Need LZ Gurus to help with CR calculation.

[Kirden]

Edited: Parts bought, new question on page 2 post #23.

 

 

Alrighty, here we go:

 

Z22 crank - 92mm

L20B rods - 145.9mm

Piston pin height - 34.8mm

Cylinder bore - 86.5mm

L20B block - 227.45mm deck height or possibly 227.20 after a shave clean.

Unshaved U67 head - 45.2cc

Flat top pistons - 0cc

Deck clearance - .75mm or .5mm after shave

 

Standard head gasket would be 1.2mm squished, but I'm not sure if that will work. We have 93 octane locally (guess this isn't the wrong coast after all :fu: )

 

The block has been sitting in the weather for a bit (3 months) and is pretty rusty on the deck so I'm hoping that a .25mm mill will clean everything up.

 

I tried using the Summit racing calculator and it comes up with 10.47:1 or 10.73:1 (unmilled vs milled) but I'm not sure if that is correct. Also trying to decide if I need a 1.2mm squished gasket or 1.5mm. Thanks in advance for the help.

[H5WAGON]

Have you checked ozdat.com ?

[EricJB]

What pistons are you using? I don't recognize the pin height. Why not bore it to 87 and use Z22 pistons?

[H5WAGON]

I put in your numbers 10.49 with 1.2 HG and 10.207 with 1.5 HG

 

Deck clearance + .75 at stock height.  5-10cc dish pistons put you in the 9's for comp ratio.

 

Waiting for money to get my project going. :angel:

[H5WAGON]

I had to edit the numbers on the ozdat app. on piston height.

[Kirden]

What pistons are you using? I don't recognize the pin height. Why not bore it to 87 and use Z22 pistons?

 

The pistons are hypereutectic mitsubishi flat pistons for the 4g64 single cam. I didn't look at the Z22 pistons because they are .05 below deck height with the rod/crank setup I plan to use and I may have to have the deck milled due to pitting from the rust.

 

I put in your numbers 10.49 with 1.2 HG and 10.207 with 1.5 HG

 

Deck clearance + .75 at stock height.  5-10cc dish pistons put you in the 9's for comp ratio.

 

Waiting for money to get my project going. :angel:

 

Looks like the summit calculator may be close then :( Looks like I may grab Z22 replacements and have them milled down if I have to mill the block.

[datzenmike]

Alrighty, here we go:

 

Z22 crank - 92mm

L20B rods - 145.9mm

Piston pin height - 34.8mm

Cylinder bore - 86.5mm

L20B block - 227.45mm deck height or possibly 227.20 after a shave clean.

Unshaved U67 head - 45.2cc

Flat top pistons - 0cc

Deck clearance - .75mm or .5mm after shave

 

Standard head gasket would be 1.2mm squished, but I'm not sure if that will work. We have 93 octane locally (guess this isn't the wrong coast after all :fu: )

 

The block has been sitting in the weather for a bit (3 months) and is pretty rusty on the deck so I'm hoping that a .25mm mill will clean everything up.

 

I tried using the Summit racing calculator and it comes up with 10.47:1 or 10.73:1 (unmilled vs milled) but I'm not sure if that is correct. Also trying to decide if I need a 1.2mm squished gasket or 1.5mm. Thanks in advance for the help.

Fuck those calculators.

 

10.53

 

11.59 with the deck shaved 0.5mm which effectively removes 5.65cc from the combustion chamber. That's more than switching to a peanut head.

[EricJB]

Unless you are planning to run a huge camshaft, I would be careful about building too much compression. I made that mistake last season with my truck.

 

L20 block bored to 89mm milled .010

 

KA pistons

 

Z22 crank and rods w/ARP bolts

 

Closed chambered head milled .030  44x37.5 valves, ported and reshaped chambers.

 

ARP studs

 

Isky .530/306

 

48DCOE's

 

1 3/4 merged header.

 

With the timing set at 34 total, running straight 92 octane, it pushed the head gasket clean out the side of the motor, and broke ring lands on two pistons. On the 2nd pass on the motor. 

 

Compression was at 215lbs.

 

I had to advance the cam timing, and tighten up the exhaust lash to get it down to 195. Back the timing down to 32, and mix 110 leaded with 92, 2 to 1 to make it live. And it still pushed head gaskets. I tried 3 brands of gaskets, Felpro being the winner. Copper is next.

 

The moral of the story is, make sure the camshaft you use is compatible with the comp ratio. I bought isky's 2nd to biggest one and it wasn't enough. 

 

 

 

 

[Kirden]

Haha, thanks Mike. Good stuff. I'm pretty sure I'll have to mill the deck some to clean it up but I'll try to get as little shaved as possible. Looks like I would have been better off swapping my U67 onto a stock Z22... Oh well, the only Z22 short block I've found is $400 and I already have the L20. $400 in machining might get it ready...

[Kirden]

Wow Eric. If only I didn't have to bore it to 89mm I would run KA pistons and the open chambered head :P

 

That setup sounds like it would be awesome, but you need a copper gasket. I have just been playing with numbers in my head and had hoped to have finally found something interesting, but the CR is too high. If it was 10:1 or just below it would be fine.

[datzenmike]

There is plenty of 'meat' on the open chamber head you can grind off. Specially to relieve around the valves to reduce shrouding.

 

Oh the motor becomes a 2161cc size.

[EricJB]

IMO, unshrouding the valves will get you more flow than enlarging the ports, especially on a u67.

[datzenmike]

You can also grind away some of the block in the valve area too. Just a crescent shape besides the intake and exhaust. Not sure how far down... surely not as far as the top ring though. Scribe a line using the head gasket. All this will help lower the compression.

[Kirden]

Alright, so I'll talk to my machinist and have the head work lined up focusing on unshrouding the valves. Then focus more on the pistons one I know my new head volume.

[EricJB]

I would post up some chamber pics, but I cant get the paste thing to work.

 

Edit. got it.

 

 

[Kirden]

wow that's very nice. What did you use to mark the outline of the bore? Looks like you put something on the head and torqued it down to get correct placement.

 

Talked to the machinist and they are taking off from tomorrow till after the first. Guess that gives me more time to plan this out.

[EricJB]

Put the dowels in, drop the head gasket on and scribe. Not my best work, but it makes the truck move. Here is another before knocking the seats out.

 

 

[Kirden]

Didn't want to start a new thread for this so zombie attack!

 

Alright, according to Ozdat's engine design, if my head and block have not been milled, my setup will create a 2.213L engine with 8.696:1 CR using the U67 head and stock squished head gasket size.

 

Z22 crank

L20B block bored to 87.5mm

28.25mm pin height pistons (-15cc)

152.5mm rods

 

Now I'm planning for 0.25-0.5mm shaved off the block to clear the corrosion leaving me at 8.8-9:1 CR. Pistons will be 0.2-0.45mm below deck height.

 

Here is the issue I'm running into. With that much dish on the pistons and an open chambered head, I may run into detonation problems. Would it be worth swapping to a closed chamber head to create a better combustion chamber? The Ozdat calc only has the V91 info for closed chambered heads and says 41ccs, so CR goes to the 9.3-9.6:1 area, which is still drivable on the local 93 octane. Could do some unshrouding to bring the CR back down if needed.

 

So what would be the best bet? Closed chamber unshrouded to lower CR and give a better squish, or open and keep the CR lower to reduce detonation. This will not be a high RPM engine. The cam I plan to get is rated to make power up to 6600 rpms.

[zed]

 I believe in the good effects of a tight squish / quench setup. I'm not an expert, but I modified my L18 for high compression - calculated about 10.5 to 11:1. It has a shaved V912 head, L28 flat tops, decked block. It pulls a trailer at 100km/h quite easily. I only have to back the timing off a few degrees if I run it in very hot temps - like 35 - 40C

[datzenmike]

Didn't want to start a new thread for this so zombie attack!

 

Alright, according to Ozdat's engine design, if my head and block have not been milled, my setup will create a 2.213L engine with 8.696:1 CR using the U67 head and stock squished head gasket size.

 

 

Z22 crank

L20B block bored to 87.5mm

28.25mm pin height pistons (-15cc)

152.5mm rods

 

 

The above assuming -15 is the dish???

I get 8.722 with open chamber head and 9.20 with closed

 

Now I'm planning for 0.25-0.5mm shaved off the block to clear the corrosion leaving me at 8.8-9:1 CR. Pistons will be 0.2-0.45mm below deck height.

The above but with 0.5mm shave off the block (this will leave 0.2mm above piston)

9.059 with open head and 9.58 closed

 

 

Closed chamber heads only work when there is a quench area. This is the place where the top of the piston is separated from the head by only the gasket thickness. With a 15cc dish piston there won't be much of that, only a compression increase. To get the benefits of a closed chamber head you really need flattop pistons. This provides a pinch area that violently forces the air into the combustion chamber in the head maximizing turbulence. . 

[Kirden]

Yes, 15cc dish. Looks like your calculations aren't far from what ozdat says.

 

So, should I trade the U67 for a closed chamber head? Really just trying to figure out if the quench area is something I need to worry about. This will be in a street driven truck. Aside from the occasional spirited run, there will be no "track time."

 

Since higher CR increases the chance of detonation, but peanut heads reduce detonation, would a stock peanut and a stock U67 be similar? My gut tells me to use what I have and see if it works, but right now everything is apart so it's much easier to make any changes now.

 

Eventually I do want a supercharger, but that will probably be years and a rebuild down the line.

 

Edit: and datzenmike to the rescue. Thank you sir. This post was made before you added to your earlier respone so please disregard. Looks like I'll stick to the U67

[datzenmike]

Closed chamber heads only work when there is a quench area. This is the place where the top of the piston is separated from the head by only the gasket thickness. With a 15cc dish piston there won't be much of that, only a compression increase. To get the benefits of a closed chamber head you really need flattop pistons. This provides a pinch area that violently forces the air into the combustion chamber in the head maximizing turbulence. . 

.

I'm saying there will be almost no advantage to a closed chamber head as there is a huge 15cc dish on these pistons. Flattops are needed for full effect. There will be a small ring around the outside of the piston that will 'pinch' but not enough to have much of an effect.

 

The piston on the far left is a 15cc dish and the small raised rim around the outside is the 'quench' area... IF it were used with a closed chamber head. To get the full benefit of a closed chamber head you should use a flattop piston like the 3rd one over to the right.

 

...................... Z24.................................Z22(truck).....................Z20E..........................L20B

[Kirden]

I'm needing advice on which parts to take to the machinist. I currently have rods, pistons, pins, rings, engine block, and a stock U67 head in unknown condition.

 

The block needs to be bored over to 87.5mm so that was a no brainer, and the pistons need to be pressed onto the rods. I want to have the crank checked and either need to have the machinist measure the crank and rods for bearing size, or figure out how to do it on my own. The head needs to be checked for warpage and I'll possibly have the valves unshrouded, but that is something I may do myself.

 

So the question is, what else should I bring? I will assemble this engine myself to save money, but I also want to make sure I have everything ready prior to starting the assembly. For now I will either use the stock U67 head or the open A87 from my L18 (known running condition). Should I disassemble the head prior to taking it to the machinist?

 

Btw, here are the pistons I finally decided to use (The picture is not correct, they are dished with no valve reliefs):

http://www.summitracing.com/parts/slp-h895cp/overview/make/ford

 

So:

87.5mm bore

U67 or open A89 from L18

-15 dish pistons (28.25 pin height)

6" rods

Z22 Crank

1.5mm, 88mm bore Nismo gasket

 

I get around 8.5:1 CR with U67, not sure if the open A89 has a smaller chamber but CR would go up if it does.

[datzenmike]

I'm needing advice on which parts to take to the machinist. I currently have rods, pistons, pins, rings, engine block, and a stock U67 head in unknown condition.

 

The block needs to be bored over to 87.5mm so that was a no brainer, and the pistons need to be pressed onto the rods. I want to have the crank checked and either need to have the machinist measure the crank and rods for bearing size, or figure out how to do it on my own. The head needs to be checked for warpage and I'll possibly have the valves unshrouded, but that is something I may do myself.

 

So the question is, what else should I bring? I will assemble this engine myself to save money, but I also want to make sure I have everything ready prior to starting the assembly. For now I will either use the stock U67 head or the open A87 from my L18 (known running condition). Should I disassemble the head prior to taking it to the machinist?

 

Btw, here are the pistons I finally decided to use (The picture is not correct, they are dished with no valve reliefs):

http://www.summitracing.com/parts/slp-h895cp/overview/make/ford

 

So:

87.5mm bore

U67 or open A89 from L18

-15 dish pistons (28.25 pin height)

6" rods

Z22 Crank

1.5mm, 88mm bore Nismo gasket

 

I get around 8.5:1 CR with U67, not sure if the open A89 has a smaller chamber but CR would go up if it does.

 

I agree 8.53 with Nismo gasket and 8.72 with a stock gasket

 

Also 8.8 with a 0.5mm shave off the block and Nismo gasket.

[Kirden]

Thank Mike :thumbup:

 

So would the L18s open A89 have the same chamber size as the U67? Just thinking it may be easier to use the stock A89 and rebuild the U67 down the road for more performance. That way the truck wouldn't have to be down while the U67 gets it's eventual rebuild.