Engine loses power around 5000RPM

[hemiken]

I had the same problem. Thought it was electrical because it felt electrical.  Not saying yours isn't, but mine used to nose over at 3000 revs.  Pulled off a tappet cover, brought number one piston to top dead, filled the cylinder with air and removed an intake spring.  Checked the spring on a spring gauge and had found that they had gone soft, when it happened, it happened suddenly out of the blue.  Changed springs and has been great ever since.

[Jacksboys]

I had the same problem. Thought it was electrical because it felt electrical.  Not saying yours isn't, but mine used to nose over at 3000 revs.  Pulled off a tappet cover, brought number one piston to top dead, filled the cylinder with air and removed an intake spring.  Checked the spring on a spring gauge and had found that they had gone soft, when it happened, it happened suddenly out of the blue.  Changed springs and has been great ever since.

I would consider this, but since it happened at 3000 rpm with one distributor and now around 4500-5000 with a different distributor, I would have to lean toward an electrical issue.   

[Jacksboys]

I'm sure it's electrical, but this can be maddening.    It could be something as simple as an old original wire having higher resistance than it should, or a connection that is a little loose, or has some corrosion. I'm sorry I can't suggest anything at this point.   

   Mike

I am just glad to see everyone is reading about it   

[Jacksboys]

Well, I checked the cap and it is a vented version, so I doubt that is the problem.  I was very busy today, so if I have time tomorrow and it does not rain, I will test a couple of other things.

[Jacksboys]

Well since I had a spare ecu I changed it out and nothing changed.  Well, at least I have figured out what is not wrong with it so far. 

I think I may have a problem elsewhere:
 While the engine was warming up, I grabbed my timing light and put it on the #1 cylinder. It showed 20 degrees initial and 30 degrees total (where I set it).  When I let off of the throttle, the timing stayed at 30 degrees  So I revved it again and it just barely went below 30 at idle.   

I then put the timing light on the #2 cylinder and the timing appeared to be jumping at odd intervals.  For example, I would see the same timing marks as with the #1 cylinder and then on the next flash, I would not see them. I know the the #1 and #2 wires are on opposite sides of the distributor cap, but why would the timing intervals be jumping around like that?   Is this normal? 

[Super Blue 72]

Sorry jacksboys, timing isn't my specialty.    Maybe someone else can chime in.

[matt63]

The timing marks are for #1 cylinder at TDC so they would not be of use for #2.  If your "all in" timing is 30 degrees I would advance it to 34-36 and see what happens.  This is where it should be.  This will also advance your timing at idle which could be a problem.  You can't usually get such a small mechanical advance (10 degrees) without going out of your way.  I'm assuming you have an adjustable MP or MSD distributor.  Typically 20 degrees of mechanical advance will be good as it will allow you to have 15 degrees at idle and 35 overall or thereabouts.

[Chryco Psycho]

the advance plate may be sticking ,or the springs could be broken
1 & 6 are opposite on the cap & in the firing order so you should be able to time off #6 CYL AS WELL

[Jacksboys]

the advance plate may be sticking ,or the springs could be broken
1 & 6 are opposite on the cap & in the firing order so you should be able to time off #6 CYL AS WELL

I feel like an idiot now.  I was thinking about what I typed earlier and realized I ment to say that I tested the timing on #3 cylinder (not #2).  Thanks Chryco, you are correct, I looked at the distributor cap incorrectly.

Ok, when testing the #3 cylinder, it should keep a steady timing like #1, right?

[Jacksboys]

The timing marks are for #1 cylinder at TDC so they would not be of use for #2.  If your "all in" timing is 30 degrees I would advance it to 34-36 and see what happens.  This is where it should be.  This will also advance your timing at idle which could be a problem.  You can't usually get such a small mechanical advance (10 degrees) without going out of your way.  I'm assuming you have an adjustable MP or MSD distributor.  Typically 20 degrees of mechanical advance will be good as it will allow you to have 15 degrees at idle and 35 overall or thereabouts.

Matt,
The distrubutor had this type of advancement when I got it from my father, who inturn received it like this new.  I do like the high initial advance but I do not want to go any higher than 20 initial.  I would change it to 35 total, but I am not sure how to adjust the distributor to keep it at 20 initial.  Do you know how?

[Chryco Psycho]

I have welded the advance slots closed to limit advance to 16* or so
 I assume you mean the 3 rd cyl on the right side / #6 cylinder & yes it should time the same as #1 cylinder

[Jacksboys]

I have welded the advance slots closed to limit advance to 16* or so
 I assume you mean the 3 rd cyl on the right side / #6 cylinder & yes it should time the same as #1 cylinder

I will look at the distributor slots sometime soon.   

No, I actually mean #3 cylinder (the one right behind #1).  I hooked it up to the timing light and it appeared to have a jumpy timing mark.   

[matt63]

Matt,
The distrubutor had this type of advancement when I got it from my father, who inturn received it like this new.  I do like the high initial advance but I do not want to go any higher than 20 initial.  I would change it to 35 total, but I am not sure how to adjust the distributor to keep it at 20 initial.  Do you know how?

I didn't read all the posts so I don't what distributor you have.  If you have the MP distributor with adjustable mechanical advance you can reduce/increase the mechanical advance by loosening 2 set screws and readjusting.  There are probably better instructions out there.  If it is the non-adjustable then it is more difficult per CP's instructions.  What do you have?

[Jacksboys]

I didn't read all the posts so I don't what distributor you have.  If you have the MP distributor with adjustable mechanical advance you can reduce/increase the mechanical advance by loosening 2 set screws and readjusting.  There are probably better instructions out there.  If it is the non-adjustable then it is more difficult per CP's instructions.  What do you have?

It is a MP distributor, but I am not sure which type.  If I have time this weekend, I will be taking it apart and making sure everything inside looks correct.

[matt63]

If you get a photo of the inside with the rotor removed we should be able to tell you how to adjust it.  I agree with CP that something may be wrong with it if you only have 10 degrees mechanical advance.  Usually the problem is the other way around.  Perhaps somebody has already adjusted it.  Whether the slots need welding or it is adjustable it is still a trial and error process for me at least.  With a small block you pretty much have to remove the distributor to do anything.

You mentioned earlier that you had the same engine problem with another distributor installed which suggests that the problem may be elsewhere unless the timing was not set-up properly with both units.  Either way you have to get the timing close before you can continue troubleshooting.