Head Gasket Compressed Thickness

[1972RedNeck]

Originally Posted by DISTURBED

Set all parameters back to stock and see which one comes up with close to 17:1. I just used your numbers and came up with 16.5:1. I had a really good calculator that was spot on for diesels and now i cant find it. After playing with a bunch of calculators none of them are even remotely close on stock cummins specs. They are all off by 2-3 CR

I guess I will have to dig out the calculator and do it the old fashioned way.

[1972RedNeck]

Took the bore area and multiplied it by the stroke plus .020" piston to head clearance for a total of 60.160 cubic inches or 985.849cc. Added 44.000 (assuming exact to carry significant digits) cc for the piston and 3.000cc for valves and got a total of 1032.849cc.

Then took the bore area and multiplied it by the .020" clearance for .254 cubic inches or 4.160cc and added 44cc and 3cc for a total of 51.160cc.

1032.849 divided by 51.160 reduces to 20.189:1.

Any holes in my math? I didn't figure for head gasket bore as I don't know the measurement - anyone have that off the top of their head?

[DISTURBED]

Originally Posted by 1972RedNeck

Took the bore area and multiplied it by the stroke plus .020" piston to head clearance for a total of 60.160 cubic inches or 985.849cc. Added 44.000 (assuming exact to carry significant digits) cc for the piston and 3.000cc for valves and got a total of 1032.849cc.

Then took the bore area and multiplied it by the .020" clearance for .254 cubic inches or 4.160cc and added 44cc and 3cc for a total of 51.160cc.

1032.849 divided by 51.160 reduces to 20.189:1.

Any holes in my math? I didn't figure for head gasket bore as I don't know the measurement - anyone have that off the top of their head?

Does the Pistons have a CR stamped in the top? Gasket bore is 4.151

[1972RedNeck]

Originally Posted by DISTURBED

Does the Pistons have a CR stamped in the top? Gasket bore is 4.151

It doesn't. Just the original 93 intercooled pistons.

[9724VF350]

Compression ratio calculators. Lol.

Cubes per cylinder x 16.39 + cc’s / cc’s.

Figure up valve depth and piston to head the same way you do cubic inc,, then multiply by 16.39.

[DISTURBED]

Originally Posted by 1972RedNeck

It doesn't. Just the original 93 intercooled pistons.

Almost 100% they are still 17:1 and adding .010 piston protrusion is not going to net you 3:1 or 4:1 gain. More like .5:1 gain.

[1972RedNeck]

Originally Posted by DISTURBED

Almost 100% they are still 17:1 and adding .010 piston protrusion is not going to net you 3:1 or 4:1 gain. More like .5:1 gain.

Not going to disagree with you, but my math is correct, isn't it?

[1972RedNeck]

Head gasket adds about .77cc. If I round it up to 1cc the compression comes down to 19.82:1.

[1972RedNeck]

I wish I would have measured piston bowls. 47cc bowls would make it 18.9:1 and be a lot more believable.

With stock specs and 47cc bowls the compression works out to be 17.6:1. Advertised is 17.5:1 iirc.

[Smokem]

Originally Posted by 1972RedNeck

I wish I would have measured piston bowls. 47cc bowls would make it 18.9:1 and be a lot more believable.

I have all the prints from Mahle, it's 44.2cc's, and Mahle uses a factory chamber volume value of 6.90cc's.

[9724VF350]

After figuring up a handful of little things that I'm too lazy to type all out and explain, I'm going to say you're going to fall in between 18.5 and 19, which is a tick higher than I actually expected.

[Smokem]

Originally Posted by 9724VF350

I'm going to say you're going to fall in between 18.5 and 19, which is a tick higher than I actually expected.

That is if you assume the chamber volume is 3cc's, which I would question the accuracy of.

[Rich dzl]

Someone offer a dyno and try all three head gaskets .. if you see anything change I would be surprised ..

[jasonc]

Maybe the performance on all 3 would be almost identical, but the main difference would be how clean it would be at idle.
What does the extra height from the thicker gaskets do to affect the injectors? I know you can run thinner shims, but say the truck already runs better with the thin injector washers before hand.

[DISTURBED]

Originally Posted by jasonc

Maybe the performance on all 3 would be almost identical, but the main difference would be how clean it would be at idle.
What does the extra height from the thicker gaskets do to affect the injectors? I know you can run thinner shims, but say the truck already runs better with the thin injector washers before hand.

In this situation probably nothing since the Pistons are .010 further out of the block. So it would make up for the thicker gasket

[1972RedNeck]

Originally Posted by Smokem

That is if you assume the chamber volume is 3cc's, which I would question the accuracy of.

I thought about measuring it, but I knew I couldn't get the water to lay flat due to surface tension, and it didn't dawn on me to add a little dish soap (no pun intended).

With my lazy streak, I would rather do the math than actually measure it anyways.

I'll cc my spare head tomorrow if I have time and see what I get and then correct it for the valve face depth.

[1972RedNeck]

Originally Posted by Rich dzl

Someone offer a dyno and try all three head gaskets .. if you see anything change I would be surprised ..

I used to be of this opinion until I scored a piston in my warmed over 4BT. When I rebuilt it, I went from 155° 17.5:1 pistons to 16.5:1 pistons. Everything else stayed the same.

It had to have more timing to run right, started harder, had a lot less low end torque, and lost almost 2 MPG. It sure did take off and run after about 2500 RPM though.

Ever since I have focused on whatever little bit of compression I can pick up.

Eric from The Hungry Diesel has played around with higher compression and VE pumps along with a few others and they all report greatly improved spoolup/low end torque.

I know it's backwards from the rest of the diesel world, but when you have a little old VE pump that has pathetic top end fueling, we have to make the most out of the decent bottom end.

[DISTURBED]

Originally Posted by 1972RedNeck

I thought about measuring it, but I knew I couldn't get the water to lay flat due to surface tension, and it didn't dawn on me to add a little dish soap (no pun intended).

With my lazy streak, I would rather do the math than actually measure it anyways.

I'll cc my spare head tomorrow if I have time and see what I get and then correct it for the valve face depth.

Use a piece of plexiglass with a hole drilled in it. Put grease around the valves on the head face and stick the plexiglass to the head so the grease makes a seal and pour the valves that way. This is how I have always poured components. That way you know exactly how much it is when the air bubbles disappear.

[j.fondler]

since you and I are after the same thing, high compression VE motor, and happen to be running the same cam, I sent an email off to hamilton to see what their thoughts are on minimum piston to valve. cheers

[bigstacks95]

Lemme get this straight, you put this engine together and can't CC the pistons, and didn't check piston to valve clearance? I wouldn't go off the calculator on Hamilton's website with all the changes you've made as far as decking the block and head.

IMO you HAVE to know those numbers when building an engine, from stock to 2000 horsepower it doesn't matter.

BTW Play-Dough works great for PTV clearance. Probably could use it to CC the pistons as well