed to the air cleaner? Was it a part of the air cleaner bouncing around the combustion chamber?
 

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Caress of Steel
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Discussion Starter #5
That's what it looks like. On those filter tops, there's a small metal center cap on the top and bottom sides of the filter, held together by two small screws/ bolts. I think one of those little bolts worked its way loose and fell in.

The lifter didn't twist, the roller broke off.
 

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So what of the damage is attributed to the air cleaner? Was it a part of the air cleaner bouncing around the combustion chamber?
I'd like to know this information too. I have been running open top filters for the last 7 years on, mainly due to the increased air flow for my Holley Terminator EFI and most recently Holley Sniper for the current Cobra.

I tried switching to the desired air cleaner I wanted last season, the Cobra lettered oval top...immediately had a change in performance! Bucking, sputtering, stalling...changed back over to the open top and every symptom was gone! Keep in mind that this was within 15 minutes.

Could the EFI have learned the new air flow characteristics, sure, I imagine it would. My thinking was the hood is closed 95% of the time, why mess with something that was working flawlessly anyways just for aesthetic purposes.
 

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Senior Charter Member
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Sorry To Hear...

Joe,

Can you show what you mean aout the air cleaner? I'm not getting what you are saying about the screw. I've got FE so it won't affect me, but I'm curious anyway.

Regards, Rick.
 

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I've seen very very small throttle shaft screws do A LOT more damage to a piston than that, but then no damage the lifter and cam... Can you show us the combustion chamber and the screws that hold the air cleaner assembly together?
 

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Junior Charter Member
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Speaking of top-flow filters, the Hot Rod boys did a great episode of Engine Masters where they ran different air cleaners on the dyno. My recollection is that the top-flow filter didn't do as well as conventional style. Height of filter seems to be the critical factor in flow overall, with overall surface obviously being a major factor as well.


BTW, this is a great series, worth a binge session if you haven't seen them all.
 

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FFCobra Fanatic
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I'd like to know this information too. I have been running open top filters for the last 7 years on, mainly due to the increased air flow for my Holley Terminator EFI and most recently Holley Sniper for the current Cobra.

I tried switching to the desired air cleaner I wanted last season, the Cobra lettered oval top...immediately had a change in performance! Bucking, sputtering, stalling...changed back over to the open top and every symptom was gone! Keep in mind that this was within 15 minutes.

Could the EFI have learned the new air flow characteristics, sure, I imagine it would. My thinking was the hood is closed 95% of the time, why mess with something that was working flawlessly anyways just for aesthetic purposes.
I've been running the Cobra top cover on my oval filter (2 1/2") for years and using the Holley Terminator without any problems at all. Maybe the oval filter you're trying to use is too short. The Terminator also likes a single plane manifold or a dual-plane that has been shaved down on the "splitter".
 

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Caress of Steel
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Discussion Starter #11
Here are the photos of the filter top lid - pretty sure it was one of those little allan bolts that dropped in for a visit, and photos of the rich-running combustion chamber and cylinder. How it didn't muck those up worse is beyond me. But the new Dart 351 block is in da house!
 

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Damn,

That's an expensive air cleaner, Joe. (In more ways than one.)

Sorry for your bad luck.
 

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Based on these photos, I don't believe the cam and lifter damage was related to something getting sucked into the engine. If that happened, I would expect to see damage to the top of the piston and to the combustion chamber. The foreign object should have made BOTH be pock-marked like the surface of cheap bricks, for lack of a better example. (If I come up with a better example I'll share it...) The combustion chamber should have marks just like the top of the piston. Not sure what's going on on top of the piston, but maybe that's carbon coming off relating to the combustion being completely wrong because the valve that corresponds to that lobe and lifter isn't doing what the cam grinder had in mind.

Also, I can't conceive of a way that if there was something bouncing around in the combustion chamber, that it'd leave the valve looking nice but wreck the lifter (which of course would then wreck the cam).

Sorry for your lifter failure. Don't junk the bottom end, I expect somebody would be interested in at least salvaging some things off it.
 

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Caress of Steel
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Discussion Starter #14
That makes sense, I was fully expecting to find a wrecked combustion chamber and piston when I popped the head off. But was relieved they weren't, so I can sell the bottom end and use the head on the new build.

Which leaves the question of why the lifter failed. Other than the curse left on this block by the previous owner.
 

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Those pictures you posted don't show any damage on the piston, cc, and valves. Nothing shiny...

IOW, no presence of debris. A roller won't snap like that unless a clearance issue but your pictures don't show that. I have seen damaged cc in my lifetime several times.

I am stumped

Sent from my SM-N950U using Tapatalk
 

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Junior Charter Member
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Idaho Falls

Sorry to here that Joe. Things happen all the time. We will honk on our way through Idaho Falls on our way to the Huntington Beach show. Two of us are coming from Canada.
 

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I've been running the Cobra top cover on my oval filter (2 1/2") for years and using the Holley Terminator without any problems at all. Maybe the oval filter you're trying to use is too short. The Terminator also likes a single plane manifold or a dual-plane that has been shaved down on the "splitter".
I no longer have the Fastback the Terminator was installed in. The Sniper I currently have DID NOT like the Cobra air cleaner. However, like I said, it was already "tuned" to the open top...so I'm assuming the Sniper would have changed it's parameters, I just didn't want to wait around and see as it was already driving perfectly.

I'm going to reset the Sniper on Thursday, as it's running a bit rich with my initial selections, and see if the Cobra air cleaner will work ok from the beginning as opposed too already set parameters.
 

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FFCobra Fanatic
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I no longer have the Fastback the Terminator was installed in. The Sniper I currently have DID NOT like the Cobra air cleaner. However, like I said, it was already "tuned" to the open top...so I'm assuming the Sniper would have changed it's parameters, I just didn't want to wait around and see as it was already driving perfectly.

I'm going to reset the Sniper on Thursday, as it's running a bit rich with my initial selections, and see if the Cobra air cleaner will work ok from the beginning as opposed too already set parameters.
I'm installing a Sniper on another car later this spring and will be curious how it works with the Cobra top and taller AF. Both mine (Terminator) and the other are running 331's. Should make for an interesting tune.
 
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