KAZ24 build thread / compression questions / cam / header / DONE!!

[HRH]

F that BMW piston idea. I checked at work and the boss laughed, said get a new car. $1000 for a set of those pistons through altrom. No picture either. So regardless of if they would work (probably not) we won't be getting those. Going down to play with plumber's putty on the head now. May just go that route.

[datzenmike]

Don't need spool gun. Mklotz suggested keeping the cable as straight as possible, maybe set welder up on table, pull cable straight out from it to work area. Use thickest wire you can so it's stiffer and won't kink. Aliminum tends to rub off on inside cable so best to keep one cable just for aluminum. Probably best with shield gas. Best results with power turned way up. Go to scrap yard for some scrap pieces and practice. Set head in jig to keep level and fill with water.... Do-able.

[HRH]

Ran into another problem. The head is actually designed well for flow, and I mocked it up with 9cc less material with some plumber's putty. I don't think it's a good idea. I think a better piston is a better idea. Apparently one of my buddies is a dealer for Arias, so I could get a set down to $500, but still we're on a methhead budget here. Hell, half thinking of putting on the Z24 head and running a carb! Just kidding. But I wouldn't mind using the Z24 head, if I could adapt the KA EFI stuff to it easily. Like I said, it's not going to be a high-rpm motor, we're looking for torque and mileage.

[datzenmike]

I've lost track...... Z24 with 2cc dish KA pistons and KA24E head? Correct?

[HRH]

Yes, that is what I want to do, but with the most compression as possible. Maybe I should just save up and get some 10.7:1 Arias pistons. Think I can run pump gas with that? :)

[datzenmike]

Kicking around so many things I had a senior's moment.

 

Z24 stock bore with 2cc dished KA24E pistons and KA24E head is 9.03 compression.

 

If you weld in just 5cc you will have over 9.6 compression.

[HRH]

Yeah, but look at the shape of the KA head. I'm fairly convinced that any welding to take up material will yield a negative flow result. Think maybe I'll go back to my original idea, mock up the chain, and see if I can weasel .030 off the head and take up the slack. That would at least get me 9.1 ish, which I suppose would work.

 

The problem I'm running into is unlike the L, where you can mix and match part cheaply to make good combos, the KA/Z24 doesn't really have that option. The only other option I haven't checked out is the QR25DE piston, which is 89mm, and looks as if it's nearly a flattop, but I can't find any good pictures. Plus, the KA piston from a wide angle view looks like it's not dished either, but it is.

 

Why couldn't we just have had the 2.5l diesel option in the US?! Fucking bullshit.

[datzenmike]

Z24 stock bore with 2cc dished KA24E pistons and KA24E head is 9.03 compression.

 

 

 

I'm saying you have 9 compression stock, (with KA pistons) right now...... without milling the head.

[HRH]

Wait a minute, can't be. The Z24/KA blocks are identical in bore and height. Regardless of which block I'm using, if I'm using the KA pistons with the KA head, it's still 8.6:1.

[HRH]

You know what, I think I have a plan. I'm ditching the high-compression crap and just building the Z24 bottom end and KA head to stock specs. Then, I'm going to save up for a megasquirt and dig the turbo I have squirreled away out of storage. Grabbed one off a Dodge/Mitsu 2.2 liter LeBaron back in the day. Good candidate for rebuilding. That will solve the pussy 8.6:1 compression problem! Probably be a while before I do that though. I'm just thinking I'd rather get the motor out and a new one in asap, and worry about building a better motor for something else. Better yet, I might be able to find a supercharger to fit up to it. Hmmmmm.

 

So the verdict of this thread is if you want high compression in an NA KA, you better pony up some dough for the pistons and a good cam. Otherwise it's a waste of time and money.

[datzenmike]

Two pages of kickin ideas and I got lost. Yes found my error, I used your head cc number of 62cc. (maybe that head is milled?) I got 65cc from KAT.org and stock KA-E compression works out to 8.6 using that number. Oh yeah the KA dish is 2.8cc not 2cc so I was out almost 4cc. Funny what a few cc's will do.

[HRH]

I think they must take the head gasket into account or something. With .030 thick gasket, that would make another 3 ccs. I measured it out with a syringe, not much error. Unless they meant the DOHC? Anyway, yeah, I've beat this motor option to death. Have half a mind to use a 20B block so I could use flat tops like I did in the 510, but then they'd be so much smaller at 85ishmm vs. 89. Damn puny. Still would like to see a set of QR25 pistons, but chances are the pin isn't in the correct location anyway. Then we start on custom rods which are just as much as custom pistons.

[HRH]

Okay, so I've been playing around with this motor still. Disregard the previous posts regarding milling not a good idea. I just dicked around with it and set it up in the basement. .030 is doable with minimal extra chain slack. It should be able to be taken out without getting the chain too close to the tension side. That will get me close to 9.2:1, which is the same as if I had the 240sx pistons to begin with. So that's good. .060 is an awful lot, pretty sure that's going to cause excessive chain slack and cam retardation problems.

With .030, it's going to retard the cam timing 10.8 degrees if my math is correct. 360*.030 is what I used. Seems to make sense to me, Datzenmike, correct me if I'm wrong. The way I figured is the relation on the tension side stays the same, the slack side scoots in and rotates the gear counter clockwise .030 which retards the cam timing.

So then we can make another hole to account for that. There may already be one at 11 or 12 degrees retarded on the Nismo cam gear copy, can't remember. Anyway, here's some pictures:

[datzenmike]

Matt chain slack = cam advance. I know sounds wrong but it is. The tension side is always tight. Imagine the cam and crank at TDC on a normal engine. Now imagine the head shaved 0.030" and it plops down on the gasket closer to the block by 0.030" and adding 0.030" of slack (on both sides) The crank now has to turn slightly ahead to remove the slack and is now ahead or advanced relative to the cam. Simple right???? :lol:

[HRH]

Hmmmm, I can't see it. The right side with the straight guide should stay the same, yet, so moving it down .030 would rotate the cam counter clockwise, while the tensioner picks up the extra slack. Since the motor spins clockwise, that means the cam would be further away from the original point, SHIT, yes, which would advance the cam, not retard it! Ha, was thinking bass ackwards. Okay.

 

What about that math on the amount of degrees? I keep thinking I'm missing something.

 

{EDIT 6-18-11}

 

Was kicking this idea around for the past few days. Cutting off the head retards the cam. Reason being is the tension side stays the same, the slack side (with tensioner) is the only side that can pick up the chain slack from the .030 clearance of head. Thus, cam gear rotates counter-clockwise, and if this is at TDC, then the cam lobes will be further away and will come down after TDC, thus retarding the cam.

 

Consequently, the fix is to advance the cam via the #2 or #3 hole. I had it on #2 to begin with and mileage wasn't that great, though it had plenty of torque and I drove it to Canby that way with no issues. However, on #3, the truck still has plenty of power, but it definitely shifted the powerband up. 3500 rpm and above has excellent pull now. The other good thing is that lessens the hp at lower rpm and lets you take advantage of the torque. As a result, the latest mileage was 22.26 vs 20.5 average on Canby 2011 trip.

 

So if you chop a bunch off the KA head on this combo, use #3 hole.

[datzenmike]

Each tooth is 9 degrees if that helps. What's the distance from tooth to tooth? That distance is 9 degrees so 0.060 would be something like 3? degrees.

[HRH]

Okay, think I figured it out. The gear is 4.94 inches in diameter. 360 degrees divided by 4.94 = 72.87 degrees/inch. 72.87*.030" = 2.18 degrees.

 

I think this is correct. Need to run it by a math major or find a formula online. The only thing it doesn't take into account is the circumference of the gear, and the fact that it's rotating to the left, but I think that doesn't matter as it's technically just moving downwards. Any math majors feel free to correct me. I'll dig around on this more later.

[datzenmike]

4.94" diameter solve for circumference. Pi x R squared

 

4.94 / 2 = 2.47 x 2.47 = 6.1 x pi (3.14) = 19.15" around the outside of the sprocket.

 

How many 0.030 " are there in 19.15"... 19.15 / 0.030 = 638.33333

 

360 / 638.333 = .5637 degrees for every 0.030" removed from head

 

 

 

As a check ... there are 40 teeth on the sprocket. so 360 / 40 = 9 degrees between teeth (as I stated earlier) if 0.030" = .5637 degrees then 9 / .5637 = 15.96 x 0.030" = 0.47" between teeth. Someone measure the tooth to tooth distance. If about 1/2 " then I must be close.

 

As I see it shaving the head has almost negligible effect on cam timing but a huge effect on slack.

 

 

Matt not saying I'm right but would love to discuss this as I never ever use math outside of school. That is until ratsun. If my teacher had taught us using cylinder volume and compression ratios it would have been way different. :lol:

[HRH]

Haha, I did that same calculation you posted up as well, just thought it seemed a little TOO low of a change. But perhaps not. I happen to have a cam gear here at NAPA, I'm going to go pull it and check!

 

I completely agree, I never liked math, wasn't ever really good at it, but it's very necessary in finding out motor problems or differential gearing, etc. If they would have presented it that way in school, I'll bet I would have worked harder at understanding mathematics!

[HRH]

Okay I have the cam gear on the counter, and yes, it does appear that .5 of a degree is correct. However, the tooth distance is not, but I'm measuring point to point. The outside of the middle of the teeth is however at .47 roughly.

 

So I think we have hit the nail on the head. I'm betting that last calculation involving the circumference is correct, but I'll still look when I get a chance and see if I can find an exact formula. I should by a cam book I saw in the Z Motorsports catalog. All about degreeing in cams, etc. That's Z Motorsports in California. I bought lash pads from them at one time.

 

So for only half a degree, I may not have to do anything to the cam. In fact, half a degree advanced might actually work to my advantage, kind of like when you move the intake and exhaust cams slightly on the 240 DOHC KA, it opens it up and is a free performance gain. Not huge, but still free hp.

[HRH]

Okay, so I finished tweaking the chain guide rail, reamed out the bottom hole a bit, should be good for final assembly. Then I took everything off to take the crank back out so I can go over it with steel wool. I was stupid enough to store it, but not coat it with WD40 or assembly lube, so little itty bitty rust spots formed on the nicely polished surfaces. Basically just the condensation in the bag and the basement.

Anyway, have some fine steel wool and I'll be cleaning that tonight. When I took the crank out, I noticed some little scuffs on the bearings. Doesn't look bad too me, I think they'll be fine, as it should just be wearing through the coating, but I thought I'd throw up the pictures and get some input. The last ones I put together I never had the crank out again, so I didn't get to see anything like this. And that motor is in the race car and I'm sure it's bearings are fine with the way I abuse it, otherwise I would have thrown something through the block already.

There has been some minimal turning of the crank while dicking with the chain, but not much. Had a good coating of assembly lube on them. I'm pretty sure it just ate a little through the protective bearing coating, but it's just down to some tin, not to the copper below. Anyway, if anyone thinks that's bad, let me know. I think it's probably fine, the crank was trued, bearings are new, block was inspected, crank is from the same block, etc. There isn't any depth to the scuffs.

[datzenmike]

Looks fine. Was it torqued down?Underside of bearing clean?

[HRH]

Yeah, it was torqued down, bearing looks fine, didn't yank it out of the block yet but check it carefully before putting the shell in. On a side note, does anyone know how tedious it is to polish a crank by hand with fine steel wool? Fuck me, spent 30 minutes on it. Going to go blow it out really well in the garage now.

[HRH]

Well well, found some unpleasantness. Starting going nuts on the top of the block, getting it blocked down to clean off the old grime and see if I could get the scratches out. Got almost all the scratches out, decided to take it back to the machine shop and have them clearance the block EVER SO SLIGHTLY. They mentioned it when I had it bored, at the time I thought it was going to go together quicker.

 

So then I saw the inevitable issues that hadn't been there until I shaved off some material. Cracks, very very slight, but cracks nonetheless in between the water journals, heading towards the head bolt holes. I *might* be able to get rid of them with the block clearance, as I can't quite tell if they're just cracks or fissures. Think I'm going to call the Datsun guru tomorrow and see if he can't weld a bead on those spots and then I'll have it cleaned/clearanced and not have to worry about it. Rather annoying. And don't say the Z24 is prone to cracks. All the L/Z blocks are prone to cracks. I have a feeling a 26 year old block will have those issues, especially since the water jacket is fairly open there, with the two other teardrops next to the head bolt holes. These cracks actually aren't a problem to block robustness unless a full race block. However, I don't like cracks. (My machinist confirmed that.)

 

Anyway, we'll see if we can't rectify this rather cheaply and quickly with some welding. I really wish Nissan would have just optioned the hardbody with the turbo diesel stateside, and then I'd have all the power I needed and a motor that would last 500,000 or more. :(

[HRH]

Here's some pictures of the welds before I cleaned them the rest of the way and had the block surfaced. These cracks really aren't of concern, I just don't like cracks so figured while it was out, might as well fix them. (Read Datzenmike's post in the cracked block thread in general)