Do all turbo heads crack?

[SVO2.3]

Seems like everything I see says they do. Can you tell while it's together? Will a big valve install be a remedy? (I doubt it)

[Raven855]

The heads from an 89 TC have hardened seats and have less tendency to crack. The large valve will not fix the issue but putting hardened seats in helps!

[SVOBoyd]

It's funny I was just talking to my machinist about doing a valve job and installing hardened seats in my 2.3 head. He said the exhaust seats are what cracks and this is mainly due to too high exhaust gas temperatures (EGT) from running lean (keep in mind he was not talking specifically about the 2.3 head but in general terms). His thoughts were if you're running EGT hot enough to crack the seats and you install hardened seats then you're chances of dropping a seat into the cylinder is fairly high.

I have read at least one thread on here where Mike explained that running a manual boost controller can cause increased EGT: "When the EEC can no longer lower load (aka boost), it leaves only reducing timing more. Which will dramatically increase chamber temp and EGT values. Over the long run this often results in severely reduced service life of exhaust valves, exhaust valve seats, and all other up-front exhaust components."

My take is we have two issues with our engines that can lead to cracked seats; running lean (maybe from engine mods or other issues), and using a manual boost controller (what Mike said). So do the 2.3 turbo heads have an inherent issue with seats cracking or do they crack due to abuse? If there is an inherent issue with the seats cracking then it might be a good idea to install hardened seats otherwise it may not be a good idea. I'm just trying to weigh the pros and cons of installing hardened seats, I'd rather not lose a bottom end trying to stop the head from cracking.

[MikeFleming]

My take is we have two issues with our engines that can lead to cracked seats; running lean (maybe from engine mods or other issues), and using a manual boost controller (what Mike said). So do the 2.3 turbo heads have an inherent issue with seats cracking or do they crack due to abuse? If there is an inherent issue with the seats cracking then it might be a good idea to install hardened seats otherwise it may not be a good idea. I'm just trying to weigh the pros and cons of installing hardened seats, I'd rather not lose a bottom end trying to stop the head from cracking.

This 1972-3 era designed head was intended for HP ratings in the 75-125 range. So the materials, material thicknesses, coolant flow, etc. are all designed around those parameters. When operated in those power (thermal load) ranges, they do just fine.

However when doubling the power output (thermal load), they get marginal. Therein lies the main issue - if we make more power, thusly increasing the amount of heat the engine has to handle, the rate of failure increases, aka reliability/survivability goes down.

We can now add more fuel and use different engine management computers to keep from "running lean" (which only means adding excessive amounts of [liquid] fuel for internal cooling due to fuel evaporation), we can control timing and boost (thermal load) together and we can learn to lift off the throttle when it first starts pinging - rather than pushing the eng mgmt system into full retard under load. Well, two out of three then.

Hardened seats will wear less even at elevated temps. However exhaust valve stems, guides, seals, etc will still see those high EGT values. And their life will be reduced accordingly. So it's a "win-some" kinda thing.

While we're on the subject of high EGT, remember the exhaust manifold, turbine housing and all associated threaded fasteners have the same issues - the high temps shorten their useful service lives.

If only there was a properly-designed, good quality aluminum head that we could use. That would be sweet! I can dream, can't I?

[SVOBoyd]

If only there was a properly-designed, good quality aluminum head that we could use. That would be sweet! I can dream, can't I?

Don't forget cheap!

[SVOBoyd]

I probably will just go with the valve job and not worry about the hardened seats. Do you guys think it would be worth going to stainless valves?
Si valves has theseThe catalog says they are stainless steel forgings with chrome stems, stellite tips, and swirl polishing)
1.75" intake valve, single groove, 4.757" length, part no. SEV-2.3-IS
1.50" exhuast valve, single groove, 4.757" length, part no. SEV-2.3-ES

[MikeFleming]

For the exhaust side you need something much better [at high-temp survival] than typical stainless (300-series). Inconel is recommended.

1.75 is too small, iirc 1.79 is the factory size

[SVOBoyd]

For the exhaust side you need something much better [at high-temp survival] than typical stainless (300-series). Inconel is recommended.

1.75 is too small, iirc 1.79 is the factory size

Thanks Mike!

[SVO2.3]

are there any symptoms for cracked heads?

[MikeFleming]

are there any symptoms for cracked heads?

Varies. At the worst, when a crack goes all the way from the combustion chamber into coolant, you'd see lots of dirty coolant and foaming/blow-off at the radiator cap under load. Sometimes just exhaust seat/valve leakage for small cracks that aren't all the way through the metal yet.

In any case visual/mag inspection is usually the first way we know about cracks.

As a general rule, once cracks go through to coolant, the head is done. Some folks claim to have had success with welding but the cost is high while the success rate is low.

[svslow]

are there any symptoms for cracked heads?

With my experience with cracked heads on SVOs they never really cracked very far. My first Svo had cracks in every exhaust valve seat and it never effected drivability or anything.

[Raven855]

The factory set up was to induction harden the exhaust seat. This area is very thin and can wear away, leading to a recessed or sinking valve. If you simply do a valve job without installing a seat for a turbo application (like a stellite seat) you will find that cracks will appear in short order because the valve job takes off whatever hardening was present. The general consensus from the head porters I have talked with is that a head with small cracks, in the neighborhood of 1/8-3/16", can generally be used and will not be a problem. A seat insert will take care of the issue. Pressure testing and magnafluxing is still required though.

[Laredo]

Varies. At the worst, when a crack goes all the way from the combustion chamber into coolant, you'd see lots of dirty coolant and foaming/blow-off at the radiator cap under load....

Another symptom that often can occur before it gets to the foaming/blowoff stage is cold-start misfires for a few seconds at startup, until all the coolant is blown out of of the cylinder that seeps in after the previous engine shut-down.

[DaveS]

Resurrecting an old thread....I pulled the head off of my '86 mostly daily driver over the weekend due to a bad compression reading in #1 and #2. It is obviously a blown head gasket and I can see the root cause due to the torque of the head bolts (or lack of) that has developed over the last 35 years. Anyway, my question is if I'm pretty confident that a new head gasket and proper installation will solve the problem, should I have any head work done? Yes, I plan to check the block and head surface for warpage but for the sake of argument, assume they are OK. Remember, daily driver and ~90,000 miles on the engine...and yes, I can drive my truck while work is being done on the '86.
Your thoughts?

[Under Pressure]

I've changed too many blown head gaskets. This last time I went with a very expensive copper head gasket. You can take a Dremel and clean up the cast flashing on the intake ports, clean it leave a little texture on the intake ports, polish the exports. Should run strong.

[DaveS]

Thanks, that is what I am inclined to do. There was so much crap after 35 years that just cleaning it should make a huge difference!
Thanks for your input.

[DaveS]

Thought I'd give an update....I opted not to do any head work, cleaned things up and installed a new head gasket (among other things). There are now about 1500 daily driver miles on the car and it is doing fine.