RPM Air Gap= bad low end torque? - Team Camaro Tech
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post #1 of 47 (permalink) Old Jul 29th, 09, 07:36 AM Thread Starter
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Post RPM Air Gap= bad low end torque?

I have a edelbrock 650 AVS carb, Air Gap intake, Lunati Voodoo cam specs 268/276 .489"/.504", 186 double humps, Accel billet distributor, M-22 trans with a 3.36 rear gear, and other bolt on's. My problem is if I start to engauge the clutch anywhere below 1,500 rpm I will get a pop through the carb and is very sluggish all around below 2,000 rpm. I have run my timing at 8* initial, 25 mechanical, and 10 vacuum. I have also tried 12*, 14*, and 16* initial with and without vacuum advance; and non got rid of the popping. I have the correct metering rod springs in the carb for my 9 hg idle vacuum (yellow) and have tried several other springs and accelerator pump combination's to see if it wants more or less fuel with no luck. Even though it is a moderate sized cam I am considering the Air Gap's long big runners to be hurting my fuel signal and air velocity at lower RPM's (below 2,000 rpm). I would be glad to swap to a performer I have laying around if it means gaining low end torque without a pop. It will be in a 3300 pound daily driver/ 1/4 mile thrasher. Sorry for the long post but I want to get as much information out as possible to narrow down the problem. Any help would be appreciated.
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post #2 of 47 (permalink) Old Jul 29th, 09, 07:59 AM
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Re: RPM Air Gap= bad low end torque?

What size motor do you have? 327? 350? I would imagine you would have to slip the clutch a good deal now with the 3.36 gear and the M22 trans regardless of what intake is on it.

A performer intake will definitely give you much more off idle torque, and it should coincide with the power band of your cam if your running it in a 350.

For the future, I would think about a 3.73 gear for that M22. It will make take off a lot easier.

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post #3 of 47 (permalink) Old Jul 29th, 09, 08:04 AM
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Re: RPM Air Gap= bad low end torque?

Regardless of which intake you use, popping through the carb shouldn't happen. You've got to look more closely into that.

'67 rs - ordered new by my Grandfather
327 L30, K-K, Deluxe int, tach & gauges, 12 bolt posi, 4 speed.

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post #4 of 47 (permalink) Old Jul 29th, 09, 08:14 AM Thread Starter
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Re: RPM Air Gap= bad low end torque?

Sorry, it is a 350. I didn't want to go with a gear steeper than 3.36 for a year round daily driver. You are right about the clutch, you have to slip it quite a bit. But I wanted to run a m-22 because I have had M-20's and always wanted to hear the whine of a M-22 and the price for the trans was right.
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post #5 of 47 (permalink) Old Jul 29th, 09, 08:14 AM
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Re: RPM Air Gap= bad low end torque?

Its not the Air Gap... The popping threw the carb scares me... I would check the carb, ignition or a vacuum leak, i know have already but it could be a coil going bad (mine did) or it could be a bad pickup module (mine did) and it could be valves need adjusting or a bent push rod... Did you check to see if all cylinders are firring it could even be a bad plug or wire..

Can you give use more info on how it runs at idle, is it cold blooded, dose it diesel, dose it smoke, and what do the plugs look like all of them, this will help you eliminate a bad cylinder problems. But a compression test or leak down would be nice to.

Heres a good link www.4secondsflat.com talk to Don and give him a call...

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post #6 of 47 (permalink) Old Jul 29th, 09, 08:46 AM Thread Starter
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Re: RPM Air Gap= bad low end torque?

I just put in a new accel coil thinking the MSD was going bad because of the resistance through the windings. Carb is in great shape, all new vacuum lines, with no leaks in lines or intake. A couple weeks ago I pulled the intake, push rods, and lifters thinking I might have a wiped lobe or two. It turned out to be in great shape. But I did find out I can't run the correct half turn lash because of the Moroso high volume oil pump puts out so much pressure that the lash on the rockers dosen't push on the lifters; instead it pushes on the valves themselves. All of the plugs are firing and look in good clean shape with some white on the electrode showing good clean burning plugs. It takes a little longer to warm up compared to other intakes I've had but I have never had an intake with out an exhaust crossover. The engine only has about 100 miles on it and has chrome moly rings which seem to still be breaking in because of blue smoke I get on start up alone. If the smoke upon startup doesn't go away than I will try umbrella seals on the valves. I am almost certain the distributor is in good shape because I swapped in an old Mallory dual point I had laying around and it didn't run any differently. I have gone back to the accel soon after.
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post #7 of 47 (permalink) Old Jul 29th, 09, 08:54 AM
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Re: RPM Air Gap= bad low end torque?

OK something doesn't add up with the lash... What lifters sounds like hydraulics but you cant put a half turn on it because of the oil Moroso pump.. How did you find this out and did you call your motor guy or Moroso tech.... The problem is in your valve lash/timing.

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post #8 of 47 (permalink) Old Jul 29th, 09, 09:06 AM
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Re: RPM Air Gap= bad low end torque?

My guess is that with the valve lash not set correctly do to whatever reason that with hydraulic lifters your hole valve train timing is off.

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post #9 of 47 (permalink) Old Jul 29th, 09, 09:57 AM
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Re: RPM Air Gap= bad low end torque?

I'm with Skip on this. Too tight on the intakes somehow- just one would be responsible for the popping!

'67 rs - ordered new by my Grandfather
327 L30, K-K, Deluxe int, tach & gauges, 12 bolt posi, 4 speed.

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post #10 of 47 (permalink) Old Jul 29th, 09, 10:09 AM
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Re: RPM Air Gap= bad low end torque?

What did you set your lash to? It's usually more than a 1/4 turn. Factory is 1 full turn past zero lash. Aftermarket is usually 1/2-3/4 turn. I haven't seen a cam company that recommends 1/4 turn. I agree with Skip and Tom. It sounds like your issue is with the valve adjustment.

On a side note, I read that this is a daily driver/1/4 mile thrasher. Does this mean this car will be driven in the cold weather months as well? I ask because I ran a RPM Air Gap and during the cold months the air gap feature does not allow proper atomization of the air/fuel mixture to occur, thus robbing you of power. I switched to a regular RPM manifold and picked up a difference in power that you could feel and this was in the summer months as well as the winter months. In the winter, the car would idle better, start easier and overall just rode better. Some will say what I just described is not possible, but I experienced it first hand. For a car that ONLY sees the summer months, the air gap feature is great, but if the car is driven in cold months, then the air gap, in my opinion, leaves hp and tq on the table.

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post #11 of 47 (permalink) Old Jul 29th, 09, 12:51 PM Thread Starter
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Re: RPM Air Gap= bad low end torque?

Thanks for letting me know about the air gap in cold weather. I asked about it a few monthes ago and couldn't get a definite anwser. Tomarro I will be swpping in a performer since it sounds like it has better power in the power band of a daily driver and much nicer running in freezing weather.

My lash is currently 0 at this time. When I pulled the intake, rockers, pushrods, and lifters a few weeks ago I noticed that when I put 1/4-1/2 lash it pushes on the valves instead of the hydraulic lifters. So I had the lifters out on my bench and it was very hard to push on the lifters because there was so much oil in the lifters. Thats why it was easier for the rocker to push on the valvespring to open the valve than it was to push on the lifters. Upon cold startup I have 85 psi oil pressure and around 50 once warmed up at 2000 rpm. Anyone that has used a moroso high volume oil pump will know what I am talking about. Running zero lash is just a band aid to keep the engine running well until I can swap oil pumps. Before I pulled the lifters, rockers, and pushrods I know I had some hung open exhaust valves because I could hear it in the exhaust. But since I have zero lash on all valves, I know for certain I don't have a valve(s) hung open. Thanks for the help so far.
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post #12 of 47 (permalink) Old Jul 29th, 09, 01:06 PM
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Re: RPM Air Gap= bad low end torque?

Once you verify the valve setting , I would go back to the carb. Sounds like you have a lean out or stumble that may be caused by the lack of pump shot.
I am not a fan of this edlebrock carb but if thats all you have to work with , then start looking at your accel pump shots. The 268 cam is not all that bad but if it is not properly dialed in, (retarded at the cam) it will cause problems, especially with that 336 gear, I am in favor of 373.
I too agree, its not the airgap, have one now but with a holley.

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post #13 of 47 (permalink) Old Jul 29th, 09, 06:13 PM
 
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Re: RPM Air Gap= bad low end torque?

Set the sucker warm idling w/ you spinning each p/r between your thumb and finger until it stop's clicking/spinning and THEN say a 1/2 turn more!!

NOTE!! This is an old "feelie" deal here that works GREAT once you get that feel!.

This is how the older Mechanic's around my small country town taught this pup way back it the mid '60's!

And I'm paying them back by explaining how to do this to you!

pdq67



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post #14 of 47 (permalink) Old Jul 29th, 09, 06:29 PM
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Re: RPM Air Gap= bad low end torque?

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Originally Posted by zdld17 View Post
Once you verify the valve setting , I would go back to the carb. Sounds like you have a lean out or stumble that may be caused by the lack of pump shot.
I am not a fan of this edlebrock carb but if thats all you have to work with , then start looking at your accel pump shots. The 268 cam is not all that bad but if it is not properly dialed in, (retarded at the cam) it will cause problems, especially with that 336 gear, I am in favor of 373.
I too agree, its not the airgap, have one now but with a holley.

X2
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post #15 of 47 (permalink) Old Jul 29th, 09, 06:32 PM
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Re: RPM Air Gap= bad low end torque?

It's not the airgap. And oil pumps don't cause lifter problems like yours. My little stock 305 HR and my 283 both have 80# oil pressure and it doesn't phase the lifters.I would do 2 things, adjust valves correctly and investigate the possibility of having used the wrong lifters. We had a thread a few years ago about some lifters with the oil holes in the wrong place in regard to height on the lifter body. And lots of imported stuff out there now to beware of as well.

And I agree with Don on the lean pop if correct valve lash doesn't fix it. And I have had problems with the Edelbrock umbrella type acc pump, they get brittle and/or little nicks and quitcha.

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