68 c10 327 with no power

[vettetlb]

Ok guys. I need some help, thoughts, or ideas.
My 68 327 just won't accelerate.
Original 327, edelbrock manifold and carb. HEI distributor. Headers. 700r4 trans. Had the stock cam until just a couple weeks ago. Thought maybe the cam was worn out so put in a 268 cam. Same issue.
Revs great at idle and sounds strong.
Get out on the road and it just wont go. No bog, no missfire. Just lazily inreases speed up. Takes forever to get up to 70 and wont go much past.
Timing at 7 btdc. Mechanical and vacuum advance both work although i don't know my total timing. Vacuum at 18. Fuel pressure at bouncy 6-7 psi.
Thoughts?

[Steeveedee]

Check to see if the rotor has burned through. If that's OK, put a vacuum gauge on it and run it up to 2000 RPM. If the vacuum falls off after about 30 seconds, you have a clogged exhaust system. It looks like you've covered the normal bases, so I'm throwing out an unusual one.

[68Gold/white]

You could have a timing mark issue, or balancer slip (yes even if its new).
I'd advance the cam 2-3 degrees at a time. Go out and drive it, see what it does. See if it pings under a load (like going up hill, or from standing still). If it doesn't ping, give it a little more timing. When you get it to the point where it does ping, back it off 2 degrees. Go drive it more see how it does...

[Greasey Harley]

Originally Posted by 68Gold/white

You could have a timing mark issue, or balancer slip (yes even if its new).
I'd advance the cam 2-3 degrees at a time. Go out and drive it, see what it does. See if it pings under a load (like going up hill, or from standing still). If it doesn't ping, give it a little more timing. When you get it to the point where it does ping, back it off 2 degrees. Go drive it more see how it does...

^^This^^

[special-K]

That's what I think, too. Let's stick with one thread on this.

[WorkinLonghorn]

Dumb question but did you check to see if the throttle is actually opening all the way and that the secondaries are fully opening? What do the plugs look like after a FT pull up a long grade?

[Bigdav160]

Distributor advance mechanisms working?

[vettetlb]

Appreciate the input fellas. To answer some questions. Yes i validated the throttle fully opening. I have also validated the mechanical advance is working.. i will double check the rotor, but i don't recall seeing a problem with it the last time i had it apart. Now, as for the balancer and timing marks, you may be onto something there. I will try advancing the base timing a couple degrees at a time and see how she does.
Will report back.

[geezer#99]

You likely have two problems.
Too much fuel pressure. You need a max of 5 psi.
Not enough timing. You need at least 12 initial.

[Mbeef61]

Fuel pressure ok. No bog. No misfire. Good vacuum. Revs ok.

What’s the trans doing? Is it shifting? Shudder? Noises? Could be stuck in a higher gear. Bad torque converter. Low fluid? Bad fluid?

[vettetlb]

It was doing the same thing when i had the turbo 350 trans in it. I swapped out some time ago for a 700r4. This prolems has been around since i bought the truck several years ago. I always just attributed the problem to a tired cam. I finally decided to go ahead and change out the cam. And wouldn't ya know it...same f@#$in thing.
It was mentioned earlier about the timing. If that outer ring has moved, that would make sense. I set the base timing according to the timing mark on the balancer. I can see where if the timing was severely retarded, it would definitely cause a lack of power. As i haven't changed out the balancer, it could be the problem.
And yes the trans shifts through all 4 gears without any issues. I have the kit installed for the lock up converter and a toggle switch to kill power to the converter completely.

[weim55]

I see questions like yours here on the board all the time and even though I am completely qualified to trace down the problems it’s basically impossible to do that Without actually having the truck in front of me. I could listen dozens of things that could cause your issue. Find a good shop in your area that specializes in older vehicles has a good reputation and take it there for a diagnosis. A sharp mechanic with plenty of experience on old stuff will have this figured out with an hour of shop time no sweat.......

Steve weim55 Colorado

[BCOWANWHEELS]

Do a compression check 1st thing, bet your cam lobes have gone flat............

[mr.precision]

Could be a number of things..... first thing I would do it bring the #1 cylinder up to TDC and have a look at the timing marks on the dampener. Bet they are off. If that be the case, chalk mark TDC and see if you can get approx 10 deg advance to start off. Vacuum advance disconnected and blocked off, of course.

[OldMoparsRule]

I agree 100% with establishing the correct timing baseline.

On my HEI distributor, the springs that allowed the timing to advance were heavy. I switched the springs to lighter springs (Advance Curve Kit - $9 at the auto parts store), which allowed the timing to advance sooner (less rpm). That really woke up my engine.

I hope this helps!

Thanks,
OldMoparsRule!

[68 P.O.S.]

Timing timing timing. Set it at 12 to start and you'll notice an immediate difference. Which HEI do you have, stock or aftermarket? It needs to be curved as well to set the timing correctly so you can set your total timing to 36 degrees. The carb needs fuel pressure restricted to 5.5 psi and the floats need to be adjusted to Edelbrock specs to stop flooding. A heat insulating gasket needs to be used as well (Edelbrock 9266) to stop fuel percolation. You're also gonna need a calibration kit to change rods, jets, and step-up springs. Let us know about your HEI and we can help you get it curved right. Need to know how many degrees of mechanical and vacuum advance it provides.

[68Gold/white]

Original post does NOT mention flooding issue....drive ability would be noticeably compromised IF it were flooding also, to go along with the lack of power. Fuel pressure COULD become an issue in the future, though...

[68 P.O.S.]

Originally Posted by 68Gold/white

Original post does NOT mention flooding issue....drive ability would be noticeably compromised IF it were flooding also, to go along with the lack of power. Fuel pressure COULD become an issue in the future, though...

Ok, so that doesn't mean he doesn't have this issue, which is contributing to the total problem. High fuel pressure and/or out of spec floats WILL make an Edelbrock carb flood. No heat insulating gasket or spacer WILL make an Edelbrock carb percolate fuel. If you didn't notice from his description, his driveablity IS waaay compromised.

[palallin]

Wil a stock, mechanical fuel pump generate over pressure?

[68 P.O.S.]

Yes, a stock pump can produce too much pressure. It's kind of a crap shoot, people here have had no problem running a stock fuel pump, while others (me included) have had flooding issues. Edelbrock suggests either using a fuel pressure regulator set to 5.5 psi, or buy their Performer RPM fuel pump which puts out the correct amount of pressure. I'm using the fuel pump and it works great, it's just not cheap.

[68Gold/white]

Originally Posted by palallin

Wil a stock, mechanical fuel pump generate over pressure?

Most mechanical fuel pumps, regardless of what name one the box, are not made in America. Quality control may be an issue. Many here and other internet have reported mechanical pumps over pressuring carbs.........

[sloGMC]

Originally Posted by 68Gold/white

You could have a timing mark issue, or balancer slip (yes even if its new).
I'd advance the cam 2-3 degrees at a time. Go out and drive it, see what it does. See if it pings under a load (like going up hill, or from standing still). If it doesn't ping, give it a little more timing. When you get it to the point where it does ping, back it off 2 degrees. Go drive it more see how it does...

If you suspect a slipping balancer or timing mark issue, why would you run straight into changing the cam timing? Altering cam timing seems entirely unnecessary on a generic street engine and I would be surprised to find out that either the dots on the timing chain or the dowel in the cam are improperly placed. Misaligned pointer or timing tape (or lack there of), or misaligned timing gears, seem far more likely. If the balancer is the problem it should just be replaced.

The engine could be going through an entire lean-cycle. Maybe the secondaries are opening way too soon. Or, maybe the engine is just a tired old dog.

[68Gold/white]

Originally Posted by sloGMC

If you suspect a slipping balancer or timing mark issue, why would you run straight into changing the cam timing? Altering cam timing seems entirely unnecessary on a generic street engine and I would be surprised to find out that either the dots on the timing chain or the dowel in the cam are improperly placed. Misaligned pointer or timing tape (or lack there of), or misaligned timing gears, seem far more likely. If the balancer is the problem it should just be replaced.

The engine could be going through an entire lean-cycle. Maybe the secondaries are opening way too soon. Or, maybe the engine is just a tired old dog.

Congrats on reading my error. Should have left out the word cam. Altering cam timing on an original old dog 327 would be a goofy idea, as you stated...LOL

[MySons68C20]

Check for a clogged fuel filter 1st....thinking the bouncing fuel pressure at idle may be the cause. Fuel starvation doesn't always show up free revving in neutral but under load = no power.
Total timing as others have said....a dial back timing light makes checking this easier.
Compression check too since this has been an issue with both camshafts.

[sloGMC]

Originally Posted by 68Gold/white

Congrats on reading my error. Should have left out the word cam. Altering cam timing on an original old dog 327 would be a goofy idea, as you stated...LOL

Ahh, very good then. Didn't know if you guys all knew of something I hadn't heard of, but didn't want someone running down that track either for (probably) a tuning issue only.