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Difficulty of replacing head gaskets 350.

76k5blazerr

76k5blazerr

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I was wondering how difficult it is to replace the head gaskets on a first gen 350. Mine is like a 82 or 83 I think and I'm pretty sure my drivers side head gasket is going bad, on cold starts there is much more water droplets coming out the driver side exhaust than the passenger side, and much more exhaust "steam" or whatever you call it when you cold start a car and see "smoke" coming out until it's warm. Also I can see on my engine that there's much more oily crap around the drivers side head than the passenger. And on top of all that I fill up my radiator once and a wile and then it drops down after a few weeks. What I'm asking is how involved is a head gasket job, my mechanical ability is not the issue, I know I can do it, just don't no how long it will take and what all has to be removed from the motor to do it? Valves, pushrods? I don't think the Pistons have to come out but do they? Anytging else, or advice on the job? Thanks.
 
76k5blazerr said:
I was wondering how difficult it is to replace the head gaskets on a first gen 350. Mine is like a 82 or 83 I think and I'm pretty sure my drivers side head gasket is going bad, on cold starts there is much more water droplets coming out the driver side exhaust than the passenger side, and much more exhaust "steam" or whatever you call it when you cold start a car and see "smoke" coming out until it's warm. Also I can see on my engine that there's much more oily crap around the drivers side head than the passenger. And on top of all that I fill up my radiator once and a wile and then it drops down after a few weeks. What I'm asking is how involved is a head gasket job, my mechanical ability is not the issue, I know I can do it, just don't no how long it will take and what all has to be removed from the motor to do it? Valves, pushrods? I don't think the Pistons have to come out but do they? Anytging else, or advice on the job? Thanks.
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It's actually not too bad of a job. Depending on your skill level and tools, I'd say 2 hours to tear down and 3-5 to assemble, tune, etc.

But...I think you may have more issues than a head gasket. The smoke on start-up is probably coming from some combination of worn guides, valve stems, seals, etc and the heads will probably require a rebuild or at least new seals.

The steam issue could be the gaskets but I would do a leak down test before I did anything. Autozone and others rent the tester for free and I'd want to make sure the rings, cylinder walls, etc aren't the issue.

You mentioned oil on the head? Where is it coming from? Leaking from a v/c gasket or steaming from a breather? Really would want to do a leak down test before you go to far.
 
I didn't mean to imply that the truck was smoking on start up, I meant it just had more of the exhaust fumes coming out the driver side pipe, you know the fumes how you can see them on a cold start on all cars? It has more coming out the driver side. What do you think about that?
 
If the truck is still unmolested under the hood,it may have a heat riser or EFE valve on the passenger side exhaust manifold,between it and the pipe,it has a butterfly valve inside it that closes when the engine is cold,and that forces the exhaust to flow up under the intake manifold,in passages cast into it,that heat up the base of the carb or throttle body and it then exits out the drivers side exhaust manifold..
This can make it appear that side is doing more "exhausting" than the other--it is normal for some steam to appear after a cold start,some engines take quite a while to burn off all the water vapor in the combustion chamber and exhaust system....

If you dont see milky oil on your dipstick,or have pressure building up in the radiator or hoses,it may not be a head gasket leak,it could be a crack between the valve seats in a head,or your just losing coolant elsewhere,like maybe the water pump weep hole...
Some shops use the emission tester "sniffer" to detect hydrocarbons in the coolant by holding it over the radiator cap opening with the cap off,after a cold start--some also use special dyes that glow under a black light..usually if it leaks bad enough to lose coolant you'll see bubbles in the coolant or surges of air gushing when you rev it up with the cap off though..
 
Ok well I'm about to change the oil in a week or so and I will look for anything that's not normal oil, in the oil, and if the oil is fine does that mean my head gaskets are fine?
 
No,they can still weep coolant slowly---original head gaskets are usually shim steel and they rust away slowly,all it takes is one tiny spot to let coolant into a cylinder..if it leaks close to an exhaust valve it might get blown out the exhaust and never get past the rings and into the oil..

If coolant gets in a cylinder,it may get blown out the tailpipe as vapor, or when the gasket leaks a bit worse,it might end up building up in a cylinder after sitting overnight or longer,and you'll notice the engine will "bind" after it turns over once or twice,then cranks and starts,and it may run rough a few seconds until the coolant gets expelled out the exhaust valve into the exhaust..you may see a puff of steam out of a tailpipe,and if you pull the spark plugs out after a cold start,you may see one has drops of coolant on it,that'll be the guilty cylinder where the gasket is leaking..

For what its worth,I have had several vehicles that worried me as far as seeing "excessive" steam from the tailpipe(s),but they didn't use a lot of coolant in a short time and I didn't smell anti-freeze at the tailpipes,so I just ignored the steam--kept the radiator full,and drive them a long time with no real problems....

Another vehicle I had suddenly had the upper hose blow up like a balloon and pop one day,and did it again right after I installed a new hose,I was thinking it was just an old crappy hose that failed...nope!--the head gasket blew and it was pumping 100+ lbs of compression into the cooling system..the hose was the weakest thing I guess--glad it was,the radiator would have been 300+ bucks for that truck..

Dont want to discourage you,but I have pulled heads and replaced gaskets,and "while I was in there" I decided to have the valves done,or just lapped them with compound,put new valve stem seals on,etc...then after I got the engine back together,it started burning oil like crazy--tightening up the valves will make rings that were equally worn, start leaking and let oil blow by them...
Also some engines that get anti-freeze in the oil,will lose a rod or main bearing shortly after the head gaskets were replaced--it eats away at the babbit material the bearing is made from...
So,its usually best to just do a rebuild or get another good running used engine in the long run most of the time..
 
So man what do you think my best bet is to do, I've already got head gaskets that came in a gasket set I bought, do you think it's worth going in there and replacing just the head gaskets? I can't afford to do a rebuild right now, what is a rebuild on a 350 if it's just a regular old deal not like high horse or something? 500 bucks? Do you think I should just drive the truck till this engine either goes out or stars having larger problems?
 
Ok, so it blows a bit of water vapor out the pipe when it's cold. Do you have an H pipe in the exhaust btw?

How about this, how does it run under normal conditions. All warmed up, does it run great?

Adding a small amount of coolant after a few weeks may or may not mean it's a head gasket. Do you have the over flow tank all hooked up still, no leaks there? No leaks where it's barely weeping around one of the radiator hoses? Your heater core isn't leaking?

If it runs great when warm, and there is no water in the oil, I would suspect you simply have a small coolant leak somewhere. I wouldn't think much about a little vapor coming out one pipe or the other when it's cold.
 
Run it. Save the gaskets for later, unless the oil is milky.

If your that worried find another engine and slowly go through it. Then if yours does blow you have one on stand by.
 
I think that's what I'm gonna do, and my exhaust is true duals, no h or x pipe. Overflow tank is hooked up and idk if I might have a few small leaks in the cooling system, and yah the motor runs good.
 
If you pull the heads, at least have them serviced. I doubt the engine has enough on it to worry about the bottom end after a fresh valve job and seals. Done it a few times on others friends rides and had no ill effect except for the better.
 
My original engine in the Burb had a failing head gasket for several months before it finally gave way enough that it filled up the no.8 cylinder one night and I couldn't start it. At that point as well, is when the oil finally received contamination.

Had 225k miles, still ran good, maybe a little low on power and smoked at start up and extended idles while on trails. I could have simply changed the gaskets and reworked the heads, but I figured with the mileage and the sludge crap that was inside the engine, it was time for a complete rebuild.

Ran me $1300 or so but I also had a roller cam and lifter kit installed. They did all the machine work and 95% assembled it.

I mean a complete rebuild. All new components in the heads, new pistons, reused only the crank and rods.
 
It is always a gamble doing head gaskets...the engine may well run perfectly again afterwards,or it might start smoking,or lose a bearing shortly after doing all that work...sometimes you win,sometimes you dont...I think just replacing the gaskets alone might be the best choice,because you risk making the rings blow by if you tighten up the valves..

My friend who runs a auto repair shop will not do head gaskets in most cases--he finds it better to put in a low mileage used engine from a salvage yard and cheaper too,instead of having an unhappy customer return with a rapping engine or a smoker...

If you dont mind spending a few days hunched over the engine under the hood taking it apart and re-assembling it,then it might be worth it...personally,after having done that, and having it not turn out for the better,and ended up pulling the engine right out to replace it,I would just remove it right away--its a lot easier to pull the engine out than be bent over under the hood 2+ days..there's only 6 bellhousing bolts,2 motor mount bolts,some wires and hoses to take off,and its out in about an hour or so on a square body truck...
 
X2 on pulling the engine vs. doing gaskets in the truck. I replaced the gaskets once, and it really sucked to have to do that kind of detailed work in the engine bay. That set of gaskets failed a year or so later and I pulled the whole engine and had it rebuilt as a 383 with aluminum heads and intake. I have since pulled the engine a couple more times and replaced the engine in my 88 K5 as well.

Pull all of your spark plugs, one by one, and check for one that is different from the others. When it gets bad enough, you will have coolant flow out of the spark plug hole. :eek1:

In my 88, I installed a GM crate engine that was the same specs as the factory engine. It was about $2,000. It runs great and has a 36k mile/3 year warranty.

A rebuild is great, if you can find a good engine guy. I had a few not so hot builds. The 383 actually ran well over 100k miles, but eventually lost a head gasket again. The block wasn't decked when it was rebuilt from a 350 to a 383, after having head gasket failures. That was the story of my new engine builder. He built me a 406 sbc with a scat 9000 cast crank and scat rods. 27k miles later, the thrust bearings went out on the crank. This time I used the best friend of a mechanic that works in my uncle's auto shop. The guy is really into details. His work has been good, but bad work from the guy who ported my heads previously, caused the engine to use oil. I pulled then engine again and had new heads put on, this time with mild porting or blending. That was $2200 down the drain for the old set of heads and another $1500 or so for new bare heads, porting, reassembling the top end and the misc. stuff for me to reinstall it.

IF, you can find a good builder, a rebuild would be the lowest cost. You could start with a used engine and have it ready to go, or ask the builder if they have the block and other parts to build what you want. The shops around here are not fast. The friend of a friend took a couple months to do the full build on my block. He was busy and he also had a new forged crank sent out to be trued and re heat treated to ensure perfect specs as they aren't always that great out of the box.

The GM crate engine was a great price for a new engine and it was fast and easy. The 406 sbc is fun when I mash the skinny pedal with double the power of the 350, but it has been a headache and build like it from scratch would cost easily 3x what the new gutless crate engine cost.

When my K5 was smoking a lot and started to use coolant, I just beat on it more, kind of hoping I would be forced to pull that pos engine (150k miles) and put a new one in it. Well, the head gasket let go when my DD 79 C20 was torn down and getting the 406 build. I owned to Chevy trucks but had to drive my grandfather's Toyota pickup to work. :thumb:
 
Well, after hearing yalls thougts I think my plan is going to be to find me a 350, blown or not running or something and start rebuilding it, I'll be doing it myself, I just want to pretty much build it back to stock specs, would like to not have to bore it, should I still have the block machined to clean it up? Think I'm just gonna slowly rebuild one as time and money allows and then I'll have it on hand for when mine goes. What do you think I could do a decent stock or close to stock spec rebuild for price wise? Few hundred bucks?
 
I had wanted to learn to do my own engine work, but it really isn't worth the trouble if you want something that is reliable and you only plan to do one or two builds.

The block should be cleaned and checked for cracks, and then an engine guy would check the tolerances and condition to see what needs done. Sometimes they can just hone the cylinders.

You could have the parts prepped and then assemble yourself, but you will miss out on the expertise of a good pro. My engine guy had little tricks and preferences to make assembly easier, less costly, and better quality. He sees the failures all the time when he tears down an engine and knows what to pay attention to when he puts one back together.

You need to talk to some engine shops and ask what costs to prep a block or rebuild a stock engine. We can tell you what we payed, but you won't likely be using the same shop.
 
I'd still call around to some machine shops, try to get recommendations from friends or whatnot. I originally started tearing mine apart to do it myself, but when I dropped off the stuff at the shop, we went over the costs of the individual prices for required or recommended machine work, plus parts.

Seriously it was going to end up costing a lot more than to just have them rebuild it from top to bottom. They deal with parts companies all the time, they can get better deals on kits, gaskets and parts. Bundle it all up in a package deal that they get everything needed and all machine work is done by them, you don't lose much time and you have someone/place that can get it rebuilt with confidence, if you found the right place.

I'm also seeing the pricing really depends on where you're located as well though, so some shopping around is in order.
 
Well hear is what I think I'm gonna do, based on yalls opinions I think I'm gonna drive this truck till the motor goes out, then buy another k5 and start really fixing this 76 up. This truck has a few other issues with it like 2 cracks in the rear of the frame so I'm just gonna drive it until I have enough money to buy another k5 probably with tbi, I'd like an 89. Then I'll start fixing this one up. On a side note, what's the best way to repair frame cracks, a repair that will last awhile. Weld up the crack or weld in like square pieces of 1/4 inch plate steel in the crack area?
 
Given the cost of rebuilding an engine it makes a lot more sense to just buy a crate engine with a warrantee.

Or buy a $300 craigslist engine and hope for the best. I've gotten away with that many times and got great engines that worked for a long time.
 
I'm running a 300 dollar craigslist one right now, have a few thousand on it now, hope it will run a few more
 
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