[mikemustang289]

My brother blew a head gasket in his vette the other day. Just days after the install of an MSA dizzy and 6al box. He said the plugs were white. I was thinking this was the result of too much timing but could a lean conditio contribut to this as well? It doesn't seem like a coincidence that a head gasket would just blow especially since the motor is nearly stock

 

[thekingofazle]

What year? FI or not?

If the plugs are white, you've got something way too lean. EFI plugs should be a good tan/brown when you pull them after normal driving.

Too much timing could cause it to detonate (it wouldn't run if it were so advanced it beat itself to death at idle), but it would be under load. If you've got enough fuel mix in there, it'll still be the right color.

I don't see how it could relate to the MSD install.

 

[mikemustang289]

its a 75. The only thing I can think of that would cause this is too much advance or too much timing since the only thing that was changed is the ignition but I don't know what he set the timing at.

As far as it running lean I wouldn't doubt that one second since he is running my old jetted down edelbrock 600 that was on my 289, but the car has ran fine, no lean surging or anything as far as I know.

 

[ford4v429]

no pinging??? detonation would be my guess too, but most folks would hear it...

 

[FEandGoingBroke]

The Gasket blew due to Inferrior Material, or Improper Installation, Age, or a Cooling issue which could have caused warpage of the heads. Those are generally the only things that will do it to a normally driven car... Hell, an occasionally raced car for that matter...

FE

 

[pedal2themetal45]

With the new ignition it may be getting better fire So fuel mixture and timming could be an issue. but white plugs indcate a lean mixture. need to get that fixed befor he has a melt down.. OH I forgot it just a Chxxy parts are a dime a dozzen..

just my .o2
tim

 

[thekingofazle]

Like Tim said, he may not have been firing a mix that lean with a normal setup - no fire, no power, no detonation.

But yeah, most people would hear the detonation required to blow a head gasket. Pull the head, and check for flatness like FE said.

And tell him he could pick up a lot of power by richening the carb up some.

 

[gorgan1314]

Maybe the gasket was ready to go anyway but he pounded it a little testing out the new ignition and helped the gasket along.

 

[Nanders]

It is possible that there is a vaccum leak causing the lean condition, which is also good for heating up the chambers nice and toasty, which in turn could have convinced the tired headgasket to yak.

Mike, you can take a put a 600 cfm carb on a big block and then stick it on a 260 with out needing to rejet it. My point is that it may not necessarily be the carb to blame just because it worked fine on a smaller motor, if that is the case and nothing else changed, the carb should have worked fine (in low rpm performance) on a larger motor.

remember that the carb meters fuel out based on the airflow running through the booster venturis. A small motor will pull the same or more air, through said carb, at high rpms than a large motor, with same said carb, would at low rpms.

To sum it up, engine displacement doesnt mean you *must* change jetting. which is why I think you may have a vaccum leak

_________________
Thou shalt make it loud while keeping it fast, and thou shalt make plumes of tire-smoke as a burnt offering to the Lord your God, as these things are pleasing to Him.

Nanders 4:11

<font size=-1>[ This Message was edited by: Nanders on 4/14/06 11:49am ]</font>

<font size=-1>[ This Message was edited by: Nanders on 4/14/06 11:52am ]</font>

 

[thekingofazle]

After thinking a little bit, if the engine was running lean on the primaries AND the timing was a little too advanced - at part throttle and low load situations, you could have been running the engine lean - not detonating because of low load, but still running way hot. This could have warped the head over time and caused the gasket to expire. This could have been happening before or after the new carb.

In fact, if it happened with the old one, and then you put a more efficient carb on it, you could have been making much more power than the old lean carb, and you blew the weakened head gasket once you put the new carb on.

The reason it didn't ping under heavy acceleration, though, could be because the secondaries richened it up enough that it wasn't in the danger zone while you were hard on it, just at part throttle.

Its a wild guess, but when you pull it apart, check the head straightness.

Too much initial timing with a slow (read: MSD stock) advance curve could also make it ping at low revs, but not at higher.

I think it put more power into it than it had been seeing and possibly ran the timing too advanced, and the head had warped over time, allowing the extra power to kill the gasket.



<font size=-1>[ This Message was edited by: thekingofazle on 4/14/06 1:27pm ]</font>

 

[mikemustang289]

that carb has been on the car for over a year and its been driven daily, He just put the MSD system on last week and only a few days later the head gasket blows, seems kind of add and I'm just wondering if that was the cause or if it's just a coincidence.

 

[thekingofazle]

well the MSD is probably firing the lean mix a lot better (its harder to light a lean cylinder.) and making enough power to blow the gasket.

Or it could have just built up over time and just finally blew coincidentally.

Just put it back together right and check all the surfaces. And make sure the carb is right.

 

[FEandGoingBroke]

Coincidence... That's all!!

 

[mikemustang289]

seems like it, I think its just a result of old headgaskets and the hotter weather. They looked like junk headgaskets anyway.

 

[My427stang]

Detonation will take out ring lands, gaskets, all kind of things due to uncotrlled combustion. Whether or not that happened to your brother, who knows.

However, remember that detonation happens when some surface is too hot and it ignites

A lean mixture is more likely to detonate, as is too much advance. So in either case, Ir ecommend your brother getis it squared away before he has to buy pistons

Easy rule of thumb. Put the Carb back to Holley-stock for jetting for now. Set the timing to 36-38 degrees total, and I bet he'll be right there