I purchased a '98 ZR2 Blazer from the original owner last week. 128k on the 4.3 Vortecmotor, decent maintenance, does not appear to have been abused or trashed on. I also own a '97 Silverado with a Vortec 5.7, so I am somewhat familiar with the Vortec series of motors.

As I tend to do, I am going through it mechanically to do 'mid-life' maintenance - belt, hoses, thermostat, plugs, wires, cap, rotor, O2 sensors, trans filter, fuel filter, and anything else I can think of. While I have everything apart, I am doing the MPFI conversion (just like I did on my Silverado).

I know the early Vortecs were prone to intake manifold gasket failure due to dissimilar metals used between the block and the intake. I was under the presumption that Chevy had this figured out and fixed by 1998.

Is my presumption correct? Should I just keep going and proactively replace the intake manifold gasket? I have no reason to believe it is leaking, but I would hate to have it develop a problem 10k after I had everything apart.

Thanks,
-Eric

 

If you've already got it down to the lower intake, you might as well change out the gaskets. It really isn't that much more work to get all the way down to them from that point.

My intake gaskets started to go on my Bravada at ~75k and I just replaced them a month or so ago at 82k.

 

I would followan old mechanics creed; "If it ain't broke don't fix it". If the lower intake gaskets are not leaking why change them, you could actually cause the very problem you are trying to solve...I know that all the parts are already off and easier to get at. In my opinion I would just recheck torque specs and leave it at that and move on...it is sealed good for now if you break that seal there are no guarantees that the new gasket would seal any better....

 

Your presumption is not correct - this continues to be an issue with later model Vortecs.

If you don't have a problem, I'd say don't pull the intake manifold. It's a pain and takes another 4-5 hours of work to get it off, clean everything and re-install even if you have other stuff off the top already.

 

Hmm.. Don't think it takes anywhere near that long... If you're into preventative maintenance, do it. Especially on a problem area such as this. If it leaks into the engine, you may not catch it until it is too late.

 

Pilgrim- I guess I was mis-informed as to when GM got thisproblem addressed. Thanks for letting me know! Should I go with an aftermarket Fel-Pro gasket, or go with the revised GM replacement gasket?

Swartlkk- Preventative maintenance... Yeah, that's me. Also, this will end up being the wife's daily driver. She is not as 'in tune' to vehicle changes as I am. So when something goes wrong, she doesn't notice right away.

And even if it takes a few hours to complete, that is not a problem either. I have a shop to work in and the Blazer is not in daily driver service yet.

Keep the info coming...

Thanks,
-Eric

 

You may be right that 4-5 hours is too long, but considering that I had to loosen the entire PS/AC bracket on the driver's front of the motor and pull it forward to get the manifold off, that added some time. Also, I took GREAT pains to make sure that the underside of the manifold and the contact surfeces on the heads were extremely clean. I probably spent an hour just scraping them and double-checking. I definitely couldn't have done it in less than 3 hours.

I have a general rule for the time it takes for any mechanical procedure:

1) Figure out the maximum amount of time it could POSSIBLY require, bad luck included.
2) Double that number of hours, than add another half.
3) Use the result as your estimate.

Ex: a job that should take 5 hours with bad luck will required (5x2= 10) + (5 x 1/2 = 2.5) = 12.5 hours.

I have proven this many times over the last 30 years. Once in a great while I manage to do better if it's the third or fourth time I've done the same procedure.

[sm=happybounce.gif]

 

>> 1) Figure out the maximum amount of time it could POSSIBLY require, bad luck included.
>> 2) Double that number of hours, than add another half.
>> 3) Use the result as your estimate.

So that is what I have been doing wrong all these years. I thought that formula only applied to how much a given project will cost!

-Eric

 

OOOOOoooooo, good point!

I vote: BOTH!

 

If your still going to change the gaskets out, I would go with fel-pro. If you get OEM from the dealer, you'll just get the same crummy gasket. I had a dealer install gaskets on mine and it failed within 1000 miles. I was so mad that i ended up replacing the gaskets myself with fel-pro, That was 8 months ago and 6K later its still holding well. I was very pleased with the fel-pro quality.