Volvo Owners Club Forum - View Single Post

blueosprey90 · May 28th, 2020, 03:10

I know a guy named Hap Waldrop who has an engine building shop called Acme Speed Shop. He is a good old boy from Greenville, South Carolina who probably used to run moonshine and needed a fast engine to outrun the revenuers. He likes to talk and you might accuse him of being a bit long winded. But I'll share some of his wisdom.

"I don't like using head thickness as a way to figure compression ratio, too many variables to foul the job up, valve height for one. As mentioned above CC volume measuring the combustion chambers is the more accurate way to do this, and while it may seem beyond the novice engine builder's skill set, it really isn't, and can be a fun project.

Things you need to have to know what your current CR is and how to plan for your target CR, while keeping in mind this is being done by a novice and with a budget in mind.

A feeding tube syringe, you can get one at your local drug store for a couple of dollars, get the biggest one you can, remember CC and ML is the same thing in this regard.

A piece of plexiglass bigger than the combustion chamber with a few holes drilled in it 1/4" will work fine, and having a chamfered counter bore around the drilled holes aids in helping get the fluid in the chamber. You can use grease to seal the plexiglass to the head deck for CC volume checking. The holes are for filling the chamber, you'll notice even when you level the head on the workbench you may have to chase a few air bubbles to get the chamber filled with fluid, this is where a few well placed drilled holes will aid you.

OK now you need something to measure depth, ideally a depth micrometer would be the tool of choice, and if you don't mind buying one, then you can find them online reasonably. OK lets assume you don't want to buy a depth mic, you can do this job with a dial caliper, just check your finding many times and look for repeatable numbers. Also the dial caliper will come in handy for other aspects of this job, measuring the bore size of the head gasket for example. You need to measure depth in two ways in this job, your piston to block deck height with the piston at TDC, remember to only measure this at the piston pin axis which is at 12 and 6 o'clock when facing the front of the engine, the piston at any other point can be rocked one way, or the other and that would give you inaccurate measurements. The second place you will use a depth measurement would be in the chamber when figuring how much to take off your head, I'll explain that in a minute.

OK, lets say the head is off the engine, and on the workbench, the combustion chambers have been fairly well cleaned, and ridded of carbon deposits that would askew your findings. The block deck has old head gasket debris scrapped off and is clean enough to take a deck height measurement. OK record your piston to block deck height, record that data, measure the bore on your head gasket, most head gaskets I find to be a good .080" or so over standard bore size, but still measure, never assume.

OK now with the head level on a bench, and yes use a level you want the head as level as you can get it. With the valves and springs installed, as well as a spark plugs installed you now can check your current chamber volume. Get your plexiglass plate, smear some grease around the combustion chamber for sealing the plate, make sure not to get any grease inside the combustion chamber as this would take up volume and askew your findings. OK now put the plexiglass plate over the chamber and fill with liquid from your ML feeding syringe, make sure you start off at the highest volume the syringe allows, fill the chamber and see how much liquid you used to fill the chamber. Now say the head has a big chamber volume, and say the biggest feeding tube syringe you can find is 50 ML, don't worry, you can do this with more than one filling of the syringe, just keep close look on how much your total ends up being as for how much liquid you put into the chamber, repeat the process to make sure your findings are accurate. For example say you are using a 50 ML syringe and you fully fill the syringe to 50 ML mark and use all of it in the chamber and still need more liquid, simply fill it again to given mark, than add the extra fluid until the chamber is filled, then add up to the two amounts, and you have your volume.

OK, now lets say you have all your data to know what your current CR is.

Bore size
Engine stroke
Piston to block deck height
Piston dish volume, if using a dished piston then you would fluid fill it as well and see what the CC volume of the dish is, in the case of a flat top piston most CR calculators will just have you enter a 0 zero amount here.
Head gasket bore size
Head gasket compressed thickness
Combustion chamber volume

OK, these days with the internet, this job is much easier, you can simply enter your data on a online CR calculator, and hit the convert/calculate button, this sure beats the long math I did many years ago to figure this out.

Here a CR calculator I used many times.

https://www.rbracing-rsr.com/compstaticcalc.html

OK enter your data and see where your CR currently is, with these old engines is almost always a given you are not the first one there, so seeing where you really are is big time important. I tell folks, assumption is the mother of all mistakes.

OK, now you know where you are and it is now time to figure out what you need to do to get to your CR target. On some engines it may aid you, if doing a complete rebuild to incorporate block resurfacing into this equation. … this would lessen the amount you would have to remove from the head to get to your CR target. ….

OK so at this point say the way we are raising the CR is only going to be head resurfacing, so with the CR calculator just insert lesser CC volume amounts into the calculator until your reach your target CR. Now back at the work bench with the head still leveled and all of the previous liquid removed from the prior test, put the amount of liquid/volume into the chamber that the calculator showed you would reach your target CR. Now with this test there is no need to use the plexiglass plate, because the level will now be below the top edge of the chamber. OK now here's where the second depth measurement will be taken, you need to see how far down into the chamber you measure before you hit the liquid. Now I cannot always see when the end of the mic, or dial caliper when it hits the surface of the liquid, and you for sure want to sneak up on it, so I simply move the depth probe gradually deeper, checking it by rubbing it across my arm to see if I feel the wetness of the liquid. Once you feel wetness, double check your measurements a few times, even backing off your measurement to make sure you have for sure gotten the exact measurement of the where the probe touches off on the liquid. OK now record this figure, this is how much you will need to take off your head to reach your target CR.

A word on what liquid to use, any thin liquid will work, I use the green rubbing alcohol, it's cheap, and easy to find.

Hopefully this reads in a way one understands this, is really a simple, and fun project that takes out the guesswork, and way more accurate than using head casting thicknesses. I tried my best to describe how you can do this with simple and cheap tools, yes I have a big nice 100ML glass burret and stand, head stand pedestals, depth mics, because I do this sort of work often, but you can still do this, and get accurate data without making the investment in tools a professional would, and accomplish your goal.

Yes this is harder than simply asking on the forum "how much should I cut off my head" , but remember what I said about assumption, it is better to be accurate, and not create a unworkable fix. This is like the old carpenter's saying, "measure twice, cut once"

Here's a a video, showing how to take your cylinder head combustion chamber volume. This guy has all the stuff a pro would use, head stands, a 100ML vertical glass burret on a stand, but you can use stack of books, a couple 2x4 pieces for the stand, etc., you're just trying to level the cylinder head on your work bench. Then in place of the glass burret you can use the 50-60ml feeding tube syringe you can buy for a couple of bucks at the local drug store.

https://youtu.be/V7V40ZWNgCo

May 28th, 2020, 03:10	#30
blueosprey90 Master Member Last Online: Apr 25th, 2024 13:36 Join Date: May 2017 Location: New Milford, Connecticut	I know a guy named Hap Waldrop who has an engine building shop called Acme Speed Shop. He is a good old boy from Greenville, South Carolina who probably used to run moonshine and needed a fast engine to outrun the revenuers. He likes to talk and you might accuse him of being a bit long winded. But I'll share some of his wisdom. "I don't like using head thickness as a way to figure compression ratio, too many variables to foul the job up, valve height for one. As mentioned above CC volume measuring the combustion chambers is the more accurate way to do this, and while it may seem beyond the novice engine builder's skill set, it really isn't, and can be a fun project. Things you need to have to know what your current CR is and how to plan for your target CR, while keeping in mind this is being done by a novice and with a budget in mind. A feeding tube syringe, you can get one at your local drug store for a couple of dollars, get the biggest one you can, remember CC and ML is the same thing in this regard. A piece of plexiglass bigger than the combustion chamber with a few holes drilled in it 1/4" will work fine, and having a chamfered counter bore around the drilled holes aids in helping get the fluid in the chamber. You can use grease to seal the plexiglass to the head deck for CC volume checking. The holes are for filling the chamber, you'll notice even when you level the head on the workbench you may have to chase a few air bubbles to get the chamber filled with fluid, this is where a few well placed drilled holes will aid you. OK now you need something to measure depth, ideally a depth micrometer would be the tool of choice, and if you don't mind buying one, then you can find them online reasonably. OK lets assume you don't want to buy a depth mic, you can do this job with a dial caliper, just check your finding many times and look for repeatable numbers. Also the dial caliper will come in handy for other aspects of this job, measuring the bore size of the head gasket for example. You need to measure depth in two ways in this job, your piston to block deck height with the piston at TDC, remember to only measure this at the piston pin axis which is at 12 and 6 o'clock when facing the front of the engine, the piston at any other point can be rocked one way, or the other and that would give you inaccurate measurements. The second place you will use a depth measurement would be in the chamber when figuring how much to take off your head, I'll explain that in a minute. OK, lets say the head is off the engine, and on the workbench, the combustion chambers have been fairly well cleaned, and ridded of carbon deposits that would askew your findings. The block deck has old head gasket debris scrapped off and is clean enough to take a deck height measurement. OK record your piston to block deck height, record that data, measure the bore on your head gasket, most head gaskets I find to be a good .080" or so over standard bore size, but still measure, never assume. OK now with the head level on a bench, and yes use a level you want the head as level as you can get it. With the valves and springs installed, as well as a spark plugs installed you now can check your current chamber volume. Get your plexiglass plate, smear some grease around the combustion chamber for sealing the plate, make sure not to get any grease inside the combustion chamber as this would take up volume and askew your findings. OK now put the plexiglass plate over the chamber and fill with liquid from your ML feeding syringe, make sure you start off at the highest volume the syringe allows, fill the chamber and see how much liquid you used to fill the chamber. Now say the head has a big chamber volume, and say the biggest feeding tube syringe you can find is 50 ML, don't worry, you can do this with more than one filling of the syringe, just keep close look on how much your total ends up being as for how much liquid you put into the chamber, repeat the process to make sure your findings are accurate. For example say you are using a 50 ML syringe and you fully fill the syringe to 50 ML mark and use all of it in the chamber and still need more liquid, simply fill it again to given mark, than add the extra fluid until the chamber is filled, then add up to the two amounts, and you have your volume. OK, now lets say you have all your data to know what your current CR is. Bore size Engine stroke Piston to block deck height Piston dish volume, if using a dished piston then you would fluid fill it as well and see what the CC volume of the dish is, in the case of a flat top piston most CR calculators will just have you enter a 0 zero amount here. Head gasket bore size Head gasket compressed thickness Combustion chamber volume OK, these days with the internet, this job is much easier, you can simply enter your data on a online CR calculator, and hit the convert/calculate button, this sure beats the long math I did many years ago to figure this out. Here a CR calculator I used many times. https://www.rbracing-rsr.com/compstaticcalc.html OK enter your data and see where your CR currently is, with these old engines is almost always a given you are not the first one there, so seeing where you really are is big time important. I tell folks, assumption is the mother of all mistakes. OK, now you know where you are and it is now time to figure out what you need to do to get to your CR target. On some engines it may aid you, if doing a complete rebuild to incorporate block resurfacing into this equation. … this would lessen the amount you would have to remove from the head to get to your CR target. …. OK so at this point say the way we are raising the CR is only going to be head resurfacing, so with the CR calculator just insert lesser CC volume amounts into the calculator until your reach your target CR. Now back at the work bench with the head still leveled and all of the previous liquid removed from the prior test, put the amount of liquid/volume into the chamber that the calculator showed you would reach your target CR. Now with this test there is no need to use the plexiglass plate, because the level will now be below the top edge of the chamber. OK now here's where the second depth measurement will be taken, you need to see how far down into the chamber you measure before you hit the liquid. Now I cannot always see when the end of the mic, or dial caliper when it hits the surface of the liquid, and you for sure want to sneak up on it, so I simply move the depth probe gradually deeper, checking it by rubbing it across my arm to see if I feel the wetness of the liquid. Once you feel wetness, double check your measurements a few times, even backing off your measurement to make sure you have for sure gotten the exact measurement of the where the probe touches off on the liquid. OK now record this figure, this is how much you will need to take off your head to reach your target CR. A word on what liquid to use, any thin liquid will work, I use the green rubbing alcohol, it's cheap, and easy to find. Hopefully this reads in a way one understands this, is really a simple, and fun project that takes out the guesswork, and way more accurate than using head casting thicknesses. I tried my best to describe how you can do this with simple and cheap tools, yes I have a big nice 100ML glass burret and stand, head stand pedestals, depth mics, because I do this sort of work often, but you can still do this, and get accurate data without making the investment in tools a professional would, and accomplish your goal. Yes this is harder than simply asking on the forum "how much should I cut off my head" , but remember what I said about assumption, it is better to be accurate, and not create a unworkable fix. This is like the old carpenter's saying, "measure twice, cut once" Here's a a video, showing how to take your cylinder head combustion chamber volume. This guy has all the stuff a pro would use, head stands, a 100ML vertical glass burret on a stand, but you can use stack of books, a couple 2x4 pieces for the stand, etc., you're just trying to level the cylinder head on your work bench. Then in place of the glass burret you can use the 50-60ml feeding tube syringe you can buy for a couple of bucks at the local drug store. https://youtu.be/V7V40ZWNgCo Last edited by blueosprey90; May 28th, 2020 at 03:14.