What would cause 'dimpling' on the engine block face?

[Launchpad McQ]

I'm attempting to bring the 'seized' A4 back to life in my recently purchased Catalina 30. I considered starting a 'build thread' but I hate to add duplicate info and there seems to be some superb ones already out there. To the issue at hand: After pulling the head, scraping the block (carefully) to remove the old head gasket material, I noticed that the surface of the block is 'dimpled' between the cylinder and the valves on #4, #3, and #2 getting progressively smoother toward the front of the block. #1 has almost no 'dimpling.'

My three-part question:
1. Why?
2. Is this condition acceptable?
3. I realize the port-side, rear stud at some point was broken and re-threaded. Could this be a contributing factor? i.e. Water seepage.

If this has been addressed before I apologize but I couldn't find anything relevant and as always thanks for any responses gents!

[lat 64]

I was unclear what you meant by dimples. This is what I see:
you have some rust pitting between valves and cylinders—not life threatening.

The head seems to have been surfaced by a broach-cutter style milling machine. That's the tiny wavy lines I see in the surface at the lower left. IMHO this is the best way to cut a head gasket surface.

I think it's savable, but it should be dismantled carefully. Go slow and let us see it along the way. The valve seats should be examined for rust pitting. If they are, then a bit of attention there and dress them as per you favorite machinist's recommendation.


Cheers'

Russ

[Administrator]

Cat 30.

We have a bunch of those guys here. They'll brief you regarding the exhaust system and the potential for water intrusion which might explain those dimples towards the lower end.

Bill

[hanleyclifford]

I agree that there appears to be some water seepage between head and block but I don't regard that as serious unless the head or block is warped at the surface. Of far greater importance is the condition of the cylinders standing in the cooling jacket. Since you did not pressure test the block and manifold before disassembly you will have to rely on your machine shop for that information. Like Russ said, proceed carefully with disassembly labelling valves and lifters to make sure they eventually get back to their original holes if OK.

[ndutton]

It's starting to add up

I'm certain the surface condition is due to water incursion through the exhaust. Here are the reasons why:

• The block surface damage is limited to the area of the combustion chamber. Tells me the head gasket was intact and doing its job.
• The damage worsens toward the rear of the engine. That's the low end and naturally where the water would enter first.
• You have a Catalina 30. The Catalina 30 has one of the most challenging and marginal exhaust systems known to man.

Here are some suggestions to minimize the risk of future incursion:

1. Redesign the exhaust hot section so immediately after the manifold outlet it rises vertically as high as the galley cabinetry will allow. Pay special attention to heat shielding in the area.
2. Locate the water injection fitting as close as possible to the waterlift muffler on the downhill leg of the hot section.
3. Use a vented loop at the top of the raw water injection hose rather than an anti-siphon valve. The vent never needs maintenance, service or inspection. It always works.
4. Adjust your carburetor a little rich so the engine starts instantly, even cold with the application of full choke. Hard starting with the sea intake valve open is virtually a guaranty of water incursion in the C-30. Having a second start button in the engine compartment (IMPORTANT - must be ignition protected) allows you to start the engine with the valve closed, then open it as soon as she fires. It's a little hard on the impeller but the alternative (risk of water incursion) is far worse.

[thatch]

You would be wise to pay particular attention to that rear stud hole, which appears to have been Helicoiled in the past. It is also possible that the pits in the deck surface are left over from the previous repair.
Tom

[lat 64]

You would be wise to pay particular attention to that rear stud hole, which appears to have been Helicoiled in the past. It is also possible that the pits in the deck surface are left over from the previous repair.
Tom

Agreed. The rust looks polished from the last cleaning.

[Launchpad McQ]

Thanks guys for the responses! I started the thread while drinking beers at 10pm and had a response by the time I finished my morning coffee. This has to be one of the best forums I've been on. Anyway..

This is what I see:
you have some rust pitting between valves and cylinders—not life threatening.

Thanks Lat. You nailed it. The rust pitting is definitely what I was concerned about.

I'm certain the surface condition is due to water incursion through the exhaust. Here are the reasons why:

• The block surface damage is limited to the area of the combustion chamber. Tells me the head gasket was intact and doing its job.
• The damage worsens toward the rear of the engine. That's the low end and naturally where the water would enter first.
• You have a Catalina 30. The Catalina 30 has one of the most challenging and marginal exhaust systems known to man.

Here are some suggestions to minimize the risk of future incursion:

1. Redesign the exhaust hot section so immediately after the manifold outlet it rises vertically as high as the galley cabinetry will allow. Pay special attention to heat shielding in the area.
2. Locate the water injection fitting as close as possible to the waterlift muffler on the downhill leg of the hot section.
3. Use a vented loop at the top of the raw water injection hose rather than an anti-siphon valve. The vent never needs maintenance, service or inspection. It always works.
4. Adjust your carburetor a little rich so the engine starts instantly, even cold with the application of full choke. Hard starting with the sea intake valve open is virtually a guaranty of water incursion in the C-30. Having a second start button in the engine compartment (IMPORTANT - must be ignition protected) allows you to start the engine with the valve closed, then open it as soon as she fires. It's a little hard on the impeller but the alternative (risk of water incursion) is far worse.

ndutton I'm inclined to agree with your diagnosis. I took a few more pics to try and fill in the gaps on this puzzle. I think the pitting shows better in this pic:


Here's a shot of the old exhaust hot section setup from the previous owner. I just set it back in place for illustrative purposes (ignore the vice grips on the reversing gear lever, hopefully that won't become another thread). Instead of running the exhaust up and back down he just had a "90" and to compensate for the misalignment with the muffler he used a flexible piece. I don't know jack about squat of the A4 yet but even I know better. I'll be fabricating a new hot section.

and another angle with the water injection fitting


Last but not least I'm almost embarrassed to pose this question with all of the "blocked cooling passage" threads here but after scraping the gasket material off of the head it seems that a couple of the cooling passages are so clogged they've become petrified. I tried breaking through with a pick but I'm afraid to go further until I'm 100% sure those "phantom" holes are in fact cooling passages and I'm not damaging a perfectly good head. They line up with the holes on the block but I'm just a dumb Polack and I need some verification.

[sastanley]

Launchpad, that hot section looks eerily familiar to the one I found in my C-30.

I have some before and after pics which illustrate Neil's suggestions. We'll help you get it situated. I bought some of that self-adhesive aluminum faced firewall stuff ($25) and put it under the galley countertop to disperse heat.

before



rough mockup #1



mockup in the boat #2



#3 - same exhaust wrapped -no galley installed on my C-30 in this pic. Once the clearance is identified, it is much easier to do the work with the galley removed. You can always lay a simple piece of plywood down to simulate the galley clearance during this project.

[hanleyclifford]

Leave those "phantom holes" alone; they are from an earlier design but the holes are still in the block. You're good on that. Actually your hot section while minimal IMO is not in and of itself responsible for the water intrusion. The water intrusion was more likely caused by bad starting protocol re the raw water intake valve. Still, I would do a new hot section (no galvanized, please). With risers higher is better and inject lower than what I see in the pic. Neil and Shawn have both been thru this with Cat 30s. Thanks for those excellent pictures.

[ndutton]

We've mentioned the C-30 exhaust limitations on the forum many times before but haven't really delved into doomsday stories.

So how marginal is it? Consider this: Unless the hot section is fabricated as good as can be, it's possible to have residual water from the muffler find its way into the engine simply by going on port tack and that's not an exaggeration.

[jbsoukup]

I've heard before not to use galvanized for the hot section. but I don't know why.

[hanleyclifford]

A Design Flaw?

I acquired an engine from a Catalina 30 that seized up from this very issue. Seems to be more common than I thought. It is a shame that a (flawed?) design configuration would impose this additonal burden on one specific production boat which I regard as an otherwise outstanding production vessel. A check valve or rigid starting and shut down protocols seem to be mandatory for the Catalina 30. As Neil suggested, the hot section should be redesigned for maximum possible protection.

[Dave Neptune]

The PO

McQ, not all is lost!!! I'm late chiming in so here goes. It looks to me like the PO did a quickie fix of a blown headgasket and did not do any good prep! The rust pits under the gasket are a dead giveaway. If the head was not torqued properly and not retorqued with one or two gaskets there could be some seepage, but it does not look fresh enough.
Now look at the pattern of the combustion chambers, you can see the pits are fresher and emanating from the exhaust valve and into the rest of the chamber. This can be two things and they are related! Either the exhaust was plugging up and creating a raised back pressure condition which can produces droplets of water that can condense and or bounce back into the manifold or the manifold itself may have a pinhole in it, this can be pressure tested easily. When shut down the droplets will settle and evaporate and re-condense many times working through an open exhaust valve(S) while the engine sits and leaving the pattern seen. Don't worry about the chamber area.
If the block stays in the boat remove the valves and studs and you can "HONE" with a big flat hone (did mine with a good big flat file) to see the hi & low spots. Only look to the area covered by the gasket and don't worry about the combustion area at all. The surface doses not need to be perfect but clean and free of "High spots". In fact some imperfections will actually help hold the gasket. In your case definitely use Aviation grade Permatex on the gasket surface. If you get even close all should be OK.
You can get the head surfaced in a shop, but unless it is really out I would not do so.

Dave Neptune

[thatch]

Catalina info

Along with the Catalina 30's center mounted engine configuration comes the challenge of getting the exhaust back to the transom. The factory chose to route the soft section (hose) up from the waterlift, behind the cabinetry on the port side as high as possible to a check valve and then down and out the back, a hose distance of 22 feet. Although I have never had to replace mine, I hear that that job is a bear.
Note to John: Galvanized pipe is not recommended for the hot section because of it's tendancy to "off-gas" when heated. I have found however that the galvanizing can be removed by using a blow torch and a wire brush. Of course this should only be done in a well ventilated area and only if black pipe is not available.
Tom