Stingraynut

Last week I had the valve seals replaced on my 1988. The workshop removed all the rockers and then pressurised each cylinder to hold up the valves while they fitted the valve seals.

They rang me to say that cyl#4 had leaked air into the coolant system and water had squirted out of one or more of the disconnected hoses under great pressure. The compressor was set at 90psi.

Cylinder #6 showed faint signs of the same.

The crazy thing is that my car has been running the best ever – I even posted about it a few weeks ago -http://forums.corvetteforum.com/showthread.php?t=1074821&forum_id=48

I am still driving it and it has never run better.
It is not running hot.
There is no sign of water in the oil.
No milky residue on the oilfiller cap.
Hasn’t lost any coolant since leaving the workshop.
No bubbles in the radiator when reving to about 2000rpm.
BTW I did the TB Bypass 2 years ago.

I don’t want to damage the engine and also don’t want the expense of a head recondition. Logic tells me there is no way air should get into the cooling system.

One friend has suggested that if the inlet valve was badly seated, air could have escaped into the plenum and then into the coolant through an intake manifold leak.

Another friend says I am ‘in denial’ and had better have the head pulled quickly.

I’d appreciate hearing from anyone who has experience with blown head gaskets or who knows of a way that the compressed air could enter the coolant but apparently not happen when I’m driving.

Thanks

S’nut

MtlSphere

I dunno...kinda sounds like a case of "typical mechanic" trying to squeeze a few more bucks outta you for a repair.

Then again you could be in denial...

Do a compression test yourself. The gauge isn't that expensive and the peace of mind is priceless. Run the engine up to operating temperature and then pull all the plugs. It helps to wear a pair of mechanix gloves when working around hot headers. Install the gauge in each cylinder and turn the engine over at least a couple of revolutions with the starter...record the highest reading in each cylinder. When you've recorded all eight compare the values. They should all be very nearly the same. If one or two are down you'll see it right away and know for sure.

Besides pulling the heads for a gasket job will give you the oppurtunity to install that new intake you've been wanting, and those new rocker arms you've been thinking about...

Corvette0096

When my head gasket went it was pushing the water into the over flow tank. But I could see bubbles after the thermostat was open. I would pressure test it to be safe.

rick lambert

I'm no expert for sure-just been working on engines since I was 16-now
I'm 61. But here goes-you don't have to see water in your oil or have to see any indications in your cooling system to have a blown head gasket.Think of the narrow section of the gasket between the cylinders,it may not show up in the cooling system but will definetly show up as a loss of compression between the two adjacent cylinders (next to each other) where as on the compression stroke compression
will escape into the the other cylinder.These conditions can cause further damage by actually wearing a groove in that area. I'd say the same thing your mechanic said-blown head gasket.Incidentally, if you do a compression test, all cylinders should read within 10%-two weak
ones, especially next to each other means Blown gasket or cracked head probably as high as 95% of the time-sorry.

Stingraynut

Thanks everyone - MtlSphere - the place I went to had imprtessed me with work on other cars and I was dealing with the owner who seems a very upfront straight type of bloke - but I'll bear that in mind - perhaps that's why I told them to continue doing the valve seals and put the car back together - but it's running so good, I can't believe it -

except - Rick, your description tells me that I have a blown head gasket !!

What gaskets do I need for a head overhaul ? should I get my injectors cleaned and new o rings at the same time ? anything else worth doing ?

There should be an icon there for emptying pockets! I'd use it on this one.

S'nut

severe-1

Perhaps it only leaks when cold.

Heads don't get to the proper torque until they warm up and expand.
More so for aluminum heads.

Try a cold leak down then a hot one.

If your hurting for bucs, you might get away with a retorque.

Besides, whats the worst that could happen? (vaporized money and new heads?)

KAZ2

You don't say how many miles are on your 88, but, from some of the stories we have read on this forum it looks as if you have been given the best "heads up" that you can re a blown head gasket. I know it is damn bad news (I worry about my 87), but, you most likely haven't done any damage to the bottom end and will be able to pull the heads and go with some of the much better head /manifold gaskets available. Mine needs the valve seals replaced, and, I may just take mine down this year and get the heads done (new valve springs/etc) as a preemptive strike and cheaper than a rebuild.

rick lambert

On a 27 year old car I wouldn't count on retorqueing the heads as a cure-and if their under the hood now it'll probably save some bucks to do it now versus later.Good luck, and if you do have them replace the head gaskets ask them to show you where it was and let us know.

MtlSphere

If you pay someone for this kinda repair you're going to pay alot.

But in all honesty this a job you can do yourself. The C4 is by far the easiest car you could ever do a head gasket job on. The clamshell is a gift from the gods. I know that looking at the engine it seems like a lot of work (and it is) but the satisfaction you'll get from doing it yourself is...well...priceless.

Besides a torque wrench and a few sizes of the torx type drivers, hand tools are all that you need. You'll need a upper intake gasket set, the head gaskets, valve cover gaskets (optional if yours are in good shape) and exhaust gaskets. The upper set will have everything you need; RTV for the china walls and even a new gasket for the distributor.

Lemme see...disconnect the battery, drain the coolant...then...

Asscessories off the front of the heads, air cleaner ducting, fuel lines, serp belt, A/C, air pump and brackets, etc...

Pull the valve covers, distributor, plenum, runners, radiator hose, intake...keep track of the vacuum lines and power brake line.

Remove the exhaust manifolds and wire them away from the heads.

Then loosen the rocker arms and remove the pushrods, pull the head bolts and yank off the heads! Clean the mating surfaces and install the new head gaskets. Installation is the reverse of removal. Follow the recommended torqueing sequence

Of course I left out alot of the little things like turning the engine to #1 TDC before you start, marking the distributor/rotor bug relation, and adjusting the valves when you're done but that's just gravy anyway!

Sounds like fun!!

Stingraynut

MtlSphere - "sounds like fun" you have a weird sense of humour! it doesn't sound at all like fun to me!!!!

I appreciate your info very much. There was a time when I'd tackle this job and learn from it, but my back is in bad condition so I'll have to pay the experts on this one. Hence my comments on the 'empty pockets' icon.

The info on the gaskets is very handy, I will order all the necessary parts first.

The workshop have suggested I get the head skimmed to ensure it's flat and I thought of cleaning the injectors and replacing the O rings while everything is apart - is all that a good idea?

I think that when they recondition the heads they also replace the valve guides and lap in the valves? is that right/normal?

What else should I get done?

Is there anything reasonably inexpensive that I could I do to improve the heads, get more HP etc?

Rick - my 88 is 'only' 17 years old, it's done 107,000 miles

S'nut

MtlSphere

Those 113 heads have a pretty small combustion chambers to begin with. The heads can be checked for warpage. I would make sure that they need milling before actually doing it. If they aren't warped leave them alone...then again milling them can increase your HP by increasing your compression ratio. They're like 58cc to begin with. But be aware that milling the heads requires milling the intake by the same amount to keep the mating surfaces inline.

Here again these are just my opinions...cleaning the injectors? Nah...unless you've been having difficulty with them. Replacing the O-rings? Definitley! If you take them out and you will to have the intake milled to match the heads; never re-use O-rings. Just a few penny's of cheap insurance.

A good valve job will replace the seals and guides, check the valves to see if any are bent and then reface the valves and seats and lap them in. Check the springs for proper height and tension, replace any that are weak. I prefer to change them as a set if I find any that are weak. You might ask them about a 3-angle valve job, helps improve flow a bit. Gasket matching the ports, both intake and exhaust are good for a few ponies. Beyond that it gets expensive. While it's apart you can use your Dremel to open up the plenum and runners and gasket match those pieces as well.

Making HP is all about moving air. Both in and out. The more air you make the engine breathe the more fuel you can add to that air (that's where the power is), the more power it will make!

There are the usual suspects...K&N filter, open the air cleaner lid, de-screen the MAF. In addition this would be a great time to add 1.6 rockers, there's a few ponies. And add long tube headers. I hear guys talking all the time on here about TPIS and Hooker, all big dollar headers. I opted for Heddman hedders from Summit racing for about $125.00 and the fit was great! A few exhaust mods like a cat-back and Flowmasters...

You know, the list is endless...will it ever end?LOL

RacerX70CC

Have the cooling system tested with block test fluid (turns from blue to yellow if gases are in the cooling system) before condemning the head gaskets. If it fails that test... you know what's next.

Stingraynut

MtlSphere, thanks again for the info - I hadn't thought about the milling intake as well as head surface, I wonder if the machine shop does that as a matter of course - appreciate the tip off anyway, that's something I can make sure of - if it needs milling.

"3-angle valve job, helps improve flow a bit." - I don't know this, can you explain please ?

Thanks also for thoughts on injectors, they're all working fine, as far as I know. O rings, yes will replace.

I'll check out the Hedman headers. A friend has just bought a crate engine (reconditioned I think) which has Vortec heads and was rated at 300hp - so I was wondering whether I'd be better off spending the money on a better head than reconning mine ? I admit I don't know much about them, how they fit, how much etc, am planning to check that out next week.

My idle was a bit uneven today, coolant temps cool and otherwise the car is running fine. New oil seems to be getting dirty quickly - have done 300+kms since oil change which was done last week when I had the valve seals replaced and discovered the suspected blown gasket.

Racer - I'll check with the radiator shop to see if they have this block test fluid - my coolant is bright green - do you pour in a bottle of this blue fluid or do you start with fresh clear water as coolant ?

Thanks again, I appreciate all your advice and info. The more I know the less can go wrong (hmmmm.....I hope)

S'nut

Stingraynut

MtlSphere - which Hedman headers did you get? there seems to be several options. Did they bolt straight to the standard exhaust flange ?
What sort of improvement did they make ?

S'nut

ittlfly

The block tester kit is one that is sold for about $30. You can get it over the net or maybe at a local parts store. It takes about 5 minutes to do the testing. It sucks up coolant vapors through a tube that contains the blue dye. If the dye turns green, there are exhaust gases in the coolant which indicates a a problem. Blown headgasket , or worse.

pwrful c4

J Z06

When my head gaskets blew in my "boosted" mustang gt, the symptoms we're high temps, overflow bottle had bubbles(ala corvette 0096) and the car WREAKED of anti-freeze.

Also, your oil may look like a milkshake due to the introduction of of coolant in to the oil which I was told is MURDER to the bearings.

Stingraynut

Thanks Jay383 but as you'll see from my posts above, I have none of those symptoms.

Itlfly - thanks for block tester info.

MtlSphere - darn headers won't fit my car - converted to Right Hand drive and steering column gets in the way.

S'nut

65Z01

I would definitely do a pressure check on the radiator with a warm engine. If indeed air pressure was pumping out water you should see some indication on the pressure testor.

Next would be, as recommended, a compression test on each cylinder.

If you do the heads go with a 5-angle valve job. Here the valve seal is at 45deg and the valve mating surface is nearly the same. Then two additional cuts are made on each side of the valve sealing surface, each 15deg apart the result goes like this: 90,75, 60,(45), 30,15,0.

It has been found that when air flows at high velocity around a bend of 15deg or less it "looks" like a smooth round bend to the air; if air must make abrupt changes, i.e. >15deg it is slowed somewhat. Admittedly the difference on a nearly stock engine, between a 3-angle and a 5-angle valve job may not amount to very much gain but every little bit helps.

Also doing a back cut on the valves helps with air flow past the valve as does a necked valve stem.

Stingraynut

Hi 65Z01, I seem to remember reading that air thinks 15 degree bends are smooth a long time ago but had forgotten it, thanks for info.

As you say, if I don't change anything else the improvement will not be much, but it's good to know and think about. So now I understand the 3 angle and 5 angle cut.

The pressure check on the rad with a warm engine is a good place to start - I'll organise that next week. If I get extra pressure on revs ? then I'll try the block tester, if I can locate one, and go from there.

S'nut