Air Cleaner woes - Team Camaro Tech
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post #1 of 15 (permalink) Old Jul 4th, 00, 04:20 PM Thread Starter
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Tried a nice, new, shiny air cleaner on my 69 SS/396, turned out to be a bad idea. It ran fine for about 15 miles, then started to "miss", and run like crap. Thought it was a plug wire, or something in the distributor, but I figured I'd just pull the air filter off first to see what happened. Fixed the probably immediately. What would be a good filter to use, that would give me clearance with the SS hood? I had a cheap Edelbrock triangle air cleaner, and performance wise it was fine, but I didn't like the look, and was told by several people they don't "filter" very well. Also, how important is the hose from the valve cover to the air cleaner? I never knocked out the hole on my M/T aftermarket covers, and haven't been using the fitting in the air cleaners, I think this is where the PCV valve goes on most cars? I'm confused, what would be a good filter, and do I need the hose into the valve cover? Oh yea, it's a Holley 750 DP, and runs great with no filter, or with the old Edelbrock triangle filters. Any suggestions would be welcome!
Thanks.........KZ http://www.geocities.com/kz1000ltd/
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post #2 of 15 (permalink) Old Jul 4th, 00, 08:32 PM
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KZ1000, you ask how important is the hose going from the valve cover to the air cleaner. I think its pretty important if it's being used as the crankcase breather, which is it's only purpose as far as I know. If you have a pcv valve properly hooked up to a vacuum source, then you need a crankcase breather someplace. I knock out the hole in my valve cover and just use a stand alone breather cap, but a hose to the air cleaner works as well. Of course, none of this explains why it runs good with the old air cleaner or no air cleaner, but poorly with the new air cleaner.
post #3 of 15 (permalink) Old Jul 5th, 00, 02:33 AM Thread Starter
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Rich, I knocked out the hole on one side, where I use the standalone breather cap, but not the other side. The breather cap is also where I put the oil, not that it makes any difference. Do I need another hole on the other valve cover, for crankcase ventilation, and maybe run that one to the air cleaner? I don't think I need a PCV valve, as smog control is not much of a consideration, I can get my car inspected several places without even opening the hood!
Once again, thanks for the help! KZ http://www.geocities.com/kz1000ltd/
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post #4 of 15 (permalink) Old Jul 5th, 00, 03:05 AM
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if clearance is the problem,get a dropbase aircleaner,i have a flat hood and had that problem.

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post #5 of 15 (permalink) Old Jul 5th, 00, 03:38 AM
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kz - I think your new aircleaner might be too close to the top of the air-horn (think that's what it's called). How tall is your element? If 3" see if a 4" will fit and clear the hood. (I have a 3" and had a 1" spacer under the carb and it all fit under my SS hood.) What type filter element did you get? A cheap paper element might be choking it out a bit!

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post #6 of 15 (permalink) Old Jul 5th, 00, 05:09 AM Thread Starter
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It was a cheapy, I think I know why now.....
but it sure looked good for those 15 miles!!
Maybe I'll just save it for the Car Show!
It's very thin, and very small in diameter.
I don't think clearance would be an issue, so I'll get a bigger one. I looked at a K&N filter, but there's no way it would have fit, much too tall. Any suggestions? Do I still need to knock a hole out of the other valve cover, and run a hose to it? KZ
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post #7 of 15 (permalink) Old Jul 5th, 00, 07:36 AM
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KZ, When I read your original post I got the false impression that you had a pcv valve, but not a breather cap. If you already have a breather cap, then running a hose from the other valve cover to the air cleaner would not be needed. However, in my opinion, you should hook up a pcv valve to complete the system. Not so much for smog control, but to clean the crankcase of blow-by gases. I have heard that if those gases remain in the crankcase, they form deposits and sludge, shortening engine life and even hurting performance. It sounds like all you need to do is knock out a hole in the other valve cover and install a pcv valve in it. Then run a hose from the pcv valve to the big vacuum fitting on the Carb, not the air cleaner. Remember, the pcv valve needs to be connected to a vacuum source, so it can suck dirty air from the crankcase. In the mean time, the breather cap that you already have, will allow clean air to be drawn in.
By the way, I use a fram air cleaner element with a 14" diameter and 4" high. It clears my flat hood. But then again, I have a small block. I have always heard to use the biggest air cleaner you can get away with.

[This message has been edited by Rich253 (edited 07-05-2000).]
post #8 of 15 (permalink) Old Jul 5th, 00, 12:05 PM
 
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lose the 10" air cleaner and buy the 14" and say goodby to your problem
post #9 of 15 (permalink) Old Jul 5th, 00, 01:53 PM
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Check the clearance behind the filter base to ensure that it does not hit or rest against the distributor cap, Could you have a bad coil wire and it is arching to the filter base? The original filter bases have a hump indented to clear the coil, does this one have one? Or try moving the coil.
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post #10 of 15 (permalink) Old Jul 6th, 00, 08:00 AM
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I have a 69 and have run a 4" K&N on a drop base air cleaner with the SS hood with no problems. This is with a Performer RPM manifold. I think if you had a thin element, you experienced airflow problems into the carb making an over-rich condition. I've heard of some real cheap filters getting sucked into the carb. As far as the breather, I've done it both ways. Although I like the looks better with a K&N breather on each valve cover, I've gone back to a pcv on one of them to eliminated the contaminant buildup mentioned earlier. Twin breathers will only prevent pressure buildup but won't purge the crankcase.
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post #11 of 15 (permalink) Old Jul 9th, 00, 01:46 PM Thread Starter
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UPDATE: Well, just when you think you've got something figured out.......I put a new K&N drop filter on her, added the PCV valve on the passenger side valve cover, fired her up, ran great. For about 15 miles. However, this time, when I took the air cleaner off, it wouldn't stop running like crap. Limped her home, pulled out the spark plugs, they were all black (gas fouled I believe). Therefore, I replaced them all, fired it up, still running like crap. Well, I noticed a little junk in the fuel filter, so I replaced it, ran the carb dry several times, beat on the bowls, thought something might have made it's way in there, no luck. It's running rich and fouling the plugs. Mind you, none of these problems were happening until I tried to screw with the air cleaner. Anyway, to make a long story short (too late) I took the carb off, a Holley 750 DP, and replaced it with a Holley 600 that came with the car. Man, I'm glad no one wanted it! Anyway, that cured the problem, for now. Apparently, my 750 DP crapped out on me, now I have to figure out what's wrong with it. I guess I'll take it apart and look for some dirt. I've rebuilt many a motorcycle carb, but never an automotive carb. Can't be too hard, famous last words...... Anyway, I'm just wondering if there's any way I could have damaged the carb, just by putting a restrictive air cleaner on it? Whose got a bright idea? How about, "If it ain't broke, don't fix it?" Oh well, you live and learn.
KZ http://www.geocities.com/kz1000ltd/

[This message has been edited by kz1000ltd (edited 07-09-2000).]

[This message has been edited by kz1000ltd (edited 07-09-2000).]
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post #12 of 15 (permalink) Old Jul 10th, 00, 02:28 AM
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My first piece of advice would be to scrap the holley & buy a carter/edelbrock. But that can cost some mucho bucks. One of the nice things about holley's is their ease of rebuilding. Take the list number off the front off the airhorn, go down to your local holley distributor and buy a carb kit. It'll have all the necessary parts,gaskets & instructions you'll need. When you've taken the metering blocks away from the main body, run some compressed air through the orifices to dislodge any foreign material. Do you have a spare electric fuel pump? If so, you can set the bowl level on the bench by hooking it up and pumping from a coffee can or something similar. Just remember when reassembling the carb, "clean,clean,clean, dirt is your enemy".

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post #13 of 15 (permalink) Old Jul 10th, 00, 05:07 PM
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If you had any backfiring, the power valve may have a ruptured diaphram.
You can test it by placing a small suction cup over the carb body end of the valve and causing it to suck on the diaphram. If the cup won't hold the plunger in, it's probably bad.
I've also tested these by pressing in on the plunger and holding it against my palm tightly and releasing the plunger. If the plunger moves back when your palm is removed it is OK, holding vaccum. This second way is not as reliable as it's hard to get a seal against your palm.
Find a kid and steal one of his his rubber darts.
Any replacement should match the number on the side of the valve. That's the opening vaccum in inches. Usually a 65= 6.5 inches of vaccum opening point.

Holleys are also sensitive to dirt, you need to run a paper fuel filter. The bronze ones at the inlets are not good. The air bleeds inside the airhorn can also get plugged and cause a rich condition.
Squirt carb cleaner in every hole, and blow out with compressed air.
Just fuel drying out in the bowls can leave residue and cause plugging. The idle passages and idle feed restriction are the smallest jets in the carb. But plugging of these would cause a lean condition not rich.
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[This message has been edited by davidpozzi (edited 07-10-2000).]
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post #14 of 15 (permalink) Old Jul 11th, 00, 12:48 AM
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I have a Holley 700 DP on my 355. When I bought the car, it was extremely rich. The primary cuprit was that the power valve was finger loose from vibration I assume. Once tightened most of the richness went away. A minor contributor was too high fuel pressure. A regulator cured that.
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post #15 of 15 (permalink) Old Jul 11th, 00, 04:27 AM Thread Starter
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Davidpozzi,
The only time it backfired was the day it was installed, I poured a little gas in there to prime it, and it backfired once, and then started right up. This was back in March, I probably but a couple thousand miles on it since then, without any problems at all until this whole air cleaner incident. I'm beginning to think it was just a coincidence.....I will check it out, but where is it located, physically, on the carb, and what does it look like? Also, I think I'm just going to add another filter, back at the gas tank, a paper filter like you suggested. Also, I've got a fuel pressure gauge on the double pumper, and it was always between 7-9 psi, which I believe is fine for my setup. Thanks for your help......KZ

[This message has been edited by kz1000ltd (edited 07-11-2000).]
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