Bizzare Engine Problem

[FSAE]

Engine: Chevy 305
Crank and Pistons: 20cc dished, Stock Recently rebuilt, very solid
Heads: New 1984 305 HO heads 1.94 int, 1.5 exhaust
Intake: New Edelbrock Performer RPM series, 1500-6500 rpm
Carb: New Edelbrock 600 CFM
Exhaust: Hooker 1 5/8" headers, 2.5" exhaust single muffler
Distrubtor: New MSI HEI
Cam: Comp Cams 280H - .48" lift 230/230 duration, hydraulic flat tappet, came with springs. rated for 2000-6000 rpm, 2000 stall
Stall: stock 1300-1500 rpm.
Rockers: New Roller Bearings


Problem
Car requires much more throttle than before to idle. Will run decent out of gear, but will randomly stall and die after 10 seconds or an hour ( very random ). Seems to be slightly misfiring when no load is on the engine. When load is applied it stalls. I have to power brake and can barely stop in order to keep it alive, unless I constantly put it in neutral when going less than 10 mph. Power will randomly drop between 4000 and 6500 rpm with WOT, then sometimes after half a second picks back up for 1000 rpm. Seems sluggish. Sounds healthy in high rpm, and revs very well ( up to 8000 rpm with a high quality tach, which I don't plan on replicating for the sake of the lower end ).

Here's how some of the systems are working. ( a * means that it was crappy after I put in the cam, and either replaced or reworked with no change in the problem ):

Vacuum is perfect.*
Carb is brand new and works great. *
Heads are brand new and perfect. *
Distributor is new and adjusted spot on. *
Fuel pump isn't perfect, but get's the job done.
Rockers are perfectly adjusted *
Stall is stock but should not be causing this.

I have been told that the distributor could be off a tooth or two. Now how this would effect anything is beyond me, but my latest shop guy suggested it. As far as I know, as long as it lines up with the oil pump and slides in you are fine, then set the ignition timing right. He says it would make a big difference. Could this be a possibility with my symptoms?

I recently checked the rockers for valve lift to see if the cam was wiped considering I use any 10w-30 oil I can get, but that wasn't the case, all rockers opened the valves perfectly and equally.

I have taken it to a dozen shops in the past 6 months since I installed the cam, and have had no answers, but a lot of tuning checks. The last shop I took it too suggested that the distributor could be off a tooth or two. I simply drop it in and get the oil pump thing to match. I then match up the spark plugs and turn it to get the timing right. I don't see how not putting it on the exact tooth would make any difference....

My compression is a lazy 8.5:1, so I know 230 duration is a bit much, but it shouldn't be causing this.

If any one has any ideas please let me know and thanks in advance. I've tried a lot of things and can't list them all, but this is the basics.

[Marks71BB]

You are correct about the distributor, makes no diffrence where its "clocked".

The RPM cam in itself could be the majoity of your issue. What rpm can you get it to idle at?

[SS2001]

Sounds like more than 1 issue causing your problems.
Was the cam properly broken in?
Check to see if your fuel pump is maintaining good pressure thru the rev range. It may be dropping off a bit.
Your stock converter is not helping the idle situation. With your setup I would change to a good quality 2500 stall (10 or 11 inch).
Just a couple of thoughts for starters.

[FSAE]

I can get it to idle out of gear at possibly 800 rpm, but at about anything under 1000 rpm, it will stall in a matter of seconds. At 800 rpm I have to rev it every few seconds to keep it from dropping down and stalling. Even at 1200 rpm it will randomly stall after awhile. Then to get it running again it takes upwards of 50% throttle sometimes, leaving it slightly flooded until I give it a nearly full throttle rev.

I know the stall is not helping and I plan on getting one, but it is not the main problem. If this only happened under load it would be. I have not checked the fuel pressure, and sometimes the clear filter is full and sometimes it's empty ( completely random ). I did take off the high performance pump and put on a new stock pump just before putting the cam in because the car was dropping power at 4500 rpm all the time ( turned out I had ignition too far advanced ). I haven't put back on the higher volume fuel pump yet. If I hold rpms at 5000 rpm, it will keep power up to 6000-6500 before dropping, but if I give it WOT from 1000 rpm, it will bog down before 5000 rpm.

Overall the car is quite sluggish as well. Half the power of what it should.

PS thanks for the quick responses

Edit: I've also heard that stock fuel lines could be problem. I have the original tiny metal tubes, and have had to bend them just a tiny bit to change fuel pumps.

[Marks71BB]

Did you do anything with the carb when you changed cams? I would definatly get a higher stall converter and look at tuning the carb.

[SS2001]

I am not familiar with your particular cam, but it is common for a cammed smallblock to have to idle at ~1000 rpm.
Something else - even if it is new, the ignition module could be faulty. They can cause all kinds of wierd issues. I have heard the cheapies are known for this. Also the GM modules are supposed to be better than the aftermarket ones. I don't think you can test it, but maybe try a different one and see if it makes a difference.
I would put the higher volume fuel pump back on.

[FSAE]

I just put a new edelbrock 600 cfm carb on. It was also timed and tuned by a shop.

If my spark plug gap is too small, could it be causing this? I put new spark plugs in awhile after the cam was put in. It didn't seem to make a difference, but I never did adjust the gap. I could be running .035" instead of .045". The distributor was replaced after I already had the problem. All it did was smooth out my idle because the old ones bearings were shot and it bounced the idle all over, no difference for this problem.

The problem is that even if I have a 2500 stall, the car will never be able to stay alive in first gear unless I put it in neutral or else power brake, because the engine cannot stay alive in drive unless it is above 1100 rpm and it needs nearly half of the primaries.

Another thing is, that when I installed the cam I did not degree it. Simply lined up the dots and double checked them a dozen times. I've been told that my timing chain could have come loose or else skipped a tooth or two, or that it could have come faulty and several degrees off from Comp Cams ( sometimes up to 10* ).

[rscamaro73]

Just an odd question - what do your headlights look like when you drive at night ? Are they dim ? I ask because maybe your alternator could be going out and your state of charge could be affecting the voltage the distributor it seeing...

[FSAE]

Brand new alternator, lights are quite bright. Good suggestion though, my old one had no bearings left.

[middleagecrisis]

Your converter is too tight for that cam. I've run that same cam and it needs a 2000/2200 stall minimum (in a 400 SBC w/10-1 compression)), especially in a small displacement engine like your 305. The fact that it runs great, except in gear at idle, should be an obvious sign. A 2200 stall will still let you idle at 1000, but the load on the motor will much less. I think you have multiple problems, but you'll never get it to idle at 800-1000 in gear without a looser converter. Also, your compression is way to low for that cam, which will contribute to idle problems. Sorry to not have an easier answer for you, but I think you should consider switching to a smaller duration cam, something like 218 or 212 @ .050. You could keep your stock converter with either of those cams.

[Marks71BB]

Yep, what he said^^^ too much cam for the converter and the motor.

[insane4fbodys]

Well if this engine stalls with no load and idling, the stall isn't the only problem. Sounds like the float level is off in the carb. I would check the fuel level and the fuel filter. It could be a restriction and causing fuel problems. If you have a chance, use a different carb to see if it changes. Maybe something to look at.

[FSAE]

that is something I have been looking at for awhile. I am hoping to put flat top pistons in this summer = 9.5 CR. I am debating if I should switch to a 262H cam in a few weeks and keep the 280H cam and lifters ( in order ) and wait to put it back in till I rebuild the bottom end this summer. Could the random power drop offs at 4500-6000 rpm be because of low CR? Also could this contribute to the slight misfiring while at idle ( 1500 rpm )?

On the stall, I understand that it is dropping so much in gear because of the stock stall converter, but I don't see why it suffers the same exact symptoms in or out of gear at the same rpms ( 1000-1500 )? In other words the car will stall below 1200 rpm in or out of gear, it runs fine for a few seconds, rpms begin to drop, and it just exponentially drops till the motor stalls.

[FSAE]

Carb is brand new. Fuel filter is as well. Like I said earlier it seems to randomly lose fuel pressure, so I am having that checked tomorrow. But the problem is very consistent, so it could be a combination. Something tells me that the fuel pump could be the high rpm drop off problem.

[FSAE]

How about this for a cam:
http://www.lunaticams.com/Product.aspx?id=2323&gid=297

Or would I need to go even milder?