Lackluster Power

[firebane]

So I was finally able to get my truck out and driving around today and found a few issues. The main issue that I found was once I hit 2500rpm the truck just loses any and all power.

My distributor when the truck is running sits at 12* BTDC and maxes out around 24-25* BTDC for a total of 36* of timing.

Its a new distributor but it was previously used so I have no idea how good of shape the coil or ignition module is. The weights on it are 375 center with 41 outers where my old truck was 375 center and outers were 106.

The truck also comes with new plugs and wires.

The only thing that I'm thinking could be the issue is the carb as its extremely unknown and I have no idea the internal shape of it. It will be the next thing on the list to go over and redo.

What doesn't make any sense to me tho is that when the truck is idling you can take it from 800rpm to 4000rpm without any issues but the second you start to drive it that is when you have no power above 2500rpm.

Thoughts?

 

[rich weyand]

Total timing does not mean what you see at idle plus what you see at 3000.

Total timing is what you see at 3000 with the vacuum advance unhooked. That is, it is base timing plus mechanical advance. What you ought to see is something like 14-16 at idle, and 34-36 at 3000.

You are about 10 degrees retarded at 3000 rpm. Plus, it looks like your HEI has been modified, because the difference between idle and 3000 rpm should be 20* on a stock HEI, and your difference is only 12*. Could be the mechanical advance is broken/sticking.

 

[firebane]

Well if that is the case then what could cause a 10 degree difference?

I was under the impression it was initial + mechanical = total.

Crap I think I may know the issue LOL. When I initially stabbed my distributor I put it at 10 degrees ATDC not BTDC. That would account for the loss of 10 degrees.

Time to go and redo my timing tomorrow LOL.

 

[rich weyand]

Total timing is initial plus mechanical.

Initial is what you see at idle with the vacuum disconnected.

Total timing is what you see at 3000 rpm with the vacuum disconnected.

Mechanical advance is the difference, which for stock HEI is 20*.

The distributor should be stabbed so that at 0* BTDC, the rotor points to about 5:00 position when looking down on it from in front and above.

Timing is set by rotating the distributor body, not during the stab.

 

[firebane]

Yeah I know. But like I said harmonic balancer was set at 10* ATDC when I put the distributor in

Which when the truck was running it was at 10* ATDC before I set it to 10* BTDC

 

[350runner]

Here are a couple hei combos. http://www.chevelles.com/forums/archive/index.php/t-327577.html
this is the reason i say not all trucks come with the same amount of mechanical in the dizzy.

Sent from the dust in front of you!

 

[firebane]

So I set the timing to 10* BTDC fired up the truck and it would simply not run. I had to retard the timing again and its almost at 8* ATDC before it runs.

Do I have a defuct distributor?

 

[rich weyand]

Sounds more like the timing tab is in the wrong location.

 

[firebane]

Sounds more like the timing tab is in the wrong location.

Originally i would have thought that too but I verified TDC and it lined up perfectly.

Ugh this is driving me batty.

Maybe I messed up on the timing gear install? But I did that with the heads off and when the #1 piston was at the top is when I put the timing chain on. Could that have something to do with this?

 

[firebane]

So I pulled out my piston stop and inserted it with a piece of tissue paper. Cranked the balancer over till it popped.

Well when it popped the 0* mark on the balancer is near 9 o'clock

So can I just get a new timing tape stick it on where its showing TDC at or am I going to have to pull the cover and reset my cam gears?

 

[350runner]

put the paper *** back in. Then pull the valve covers, rotate the crank,and watch the #1 cylinder rockers. Do they come to rest when the paper pops out? if so the timing tape should work.

Sent from the dust in front of you!

 

[rich weyand]

When the paper pops out, you know that that is the compression stroke. But the paper doesn't magically pop at TDC.

Here's another way. TDC on Number 1 for any Chevy V8 is when the keyway on the crankshaft pulley is at 45*; that is, between 1 and 2 o'clock when viewed straight on from the front. You should be able to see it from under the truck.

Of course, the other thing you can do is just adjust the timing for best idle (with the vacuum advance still connected), then advance from there until you get pinging under load, then back off 2 degrees.

 

[firebane]

I just restabbed the dizzy where the paper popped and the truck won't start.

If I heavily advance the timing it'll pop through the carb but still won't start.

I think I'm just going to pull the front end apart and make sure everything is where it should be. This is too frustrating and should be so difficult to figure out.

 

[firebane]

When the paper pops out, you know that that is the compression stroke. But the paper doesn't magically pop at TDC.

Here's another way. TDC on Number 1 for any Chevy V8 is when the keyway on the crankshaft pulley is at 45*; that is, between 1 and 2 o'clock when viewed straight on from the front. You should be able to see it from under the truck.

When the paper pops though you should be "near" TDC not 180* away from it.

Yeah I know about this little trick too.

See the thing is I did the whole TDC without the heads on so I had no idea if I was on compression stroke or if I was on exhaust stroke.

 

[firebane]

put the paper *** back in. Then pull the valve covers, rotate the crank,and watch the #1 cylinder rockers. Do they come to rest when the paper pops out? if so the timing tape should work.

Sent from the dust in front of you!

The whole reason for this excursion is because the truck will only run at 10* ATDC which means the balancer or TDC is incorrect.