Timing

[Vettefan87]

I went and talked to the guy rebuilding my motor today. He thinks that I have a lean condition, and the cylinders are getting to hot causing pre ignition, and taking the bearings out. He asked me if the shop timed the car at 3000 rpm's. I told him no, since the only way I thought you could time a car was at idle? He said that if you time the car at idle and when you get your foot into it that the computer could be advancing off the board. He said usually by 3000 rpm's the computer is done advancing the timing and that is where you need to time it, and when it comes back down to idle you just have to live with what it is. Is there any truth to that?


Justin

 

[Hib Halverson]

I went and talked to the guy rebuilding my motor today. He thinks that I have a lean condition, and the cylinders are getting to hot causing pre ignition, and taking the bearings out. He asked me if the shop timed the car at 3000 rpm's. I told him no, since the only way I thought you could time a car was at idle? He said that if you time the car at idle and when you get your foot into it that the computer could be advancing off the board. He said usually by 3000 rpm's the computer is done advancing the timing and that is where you need to time it, and when it comes back down to idle you just have to live with what it is. Is there any truth to that?


Justin

The guy may know how to rebuild an engine but for sure don't let him tune it. A basic....very basic fact of computer controlled engines is the timing is not adjustable. The engine computer controls the entire advance curve which, BTW, may or may not be done advancing by 3000 rpm. With an 87 the only adjustment that relates to spark is the base timing adjustment and that's done at idle.

 

[Vettefan87]

Ok, I have been thinking about this all day. Doesn't the distributor had something to do with the advancing of timing through the rpm band? He said that it could be bad and causing the pre ignition. The tips of all the plugs are whiter then they should be. Some where lightish brown in some spots, but for the most part they are all white. I just want to figure out why the car keeps going through bearings, because I can not afford for it to go down for a fourth time. Any and all comments are appreciated. Thanks


Justin

 

[rrubel]

How can cylinders running too hot take out the bearings? That makes no sense to me. Breaking rings, scoring the cylinders, burning valves, yes. But the bearings should be OK as long as they're getting oil, right? And the oil would keep flowing even if it got hot, unless it got over 400 degrees and started breaking down. And if it got over 400 degrees, you'd SEE that, right?
[RICHR]

 

[Vettefan87]

From what I understand which isn't a lot , that the pre ignition is creating so much force on the rods that it is causing the crank to actually flex and that is what is taking out the bearings. He said by looking at the plugs that the car is running to lean, which could be caused of timing, I think. Well hopefully the bro will step in, because I am making myself confused.


Justin

 

[rrubel]

FLEXING the crank? God, I hope not... that'd have to be one weak crank in there! I'd expect the con rods to flex and break much earlier than the crank would deflect. And I'd expect gouges in the cylinder walls as the piston is smacked around with great force, broken rings, low compression, DOGS and cats LIVING together, and other signs of the apocalypse.

Regarding running too lean. I wouldn't suspect timing at all. The car would just run really badly and if anything too rich. This is my inexpert opinion, of course, but if you're getting a very lean condition then I'd check for vacuum leaks (causing more air to enter a cylinder than the computer expects), low fuel pressure (including a starvation condition caused by bad fuel pump or clogged fuel filter), or a MAF that's reading high.

As I recently was told (and subsequently found out), TPI has a low tolerance for vacuum leaks...
[RICHR]

 

[Vettefan87]

One reason he thinks that the crank may actually be flexing is because the inner bearings are worn more then the outer bearings, and I guess that the inner bearings have less support from the block of the car. For some reason something is chewing up the bearings time after time. I have no clue what it is and it must get fixed or the car will sit for a very long time. I am just trying to narrow down the possibilities.

 

[G Winter]

are you talking rod bearings or main bearings ? If it is main bearing then you have a line bore problem , things like the top of one bearing being worn and the bottom of the next one is an idication of the line bore being off.
as for detination taking out bearings . Pistons and rings would go first. The way you discribe you plugs could just be a heat problem. Lean and heat can give about the same look. I really don't think the lean problem or whatever is causing that has nothing to do with the bearings .

 

[rrubel]

Well, dumb question. Is the crank new, and if not, is it straight? Or balanced right? If crank bearings are getting worn unevenly, first thing I'd suspect would be the CRANK!
[RICHR]

 

[tomtom72]

Hi Justin, I offer something from the peanut gallery, I'm no mechanic! If detonation was bad enough to distort main bearings the car should sound like a deisel. If you have forged pistons and forged con-rods I could believe that the rod bearings could be pounded. If cast pistons and regular con-rods then I would believe the weakest link would break first, pistons 1st then rods(?). To be sure detonation is N/G! You didn't say which bearings 4 times(?) rebuild same block/crank/rods/pistons assembly? If I got your story straight them something has to be bent or out of square. I mean if I rebuild a motor using same block & reciprocating assembly and the main B's go I think align-bore check, or & crank bent. If the rod B's go I think bent rods or bore problems or block parallel & or squareness problems and check the crank. I guess the heads could be warped so bad that when T'ed down they "pull" the block out of shape, but then if heads that bad how do you keep head gaskets in it? Oh, forgot crank end play, I think that affects rod B's. Ofcourse if you reused your block with new reciprocating assembly then the block, heads, crank end play is where I would check. If you went through all this then I apologize for sticking in my 0.02 cents. Tom

 

[SG4206]

Justin-
In addition to all the above thoughts, I would have to run a wire cleaner brush through the oil passages in the block,and then pressure feed solvent and cleaners.
Repeated bearing failure indicates someone is not diagnosing the cause correctly. I wouldn't put this back together with new parts until I checked the crank bore for straightness and diameter size.............if this is the same crank that has wiped out all the bearings ;have it checked for straightness also.

 

[Vettefan87]

Ok, I just got home from school, and my father talked to him earlier today. He has no clue about how the computer aspect of the car works, and neither do I. He is now saying that the ignition could be going bad and this is causing my problems. I would think that if the ignition would go bad the car would not run period?

I am going to call him shortly and see what all was done to the crank, since he didn't turn the crank himself. The shop before him turned it ten thousandths, and he had it turned another ten.


Justin

 

[Vettefan87]

I just got off the phone with him and he said with the pre detonation that the rings would show signs of it but with only 400 miles on the motor he said you can't. He said the crank would flex before you would break a rod since the crank is laying flat and the rods are vertical. He is putting a new knock sensor in it, and I told him to put a little higher volume oil pump in the car also. He thinks that it is something electrical causing the pre detonation, either in the distributor, the igniton, or the timing. So somehow I have to fix this or find the bad electrical part.


Justin

 

[vetteboy86]

Ok justin I just talked to Ted. He said it is possible that the crank that got put into your car might not be the one that came out of it. Maybe Kaleys got them screwed up. Also that we should call Shaker and ask if they can check the crank for straightness.


Craig

 

[Vettefan87]

When I talked to Heith earlier today he said that, that is the first thing they do before they turn it. If it isn't straight then they don't even turn it, is what I got from him. How would I tell if the crank that I have is the crank that should be with the car?


Justin

 

[Hib Halverson]

Vettefan87---Find a new rebuilder.

My guess is he's bull-****ting you to cover a lousy rebuild. If you're engine is repeatedly going through bearings, the problem is something other than the BS he's giving you about pre-ignition. In fact, your rebuilder doesn't even know the difference between "pre-ignition" and "detonation" because he's calling this mythical problem "pre-ignition" but is having you chase down an ignition timing problem which, if it existed, would be causing "detonation" (aka: ping or knock).

You asked about the distributor...the 87 HEI distributor has no mechanical advance . All spark advance functions are electronic and controlled by either the ign. module inside the distributor for a very short time during start-up and then by the ECM once the engine is running.

You don't have detonation because the computer's EST will dial-in knock retard when it senses it. Also, the Hypertech Thermomaster doesn't have enough timing in it to cause massive detonation, anyway. Plus!....if your engine could even have detonation bad enough to damage bearings, you'd hear it...as would people standing on the sidewalk as you went by. Lastly, if you truly had detonation that bad (or true pre-ignition) you'd have serious spark plug damage that would be obvious. You state the plugs are colored with white and brown which is generally considered normal, although with the heavily-additive-laced unleaded fuels of today, "reading" spark plugs for colors is a very inaccurate way to gauge an engine's combustion dynamics.

No small block Chevy in any street high performance application needs a high-volume pump. In fact, only a very few specialized, very high rpm, all-out-racing engines need such a thing. Why? Because the SBV8 oiling system is an outstanding design. The only thing you need is to change the oil pump pressure relief valve spring to PN 3848911 which should give 60psi hot oil pressure with 10W30 oil at most rpms above idle. In fact, if this "rebuilder" did not already do that, you've got even more evidence that you need to recommend this guy to your enemies.

It is possible you've got a bad crankshaft, and I'd check it for straightness and journal size but I'd also be looking at the block's main bearing bores. I'd be looking for a problem with the oil passages in the block.

Once again....find a new repair shop.

 

[Vettefan87]

Vettefan87---Find a new rebuilder.

My guess is he's bull-****ting you to cover a lousy rebuild. If you're engine is repeatedly going through bearings, the problem is something other than the BS he's giving you about pre-ignition. In fact, your rebuilder doesn't even know the difference between "pre-ignition" and "detonation" because he's calling this mythical problem "pre-ignition" but is having you chase down an ignition timing problem which, if it existed, would be causing "detonation" (aka: ping or knock).

You asked about the distributor...the 87 HEI distributor has no mechanical advance . All spark advance functions are electronic and controlled by either the ign. module inside the distributor for a very short time during start-up and then by the ECM once the engine is running.

You don't have detonation because the computer's EST will dial-in knock retard when it senses it. Also, the Hypertech Thermomaster doesn't have enough timing in it to cause massive detonation, anyway. Plus!....if your engine could even have detonation bad enough to damage bearings, you'd hear it...as would people standing on the sidewalk as you went by. Lastly, if you truly had detonation that bad (or true pre-ignition) you'd have serious spark plug damage that would be obvious. You state the plugs are colored with white and brown which is generally considered normal, although with the heavily-additive-laced unleaded fuels of today, "reading" spark plugs for colors is a very inaccurate way to gauge an engine's combustion dynamics.

No small block Chevy in any street high performance application needs a high-volume pump. In fact, only a very few specialized, very high rpm, all-out-racing engines need such a thing. Why? Because the SBV8 oiling system is an outstanding design. The only thing you need is to change the oil pump pressure relief valve spring to PN 3848911 which should give 60psi hot oil pressure with 10W30 oil at most rpms above idle. In fact, if this "rebuilder" did not already do that, you've got even more evidence that you need to recommend this guy to your enemies.

It is possible you've got a bad crankshaft, and I'd check it for straightness and journal size but I'd also be looking at the block's main bearing bores. I'd be looking for a problem with the oil passages in the block.

Once again....find a new repair shop.

So you are saying that in no way a electrical system on the car is causing this? I sent my injectors out to get tested. All of them failed the flow test and the spray pattern, and two of them were leaking. They cleaned them, and what not, and tested them again, and they all passed. You provide great information, but with no real solutions to my problem, that I can see. Something is causing this, the motor has been rebuilt twice already the first due to a blown head gasket then the motor lasted 1500 miles, and had to be pulled again, because every main bearing was scored. This last time after 450 miles the outer bearings were scored a little and the inner ones were completely gone. If this is a mechanical problem, a rebuilder problem, then what are they not doing right? If this rebuilder has no clue how to rebuild a motor, how can he be in business? Could the leaking injectors play a part in how the engine has been going through bearings?

The only problem I have now is the crank tested out fine and the motor will be all assembled other then the plenum and the runners tomorrow. When the shop that is putting the motor back in starts the car what should they be monitoring? Fuel pressure, air fuel mixture, timing? I ordered a adjustable fuel pressure regulator. Other then the injectors being tested and the regulator I don't know what else to do to prevent this a fourth time, any other suggestions? Sorry it is so long and thanks Hib for your comments.


Justin

 

[rrubel]

I think Hib gave you a pointer with this sentence:
"It is possible you've got a bad crankshaft, and I'd check it for straightness and journal size but I'd also be looking at the block's main bearing bores. I'd be looking for a problem with the oil passages in the block."

[RICHR]

 

[vettered91]

Vettefan87,

I agree with Hib's post. After two fails of your engine with these guy, maybe it is time to look out for another mechanic and check everything step by step.

You can get some clues here, but I think it's going to be the rebuilder the one to do the evaluation and get the job done. I really don't trust the one you have now.

Good luck and keep us posted!

George.

 

[kingkeith427]

If your rebuilder has not checked the line bore of your main bearings he is doing a bad job. If it is not line bored it will wear your bearings unevenly and lead to premature failure of the bearings. FIND A NEW REBUILDER THAT DOES EVERYTHING HIMSELF ONSITE.