Very good question, and one I hadn't thought of.

But, one I did think of is valve train geometry. Does a .025" cut require a shorter push rod?

On top of that, I just cc'd one combustion chamber. Yes, it was a quick go but the head was laying there as was the burette, piece of plexiglas, 2 valves, and a spark plug. I know I was supposed to be packing for the trip tomorrow, but..... Anyway, I digress. The one and only chamber I've cc'd measured 72.4 and not the 69 I was expecting. Bummer! That gives a CR of 8.88.

So, in for a penny in for a pound, how much has to be taken off the head to take off about 4 cc's? And, if that's added to taking .025" off the block, what does that do to valve train geometry? And, how much has to be taken off the intake, which btw I can probably do on my mill.

What was Stang's quote: "Power(hp/tq) is a mind altering dilema. How much is enough? Dwell on it too much and you loose sight of the original objective." What was the original objective?

 

If you deck the block and or cut the cylinder heads you will almost definiately have to
have the intake cut to make it fit properly. A good automotive machine shop will have
the specs as to how much to cut from both the bottom and side sealing surfaces or the
intake, depending upon how much the block and heads were cut.

 

Thanks. That's what I was hoping for. Woke up in the night thinking about it. Ugh!

But, I did have a thought that turned out to be a good one - ATF takes a long time to flow and I read the burette quickly after cc'ing the head. Read it again this morning and there was a 1.6 cc difference. So, the combustion chamber I checked was really 70.8 cc's. That's still too much as it gives a 9.02:1 CR if zero-decked and all else, but that means less to cut from the head.

And, with that having been said I'm ready to head out to see the grandkids. Will monitor FTE and would appreciate any and all comments about the forming plan re heads, block, manifold, etc.

 

I didn't need anything special to be done wrt my intake manifold when my block & heads were machined, the gaskets allow a certain amount of leeway.

But it is something that needs to be paid attention to.

 

Still planning on smoothing the combustion chambers (making them bigger)?

I do believe one of those books mentioned earlier(cough)(How to build High Performance Ford engines)(cough) has the formula for how much to cut from the intake.

 

Thanks, but I might rely on the guy doing the cutting for that info.

Boy, is it hard to drain a swamp!

 

Well, I'm back from the travels of last week and have been measuring deck height on these pistons and need your input. I didn't want to put the rings on the pistons as these aren't the pistons I'm going to use so used the following process:

1. Measured the piston diameter vs the bore and found ~.020" difference.
2. Cut .010" brass shim stock into strips and used a strip on the front of the piston and one on the back to keep it from rocking
3. With the piston truly at TDC (determined w/a dial indicator) I measured the depth the piston was down in the bore (using a depth mike) at the front, at the rear, at the inside, and at the outside
4. Found the average of the readings

The results are below, with the #'s showing how far each piston is down in the block, in thousandths of an inch. But, the question becomes how much to take off? If I'm shooting for .039" quench, but do I deck to get an average of that? Or, do I shoot for no more than .039"? Or no less than .039?

And, here's another approach/thought. First, factory spec's call for a rod length range of .003", which probably accounts for some of the variances I'm seeing. But, there are probably variances in crank throw. Obviously I can pull and measure the rods & pistons. But, they are what they are. So, can I move the piston/rod pairs around to even out the block-height variances? IOW, can I put the #2 piston/rod combo in the #5 hole if doing so would minimize the variances?

And, I need to keep reminding myself, this isn't a race engine. It is going to cost $350 to deck the block ($150), mill the heads ($100), and mill the intake manifold ($100) if needed. So, I don't really want to go back and have more work done on the rods or crank.

THOUGHTS???????

 

It looks like one bank of your block is taller than the other. You could have that bank milled some to bring it closer to the height of the other bank. A cheaper way to get
it more balanced would be to cc the heads combustion chamber volume. You would
probably find that one head holds more volume than the other. If so you could put
the larger volume head on the short side of the block and the less volume head on
the taller side which would have the effect of getting both sides more equal. The
correct way to do it on a more expensive engine is to index the crankshaft and have
the stroke equalized. The rods would also have to be bushed in the small end to
correct the center to center distance. This would get many of the variables under
control so the block could then be machined for deck height that is equal.

 

Yes, I'm sure the block is higher on one side than the other by ~.012". So, I'll have that side milled more than the other, and it doesn't cost any more to mill more than less. So, the question is how much to mill so I get the quench right. If every piston were the same distance in the hole, at least on the same bank, then it would be easy - mill that much less .020" for the taller pistons I'll use. But, with variances of .0039" and .0050" per bank, they aren't the same.

As for the heads, I'm cc'ing between typing. So far the one head I've gotten done is 71.0; 70.8; 70.8; and 71.6 cc's. And, the last one is the only one I've done any polishing in, so maybe that's the main difference.

 

My opinions so don't get offended:

1. I would not use those numbers. I would get the block line honed and then decked the minimum amount necessary to get them flat and even side to side, front to back and bank to bank.

2. Measure with the parts you plan on using.

3. Swapping pistons/rods/piston pins around is common. NOT for height, but for weight and balancing the rotating mass.

4. Did you measure the pistons at multiple places around the circumference? They are machined oval to account for thermal expansion....

There should not be more than a couple thousandths difference in all the piston/rod heights. With factory parts, you should have those measurements within a couple thousandths across the board(block). Something is worn/bent/crooked/wrong in your sets. Did you use worn bearings in the rods? I bet those old pistons have differences in height due to age and thermal shifting.

The depths to which you are delving is way beyond normal rebuild. The steps you are taking is stuff I was doing for engines turning 9k rpm all day long.

One more thing... I would find a new machine shop. Way too expensive.

 

Old Hickory saw it too about the height difference in the block.

I would rather have all the parts equal in size and weight than compensate.

 

Gary pointed out the deck height difference in post 145.
Whichever pistons you go with I think you ought to just zero deck and use a .040" head gasket.
There will be no mistakes as to quench and static CR.

Gary,
2/10 of a CC is very close.
If I were you I would ease all the sharp edges in all the combustion chambers, then check.
And remove needed material from the smaller ones to equalize.
Then you would know where your static #'s are and will help you decide which pistons to go with to arrive at 9.5:1

 

Guys - Thanks for the responses. But, I'm kinda running out of steam on this quest. Things are piling up around me and the realization has set in that I'm selling the pickup soon anyway. Here's what's happening:

• I took on a powder-coating job for a guy of bumpers and window trim for a '71 Javelin.
• Drove the wife's Subie over to get the Javelin parts and a head gasket let go. Gasket set and head bolts on order.
• Fired up my 136K ML320 to put it back in service and realized the alternator was grumbling. Replaced it for $250, but while on the lift realized that the tires aren't just flat-spotted due to bad shocks, but are bald on the inside edges. Shocks/struts ordered for $500 and tires will be another 500. Drove it to see Dad and the check engine light came on - fuel trim problems.
• Dad is going down hill fast. There has been noticeable change due to dementia in the last 2 weeks. That means lots of things, including that I may have his pickup much sooner than expected, and it is a 351M so no engine swap.

The plan has been all along to sell this truck and restore Dad's when I get it, but had no idea it'd be soon. And, today I found a guy w/an '81 F150 4x4 w/a built 351M but a blown clutch. He wants $600 for it and I can see swapping engines and beds w/Dad's and having two trucks that run, but Dad's keeper would have a strong engine and a good bed.

So, long story to say I'm not sure I'm willing to put another $250 or more in an engine for a truck I'm going to sell soon. Won't it run well set up the way it is? I know I won't have quench, but I won't have 9.5:1 either so don't really need it - right?

I hope I haven't "led you on", but things are changing and/or realization is setting in. Maybe I'll feel differently tomorrow, but ........

 

Really sorry to hear about your father Gary.


This truck was running when you started, there's no reason it shouldn't run now.

I'd be tempted to put a clutch into the $600 truck and shelve your engine efficiency project until time and motivation come back around.

You'd have the parts you need for your dad's truck and could flip it after swapping them.

 

Jim - Thanks. We've know about the dementia for a couple of years, and even have a fair understanding of what transpires since his mother appears to have had it and at least one brother did as well. But, things really seem to be progressing.

I'm thinking the efficiency effort should now move to Dad's truck, when I get it. As you say, put a clutch in the one I'm gonna look at today, when I get the time, and then swap parts between it and Dad's when the time comes. Then sell that one, but maybe not until I've "restified" Dad's since it badly needs cab corners and other work, followed by a paint job.

Anyway, thanks again. I didn't see this coming this quickly, but should have. And, with the other vehicle problems I'm now swamped with work.

I'll let y'all know where things go.