Deck height

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LTOP said:
He either means 3.395 or his block is bored .050 over with .005 attributed to wear.
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Sorry for the confusion, reading these gauges is something I do not do often, yes 3.395. So why smaller? Than stock? Is that typical?
 
krazykuda said:
Ok, let me see if I can answer your questions.

2. Yes, to measure compressed thickness of your head gasket, the most accurate way is to get one like you plan to use and torque it down on the engine, then take it off and measure the thickness and diameter of the fire ring. (or save a used one if you have one just like that has already been compressed).

3. For volume above the piston at TDC; If you have flat tops, you can just measure how far down the piston is at TDC, and the diameter of the cylinder bore and calculate from there.

You can also use the water method with the cover plate as described in the compression check thread.

You could also try to do both to check for accuracy, but they should come out the same if done correctly.

4. I don't get how your bore is 3.95 when is should be 3.40, and you say that it's smaller. Isn't 3.95" bigger than 3.40"?

5. I usually just use the stock stroke numbers from the books to calculate swept volume, but if you don't think that your engine is "to the book" then find BDC and measure the depth of the piston in the bore at TDC & BDC, then take the difference.

6. I recommend the liquid method if you can't measure it easily. (It's much easier if it makes a perfect cylinder and no other "variations" to calculate with bore and depth). The liquid method accounts for everything in your engine, but is not practical to measure at BDC (the water tends to leak when you are trying to fill this much volume). You can just use the bore diameter that you measure at the top, I don't think a little wear will affect the results that much.
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2-I plan to use a cheap fel-pro head gasket on this engine, ( just to get it running ) Can I use Kids formula above and still be Ok?

Quote from Kid: Felpro is .037 thick for both 3.4 and 3.510 bore gaskets

Can you explain....why does he mention two different size bore gaskets?

Arent these steel gaskets no longer avail.....

Quote from kid: stock steel "shim" gasket is .021 thick for both 3.4 and 3.510 bore

I plan to ultimately use a Victor Reinz head gasket. This is what has been recommended to me, what is your opinion on this gasket, I have been told it will handle up to 12.1 static compression ratio.

Not sure why this is desirable for what I am doing but what do I know and my thinking is that it must just be a better head gasket. Maybe its overkill for my application.

3- I have measured ( see attached pictures )

Cylinder bore diam is 3.395 and a deck height of approx .155 thou.

I say approx cause measuring in this fashion is not the way to do it, clearly with even the slightest inclination of the tool the measurements can jump anywhere from .140-.170 thou.

I plan to get a proper depth gauge from e-bay and measure this correctly. At this point though I am certain that .155 thousands is pretty darn close.

Can you explain why the small cylinder bore, I have checked and double checked. I am certain that is where it is at. Is this common?

5- What are the stock stroke numbers, where would I find this info. Id like to see a listing, was this number changed at all for 225s or did it remain the same even through the hydraulics?

Isnt it true that I will need to decide what to do with my cylinder head before proceeding any further. Isnt it true that oversize valves will affect the final outcome of the measured CCs ? What is the usual volume of these heads. Can we use this just so that you and I can continue moving forward on this whilst I decide what I am going to do?

I would like to know how much slight variances within these numbers will change things. For instance lets say engine started out with a 3.40 slug and was overbored 60 thousands. I am assuming that means we now have a 3.46 bore diam. ( or is that 3.460) Please tell me how to display the correct figure.

So lets say we have that 3.46 ( or 3.460 ) bore diam but have the same deck clearance of .155 thous. Combine that with a standard slant combustion chamber volume of _____

Sorry I do not know what this is but it seems to me I remember reading 55 or 65 CCs ?

How much will that overbore mean to the compression ratio. Overbore would decrease the compression ratio from what I have read and that does make perfect sense to me but Id like to know how much of a difference that will make.

Same scenario with maybe a taller deck height, lets say we have a standard 3.4 bore diam, but instead of .155 deck height we are at the extreme of .210 below deck. How much will that effect compression ratio assuming we are safe to use Kids compressed Fel-Pro head gasket thickness of .37 thous. thick.

Hope you get where I am coming from and the reason for all the questions is because the engine that I care about at this point is in my truck in the garage, freshly re-built but internal statistics un-known. I plan to be an expert on all of this after completing this engine and will use what I have learned here to optimize the engine I care about.

One last thing: Would it be possible to do all of this sort of work with the head on the engine? Too be honest I am absolutely shocked at the small amount of piston overlap that a slant has.

The engine that is in my restored truck has some issues, I was finding TDC using the screwdriver in the hole method ( thru the sparkplug hole and feeling for when it come up and dropped )

I know now that a B.S way of doing it. The overlap is so mimimal ( maybe they are not all the same ? ) I do not see how any of these set-up procedures can be done....even degreeing a cam whilst the engine has its head on.

What can you say about all of this?

Thank-you for your time this weekend
 

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on the bore my guess is there is some carbon up above the top ring and your getting fouled by some carbon buildup.

FYI the felpro and victor gaskets are the same, Madmax runs a felpro at 12.5:1 in the mid 11's...

as far as the gaskets go they make both standard bore and the .110 over in all three brands, even seen a couple .060 overs.
 
805moparkid said:
on the bore my guess is there is some carbon up above the top ring and your getting fouled by some carbon buildup.

FYI the felpro and victor gaskets are the same, Madmax runs a felpro at 12.5:1 in the mid 11's...

as far as the gaskets go they make both standard bore and the .110 over in all three brands, even seen a couple .060 overs.
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I had no idea about the oversize gaskets. Victor and Fel-pro the same is interesting.....I thought one of them was much more expensive than the other :banghead:
 
Charlie, do you still sell the steel head gaskets and if so how much?
 
1930 said:
I plan to get a proper depth gauge from e-bay and measure this correctly. At this point though I am certain that .155 thousands is pretty darn close.

Can you explain why the small cylinder bore, I have checked and double checked. I am certain that is where it is at. Is this common?


Thank-you for your time this weekend
Click to expand...


Sorry, I've been absent from this thread in the past few days, I've been busy.


First, you don't need to spend money on the depth gauge from ebay if you do not have to. You can use your calipers to get a close enough measurement.

You can use a piece of 1/4" thick plelxiglass with a hole drilled in it and your calipers for measuring depth. Just use the plexi-glass plate as a moving surface. I can get some pictures to show you, but my camera battery just died while I was trying to take some shots. I can get some pictures tomorrow when the battery is charged and the sun is up.


For your question on how many numbers to show for your measurements, list them to three decimals:

.002"
.100"
.050"


Then when you talk about them, you read the three numbers and drop the decimal. For the list above, you read that as:

two thousandths
one hundred thousandths
fifty thousandths



Ok. Now the "small" cylinder bore:

According to the 68 Plymouth service manual, the 225 slant 6 has:

Bore = 3.40"
Stroke = 4.125"


You are measuring at 3.395"

This is .005" smaller than the standard bore is listed in the manual. Are you sure that there isn't any carbon build up at the top of the bore that may be affecting your measurement. You have to get it down to clean metal. Try using a 3" wire wheel on a drill and knock off the carbon build up. This will also make it easier to remove the pistons when you get to that.
 
1930 said:
Sorry for the confusion, reading these gauges is something I do not do often, yes 3.395. So why smaller? Than stock? Is that typical?
Click to expand...

No, that is out of specification for a bore. They control the bore to less than .001", especially after honing. I can't remember the exact tolerances that we used, but they were much less than .001".
 
Thanks, its no problem, the depth gauge was already purchased, I bought a fine quality antique tool at a very good price and I am glad that I did it. Collecting antique tools is another hobby.

Ill look over everything else and thanks again
 
1930 said:
2-I plan to use a cheap fel-pro head gasket on this engine, ( just to get it running ) Can I use Kids formula above and still be Ok?

Quote from Kid: Felpro is .037 thick for both 3.4 and 3.510 bore gaskets

Can you explain....why does he mention two different size bore gaskets?

Arent these steel gaskets no longer avail.....

Quote from kid: stock steel "shim" gasket is .021 thick for both 3.4 and 3.510 bore

I plan to ultimately use a Victor Reinz head gasket. This is what has been recommended to me, what is your opinion on this gasket, I have been told it will handle up to 12.1 static compression ratio.

Not sure why this is desirable for what I am doing but what do I know and my thinking is that it must just be a better head gasket. Maybe its overkill for my application.
Click to expand...


First, I would like to say, that I would use the 3.510" bore gasket.

Since your stock bore is 3.400", you should always have the fire ring in the gasket larger than the bore. If it is the same size as the bore, and you use pistons that stick up above the head deck, then the piston may hit the gasket.

You need to find out the compressed thickness for the gasket that you plan on using for the long term. Most manufacturers can give you the volume of the gasket if you contact them.


For the numbers that you gave:

Bore = 3.510"
thick = ..037"


Area of a circle = Pi/4 x Bore x Bore = (3.1416/4) x 3.51 x 3.51 = .7854 x 12.32 = 9.68 inches squared

Volume of gasket then is:

Area x thick = 9.68 x .037 = .358 cubic inches


Convert to cc's:

.358 x 16.39 = 5.9 cc
 
Here are some preliminary numbers for you to consider:


So let's calculate your swept volume (the volume that is displaced by the piston movement).

For a stock 225:

Bore = 3.40"
Stroke = 4.125"

Swept Volume:

sv = .7854 x (3.40)**2]x 4.125 = .7854 x 11.56 x 4.125 = 37.45 cubic inches


Convert to cc's:

37.45 x 16.39 = 613.8 cc


Compression = 1 + sv/cv

sv = swept volume
cv = clearance volume


so to calculate the clearance volume needed for different compressions, you rearrange the formula:

cv = sv/(comp - 1)

So for each compression, you will need this much clearance volume (volume above the piston at TDC).

7.0 = 102.3 cc
8.0 = 87.7 cc
9.0 = 76.7 cc
9.5 = 72.2 cc
10.0 = 68.2 cc
10.5 = 64.6 cc

These numbers include the volume above the piston to the head deck, head gasket, and cylinder head combustion chamber volume.

If you measure and post your head cc's, then we can help you figure out where you need to go for your target compression.

Get your head gasket volume, and your head volume, and we can calculate where your piston needs to be.

You can take it now for a good ball park. If you plan to put in larger valves, then measure them after the headwork is done and we can adjust the measurements, but I don't think that changing the valve size will make that much difference. It is how much they will need to mill off the head/block face to make it true and square that will make the most difference.
 
Thanks for all your time with this, I will need to digest it over this up-coming week and see what I can walk away with from it. I may have more questions.

I was able to figure out how to use some of these on-line calculators and so that makes things much easier and less time consuming but I still do envy your firm grasp of the details involved with figuring out the formulas the hard way.
 
krazykuda said:
First, I would like to say, that I would use the 3.510" bore gasket.

Since your stock bore is 3.400", you should always have the fire ring in the gasket larger than the bore. If it is the same size as the bore, and you use pistons that stick up above the head deck, then the piston may hit the gasket.

You need to find out the compressed thickness for the gasket that you plan on using for the long term. Most manufacturers can give you the volume of the gasket if you contact them.


For the numbers that you gave:

Bore = 3.510"
thick = ..037"


Area of a circle = Pi/4 x Bore x Bore = (3.1416/4) x 3.51 x 3.51 = .7854 x 12.32 = 9.68 inches squared

Volume of gasket then is:

Area x thick = 9.68 x .037 = .358 cubic inches


Convert to cc's:

.358 x 16.39 = 5.9 cc
Click to expand...
I called Napa and inquired on oversized head gasket, main store or distribution center. They knew nothing about oversized gasket.

I inquired directly about the 3.510 head agsket and again they said only a standard bore. I asked if oversized was avail in other manufacturers gaskets, they gave me a number for a local engine parts W.H dist and although they carry many different names they again were un-aware of any oversized head gaskets. Just the standard bore.

Any suggestions?
 
krazykuda said:
Here are some preliminary numbers for you to consider:


So let's calculate your swept volume (the volume that is displaced by the piston movement).

For a stock 225:

Bore = 3.40"
Stroke = 4.125"

Swept Volume:

sv = .7854 x (3.40)**2]x 4.125 = .7854 x 11.56 x 4.125 = 37.45 cubic inches


Convert to cc's:

37.45 x 16.39 = 613.8 cc


Compression = 1 + sv/cv

sv = swept volume
cv = clearance volume


so to calculate the clearance volume needed for different compressions, you rearrange the formula:

cv = sv/(comp - 1)

So for each compression, you will need this much clearance volume (volume above the piston at TDC).

7.0 = 102.3 cc
8.0 = 87.7 cc
9.0 = 76.7 cc
9.5 = 72.2 cc
10.0 = 68.2 cc
10.5 = 64.6 cc

These numbers include the volume above the piston to the head deck, head gasket, and cylinder head combustion chamber volume.

If you measure and post your head cc's, then we can help you figure out where you need to go for your target compression.

Get your head gasket volume, and your head volume, and we can calculate where your piston needs to be.

You can take it now for a good ball park. If you plan to put in larger valves, then measure them after the headwork is done and we can adjust the measurements, but I don't think that changing the valve size will make that much difference. It is how much they will need to mill off the head/block face to make it true and square that will make the most difference.
Click to expand...

Local tractor supply store ( tractor supply was no help ) had a 60 cc syringe on the shelf for 2.35 cents. Yu might not beleive what they are asking for these things on e-bay.


quote: after the headwork is done and we can adjust the measurements.....

How are these adjusted after the fact of the headwork being done ?

Hopefully I will have everything else needed to get these measurements by the time next weekend rolls around, see my post above on the head gasket situation.

Thanks
 
Charrlie_S said:
I was unaware of this. How would you order the size you want? Do you have any part numbers available?
Click to expand...

To be honest i dont know, when i had to do a head gasket in 07 i got a standard bore felpro but most all i get now are the .110 overs. I dont know if they just throw in a gasket or if they maybe stopped making the standards and .060's
 
805moparkid said:
To be honest i dont know, when i had to do a head gasket in 07 i got a standard bore felpro but most all i get now are the .110 overs. I dont know if they just throw in a gasket or if they maybe stopped making the standards and .060's
Click to expand...
Where do you get the ............now are the .110 overs............maybe clarify. I called Napa and other places and there is no oversized gasket.
 
To the best of my knowledge/memory, Every slant six head gasket I have measured is just about a 3.500 bore. Even the factory steel shim gasket. I understand there is an Austrailian made "big bore" gasket, but I have not seen one, as I have never overbored greater the .060. There are several different thicknesses, of gasket depending on manufacturer. Solid copper head gaskets are available in any bore dia, and any thickness, up to about .100 thick.
I will try to remember to measure the bore dia of different gaskets I have on hand, after I get back from the VA clinic.
 
1930 said:
I called Napa and inquired on oversized head gasket, main store or distribution center. They knew nothing about oversized gasket.

I inquired directly about the 3.510 head agsket and again they said only a standard bore. I asked if oversized was avail in other manufacturers gaskets, they gave me a number for a local engine parts W.H dist and although they carry many different names they again were un-aware of any oversized head gaskets. Just the standard bore.

Any suggestions?
Click to expand...

I would find out what gaskets are available and ask manufacturers for diameter, thickness, and cc's for their gaskets.

I still would use a gasket larger than the bore.
 
1930 said:
Local tractor supply store ( tractor supply was no help ) had a 60 cc syringe on the shelf for 2.35 cents. Yu might not beleive what they are asking for these things on e-bay.


quote: after the headwork is done and we can adjust the measurements.....

How are these adjusted after the fact of the headwork being done ?

Hopefully I will have everything else needed to get these measurements by the time next weekend rolls around, see my post above on the head gasket situation.

Thanks
Click to expand...


Yes, we can adjust the measurements after the heads are done, but it would be good to know where we are starting.
 
Charrlie_S said:
To the best of my knowledge/memory, Every slant six head gasket I have measured is just about a 3.500 bore. Even the factory steel shim gasket. I understand there is an Austrailian made "big bore" gasket, but I have not seen one, as I have never overbored greater the .060. There are several different thicknesses, of gasket depending on manufacturer. Solid copper head gaskets are available in any bore dia, and any thickness, up to about .100 thick.
I will try to remember to measure the bore dia of different gaskets I have on hand, after I get back from the VA clinic.
Click to expand...

Please measure thickness with bore.
 
krazykuda said:
I would find out what gaskets are available and ask manufacturers for diameter, thickness, and cc's for their gaskets.

I still would use a gasket larger than the bore.
Click to expand...
I will get the only gasket ( Fel-Pro Gasket ) avail and this is the standard bore, I will measure that and post what I find.
 
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