Timing help needed

[SDlivin]

I had another thread (buried now) going on in regards to this challenge, but thought I would start off fresh with the problems I am experiencing and the information I have at hand. Any and all help / suggestions of course are appreciated.

Recently did the Explorer Serp Swap, in the middle of which I made the (in hindsight, stupid) decision to replace the Cam and intake. Engine ran fine previously to the swap, was just looking for a little more HP and Torque.

351 non-efi
New Edelbrock Performer Plus Camshaft and lifters
Used Edelbrock RPM Intake Manifold.
Newer 1405 Edelbrock Carb (was on the old stock intake)
Vacuum Pressure @ idle slightly oscillates a little between 9-11, as rpms/timing increases pressure steadily goes up to around 20 in direct relation to rpms.
Timing, with timing light @ '0'. I am showing it around 20 ATC around 600 rpm, with increase in timing (by turning dizzy) timing steadily goes towards the '0' mark on damper. Damper goes from left to right, ATC, 10, 0, 10, 20, 30 BTC. With Vacuum advance plugged.

Even with vacuum low, engine idles just fine.

Problem I have is engine run-on, and NO power from 0-5-10 MPH, I literally have to keep the rpm's revved high on take-off to make it through that dead period, then the rest of the time truck runs fine, just the problem between 0-10mph. I might be thinking too much in to this, but it appears to get worse as engine warms up, and the gap between 2nd and 3rd appears larger, as in I have to run 2nd high until shifting to 3rd to make sure there is enough rpms in third for it to pull (could be my paranoia though).
Engine does shut-off when I substantially lower the RPM's, by either the manual MSD timing controller I have, pressing brake pedal (I know I have a slight leak in the booster), and/or letting out clutch to slightly to get the rpm's really low, more often it's all three.
Shutting off the engine prior to the swap was not a problem at any idle rpm.

 

[SDlivin]

Part 2.

I am at the point where I am thinking of tearing this whole thing back down and putting the old cam and stock intake back on it, or trying a NEW Edelbrock Performer Intake, that goes with the Camshaft I bought.

Thanks for any help or suggestions!

-Robert

 

[mcdobson]

I assume when you say Explorer rpm intake you meant to say Edelbrock intake?
The Explorer intake will not fit the 351.
If you used the Explorer balancer, it is not balanced for a 351.
Your idle timing should be around 6 degrees with vacuum disconnected and plugged.
Are you using the 351 firing order and not the 302 order?
Vacuum leaks will mess everything up. Make sure you track them all down.

 

[SDlivin]

I assume when you say Explorer rpm intake you meant to say Edelbrock intake?
The Explorer intake will not fit the 351.
If you used the Explorer balancer, it is not balanced for a 351.
Your idle timing should be around 6 degrees with vacuum disconnected and plugged.
Are you using the 351 firing order and not the 302 order?
Vacuum leaks will mess everything up. Make sure you track them all down.

Correction, yes, meant to say the Edelbrock Intake, will edit accordingly.
Had the Balancer re-balanced by Damper Dudes, so good there. I did not change the firing order as that did not change from the previous stock intake.
and yes, I did the timing with vacuum plugged. So should it be 6 degrees ATC or BTC? I can get the ATC, but I think the rpms would be a little high. Keep in mind, I don't have a tach, so guessing RPM's by sound.

 

[broncnaz]

It should be set BTDC. Sounds like you have a bigger vacuum leak than you think. That would explain some of the lower readings. Swapping intakes will only see a minimal increase of vacuum readings as the RPM intake is not that much bigger than a performer intake.

So I'd check for vacuum leaks(maybe plug off the vacuum booster line see if that helps since you know theres a leak there.) and I'd also be a little suspect of the MSD timing controls if something is wrong with them you will never see good timing.
Also bump the timing up to what its supposed to be then adjust the carb to attain the RPM's you want.

 

[DirtDonk]

Exactly what he said.
Lots of other queries needed too. With new parts you have an unfortunately large chance of creating/finding vacuum leaks. A lean running engine will have some of the symptoms you describe.
A too-retarded (timing-wise) engine can also have the symptoms you describe.
The wrong firing order will just add to the misery.
Putting all three together will put you in the funny-farm in no time at all.

You may have to re-jet your carb for the new cam and manifold. Your old settings have likely been rendered ineffective and too lean. Compounding any other problems.

First and foremost, did you break-in the cam properly? This is a flat-tappet cam, right? I seem to remember we talked about it already, but things run together in my head most of the time, so I will just ask it again anyway, to make sure.
A cam going flat will give you some pretty odd symptoms, and added to the other possibilities is just not worth contemplating!

What damper are you using? If not matched to the rest, your timing marks can/will be off. If old and slipped, your marks could be off.
If something's amiss here, use some timing tape to fix it. Just verify TDC exactly and put the tape on to match your timing pointer.

What cam firing order? I can look it up, but figured I'd just ask.

Why an "RPM" manifold? I realize it was used, but it's optimized for slightly higher rpm range, so might not be helping things any. Not that you lose all your idle and low-end power with one, but it's not helping.

One reason it could be more noticeable when hot is that your choke is open and you're running at full lean mode then. Making any lean condition even worse. A half-closed choke butterfly can mask some ills, by letting the carb put more fuel into the engine.

So, to summarize, but in the long version:
Check for vacuum leaks using one of the proscribed methods.
Re-verify your firing order.
Re-verify your TDC/timing.
Check your timing light on another engine too, if you can. One of the members ran into a bad gun not long ago.
Make sure your PCV valve is correct for your engine. Using one that lets too much air into the mix won't help things either. Except maybe for high-altitude running.

 

[DirtDonk]

Firing order has nothing to do with the manifold. It's only decider is the camshaft.
Reason that comes up at all, is that many cams for this family of engines used to go with the 302 firing order, and not the 351 firing order. That's why I thought you should verify that your Performer cam had the firing order you're using.

Paul

 

[SDlivin]

woof..

Okay here we go..

I did plug the brake vacuum line at the carb port, no effect there, only drops when I have it connected and I press the brake pedal.
Agreed there must be a small vacuum leak somewhere or it wouldn't oscillate, but it is still close (i think) to were it should be. 10 or so @ idle now... would be better at say 15-18?
I did spray carb cleaner damn well everywhere to no affect. Every gasket, bolt, seal, carb linkage, vacuum port, etc..
I will get a new PVC, not sure what is in there now.
You are correct... Double checked the Firing Order for the camshaft and it is the same as the stock 351w, 1,3,7,2,6,5,4,8.

I got the 'used' RPM manifold for cheap, that's why... Thing looks brand new, but you never know right? and I also figured it really isn't that much bigger an intake, even though they advertise the rpm as operating in the 1500-6500 range, whereas the performer plus cam is in the 0-5500 range.

I did break the CAM in per the instructions, but maybe I screwed that up? not sure how I could check that now without tearing the engine down again.

Manual Choke, so only run the choke at initial cold start for a few minutes, then not needed.

Damper came with the serp set-up. Had it rebuilt and rebalanced at Damperdudes. I could have sworn I installed it and the camshaft correctly with the timing gear marks aligned and at TDC, but now as with everything else I am second guessing that too....

I've stabbed the Dizzy 20+ times by now, without much change in the timing. Can I be off a tooth, and would that move me towards the BTC range as opposed to being on the ATC side now? Could it simply be moving the Oil Pump bolt a little so I can stab the Dizzy in a slightly different spot? I only have 3" (should be plenty I would think) of movement on the Diz cap as the vacuum advance hits serp brackets.

I'll try the timing light on my 68 camaro.

 

[DirtDonk]

I did plug the brake vacuum line at the carb port, no effect there, only drops when I have it connected and I press the brake pedal.

First minor issue. When all is good, pushing on the brakes won't effect the idle. So in your case, something is either leaking in the booster, or your idle is just not strong enough, with the available vacuum, to handle the slight extra load.

Agreed there must be a small vacuum leak somewhere or it wouldn't oscillate

Nope, bad valve action can cause oscillations.
So can insufficient timing.
So can an over-lean condition

...but it is still close (i think) to were it should be. 10 or so @ idle now... would be better at say 15-18?

Yes. Great idle vacuum with a stock-ish cam should be more in the 20 to 22 range.
Mild cam, but with everything else good, including the ignition timing, should be in the 17 to 20 range.
Less mild cam should still be in the 15 to 17 range.
Any less than that, and you're just starting to get into the "weak idle characteristics" stage.

I did spray carb cleaner damn well everywhere to no affect. Every gasket, bolt, seal, carb linkage, vacuum port, etc..

A very good sign. So far, so goo. Then we can move on to the other items instead of trying to track down a leak.

I will get a new PVC, not sure what is in there now.

Sorry to make you spend more money (even if it is only a few bucks), but I think that's not a bad idea. If you don't know what's in there, best to change that circumstance.

You are correct... Double checked the Firing Order for the camshaft and it is the same as the stock 351w, 1,3,7,2,6,5,4,8.

So theoretically at least, the wires should still match from the distributor.
Good.

I did break the CAM in per the instructions, but maybe I screwed that up? not sure how I could check that now without tearing the engine down again.

Probably did ok, if you followed the directions. NO idling at all, during that first 20 to 30 minutes too, right? No twiddling with the carb, no twiddling with the timing. No walking off to answer the phone (or your wife) while you let it idle.

I've stabbed the Dizzy 20+ times by now, without much change in the timing. Can I be off a tooth, and would that move me towards the BTC range as opposed to being on the ATC side now?

No. Timing is timing, with regards to the marks and the rotor pointing towards the right wire. It doesn't know, or care, where the distributor is in relation to anything else.

Could it simply be moving the Oil Pump bolt a little so I can stab the Dizzy in a slightly different spot? I only have 3" (should be plenty I would think) of movement on the Diz cap as the vacuum advance hits serp brackets.

As long as the pump shaft and distributor shaft line up and engage, it doesn't matter where you're pointed as long as you have some clearance to adjust some timing. Your 3" is perfect.
The check is that your timing light is set on the number-one wire, your timing marks on the damper line up with the pointer, and the rotor points to the right wire.
Your light tells the tale and no dis-orientation of the gears, rotors, or physical location of the distributor will change that relationship. If it's sparking when it's lining up with the plug wire, you're getting the reading with the light and the marks.

I'll try the timing light on my 68 camaro.

Good to have a second opinion. Car-wise.

Paul

 

[DirtDonk]

I've stabbed the Dizzy 20+ times by now, without much change in the timing. Can I be off a tooth, and would that move me towards the BTC range as opposed to being on the ATC side now?

To maybe clarify what I said before. If you re-stab the dizzy and move it over one tooth, yes, you're changing the timing (ATDC or BTDC just depends on which way you turned it). But when you see that timing change indicated with the timing marks. you can simply twist the distributor body to re-time it back to the desired degree.
As long as you still have room to move it, before something hits something else, you can simply rotate without re-stabbing, to get the timing back to where you want.
Only if you run out of room, do you have to re-stab it again.

And you mentioned something before about idle speed changes.
In general, when you increase your timing advance, your idle rpm goes up. When you retard your timing, your idle rpm goes down.
When this happens, you simply re-adjust the idle at the carb. So if advancing your timing to, say, 10° BTDC runs the idle up to 1500 rpm, you turn the screw down so it will idle back down to a more normal hot-idle speed. Say about 700-800 rpm or so.

Paul

 

[DirtDonk]

What kind of ignition system are you running?

Paul

 

[jw0747]

Could be your MSD ignition controller is faulty. Check the MSD web site or call them for the name of a place near you that might be able to test it. I've had a couple of MSD boxes go bad.

 

[SDlivin]

To maybe clarify what I said before. If you re-stab the dizzy and move it over one tooth, yes, you're changing the timing (ATDC or BTDC just depends on which way you turned it). But when you see that timing change indicated with the timing marks. you can simply twist the distributor body to re-time it back to the desired degree.
As long as you still have room to move it, before something hits something else, you can simply rotate without re-stabbing, to get the timing back to where you want.
Only if you run out of room, do you have to re-stab it again.

And you mentioned something before about idle speed changes.
In general, when you increase your timing advance, your idle rpm goes up. When you retard your timing, your idle rpm goes down.
When this happens, you simply re-adjust the idle at the carb. So if advancing your timing to, say, 10° BTDC runs the idle up to 1500 rpm, you turn the screw down so it will idle back down to a more normal hot-idle speed. Say about 700-800 rpm or so.

Paul

I'll try screwing with the timing / Carb idle adjustment screw to see if I can get it to the BTC side of the damper.

MSD 6al, with Timing control module and MSD Blaster 2 coil.
Stock (as far as i know, looks very stock) Dizzy w/ vacuum advance.

 

[SDlivin]

Could be your MSD ignition controller is faulty. Check the MSD web site or call them for the name of a place near you that might be able to test it. I've had a couple of MSD boxes go bad.

Not ruling it out, but it ran fine before the swap. So, unless pure coincidence... Hoping it's not that...

I am still figuering timing as I am on the wrong side of the '0' timing mark. I'm on the ATCside, as opposed to BTC. But not sure How I would adjust it to get it to the BTC side. Simply re-stabbing the Dizzy in different minor positions doesn't seem to make a big difference, as I have to clock the diz body to get it to run right. So I am either at the far right of where it can sit, due to the vacuum advance hitting or the far left, regardless it times the same 10-20ATC.
As Paul said Timing is timing.

 

[recoiljunky]

Did you mount your timing pointer in the right place? Explorer cover and balancer use a pointer mounted on the passenger side of the engine.

 

[SDlivin]

Did you mount your timing pointer in the right place? Explorer cover and balancer use a pointer mounted on the passenger side of the engine.

Yup, used the factory mounts and fabb'ed up my own timing pointer out of thin sheet metal. Tried to match it up to exactly what it looks like in the tech article contained herein CB. With that said, it could be off a little, say +/- 5 degrees max, but not nearly as much as I need to it be.

 

[DirtDonk]

So you're saying that you run out of adjustment before you can even get it to any decent BTDC settings?

Are you able to move the distributor over just one tooth, while spinning the pump shaft to match? Or are you having to move two or three teeth over to let the distributor seat all the way?
Sounds like you're doing the one-tooth shuffle just fine, but I wanted to make sure.

If you are certain you have the correct pointer/damper combo, and still can't get things to line up quite right, what about moving the plug wires over one place? Maybe that would give you just what you need.
But really, I've never heard of an instance where you couldn't re-orient the dizzy to gain an acceptable range of adjustment for an engine, so I'm perplexed.
Except... You said you're running the Explorer front dress, but with a standard dizzy. I know that the TFI equipped distributors have a hard time, but thought that the vacuum advance type would clear. If not, you may have to do what we've had to do on the EFI conversions with Explorer front dress and grind off some of the driver's side bracket to gain some clearance for the vacuum pot.
Does that sound like it might give you enough movement?

Paul

 

[SDlivin]

So you're saying that you run out of adjustment before you can even get it to any decent BTDC settings?

Are you able to move the distributor over just one tooth, while spinning the pump shaft to match? Or are you having to move two or three teeth over to let the distributor seat all the way?
Sounds like you're doing the one-tooth shuffle just fine, but I wanted to make sure.

If you are certain you have the correct pointer/damper combo, and still can't get things to line up quite right, what about moving the plug wires over one place? Maybe that would give you just what you need.
But really, I've never heard of an instance where you couldn't re-orient the dizzy to gain an acceptable range of adjustment for an engine, so I'm perplexed.
Except... You said you're running the Explorer front dress, but with a standard dizzy. I know that the TFI equipped distributors have a hard time, but thought that the vacuum advance type would clear. If not, you may have to do what we've had to do on the EFI conversions with Explorer front dress and grind off some of the driver's side bracket to gain some clearance for the vacuum pot.
Does that sound like it might give you enough movement?

Paul

Well, with the 3" of movement I have, it appears plenty to get it to a low idle, and to a high idle. So I think there is plenty of room there. Between Low idle and high idle, it may be moving the timing from 20-10 ATC, low idle being 20ATC, high idle being 10ATC, give or take. It takes a bit of jiggling but it does appear I can move it one tooth over either way, but it doesn't really make a difference as I just end up on the farther extreme of where the dizzy body sits. So High idle may be on the far left or the far right of the 3" gap, depending on what 'tooth' I sit the diz in, with less of a range of adjustment, so it now may go from med idle to over high idle, or on the flip side, med idle to really low idle.. All this doesn't change the timing marks, still stays on the ATC side.. the lower the idle the further in the ATC range, the higher the idle the lower in the ATC range, almost to 0 if it sits real high on idle. If that makes sense. Still not sure how to get it far enough over to get the pointer on the BTC side of '0'.
Gonna try tackling it again tomorrow...

 

[broncnaz]

I'm going to say either your balancer marks are off or your timing gears were not lined up properly when installed. I'd double check your TDC against the timing marks/pointer.
Have you tried running with the higher idle speed(10 ATDC setting) does it make any differance? Whats the vaccum reading at higher idle and is it steady?

One way or the other if the timing makrs are incorrect the engine should still run fine. Now if the timing gears are incorrect or you have a ignition problem or vacuum leak then you wont get it to run correctly. Vacuum leaks can occur on the inside of the intake and are very hard to detect. Although they usually allow some oil to be sucked in so one or more spark plugs may be slightly fouled.

 

[DirtDonk]

Something doesn't sound quite right SD. If you can move it even one tooth, but still can't get it to a point BTDC, something's not reading correctly.
In my mind's eye, that 3" of movement is way more than the distance between one plug wire and the next. And that's 45° of crank rotation, or time for the next cylinder to fire!
Maybe your estimate was off slightly, but even still, one tooth of shaft displacement, or two inches of rotation is a LOT to work with.
Something's not reading correctly. Either you're not really getting a tooth's movement, or something electronic is whacked (which it doesn't sound like is possible), or something else I'm not able to think of.

Can you unplug your timing adjuster? If so, it should just to to a zero value, correct? That way you can see only what initial timing you've set in yourself, and have no electronic wizardry messing with your mind.

Give it a try anyway. And after all this back-and-forth, can you post up some pics of your setup?

Paul