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Rebuild Z22... how to do it right


poopypants720

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Ive been a lurker in the 720 boards here and there for some time now but like the title states, im rebuilding my Z22 this next month and need to speak up n get some info.

 

Already have done the research on what machine shop to go with and im very excited given all the options i have here in SoCal (sorry sealik, ive read about the horrible time youve spent with your limited options up there n learned from it) but when I get in there I want to have a solid grasp on this situation and be able to tell him in detail exactly what i want done. the finished motor will have a 2yr/24,000mile warranty on it.

 

First thing is, this truck has to be able to pass smog once everything is said and done.

 

Second, it will have a smog legal Weber 32/34 DFT carb and the ca smog legal thorley headers on it. have custom routed exhaust with a test section for the cat to go and a flowmaster muffler.... waiting will be another more performance oriented weber carb for once testing is complete. With this in mind (free breathing motor) what would likely be a good choice of lift and duration for a cam?

 

Third, Id like to increase the compression ratio if possible without swapping heads (as another head is more money and not as likely to pass smog)... can i accomplish this with a larger bore and bigger pistons and if so what size would be a good choice?

 

 

any other tips or suggestions are welcome to accomplish this goal of rebuilding a slightly more powerful motor that passes smog.......

 

 

 

but if this just isnt possible ill just look for a smog shop that WILL pass me ;).

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Increasing your compression ratio without changing heads is going to mean swapping piston heads. Not 100% sure but I think VG30E pistons would be a good option. They have the same wrist pin diameter (21 mm) and bore diameter (87 mm) and I believe same pin height (35.5mm) and whereas the Z22 has about 9cc dish pistons, the vg has only a 1 cc dish. I don't have all the info on hand to figure out the exact compression ratio, but those pistons should put you in to the low to mid 9.x:1 range.

 

There are two types of piston heads and wrist pins in the VG-E. Pressed in piston pins, and full floating pins. For sake of ease, find the pressed in piston style piston heads. My information is based on just some quick research, so no guarantees, but I think it should work.

 

Otherwise, you can overbore it to 89mm and use KA24E pistons from a truck (press in pin style), which have 2cc dish and will be similar in compression ratio but a little lower. It's also possible that both of these piston options will need a little valve clearancing, but your machine shop should be able to confirm that for you.

 

This is all slightly hypothetical, so anyone, feel free to correct me if I'm wrong somewhere. Shoot me any questions if something is not clear.

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Nice. I understand that completely and its exactly the kind of thing I was thinking... Initially ka piston heads since I was planning on possibly boring over, didn't have a clue that the dish on them was that much different and def didn't know the vg piston heads were anywhere close. Im def going to look into those....<br /><br />Thank you very much for the response.<br /><br />You have any useful knowledge on cams? I think use of the search feature is in order but so much pertains to the l series motors in the engine forum....

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I've looked into the ka swap... Personally I can't find any engines for less then the cost of a rebuild ($1,350) would be and still have to worry about the integrity of the motor swapped in............::::::::::::.

 

The lz22 mod would be fun BUT won't be smog legal in ca as it looks nothing like the z head/intake/exhaust configuration and thus won't even pass visual inspection, let alone smog... Besides I have headers and custom routed exhaust already on the truck that would be worthless, over 500 wasted, by going to a diff head............::::::::::

 

Spoke to my machinist.... couple problems with changing to either of the aforementioned piston heads...The vg30e piston actually has a smaller dish but all together is shorter. Same with the ka piston heads.... Its called the compression height and is measured from the pin to the to of the head........::::::::::::::::

 

Stock z22 pistons are 35.5mm.............:::::::::::

 

vg390e pistons are 32mm..........::::::::::

Ka24e pistons are 34 mm AND require boring out to 89 mm also they are only floating head pistons and there is no way they will match up to my current rods, no cotter pin...........::::::::::::

 

According too the machinist (trusted and in business for over 35 years) this will make the compression drop drastically and make my z22 a complete dog...............:::::::::

 

Has anyone ever used any of these pistons in practical applications or maybe know of any other piston heads that would be more likely to effectively increase compression?...........::::::::

 

Anyone used a reground cam or newly forged cam other then stock and actually been happy with the results? Whats the specs?

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Compression height was the spec I was most unsure about. The one thing I disagree with the machinist on is the ka pistons. They came in full and semi floating versions depending on the car they came in. truck ka pistons should be semi floating. but if compression height is to low that does not really matter. A lot of honda f and h series pistons are 87mm but have 22mm wrist pins so u would have to bore your rods out, and that is only if compression height is good.

 

Most people dislike how the z heads flow so there are few options for cams

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Take the Z22 block and over bore to 89mm. This will allow the use of KA24E pistons. Use your Z22 rods if they are 145.9mm long or find L20B rods as they are the same. Yes the KA pistons have a negative 1.55mm deck height but this is good as the increased bore volume plus the smaller dish would have raised the compression too high anyway. This negative 1.55mm adds about 9.6 cc of volume to the combustion chamber so... Z22 bored to 89mm, KA24E pistons on Z22/L20B rods with Z22 crank and head will have a compression of 8.469 ... big friggin' deal. It'll work and you have a 2300cc motor when done.

 

 

BTW the VG pistons have almost no dish (1cc) but have way too low a pin height ...negative 3.75mm over the stock Z22 pistons. If run in a stock bore Z22 (87mm) the compression would drop to 7.2

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whats the compression ratio on a stock z22???

 

will this really net me a significant gain in compression? will the difference in the bore at the least increase overall performance and hp? The machinist stated that this would require removing, i think it was, 80 one thousandths??? is this correct and more so can this be done without compromising block integrity? Didnt sealik just do this same thing to a z24 block and added the L head??? have there been many other folks (real world applications) that have done this ka piston swap??

 

and Mike (lockleaf too), are you sayin i can use the KA piston with the stock Z22 rods regardless of them being floating heads? What are partially floating Pistons? mind explaining the difference real quick? my machinist was just lookin up values in a big A manual on his front desk..... could he be wrong about not being able to mount the KA piston heads on the Z22 rods? mind explaining why so I can convey this info to my machinist? his manual only showed floating KA heads available...

 

lastly I checked out the cam available from AC(4x4parts.com) which is supposed to be cast billet, not reground for 199.99 (fair price??), called in and they told me specs from manufacturer read: lift-406 and duration-272 to be used with stock rockers and springs.... im not cam savvy in the least only knowing their basic function and that the lift is how far the cam lifts the valves and duration is the degrees/time its kept open/closed in a 360 degree revolution... what effects changing these values have on performance, i know not.... I want something to take advantage of my exhaust headers and weber carb but still maintain stock springs and rockers(machinist suggested using stock springs)... dont want to lose too much low end torque either just pick up a lil more of a power band.

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I think the stock CR of the Z22 is 8.3???

You would use the KA pistons from the D21 (truck)....not from the car (240sx), they have full floating pins

http://community.ratsun.net/topic/25243-ka-z24-build-compression-questions-done/page__p__362044__hl__%2Bfull+%2Bfloating__fromsearch__1#entry362044

Even if you raised the compression from 8.3 to 9.3. you're only gaining about 3 percent HP...not worth the extra cash

 

You could probably go a little more on the cam lift with the stock springs....maybe a little less on the duration?

Comp Cam has one....420 lift/260 duration/midrange power....I believe this can be run with the stock springs

All depends where you want your power band.

Guessing the stock Z22 duration is around 245???

So for every 10 degrees of duration your power band increases 500RPM

 

Oh.....and good luck :D

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To answer your question about full floating pistons vs not, full floating pistons have clips in the side of the piston head to keep the wrist pin in place because its just "floating" around in there. Semi floating the pin is pressed in to the rod to hold it in place and the piston head is all that floats. The z engines are all press fit and so are the ka truck piston heads

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whats the compression ratio on a stock z22???

 

will this really net me a significant gain in compression? will the difference in the bore at the least increase overall performance and hp? The machinist stated that this would require removing, i think it was, 80 one thousandths??? is this correct and more so can this be done without compromising block integrity? Didnt sealik just do this same thing to a z24 block and added the L head??? have there been many other folks (real world applications) that have done this ka piston swap??

 

and Mike (lockleaf too), are you sayin i can use the KA piston with the stock Z22 rods regardless of them being floating heads? What are partially floating Pistons? mind explaining the difference real quick? my machinist was just lookin up values in a big A manual on his front desk..... could he be wrong about not being able to mount the KA piston heads on the Z22 rods? mind explaining why so I can convey this info to my machinist? his manual only showed floating KA heads available...

 

lastly I checked out the cam available from AC(4x4parts.com) which is supposed to be cast billet, not reground for 199.99 (fair price??), called in and they told me specs from manufacturer read: lift-406 and duration-272 to be used with stock rockers and springs.... im not cam savvy in the least only knowing their basic function and that the lift is how far the cam lifts the valves and duration is the degrees/time its kept open/closed in a 360 degree revolution... what effects changing these values have on performance, i know not.... I want something to take advantage of my exhaust headers and weber carb but still maintain stock springs and rockers(machinist suggested using stock springs)... dont want to lose too much low end torque either just pick up a lil more of a power band.

 

The Z22 has an 87mm bore so it needs to be increased to 89mm, or 1 (one ) mm removed all the way round the bore. That's just under 0.040" of actual metal removed.

 

Just call a piston a piston. Using the word piston head is inaccurate and could be misleading. The piston pins on the KA are the same diameter as the hole in the Z22 rods. The KA rods are sized and have a bronze bushing that allows them to turn or rotate. All piston pins can rotate inside the pistons but most are press fit into the rods. Because neither the KA piston or rod actually holds the pin it is free to slide sideways and would hit the cylinder wall if there were not C clips inside the piston to prevent this. Just have the pins pressed into your Z22/L20B rods and it will act as a non floating type piston. The reason for the fully floating pins is that there is a reduction in friction and an increase in hp when using them.

 

The top of the KA rod is drilled to allow splash oiling of the floating pin.

720stuffKA24Epistonrod007Large.jpg

 

 

As for cam lift I believe the stock Z cam specs are the same as the L series. That would make the lift 0.413" and duration 248. Many cam manufacturers specify the duration at 0.050" lift so it may appear less than the stock cam.

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<br />I think the stock CR of the Z22 is 8.3???<br />You would use the KA pistons from the D21 (truck)....not from the car (240sx), they have full floating pins<br /><a href='http://community.ratsun.net/topic/25243-ka-z24-build-compression-questions-done/page__p__362044__hl__%2Bfull+%2Bfloating__fromsearch__1#entry362044' class='bbc_url' title='External link' rel='nofollow external'>http://community.rat...__1#entry362044</a><br />Even if you raised the compression from 8.3 to 9.3. you're only gaining about 3 percent HP...not worth the extra cash<br /><br />You could probably go a little more on the cam lift with the stock springs....maybe a little less on the duration?<br />Comp Cam has one....420 lift/260 duration/midrange power....I believe this can be run with the stock springs<br />All depends where you want your power band.<br />Guessing the stock Z22 duration is around 245???<br />So for every 10 degrees of duration your power band increases 500RPM<br /><br />Oh.....and good luck <img src='http://community.ratsun.net/public/style_emoticons/default/biggrin.gif' class='bbc_emoticon' alt=':D' /><br />
<br /><br /><br /> Thanks for the numbers!

 

I'm going to check out comp cams and prob give them a call, the only one I've seen previous was a newly forged cam with a 402 lift 272 duration (I'm thinking that would put my power band higher then desired) more then anything I suspect lift is what I'm looking for to take advantage of my free flowing exhaust and carb? What kinda lift could I get away with and not worry about valve clearance or switching away from stock springs?

 

As for piston choice...

Cost in this case shouldn't be a factor... Just need to know what to order and request from the machinist. My machinist is willing to add the bigger bore and pistons at the quoted cost already. Since I'm going to replace my z22 pistons anyhow ill prob chose to go for the ka piston even if its 3% more hp and an atmosphere more of compression ill take it ;)

 

 

<br />The Z22 has an 87mm bore so it needs to be increased to 89mm, or 1 (one ) mm removed all the way round the bore. That's just under 0.040" of actual metal removed.<br /><br />Just call a piston a piston. Using the word piston head is inaccurate and could be misleading. The piston pins on the KA are the same diameter as the hole in the Z22 rods. The KA rods are sized and have a bronze bushing that allows them to turn or rotate. All piston pins can rotate inside the pistons but most are press fit into the rods. Because neither the KA piston or rod actually holds the pin it is free to slide sideways and would hit the cylinder wall if there were not C clips inside the piston to prevent this. Just have the pins pressed into your Z22/L20B rods and it will act as a non floating type piston. The reason for the fully floating pins is that there is a reduction in friction and an increase in hp when using them.<br /><br />The top of the KA rod is drilled to allow splash oiling of the floating pin.<br />720stuffKA24Epistonrod007Large.jpg<br /><br /><br />As for cam lift I believe the stock Z cam specs are the same as the L series. That would make the lift 0.413" and duration 248. Many cam manufacturers specify the duration at 0.050" lift so it may appear less than the stock cam.<br />
<br /><br /><br />

 

 

 

Awesome, thanks for all the answers everyone.

 

I do now however have another question...

 

If I'm to just press the pins into the rods using the ka pistons and z22 rods is there even a need for oiling the pins (by drilling the z22 rods) and/or can I just use the ka rods in place of the z22 rods and have floating pistons instead?

 

 

Just wanted to add its a pleasure to read your guys posts on here and 720 world. Clear concise and to the point, with pictures to boot! This is what I love about learning on internet forums. I get the facts of a manual plus experience. Thanks again.

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I do now however have another question...

 

If I'm to just press the pins into the rods using the ka pistons and z22 rods is there even a need for oiling the pins (by drilling the z22 rods) ....

 

 

The oil hole is strictly for fully floating pins. Pressing the Z22 rods on will simply make then non floating....

 

The KA rods are sized and have a bronze bushing that allows them to turn or rotate. All piston pins can rotate inside the pistons but most are press fit into the rods. Because neither the KA piston or rod actually holds the pin it is free to slide sideways and would hit the cylinder wall if there were not C clips inside the piston to prevent this. Just have the pins pressed into your Z22/L20B rods and it will act as a non floating type piston. The reason for the fully floating pins is that there is a reduction in friction and an increase in hp when using them.

 

 

 

 

....and/or can I just use the ka rods in place of the z22 rods and have floating pistons instead?

 

Z22 rods are 145.9mm long, so if you were to install the KA rods (that are 165mm long) the piston would be pushed up over 18.5mm above the block surface, and would long before that, hit the underside of the head.

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The oil hole is strictly for fully floating pins. Pressing the Z22 rods on will simply make then non floating....

 

 

 

Z22 rods are 145.9mm long, so if you were to install the KA rods (that are 165mm long) the piston would be pushed up over 18.5mm above the block surface, and would long before that, hit the underside of the head.

 

Lol that makes complete sense... I'm retarded.... I was reading another thread on 720 world ( http://720world.ning.com/forum/topics/question-about-ka-pistons-for) in which something similar was being discussed but I still didn't see an outright answer and there was talk of swapping rods between a ka and z24 but bearing size was diff..... Totally forgot the block height was diff between a z22 and z24 and so of course rod length is diff...

 

Thanks.

 

 

So essentially a pressed in pin is just kept in by being wedged? No clips? I think I need to bring up the difference between the truck ka pistons then vs the car ones to my machinist... For some reason he was thinking they wouldn't work cause they were lacking a spot to be clipped in (he specifically said cotter pin, not once have you guys mentioned a cotter pin, just c clip does this machinist know what he's taking about?)... Is there anything in a parts manual to notate the difference in ka24e pistons I should tell him to look for? Like a T or D21

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I keep on forgetting to ask if boring out the z22 will cause the same failure point seen on the z24 head gaskets? And once bored out to 89mm will a z24 head gasket be what I will need to use instead of the z22 or even a ka head gasket? Are the water jacket spots the same? Or will I need to make a custom one?

 

Thanks again

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Lol that makes complete sense... I'm retarded.... I was reading another thread on 720 world ( http://720world.ning...ka-pistons-for) in which something similar was being discussed but I still didn't see an outright answer and there was talk of swapping rods between a ka and z24 but bearing size was diff..... Totally forgot the block height was diff between a z22 and z24 and so of course rod length is diff...

 

Thanks.

 

 

So essentially a pressed in pin is just kept in by being wedged? No clips? I think I need to bring up the difference between the truck ka pistons then vs the car ones to my machinist... For some reason he was thinking they wouldn't work cause they were lacking a spot to be clipped in (he specifically said cotter pin, not once have you guys mentioned a cotter pin, just c clip does this machinist know what he's taking about?)... Is there anything in a parts manual to notate the difference in ka24e pistons I should tell him to look for? Like a T or D21

 

KA and Z24 rods will swap and the rod bearings are essentially the same as the L20B/Z20/Z22. The KA crank main bearings are totally different and a KA crank would not work in a Z24 block.

 

Piston pins will push into the pistons by hand at room temperature. Rods are heated to expand the hole in the end and quickly assembled to the piston and pressed in, locking them in place

 

 

I keep on forgetting to ask if boring out the z22 will cause the same failure point seen on the z24 head gaskets? And once bored out to 89mm will a z24 head gasket be what I will need to use instead of the z22 or even a ka head gasket? Are the water jacket spots the same? Or will I need to make a custom one?

 

Thanks again

 

Z22 blocks are less prone to gasket failure than the Z24s are. I've heard the Z24 use an inferior casting or something, I suspect that owners just need to re-torque the head bolts at every tune up like the manual says. The trouble is second, or third or even eighth owners have never read the manual and just continue to drive it until they blow and just scrap the truck. Do not use the KA head gasket the oil drain back hole at the back aligns with a coolant hole... use an 89mm Z24 gasket

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Thanks mike! That's exactly what I wanted to hear....

 

Now I know exactly what to be requesting from the machinist for pistons and where to correct him if he acts like it can't be done.

 

Time to just do some cam research and decide on what will best suit my application.

 

I was reading yet again another thread that sealik had linked earlier, there was talk of milling a ka head to fitter increase compression.... Think this is a good or bad idea? My only hesitation is I'd like for there to be plenty of head for future corrections if necessary (of course I never "plan" on distorting my head but ish happens) what could be removed, if any should, without creating valve clearance or timing chain issues? Will there be valve issues with just switching over to ka pistons for that matter, no milling included? I'm only decreasing the piston to valve distance by, what, 7.5mm? Right?

 

Sorry... I keep thinking of more crap....

 

Does the head have to be "bored" as well so that the face of the piston isn't combusting against a flat surface? shouldn't the 2 match? I just want to make sure I know exactly what to request/mention to the machinist and not leave it up to chance that he will get it done in his own (even if he should know).

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I have one last question. If the comp cam is used with the 420 lift and the shallower dished ka pistons, do you think I'll have any valve clearance issues?

 

 

No clue....did you talk to that guy I PMd you about?

Ken Turtles....seems to know his shit....about Z24s that is :D

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I was reading yet again another thread that sealik had linked earlier, there was talk of milling a ka head to fitter increase compression.... Think this is a good or bad idea? My only hesitation is I'd like for there to be plenty of head for future corrections if necessary (of course I never "plan" on distorting my head but ish happens) what could be removed, if any should, without creating valve clearance or timing chain issues? Will there be valve issues with just switching over to ka pistons for that matter, no milling included? I'm only decreasing the piston to valve distance by, what, 7.5mm? Right?

 

Now you're exploring using a 12 valve KA head? Not a good idea on a small Z20 motor It has a much larger combustion chamber and your compression would drop to 7.76. Also read below...

 

Do not use the KA head gasket the oil drain back hole at the back aligns with a coolant hole... use an 89mm Z24 gasket

 

The KA head would need to be welded up because of the oil drain back hole.

 

 

 

I have one last question. If the comp cam is used with the 420 lift and the shallower dished ka pistons, do you think I'll have any valve clearance issues?

 

Don't know. Place motor at TDC and a small amount of clay or plasticine on piston top. Set the head you want on in place without gasket but don't bolt down. Rotate cam with a wrench through one turn. Remove the clay and measure the thickness of the pinch area and add 1.2mm for a crushed gasket.

 

Keep in mind the intake valves are opening and the exhaust are closing at TDC. I don't think they are at full lift. Both are closed on the compression stroke at TDC.

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Sealik, I have read many of his posts since you sent me that link (thank you) and recently pmed him, just awaiting a response.

 

Now you're exploring using a 12 valve KA head? Not a good idea on a small Z20 motor It has a much larger combustion chamber and your compression would drop to 7.76. Also read below...

 

The KA head would need to be welded up because of the oil drain back hole.

 

Don't know. Place motor at TDC and a small amount of clay or plasticine on piston top. Set the head you want on in place without gasket but don't bolt down. Rotate cam with a wrench through one turn. Remove the clay and measure the thickness of the pinch area and add 1.2mm for a crushed gasket.

 

Keep in mind the intake valves are opening and the exhaust are closing at TDC. I don't think they are at full lift. Both are closed on the compression stroke at TDC.<br />

 

Sorry for the confusion....

 

I was just wondering if milling my ZHead would be beneficial in the same manner that was being discussed regarding aka head. I want to stick with the ZHead for visual/emissions inspections. I'm thinking in the end it would only lead to further clearance issues for the valves.....

 

In your guys honest opinions, do you think going to the ka piston will even be worthwhile? Its not going to cost me a penny more for the pistons themselves but might in custom configuration work and piston modifications.

 

I'm personally not going to have the chance to check for clearance as I'm bringing him my engine in long block form and getting it rebuilt and returned in a like, although working, manner.... Thus all the questions, otherwise if tinker and check myself but I need this done sooner then later..... 1350 ain't a bad price either especially with the 2 year warranty and reputation that preceded this shop upon recommendation of being able to build a motor that would last forever.

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