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Discussion Starter #1
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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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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Discussion Starter #4
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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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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Discussion Starter #6
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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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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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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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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Discussion Starter #11
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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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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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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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.
:thumbsup:
X2
 

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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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Discussion Starter #16
Thanks again so far. Even though the Air Gap isn't causing my popping, I know it is killing my low end torque when compared to a performer. Besides, I can't have an engine that runs like crap and takes forever to warm up when cold winters set in. Remember this is being driven every day year round despite the weather. A month ago when I was running 1/2 turn lash the valves were slightly hanging open and still had the popping. I bought the Cam, lifters, and valvesprings from lunati and the part #'s on the lifter box match what is recommended for my cam. Like I said earlier, I have tried the most and least pump shot with no difference and run different metering rod springs to richen up the engine even at idle and none of it has helped.
 

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Is your electric choke hooked up on this AVS? If not or out of adjustment, hook it up or swap out to a 3310 holley carb .
I adjusted my valves one up / on down after motor was warmed up, finger spin method then tighten down 1/4 turn, has always worked for me for the last 50 years. There are other methods but this is the easiest.
The only other thing I can think of that could cause a pop besides plug fire issue, is an intake valve that is either hanging open, too tight or beginning to burn and I haven't seen a burnt valve in a long time, maybe worn out guides but not burnt valve tips.
On the AVS, pretty much like the old AFB, there is a brass sliding plunger that is worked by vacumn, Any chance that it is sticking. This plunger is what controls the meter rods.
You also have a pump shot selection arm, I think there are three of them. Have you played with them?
Lastly, a problem with some of these AFB type carbs, is the accel plunger, sometimes the rubber plunger piston rubber or leather, will curl up and roll up, causing a big plunger shot leak, in the fuel plunger well, might be worth looking at.

I say this as I have the same manifold, bigger cam, and a 3310 on an Airgap. I have tried larger carbs and they will make the motor scream but at the expense of streetability.

Just mentioning this as I have been there, done that .
 

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I doubt it is anything other than it is simply just loading up with fuel and the big load the engine is trying to pull with the manual trans and high gears isn't helping. My motor does the same if I let it idle for long periods of time, and especially on cold starts, motors run 80% less efficient on cold startups (or some big number like that) and there isn't really a way to avoid this with carbs and motors that don't make enough power at low rpm's to pull the load the car is demanding.

I have seen $20k motors in dragsters just fall on their faces when they mash the pedal to do a burn out if the driver leaves it running long enough without rapping the throttle a few times in neutral before doing a burnout or launching, there is a reason for free revving before a launch, but now that every redneck does it everywhere every time it's been turned into something else.
 

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Discussion Starter #19
The electric choke is hooked up and set up right. My plugs are all in good shape. Wouldn't the spark plugs show signs of a burnt valve(s)? When I put new valves in the heads there was very little to no play in the guides so I assume they are is pretty good shape. I have had the plunger out over a dozen times when messing with the A/F ratio and it moves freely inside the bores. I haven't seen any accelerator pump leaks, but the carb is only 5 months old. As I have said I have adjusted the accelerator pump in every position in combination with different metering rod springs and timing with no real improvement. Well at any rate I will be swapping to a performer intake and will go from there, I will report back later.
 

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The electric choke is hooked up and set up right. My plugs are all in good shape. Wouldn't the spark plugs show signs of a burnt valve(s)? When I put new valves in the heads there was very little to no play in the guides so I assume they are is pretty good shape. I have had the plunger out over a dozen times when messing with the A/F ratio and it moves freely inside the bores. I haven't seen any accelerator pump leaks, but the carb is only 5 months old. As I have said I have adjusted the accelerator pump in every position in combination with different metering rod springs and timing with no real improvement. Well at any rate I will be swapping to a performer intake and will go from there, I will report back later.
Plugs won't show burnt valves. A leaking or burnt intake valve may produce the intake popping as it can't seal off what is going on in the chamber during the cycle. I really doubt it but it could be. I am still leaning towards the valve settings or fuel transitions. I would rather see valves too loose (noisy) than too tight but usually the hyd lifter will compensate for a too tight valve, sometimes.
I believe if your idle circuits are correct, the motor will set and idle . Loading up is usually too much fuel,(and other issues ) too much fuel pressure forcing fuel past the needles then on to the bowls and out to the venturi clusters, only to be drawn in by engine vac and air. If the fuel is excessive, it will load up, etc, why most racers clean out before staging or shutting down to cut clean on big end, to read plugs for WOT. Idle characteristics are almost unimportant in a race car but if you are really into racing , you have all in order.

I agree that gearing plays a part here but if you have your combo (cam, carb, ign, timing) on the money, you can pull like gangbuster from an idle.
I will leave it there so someone can throw rocks at my theories. Worked for me for the last 50 years. The Airgap is basically a dual plane intake, made for street, it resembles the factory Z hi rise intake., its just made off its base that seperates heat from the lifter valley.
 
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