What's wrong with this picture?

[Derrick]

The car was running bad the other day so I did a compression test and found that the #8 cylinder had a compression reading of only 30. Every other cylinder was 150-155. So I decided to pull the head to see if I had a burnt valve and after pulling the intake I found this.

View attachment 18793

View attachment 18794

What's causing this?

 

[Dads C5]

What is that in there? I passed the photos on to a friend of mind in S.C. that has been racing corvettes for 10 years now. Maybe he will know.

 

[Derrick]

If it helps at all, it has a "crusty" or gritty feel to it. I'm interested to see what the head gaskets look like. I poked a screwdriver through it and it's only about 1/4" thick of buildup.

 

[Derrick]

What is the purpose of the 2 smaller square holes in the heads (one of which is plugged on both heads)? The 4 larger rectangular holes allow air and gas to enter from the intake manifold correct?

 

[yellow77]

The holes at either end of the cylinder heads are for water circulation. On nearly all small blocks, the holes at the front are tied in the intake manifold thermostat passage, but the rear holes are blocked. It was considered that there was no requirement for coolant flow from the rear of the cylinder heads, and passage would interfere with the distributor mounting. The heads are also identical, so having the port at the front and rear allows the head to mounted on either bank of cylinders.
The square port in the middle serves two purposes. When the engine is cold, a valve (not applicable to all engines) in the exhaust downpipe on one side would partially close forcing exhaust to pass from one manifold across under the carburator to the other manifold thus improving cold start atomization of fuel by warming the intake manifold. This was to improve cold driveability. In smog equipped cars, it would also serve as a passage to the EGR valve. Most performance engines block off these crossovers, and a lot of manifolds do not even have this crossover passage.
The buildup looks like the heads have never been off the engine, and it may at some time have had a heating issue. I have seen this before, and all engines have some build up, but not as bad as that. It is possible that you may have leaky head gaskets on number 8 cylinder, the back two cylinders are usually the first two cylinders in a small block to experience problems.

Hope some of this helps

Cheers

Richard

 

[TimAT]

The back 2 ports that are plugged- that's a result of dis-similar metals corrosion- the difference between the radiator, block and heads, and the action of the coolant caused that crusty goo to build up in a place with very little circulation. A combination of that, and the cooling system not getting flushed very often and that's what you get. Not a big deal. Looks ugly, but really won't cause any problems until it breaks loose and plugs something else up. In the top picture, going from right to left, that last port is the water jacket, the next two holes are the intake ports for cylinders 8 and 6, and then there is a little "double" looking port in the gasket- that is the EGR ports on some applications. THe next one is the heat crossover, then the intake ports for 4 and 2, then the water jacket.

 

[Derrick]

Thanks for the replies! You guys are correct that the car did have over heating issues at one point. When I first bought the car the temp would climb on road trips. I finally determined that I had a faulty fan clutch that wasn't disengaging. You guys are also correct that the heads haven't been off the car. I plan to swap them out with Edelbrock Performer RPMs in the next couple weeks. I'm hoping the low compression is resulting from a burnt valve or leaky head gasket or both.

 

[gmjunkie]

Looks like to me that somebody Blue Deviled it!!

Blue Devil is a Sodium Silicate Substance that will plug leaking head gaskets!!

Also will Plug and Ruin,Radiator,Heater Cores,Thermostats and Water pumps over time!!

Usually just a Cheap Quick fix prior to sale!!hnoeshnoeshnoes

 

[Adams' Apple]

Yeah...that looks like some kind of head gasket/block sealant in the rear water crossover holes. Since they are blocked off by the intake manifold, the junk can't really go anywhere, so it just piles up in that area, as there is no circulation to keep it in motion. I'd say a full flush of the cooling system would be a good idea after you get it all back together...

 

[Derrick]

The heater core leaked pretty bad after I first bought the car. Maybe the guy was trying to plug that. The water pump and thermostat also went out shortly after.

I had a chance to pull the head this afternoon. The head gasket seemed to be in really good shape but tell me if anything looks abnormal in the pics below. Keep in mind a had a compression reading of only 30 on one of these cylinders and a slight tapping could be heard in the engine.

 

[TimAT]

I'd say the cylinder on the left has a leaking intake. Set the head on your bench with the valves down- just like it's setting on the block. Take a big deep socket- 7/8 or so put it on the valve retainer and smack it with a hammer a couple of times. That will pop the keepers off and you can remove the valve and see what the seat looks like, and also you can pull the valve up 1/4" off the seat and see how loose the guide is.

While you have the head off, how much of a ridge is at the top of the cylinder?

 

[gmjunkie]

The heater core leaked pretty bad after I first bought the car. Maybe the guy was trying to plug that. The water pump and thermostat also went out shortly after.

I had a chance to pull the head this afternoon. The head gasket seemed to be in really good shape but tell me if anything looks abnormal in the pics below. Keep in mind a had a compression reading of only 30 on one of these cylinders and a slight tapping could be heard in the engine.

Well,I can see where 3 out of 4 cylinders where the head gasket has been leaking!!That cruddy crap at the water jackets at the bottom!:eyerole

 

[Derrick]

I'd say the cylinder on the left has a leaking intake. Set the head on your bench with the valves down- just like it's setting on the block. Take a big deep socket- 7/8 or so put it on the valve retainer and smack it with a hammer a couple of times. That will pop the keepers off and you can remove the valve and see what the seat looks like, and also you can pull the valve up 1/4" off the seat and see how loose the guide is.

While you have the head off, how much of a ridge is at the top of the cylinder?

Had a chance to pull the valves this afternoon. The valves are from left to right from cylinders 8 6 4 2: Again 8 is the cylinder I had the low compression reading on. I had oil on my hands that I got on the edges of the valve that looks burnt.

View attachment 18814

View attachment 18817

Valves on 8 were pretty loose about 2 or 3mm wobble back and forth. All the others were pretty tight, some I had to tap with a hammer to get out. What do you fellas think? Is this causing my low compression?

Also I pulled all the lifters just for grins and none seem to show excessive wear.

 

[TimAT]

Looks like #8 exhaust was not seating. You can try and "paint" the seat with some machinist's blue or a black magic marker, put it back in and snap it up and down on the seat a few times. See if it wipes the color off all the way around evenly.

You've got the head(s) off, it'd be a good time to get a valve job done. A good shop will fix any and all problems with the heads. Guides, valves, seats, whatever.

 

[Derrick]

...You've got the head(s) off, it'd be a good time to get a valve job done. A good shop will fix any and all problems with the heads. Guides, valves, seats, whatever.

I've been wanting aluminum heads for a long time so this was the perfect excuse. I just ordered a set of Edelbrock Performer RPM aluminum heads (64cc chambers) and a new set of crane cams 1.6 full roller rockers Hopefully this will give me enough extra power to burn out the tires. Currently I can barely get the wheels to chirp on take off.

While I have the heads off would it be a good idea to clean off the pistons. There's a bit of build up. Would a wire wheel work? I've heard varying opinions.

 

[Crimson Thunder]

Now would be a good time to change the camshaft to complement those new heads.

 

[Derrick]

Now would be a good time to change the camshaft to complement those new heads.

I'd love to, but I want to save some fun for later. I'd like to run a really aggressive cam with the new heads which will require a new intake and higher stall torque converter.

 

[raybies]

that my friend is a blocked cooling port and all you probably need to do is flush the block with some anti corrosion flush