Engine decking

[Flyingpiper59]

Yo Forum Chums,

The engine is out of the 27 and the crankshaft has been removed….. it’s ready to be taken over to the machine shop to have the Babbitt removed and the engine block hot dipped…. Does anyone have a rough idea of how many thousands can safely be removed from the top of the block before you run into the danger of pistons slapping the head….. ditto for the intake, exhaust port area….. I’ve got a little bit of pitting by the number four exhaust port on the side of the block.

As always many thanks….Cheers!

Ed

[TRDxB2]

Why bother with the exhaust/intake port issues if you use glands and rings, as long has its flat. (JB it)
Do you know if the top of the block was ever machined before?

Decking discussions
https://www.mtfca.com/discus/messages/8 ... 1543422653
https://www.mtfca.com/discus/messages/1 ... 1304083291

[Flyingpiper59]

A great question Frank….who knows if it’s been decked!

[TRDxB2]

A great question Frank….who knows if it’s been decked!

This discussion mentions a measurement from the pan up https://www.mtfca.com/discus/messages/8 ... 1543422653

[Scott_Conger]

you had original "x" rods and tin can pistons as I recall, so your engine has a 99%+ chance of not having been refreshed much less rebuilt and decked.

I'd be surprised if it didn't clean up with .005" or so

be very picky about your rebuilder; I imagine even with the best rebuilder, you'll end up with an engine that is only marginilly better than what you're turning over to him except that it will be new.

I'd wager that at least 25% of engines sent out for rebuilding would have run for another 50 years by doing a valve job and taking up the rods.

[Flyingpiper59]

To Scott’s point….stamping clearly visible…. it doesn’t look as though it’s
Been decked

[John kuehn]

Is there really a need to have the block decked? Yes others will have different opinions but sometimes people do it because they have an idea it needs to be and because they were told it needs to be right.
And yes I know you want everything flat and if you think the head needs to be that will all you need to have cleaned up. If it’s a stock head and the block hasn’t been machined .060 would be OK to have the head milled.
MHO
Lots of Model T engines have had the rods taken up, new rings , a valve job and have had the block honed and that was it and run fine. But of course it depends how much wear is in the engine.
Good luck.

[ModelTWoods]

Decking the block (cylinder head surface) is one thing. Milling and truing the manifold surface side of the block is another. I don't see a picture of your block deck surface with a straight edge on it, so I can't say that the block even needs to be decked. Maybe it does, but from the looks of the block from a side view, I looks like it might have been decked, previously; there just doesn't seem to be a lot of heigth between the top of the ports (particularly the first one from the front of the block) and the deck surface. I wouldn't take anything off if it wasn't needed. As far as the manifold surface goes; you do have a lot of pitting around the rearmost port. If the surface is true from front to back, and you have a nice, straight exhaust manifold with the gland rings, you might get by without resurfacing the manifold surface. However, only a straight edge on the manifold surface will tell you if it is true and straight. if your reason for wanting to deck the block is to increase compression, I'd recommend taking it off the head surface, if the head hasn't been previously milled excessively. Almost any stock unmilled head can have as much as .125 removed and I know of one owner who runs a head shaved .150, but even at these extremes, you're not going to see a noticable compression increase unless the milling is accompanied with high compression, domed pistons. Otherwise, you're wasting time, money, and metal.