How exactly is this done?

I've got a 351W from the early 70's (cougar or stang), so it should be a "9.480 deck height, but I want to be sure of the ACTUAL deck height before I try to build a stroker engine.

Wasting money and time isn't exactly something I like doing...

What would I have to do to measure up the deck height?

 

By definition, the deck height is measured from the centerline of the crankshaft to the deck. So you need to rig up something that marks the crank centerline that you can measure against. The makers of your stroker kit should know about your specified deck height, and use the correct height piston.

 

Yeah, I need to make sure of the deck height, otherwise I'll have my pistons 0.023" out the top of my deck haha.

 

Since the main journals are 3.000" one could get hold of a chunk of 3 inch cold rolled steel, just long enough to straddle two main journals, with the bearings and caps installed. Then using a depth micrometer the distance from this to the block deck is measured. Add an inch and a half and that is the deck height.

Using a smaller diameter piece of steel would also work but it will be difficult to hold in place and measure to.

 

You could also just reference the block casting number...

Kelly hotrod - Ford Engines Page 2

 

Thanks man! This will definitely be the easiest way to go!

The casting number on 351's is behind the starter on the lower passenger side of the vehicle, isn't it?

 

Of course if you use the casting number you have to assume no one machined the deck surface.

Also if you have a casting date around the change over period there might be uncertainty.

 

What's a change over date?

I'm not fully certain what you mean by this.

 

The change over date is the date at which Ford switched from producing 351W blocks with 9.480" deck height, to 9.503" deck height.

Ford publications say that 1969-70 engines were machined to the shorter deck height, while 1971-on blocks had the taller height. Both received the same length rods and same (compression) height pistons.

What is the casting number of your cylinder block?

 

I'll have to get that within the next few days. As of right now, I'm SUPER busy after work and don't have a chance to take a look. I'll definitely get back to you though.

 

To add to my previous post, the confusion can arise if one has a D0OE cylinder block, for instance. If made early in the year (for a 1970 model vehicle), it should be lower deck height, but if made late in the year for a 1971 model vehicle, then it should have the higher deck height.

It is imagineable that one could even get a high deck C9OE block if some of the castings were still in inventory late in 1970 and then finish machined. It all depends how things were done at the foundry and machining centers.

So the date code on your engine's cylinder block is also very important.

 

Thanks for the info, will check it out, and figure out what year 351 the previous owner used.

 

This is why there are automotive machinists. You can mill that amount if necessary from either the block or pistons to tailor the fit. Or use thinner/thicker head gaskets.

 

Another complication is the (in my opinion) terrible practice of "destroking" oversize replacement pistons which seems to have been the norm in the past, and may still be practiced.


A piston of 0.030" oversize would have a compression height reduced by 0.030" as well, to maintain the same compression ration, as described in the piston catalog that I read years ago.


Another method of measuring the deck height would be to measure the clearance from the piston top to the deck of the block before disassembly, then giving this dimension plus the removed piston and rod to a machine shop. This is of course less precise than direct measurement.

 

The way I read the referred chart is that the deck height was increased for the 74 model run.

Have you decided on a machine shop? It might be best to consult with them the possible need to square the block and determine present deck height/bore size(s) before ordering stroker kit.