Building a hybrid KA

[PureInsanity]

I started on it a few weeks ago and its coming along. Stripped everything down to bare parts (valves out of the head, all BS off intake ETC) and started porting. I have ported out way more aluminum that I thought I would at first. The biggest amouts were just trying to match port everything together. Its actually shocking how far off the ports are...well were now.

I got the spacer made up already out of some .030 sheet I had around the shop. When I have the head surfaced Im sending the lower cover also to have the corresponding .030 taken off the lower so the spacer sits down below the head and I can use a complete head gasket rather than cutting off the front and siliconing it up. As well as sending the upper cover bolted to the head to be sure its a flush fit as well.

I hadnt REALLY looked at the cyl walls till tonite (been concentrating on the top end) and decided Ill yank the block out and get it bored while Im this far in.

Last nite I IMd Devious and he had some good info for me. One thing I was thinking about was removing the PCV fittings, right at the head, from the intake and having them tapped for foggers for future use, and he said he has seen that before which made me decide to go ahead and do it. Ill just add plugs for now and close them off till I decide to spray it.

I still have a few questions tho. Devious got disconnected, I went for a smoke and he had come back and logged back off again before I got back.

Will the SOHC ECU read the DOHC dist. if rewired? We talked injectors but didnt make it to the fuel pump...will it need to be upgraded? How about the fuel lines themselves, should they be rerun w/ larger hard lines?

Also since Ill be having the block bored, is there any other block that would be a better choice for a high compression motor? I have the SOHC block in the car now, which I kinda want to keep the older syle for better selection of oil pumps, a DOHC block, and an old Z24 block, (looks to have the same front cover/oil pump style) actually the complete motor still in a parts truck w/ a popped head. (used to have a few of those motors but they got scrapped by accident when we moved the shop to a new building a few yrs ago. )

Well this should cover it for now, I havent taken any before pics of the head and intake, but Ill be sure to get some finished ones before its reassembled. Ill have tons of questions when it comes to tweaking the ECU Im sure.

[TheOne]

i think you should use a DOHC block cause of the oil squirters to the pistons, should cool it a bit more for that giggle gas you want to run later on.you may want to upgrade the fuel pump for that also, and maybe the injectors too, but i don't think you need better fuel lines, people with ka-t's don't change'em unless they change to a top feed fuel rail, and even then i believe they keep the stock lines till the fuel filter.

as for the sohc ecu reading the dist, am not sure.

[deviousKA]

PureInsanity, really, its a toss up. The z24 block isnt going to offer you anything but between the sohc and dohc you can do it many different ways.

You could keep the sohc bottom end, even get the block machined and tapped for the oil squirters, and have a wider selection of oil pumps.

Or, The dohc which already has the squirters, no frontal mods, but with limited oem fitment oil pump options.

Thats a simple way of looking at it, using nissan parts. Both of the oem oiling system have their disadvantages as well, mainly drag. An external belt driven staged oil pump in either glorified wet sump or dry sump form would bet the best option, obviously.

Sohc oem system is fairly tempting, turbo, nissan comp, and nissan comp adjustable pumps are available, also bronze drive gears.

Id say bring both your sohc and dohc blocks to your machinist and have him give you a qoute to install the squirters on the sohc, since you already have all the goods. Toyota oil squirters also work well.

BTW. that z24 block would be handy to build a wild single cam

[deviousKA]

Forgot about the ecu ?

I do not know for sure that the early ka24de distributor will work with sohc system, but, it has worked on the u12 stanza. I forgot who it was but some dude was on here that had the 1993? altima headswap on his stanza, which had sohc originally. He said the ka24de distributor worked perfectly with the sohc ecu and wiring. Double check the wiring/colors in both fsm, is the plug the same? I dont have any ka24de cars

[SSS]

FWD KA24E and KA24DE distributors output an identical signal.

Do you really need oil squirters to add further aerodynamic drag to the reciprocating assembly? Just have the pistons thermal coated.

[PureInsanity]

Thanx everyone, thats some good info and some good things to think about.

I am torn as to which way to go block wise. I already made the spacer, but that didnt take long, 30 min tops from looking at the 2 gaskets, template in hand, to trimmed, drilled and fit steel ready to use. Having the whole DE would be cool because it would appear to be a stocker. The oil pump availability issue keeps me thinking SOHC block. My SOHC block needs to be bored and the DOHC does not, just a hone and rings and ready to go. No ring ridge at all, just throw in the SOHC pistons. I already have a complete new lower end as long as the lower end interchanges, crank, bearings ETC. HMMM Ill be betting the crank wont, but the DOHC was pulled because it was supposed to have a blown head that it didnt once I tore it down. Its a core motor I got from some kid whose 240 I work on that did the swap himself...he bought the car thinking it was popped and he never tried to start it, just swapped motors. Then brought it to me to fix everything that was messed up w/ the swap. LOL! Anyhow so the crank should be good but Im guessing they are different at the front snout.

SSS if your SURE about the dist, I am 99.9% sold on using the DOHC block w/ the SOHC pistons. Between devious remembering the stanza swap and your saying it will Im all about keeping it looking as close to stock as possible. Now Ill have to get the lower front cover welded since I missed a bolt when I removed the head and broke off an ear. WHOOPS!

Injectors, Devious said 300ZX injectors should be a drop in. Line size Ill leave alone, and the pump is currently running, but may need to be replaced, Ill check the pressure when I get this beast fired off and see what I should do. BUT what are some good pumps?

Well for a half *** update, tonite I finished ALL the rough porting/ rough polish and have only to final polish now. Ill bet I have close to 8 hrs in the head and intakes so far. The final polish shouldnt take long...I hope anyway, Im tired of wearing aluminum flakes. LOL!

My dad, (who I work for) thinks Im nuts. Hes built some bad *** cars in the past, and was tweaking imports way back in the early 70s...(mostly European cars, he had an old school Mini that was FAST...I remeber that car a BMW 325 he and I did for my brother for graduation and a hand full of GTOs, 442s and Mustangs way back in the day and some customer cars he worked over...my personal favorite is the one I just finished a week ago, a 550 horse stroker small block Chevrolet ......HMMM Im way off topic here...anyhow) he isnt so sure about how much Ive taken out of the ports. But all Ive done is clean them up, remove any "bumps" in the ports and bowls, and match port it. But MAN is there a lot of alum. shavings at the bench Im working at.

BTW the reason Im trying to keep the SOHC ECU is Ive been told they are easier to reprogram via lap top and a simple program. The only wires I should have to splice are the injector wires and now possibly the dist wires. I know the connectors are different, Ill break out the wiring books and check it all out. Pretty much the only things other than gauges that will be hooked back up are the O2, TPS, injectors and dist...that I can think of off the top of my head. ALL the other stuff tacked onto the intake is gone.

Looks like Ill start breaking down the DOHC block and taking a good look at it.

[oneline180]

sounds like you got everything taken care of. i hope to see pics once its done and running.

[PureInsanity]

Well I hope I got it under control. LOL! By going w/ the DOHC block itll save me some coin on pistons and a bore on the other block. The DOHC block is in great shape. If all works out right all I should have left now is the 3 angle valve job and a head surface...all other money has been spent.

The biggest problem is the 240 is a part time project. I give it hell for a few days then fizzle out for a few days. LOL! It all depends on what condition my mud truck is in.

If I can ever find the batteries to my digital camera, Ill grab some pics of the head and intakes. I guess I could just buy batteries. LOL! I cant find the disk to my new camera so I cant load the pics off the new one to this computer. But ist all loaded to my other computer that I cant use because it has no modem (just an ethernet card for cable or DSL) and Im stuck in dial up hell where we live now...no high speed at all in this area, no cable, no DSL no nuttin. Hell theres barely electric out here. LMAO! But it SURE is nice out here.

[SSS]

SSS if your SURE about the dist, I am 99.9% sold on using the DOHC block w/ the SOHC pistons. Between devious remembering the stanza swap and your saying it will Im all about keeping it looking as close to stock as possible. BTW the reason Im trying to keep the SOHC ECU is Ive been told they are easier to reprogram via lap top and a simple program. The only wires I should have to splice are the injector wires and now possibly the dist wires. I know the connectors are different, Ill break out the wiring books and check it all out. Pretty much the only things other than gauges that will be hooked back up are the O2, TPS, injectors and dist...that I can think of off the top of my head. ALL the other stuff tacked onto the intake is gone.

I am 99.9% sure. If in doubt though, run the output of each through an oscilloscope.The guy with the stanza that did it used the SOHC ecu and the DOHC distributor, he only had to re-wire the injector plugs and the distributor plug.

[PureInsanity]

Sounds good to me. What I planned to do was hook the battery back up and put a noid into one of the injector leads and spin the dist to see if it lites up the noid.

Well I am one happy camper tonite. I broke down the DOHC block completely, honed the cylinders and they came up fine, no ring ridge, scoring or anything. I mic'd the cyl of both the DOHC and the SOHC blocks and its a standard bore so the flat top pistons will work. The crank is standard/standard, rods/mains, no scoring or anything on it also and the chain giudes even look new. So going this route will save me some money. I especially like the main girdle...very beefy looking. I may spring for the full ARP stud set.

I rough cleaned the block ,which was pretty decent inside anyhow, good enough to throw the bare block into the wash tank at work so I can clean it up real good. Basicly got the oil buildup and sand off the outside. Im gettin pretty stoked about this project again. LOL!

Anyone want to speculate what it should be putting out? Im curious and guessing it should be over 200 anyhow w/out the spray. (it damn well better be. LOL!) I plan to get it dynoed when its done and broke in but Im kinda wondering what it should be.

OH! I just thought of something, w/ this set up can I run different cams or am I stuck w/ the stock ones? Id like to atleast swap in Altima cams. If someone knows it would just save me from having to check the piston to valve clearances. Ill have to check the books at work tommorow and see what the Altima exhaust cams lift are compared to the 240 cams. Hopefully its just a better duration cam w/ no more lift, but I am doubting it. HMMMMM I wonder how much it would be to fly cut the pistons.....

[deviousKA]

Not something i usually post, but try searching this ka forum. This forum has much more (the most) technical information about NA ka24 compared to any other. You will most likely find all the information you are after, or at least reference.

I just dug this up, qouting myself here

"The ka24de does have limited valve to piston clearance. How long of duration cams and how much lift are you planning to run? For instance, a "hot" oem cam setup 248/248 at base setting (with cam gears) combined with early 89 ka24e pistons (.020" over the 34mm compression distance) yeilds less than .015" exhaust valve clearance. That is with a fresh timing chain assembly, any slack in chain retarding the cam timing will obviously provide less clearance.

This is very slim on that particular setup (to slim), but using different pistons can give a lot more room. Late 89-90 240sx or stanza ka24e pistons are .040" lower in the area that the exhaust valves come close (.020" lower than the 34mm compression distance). I would suggest an exhaust valve to piston clearance of at least .030".

As with any custom high compression and cam setup you will want to verify with your engine assembled with one of the piston tops covered in .070" or so worth of modeling clay. This adds another step to the assembly process but is a must. If you find that clearance is minimal after all of your desired components, best course of action is advancing the exhaust cam with an adjustable cam gear. If that does not do the trick with just a minor degree adjustment, you will need to flycut your piston tops. Custom pistons can be ordered/designed with valve relief/flycut, or the pistons added dome volume can be positioned away or around the valves. "

Oh, and the altima cams being 248 duration is not confirmed, it is a myth as :orion: has pointed out probably 3 or 4 times in the last week alone. Although, when in doubt always check for yourself.

This post may sound harsh although not the intent.

Your build sounds like its coming along nicely.

[hannibal]

...you guys rock...

[PureInsanity]

AHHHH but I did search Sensai. I just suck at searches for some reason. I did come up w/ a little info but not enuff to have made a positive conclusion.

Maybe I should just search your name and cut thru the misc info I dont need, since if you havent said it before you know it.

OK from what I have gathered, I have the lower comp motor that I am taking the pistons from. No I have not yet run the block #s but the quick visual clue of the AIT matches up w/ what I have. Late 89 w/ the AIT in the air box. (It is the AIT right....I cant remember, but thats a typical AIT location.)

Most likely I will be claying the pistons to be sure. Ill be doing it w/ no head gasket, but I mic'd 2 old ones and they are both .045 compressed thickness, so Ill leave the head bolts loose so the head can rise up if need be and add .045 to my figures.

Well tonite I "for real" honed the cylinders, first run was just a quick clean up to check the condition of the block. The cylinders look great now and I thoroughly cleaned the block in and out in the wash tank by hand. Sprayed the cyl. all down w/ some WD to keep them from rusting over the long weekend ( ) and Ill be painting it next week. Basic black on the block so it just looks like a nuttin special rebuild.

I forgot to look up the cam specs today, but I did get some other stuff done.

[PureInsanity]

Its been a few weeks and not much has changed. Been busy w/ my truck getting it ready for the next big mud bog event. Incab snorkle, water proof sealed box for MSD stuff I just got, removing heat and A/C box.

But anyhow, I hope to be back at it again soon. And I STILL havent clicked off any pics of my port work yet.

I do have a quick question though. Do I have to swap the SOHC rods for the DOHC rods when installing them into the DOHC block or are they the same? Its really not much hybrid anymore, just SOHC pistons in the DOHC motor at this point. After seeing that main girdle, I really wanted to use the DOHC even tho I have the filler plate made and all for the SOHC block.

[deviousKA]

Sohc/dohc 240sx rods are the same and you can you either. Only rods that are different are the ka24 truck rods, the pins are pressed instead of full float. If your using truck pistons you would have to use the rods as well, in other words dont use truck pistons.

have fun!