2000 monte 3400 head gaskets
 

our monte carlo keeps blowing the back head gaskets this will make 3 times I have replaced it I had the heads done at 2 different shops and they both pressure tested them now it has blown it again It always blow it on number 1 cyclinder i have replaced the radiator, the radiator cap put a new water pump on it, new hoses, new thermostat, new fans bleed the system on short runs it does great but on long trips it will get hot does anybody have any suggestions I really like my monte carlo but I am beginning to think it is just made to park in the yard to look pretty we talk to a place that does heads and they said the water jackets on the 3.4 gets clogged and they weld them to keep them from doing that has anybody heard of this before

I've never head of the water jackets clogging (unless you neglect regular maintenance of the cooling system).

You have what seems like an unusual problem.

Have you replaced the front head gasket or only the back one? If you have not done the front, have you compression tested the front to make sure there is no cylinder issues there? After putting it back together, did you compression test all cylinders? Do a radiator pressure test as well (covering the bases, making sure all systems are working right)?

Also, when you torque the heads down, are you using a Harbor Freight torque wrench, if so, try a better quality one (I've heard too often those tend to be a bit off).

At this point, if you have not replaced head bolts, GM recommends doing so whenever you remove them as they are torque to yield (admittedly, I've reused them a few times, but in this case, your in uncharted territory of a problem). Are you using a name brand gasket, like Fel Pro? If not, get away from the cheap ones. I assume you checked the flatness/straightness of the matting surface for the head and the block (just need a straight edge to check it, nothing fancy)?

I have never heard of an engine constantly blowing a head gasket. So these are desperate ideas.... But I would NOT weld something shut that was not done so by the factory!

head gaskets
 

I have replaced both head gaskets twice already and this will make the third time, I replaced the bolts, I run a compression test it is anywhere between 115 to a 120 lbs after i have replaced that head gasket, I checked the flatness, the head and the block both have the triangle water jackets but the gaskets has holes about the size of a pencil they said it is a pressure gasket I went to 2 different machine shops and they told me that they do over a hundred a week on the 3400 and the 3100 because the gaskets blow, It blows the gasket out to the size of the traingle then it gets into the piston The first time I changed it it was on the front side the last two times it has been on the back side I did replaced all the gaskets I get my gaskets thru the machine shop, they told me it was a common problem with the 3400 and the 3100 motors either the head gasket or the intake gasket blow but now they have changed the intake gasket to a metal one

I've done a lot of work on 3100 and 3400 cars for friends and family. Intake gaskets (nylon) last about 80,000-120,000 miles (nylon was a crap material, so switching to the aluminum gaskets is a great move). Same applies to the 3800.

As far as head gaskets on properly maintained car, those are not as common. I know a lot of 3100/3400 cars I've worked on that are still original head gaskets and well over 150,000 miles (in a couple of cases over 200,000 miles). I think in all the cars I've wrenched on with a 3100/3400, I can only think of three that had head gaskets done and both were over 150,000 and replaced with Fel Pro head gaskets and no problems ever since.

Keep in mind, the machine shop just works on the heads not the job that caused the heads to be pulled. Some people may be changing head gaskets because they are already that far in, why not go the extra steps.

If you don't know the brand gasket you were using OR it was not a Fel Pro gasket, I would recommend getting a Fel Pro head gasket (that is a commonly trusted brand for 3100/3400/3800 owners, the brand I've used with success in the past). It could come down to a poor quality gaskets in theory.

And as I suggested, have you used a good quality torque wrench (like Craftsman or Snap-On)? Or did you use a Harbor Freight one? The Harbor Freight ones are known for not being entirely accurate. And when doing head gaskets, that job is so far down, takes so much time and money, I pop for reputable gaskets and I've borrowed a better torque wrench to get the job done.

Also, is your torque spec coming from the GM/Helms book or a Chiltons/Haynes book? I ask because sometimes the info in the Chiltons/Haynes books are not 100% accurate.

Per the shop book you want to tighten the left cylinder head bolts (1-8) in sequence to 60 N·m (44 lb ft) plus an additional 95 degrees.
Below is the tightening sequence you should use for each head (per the GM/Helms shop book), if you aren't already:
https://montecarloforum.com/forum/at...1&d=1381676729

head gaskets
 

We have 2 torque wrenchs one is digtal and one is manual and they both are craftsman the gasket was Fel-pro chevorlet garage said the new specs was 39 ft lb with an additional 90 He has worked on cars a long time and never had this much problem out of a head gasket I straight edge the block took the head up 2 different machine shops and they straight edge it too said the head was just fine

At the moment, these were the best off the top of my head ideas :(

I'd curious what's causing the gasket to keep blowing. That is very uncommon.

hey
 

Ive heard of a clogged cat doin that

A clogged cat also comes with other symptoms I don't believe the OP listed. If the cat is clogged, the car's performance will be very poor (no get up and go). Those symptoms would occur prior to the head gasket blowing out.

head gaskets
 

our car has plenty of get and go as of now i have changed the back head gasket again and the intake gasket was blowed on the front Does it wire 1 3 5 against the fire wall and 2 4 6 against the radiator I just want to make sure i am wiring it right It seems like the haynes book is wiring it different than what is on the intake I am still working on it this time