jkjazzsax

I blew the head gasket when the water pump failed and I'm going to be a first timer pulling the heads on my '78 L48. I'm kind of excited to learn more, and understand that if I HAD to perform this HG replacement on any vehicle in the world, the Chevy 350 is probably the best to start on.

I'm ordering parts from zip-corvette.com today. Getting this kit and replacing all the gaskets while I'm at it (Part# EN-100) : http://www.zip-corvette.com/ProductD...L2-SR&CTitle=&

I've never done this deep in an engine before. The limit of my mechanical ability in the past has been things like replacing components like water pumps, fans, alternators, distributor caps, plugs, brakes, etc... basic to moderate auto maintenance. I think I have the aptitude for it (and a good shop manual), but I'm hesitant to try and pull this off all by myself.

I'll try and take pictures along the way and show the progress, but for right now I'm planning on beginning the tear down and rebuild within the next week.

I do not think I'll have the heads checked to see if they are true, as the engine was rebuilt before I got it a while back (by the paint on the block I would suspect about 5-10 years ago).

I have an oil leak at the pan, so I'm replacing the gasket there too, which comes in the kit.

Any pitfalls I should think about before undertaking this? Anything else I should consider doing while I'm in there with the engine all torn apart? My budget is around $200 for the whole job.

jkjazzsax

Looking down on the exhaust manifold, you can see where the exhaust leak was before, now it is leaking out water as well and not just exhaust

Roco71

Its really not that hard it just takes time. The one thing that can get you real sideways is braking a exhaust stud or bolt off in the head. I assume that you are following some sort of repair manual are you? Remember to drain the coolant first or you will fill the crank case with it. Use sealant on the bolts when you re-install them.

I see that you have headers makes the exhaust part a little easier

CaseyJones

Changing a heads gasket is easy if you are careful. Heads are heavy so be careful when you break it loose and heave-ho it over the fender. Changing the oil pan gasket is difficult with the engine in the car but it can be done as part of the steering has to be removed or unbolted. Take your time, follow instructions, and don't be afraid to ask for help. This is a great source of information with plenty of experienced help. Good luck!

jkjazzsax

Thanks for the tips! I've been spraying PB Blaster on those exhaust header bolts for a few days, and will continue to do so. I know they can be a b*tch to get off so I'm trying to think ahead... obviously they look a tad bit rusted from the pictures.

I do have a good shop manual for the '78 which I'll be following religiously.

I have a 1-car detached workshop so this is going to be a lot easier. I don't own a torque wrench so I'll be picking one of those up today... rated for 5-80lbs. The gaskets are on order, and should be here by tomorrow or Wednesday.

After I clean up the shop tonight and lay down a lot of cardboard on the floor I'll drain the coolant from the radiator... which reminds me... I need to get a drip pan

billla

You'll do just fine. Key is to work slowly and methodically - don't buy into someone telling you it's an hour job

Most common mistake I've seen are missing the head bolts below the exhaust manifolds and then prying the heads off - but as you've got a shop manual and can see the torque sequence, you'll double-check where all the bolts are. This is followed by failing to put sealant on the head and intake bolts.

Replacing the intake will be the toughest part with the engine in the car - once the gaskets and the end RTV is in place you just have to be careful settling it into place. A little Gasgacinch to hold the gaskets in place helps a bunch...and then just take it slow.

Looking forward to the pics!

jkjazzsax

Haha! I've always been in the mindset to look up the labor hours for a job online, multiply that by about 1.5 or 2, and that's how long it'll take me.

labor hours say 10.5 hours :P Guess I can plan on 15-20!

Vette5.5

For what you're now talking about doing with the pan and all, probably give some serious consideration, of just pulling the motor. Plus are you sure it's the pan gasket, and not the rear main seal. You may want to list your location, as some hear may have equipment/tools to lend, and maybe even give a hand. Keep in mind, if the new head gaskets are thicker than the originals, you'll need to adjust the valves. Probably do it no matter what anyway. The manual should show you this. Probably step back for a bit and give this a little more thought, before rushing into things.

billla

For the oil pan, I'd agree with this completely.

billla

Good for you Seriously, I see folks sometimes get an "I will get this done in X amount of time" mindset...and it's always a Bad Thing. Realistically, it's a (long) day job if done carefully and if you have all the parts, sealants, gaskets, etc.

It'll make things quicker if you set the engine to around 10 degrees BTDC before you start taking things apart - remember that part of the process will be adjusting the valves and (re)setting the timing...

78 silver 78

One more thing, Head bolts are three different lengths. I would buy a torque wrench that goes to 150#. Mine took 2 days to finnish: ie, take all apart, clean parts, put back together, adjust lifters, Fire up engine.

63split63

Be sure to have the head checked for cracks . It could just as well be a crack leaking into the exhaust . Cast iron heads will crack if the engine is overheated, ( ask me how I know ) . It is way better to have it checked while it is off than have to do the job all over again.

I tend to agree with the other poster who advised pulling the engine out , every time I try to do a budget job it ends up biteing me you know where !

JMO Bill

Vette5.5

Gotta go with "63split" here, as most of the time $200 bucks barely gets the hood open. As mentioned in your other post, a UV dye kit may show you more about possible head cracks. Keep in mind, these sort of coolant leaks will show up far better at running temperatures, under pressure, than just sitting there cold. Another thing, since you ran up to such high temperatures, the valve seals may of gotten cooked too. Have someone drive behind you, when really getting on it, watching for oil smoke.

jkjazzsax

I'm in Raleigh, NC. Anyone nearby?

I remember now that you mention it that the last time I had it at the mechanic, he said the rear main seal was leaking. Is that a job I can handle? I really don't want to pull the motor...

63split63

The rear main seal can be changed in the car, with the pan off . The rear main bearing cap has to be removed and an expierenced tech can slip in a new one .
Looks to me that you should decide weather to do a patch job on this engine or pull it out and rebuild it all or replace it. An overheated engine with a lot of miles on it will be a money pit . Concider a gm replacement or a quality rebuilt .
JMO Bill

jkjazzsax

Definitely going with the patch job here. The engine was rebuilt 5-10 years ago, and I don't drive it all that much. The plan is in a few years to drop a crate motor in it. It's all #'s matching and I'd like to keep it that way for now until I can drop a crate in it and rebuild the old.

7T1vette

If your water pump failed and the engine got overheated, that would cause the gasket to fail...but it also could have caused the heads to warp--especially if they are aluminum. If you still have the stock iron heads, odds are that they didn't warp; but they could. The fact that the heads/block were remachined recently doesn't make any difference. High heat can cause metal to 'move'.

If you have aluminum heads, you definitely want to get the flattness of the gasket face checked [and remachined, if necessary]. It would be best to [at least] get flatness checked on iron heads too.

The only 'tricky' areas are to keep valve train hardware identified by the cylinder number and whether it is exhaust or intake related. Also, determine if the gaskets you are purchasing require any sealer on them (or not) so that you can buy it if needed. The head gaskets should come in a kit with the intake manifold gaskets, too. If not, you need to buy them. And, you will need to decide if you want the heat riser channel blocker plates installed, or not. If you have removed or locked out the heat riser valve (right side exhaust manifold exit), you may want to install them. If you drive the car in cold weather and/or still have a working heat riser valve, you probably do not want to install them.

There are some specific things to do when getting ready to install the intake manifold...so that the 'valley' end joints will seal well after hardware installation. Ask for advice when you get ready for this. Also, buy a tube of Ultra-Black RTV sealant...it must be RTV type...not just some old silicone sealant. You will need it to beef-up the valley end seals and also seal the joints between the valley end gaskets and the intake manifold gaskets.

sly vette

You state that the water pump failed and you feel you compromised the head gasket, and that is very likely. However the pic you posted shows anti-freeze on the top of the header flange and the head gasket is lower than the header flange...So where is the water coming from?

Also if you do remove the heads you should check the heads thouroughly for damage. You will really feel bad if you re-assemble the engine with a warped head or a crack from overheating.

jkjazzsax

Ok, i will have the heads checked.

I am not sure where the coolant is coming FROM, but I can tell you that the coolant is blowing out of the top of the Exhaust Manifold gasket in the same place I had an exhaust leak. That is the exact spot that exhaust was leaking from (the top of the header, next to the gasket). Now, coolant is spraying out of there as well as dripping out of the muffler/tailpipe.

Car idles very rough, but starts. Upon reving the engine, it sounds fine.

Any other ideas?

jkjazzsax

Figured I'd post some more pics before I rip her apart Please see my previous post for info on where the coolant is coming out of.


Her before I rip her apart....



The new water pump, replacing a 33 year old water pump... what I believe the be the original culprit of all this mess.


Passengers side engine compartment view:



Drivers side engine compartment view:




old water pump:



old thermostat: