Two engine questions: pistons and dowels

1. When I removed the head, I only saw one dowel. I'm fairly certain the POs did some head work, and from the work I've seen on this truck they were more like Dr. Frankenstein than ASE certified. Is this a problem only having one dowel? It's the left rear dowel.

2. I know that on an 87 B2000 the head should be the 8-valve, but I noticed that the top of the piston have gouges cut out like a 12-valve look. Is that normal? Or are these gouges for something else entirely? (For clarification, my head is an 8-valve.)

Thanks in advance!

I cant say about the dowel pins, but the pistons valve reliefs are correct. Looks like a 3 valve piston.

I just did my '88 B2200 engine in October, can't remember if there were two alignment dowels or just one. I used wooden dowels to align without scratching the head gasket. Pistons were dished, see photo.


Here's a photo of the underside of the cylinder head after getting back from the rebuilder.

the valve reliefs are cut into the pistons like that because of the position of the valves in the head. 2 are on the front and 2 are on the rear of the piston. Just look at the head and you'll see what I mean

Thanks for the pics and the info. I guess considering it ran okay (well, until it overheated, but I believe it was a thermostat issue). I can try it with only one dowel unless someone says otherwise before I start back into it.

Thanks!

should be two for the alignment of the head gasket.

If the head or block was "decked" they may have milled them off or removed them and only replaced one. Check for a remnant of the dowel in the head or the block. Dan

mine only has one just make sure you get the head on straight and you should be ok. as for the pistons you do have the right ones like others have said I know they use the pistons in the 12 valve heads as well.

There should be 2 hollow dowels in the head. The holes in the head for the dowels are drilled deeper that the length of the dowel, so unfortunately, some machine shops will tap the dowel all the way into the head and they're a bitch to get out then.....I've seen this way too many times.

If I were you, I'd check with your local Mazda dealer and see if they have them....they probably do. I would definitely have both of them in there also......the aluminum head expands faster than the iron block when heating up, or cooling down, so I'd say you need them both if you want to get the longest life out of your new head gasket.

Here you can see the one in the rear of the block.......the front hole on the same side should have one also....mine was in the head when I took this pic.



Same motor as I am building it, and as you can see here, they are both in place before I set the head on it.

+1 to Earl. One had fallen back into the head.