Trying to solve a LT-1 engine problem

[Ronald D.]

A couple of years back I had my LT-1 engine rebuilt (1971), everything was done to it, a few months ago I noticed coolant leaking into the exhaust on the right side, long story short the head had a problem under the valve seat causing water to enter the exhaust port, I located a nice dated set of heads that were completely rebuilt and tested, so the shop said, they did look very good. So I Installed them no more coolant leaks, it sat for almost a year, never ran it yet, so yesterday I decide it's time to run it, break in the cam and finish the car up, I start it, running it at 2000-2500 and notice coolant out the right tail pipe, I assume this is what was remaining from the leak problem, but it looks like there is to much for that, I go out today and want to get another 20-30 minutes on the cam, the coolant was only down maybe 5 ounces, top it off go run it some more, more coolant, a lot, so I shut it off. I can see some moisture building on the inside of the oil cap, there is water in there I believe, so this is where I am at, when I put the heads back on last time I know I did it correctly, as also with the intake, it sure looks like it's coming apart once again, so before I start pulling stuff off I am looking for some ideas on how to find out what is the cause, The temperature got up to about 200 in 20 minutes, I have not looked for bubbles in the radiator, I know some is in the oil, this is getting old, I am just looking for a plan of attack, thanks Ron

[Joe L.]

Re: Trying to solve a LT-1 engine problem

A couple of years back I had my LT-1 engine rebuilt (1971), everything was done to it, a few months ago I noticed coolant leaking into the exhaust on the right side, long story short the head had a problem under the valve seat causing water to enter the exhaust port, I located a nice dated set of heads that were completely rebuilt and tested, so the shop said, they did look very good. So I Installed them no more coolant leaks, it sat for almost a year, never ran it yet, so yesterday I decide it's time to run it, break in the cam and finish the car up, I start it, running it at 2000-2500 and notice coolant out the right tail pipe, I assume this is what was remaining from the leak problem, but it looks like there is to much for that, I go out today and want to get another 20-30 minutes on the cam, the coolant was only down maybe 5 ounces, top it off go run it some more, more coolant, a lot, so I shut it off. I can see some moisture building on the inside of the oil cap, there is water in there I believe, so this is where I am at, when I put the heads back on last time I know I did it correctly, as also with the intake, it sure looks like it's coming apart once again, so before I start pulling stuff off I am looking for some ideas on how to find out what is the cause, The temperature got up to about 200 in 20 minutes, I have not looked for bubbles in the radiator, I know some is in the oil, this is getting old, I am just looking for a plan of attack, thanks Ron

Ron-----


Have either of the heads you've had problems with had the exhaust valve seats replaced with hardened inserts?

[Ronald D.]

Re: Trying to solve a LT-1 engine problem

Yes both have new seats, valves springs, and guides

[Joe L.]

Re: Trying to solve a LT-1 engine problem

Yes both have new seats, valves springs, and guides

Ron------

The new seats are very likely the problem. Installing hardened seats in small block cylinder heads, especially those originally machined for 1.60" exhaust valves, runs the risk of "striking water". In your case, I expect that risk has been realized. If one is installing new seats because the existing seats are too worn or receded, it's a risk one has to take if one wants to use the heads. However, if one is installing them "because everyone says you need them with unleaded gas", then that's a foolish mistake.

[Ronald D.]

Re: Trying to solve a LT-1 engine problem

Yes, on my first set of heads that was the problem, then I found two more heads and installed them, could I have had this happen twice, yes maybe, but the first set one leaked without the engine running, once replaced no leaks, then it leaks after start up, I am thinking of getting a small borescope, pressurizing the cooling system and fishing it down the intake to see if I can see the coolant leaking, and or in the spark plug holes, before just tearing it apart again

[Michael W.]

Re: Trying to solve a LT-1 engine problem

If you end up having to replace the heads again, do NOT have them machined for new seats. They are simply not required contrary to old myths..

[Edward J.]

Re: Trying to solve a LT-1 engine problem

Ron, the first step is to wipe the cap and check the oil and make sure oil is not mixing in crank case, and restart car and run so what ever moisture is in the exhaust system can exit the muffler(s) sometime this can take 20 /30 minutes and don't be alarmed until all the steam is gone. steam can gather on the under the valve cover cap and cover. and then once you've done this go and re-torque the heads and intake manifold, generally I will make about 3 passes after the all bolts have been torqued. the intake is one area you have to be careful. once you get the V/covers off make sure that no anti freeze is traveling up the head bolts, head bolts are tapped into water jackets on the block I believe.

[Ronald D.]

Re: Trying to solve a LT-1 engine problem

Good ideas, I did check the oil it doesn't show any coolant, if I run the engine it will continue to pump coolant out the tail pipe, it's only on the right side, when the head bolts were installed they all got sealant put on them, removing the valve covers will be next, thanks for the ideas

[Edward J.]

Re: Trying to solve a LT-1 engine problem

Ron, it best to make sure that no coolant is left in the system, If the car is registered take for a drive, keeping a eye on the temp. make sure coolant level is topped off. after the test if all clears up you should be good to go. I myself have done hundred if not a few thousand head gaskets job. over the years and if coolant has entered the exhaust system its can take a good long road test to heat the exhaust system enough to burn off the antifreeze.

[Duke W.]

Re: Trying to solve a LT-1 engine problem

If the heat riser is installed and functioning properly it is common to see condensing steam (white "smoke") exiting the right exhaust pipe at startup, especially in cool weather.

I suggest you check that the heat riser is free and wire it open, however, it does sound like you might have coolant leaking out an exhaust seat insert, and if so, find a set of heads that don't have inserts and refresh them as necessary, but as Joe L. said, DO NOT let some machine shop install exhaust seat inserts.

Duke

[Ronald D.]

Re: Trying to solve a LT-1 engine problem

When I run the engine I don't get steam for 10 minutes, but coolant coming out the tail pipe, a lot, like a half pint, so today I am removing the valve covers and all the spark plugs to see if I can find the leak, it is becoming to tell me those valve seats are the problem, again, this will be #3 set of heads, I plan on having the car judged sometime this year, I may be done with 50 year old heads with unknown history and just install a set of new Edelbrock heads and take the point deduction, everything else on the car is matching correct except tires as all of them are, so I don't know how the after market heads will hurt me point wise, but it looks like a 3rd set of heads and I haven't driven it yet since the frame off restoration, thanks for the help, Ron

[Domenic T.]

Re: Trying to solve a LT-1 engine problem

Ron,
When I looked for leaks like yours I would pull the plugs and pressurize the cooling system. Then turn the engine over with the starter and the coolant would squirt out the cylinder that had the leak. Many times you can see it on the plug. It just might be one seat or something else that can be fixed. If it can be fixed you need to make sure that a experienced shop looks or tests for future problems.
I did the plug out at the dealer and the customer insisted on watching. It was a straight 6 cylinder and when I turned it over the water came out the spark plug hohe and blew his glasses off.

Dom

[Ronald D.]

Re: Trying to solve a LT-1 engine problem

OK here is my update, I removed the valve covers, no water in there at all, nice clean oil, I removed the spark plugs they look fine also, so next will be spin the engine over and see if any coolant comes out the holes, my guess now is no it won't, next will be remove the right exhaust manifold, I expect to see a leak at a exhaust valve, I will pressurize the system and look, if I do have insert cracks the next issue is whats next?, I am getting tired of bad heads, this will be the second set both bone be a good machine shop, not the same one, but maybe they arn't really good at all, perplexing

[Joe L.]

Re: Trying to solve a LT-1 engine problem

OK here is my update, I removed the valve covers, no water in there at all, nice clean oil, I removed the spark plugs they look fine also, so next will be spin the engine over and see if any coolant comes out the holes, my guess now is no it won't, next will be remove the right exhaust manifold, I expect to see a leak at a exhaust valve, I will pressurize the system and look, if I do have insert cracks the next issue is whats next?, I am getting tired of bad heads, this will be the second set both bone be a good machine shop, not the same one, but maybe they arn't really good at all, perplexing

Ronald------


As I mentioned previously, if they installed hardened valve seats, I expect that's your problem, assuming you actually have a problem. If you determine that there is a problem and you decide to go with another set of heads, just don't have hardened seats installed. You should be able to find a decent set of heads. Personally, I would not worry about dates, though. Have them magna-fluxed and if they check out, you should be fine.

[Patrick B.]

Re: Trying to solve a LT-1 engine problem

It sounds like your leak is from one of the heads and you have had the same problem with two other sets of heads. Of the other four heads, do all of them leak or can you use one of them along with the non-leaking head of the present set? Hardened valve seats are a bad idea because of the risk of cutting into the water jacket, but it is not a 100% risk. Of six heads, you should have two that do not leak.