'70 CDV Cylinderhead / Valve Cleaning

[HouseOfCadillacs]

Now that I have finished the front suspension rebuilt I’m continuing with the engine work. I took off the intake manifold and both heads to check on the piston and valves. While taking the heads off I noticed that all four RH rocker arm support bolts were only hand tight, maybe that was the reason for some of the valvetrain noise? I also noticed some carbon built-up around the exhaust crossover ports, seems like some of the exhaust gases leaked by the intake gasket.

There is some carbon built up on the top of the pistons and the valves but it doesn’t seem too bad. The cylinder walls are very smooth and there is no ridge on the top. On the photos it seems like the flash brings out what I assume is the factory honing pattern?! Here’s the link to the photos:

www.houseofcadillacs.com/cars/darkshadows/technical/enginework

The engine has about 82k miles on it. My plan is to remove the valves from the heads to clean them up, inspect the valve seats and then install them with new valve stem seals. I also need to clean the carbon built-up on the piston and the heads. Can anybody recommend what to use for that? I’m thinking brake cleaner and wire brush. I also heard that it would be good to use some lapping compound on the valves and valve seals?!

After that I need to clean the intake manifold but don’t have a plan for that yet. Should I take it to a machine shop to get it soda-blasted or is there another way of doing this?

Btw, I’d love to hear any other ideas for what to check on the heads/intake, block while I have the engine apart.

Thanks,
Stephan

[Dave Shepherd]

Did you have good even compression in all cylinders before taking it apart, this would tell what would be done to the heads, you could lap the valves in lightly and check seat to valve face contact, also check the guides for wear. Don't too aggresive with the wire brush on the pistons, don't really want to scratch them or get wire brush particles in the engine. Do you mean cleaning in the manifold ports?

[HouseOfCadillacs]

Compression test and cylinder leak-down test was done earlier this year. Pressures were relatively even and all at least 162.5 psi.
Cyl.  Dry        Wet      MMO
#1   171.0     193.0     169.0
#2   186.0     185.5     174.5
#3   164.0     173.5     155.5
#4   170.0     176.0     181.0
#5   166.0     177.0     161.0
#6   162.5     173.0     164.5
#7   164.5     173.5     157.0
#8   162.5     177.5     170.0

Yeah, I meant to the intake manifold ports. Can't really get a wire brush in there.

Thanks,
Stephan

[Dave Shepherd]

Stephen if no pitting on the seats or valve faces and the guide clearance is good, done carefully a lapping job should do it.  I don't know if you have the experience to inspect the valves, margins and faces but that is what I would do. As for the manifold, I would not get " crazy" try to clean that down to metal, do the best you can with solvents.

[HouseOfCadillacs]

I plan on removing the valves this week and if something looks obviously wrong I'll consult with some of the seasoned mechanics at work. For the intake & crossover ports I'll just put it in a parts washer and run the cleaning solution through it until it is somewhat clean. I understand that it doesn't have to be perfect but at least I'll give it a shot.

Thanks,
Stephan