KA Dual Cam Head on Single Cam Block???

[rsmithdrift]

Is it possible or are their comaptability issues???

I"m asking for a friend... He needs to know ASAP and I searched and cant find anything like this... The bolts all seem to line up... so is it possible or do some of the ports not line up properly or will something interfere or what???

If it wont work please explain why...

[Kalypso]

doesn't line up, dont remember y exactly

ka-t.org they talk about this

[rsmithdrift]

so does anybody know why?? Is it the ports for the coolant maybe??

[chaosli]

head bolts are different size its smaller on the sohc block
also the you need a custom timing cover the dohc timing cover dosent bolt up

[breadbox]

Don't do it. not worth it. DOHC blocks aren't that hard to find.

[rsmithdrift]

Don't do it. not worth it. DOHC blocks aren't that hard to find.

Well like I said I'm not asking for myself... The reason I ask is a friend of mine just had a motor built at a shop by a guy that built and races a 240sx in SCCA competition and he rebuilds his engine constantly for racing purposes. Well the motor he had built is a 10:1 compression with wiseco pistons and rods DOHC KA and lightweight flywheel/pully's and honed/balanced crank cometic metal head gasket ARP studs... the works. All the head work was redone also so everything is brand new and ready to go.

Well he was driving it (slowly for break in purposes) the last couple days and suddenly it started getting hot. He let it cool down completely and noticed it was low on coolant so the mechanic told him to bring it back by the shop and they'd do a leak/preassure test on the cooling system. He leftfor the shop and within a minute it started running hot again... He let it cool back to normal and started going again and didn't get a block down the road and it overheated again. He started it after it cooled with the coolant cap off and it blew up on him (blew all the compression through the radiator indicating blown head gasket) and he checked the oil and sure enough it was full of coolant all of a sudden.

How the hell do you blow a less that 2 day old cometic head gasket??? So I then realised that the guy that built the engine said he used a SOHC block instead of the DOHC block it had in it and when I aked him how the head could fit on the head he said it bolted right up. I just gave him an blank look like how the hell... Apparently he swapped blocks with an SOHC block he had lying around in the shop so he could have the DOHC block overbored to match his race car engine so he could have a backup engine that's legal in SCCA competition. He claims everything is the same and bolts up perfectly fine the only difference being where the pully's and knock sensor line up, etc. So we are thinking that maybe a coolant port for the block doens't line up with the head properly and that's why it blew the gasket. He hasn't gone above 25% throttle or over 3k rpm since he got it yet. This just doesn't make sense... How do you blow a cometic metal head gasket in less than 200 miles of it being installed if everything lines up right??

[kyhunter89]

I've read on this site that you can run like that, and you have to either use a certain timing chain cover from one or the other. I'd bet the overheating problem lies elsewhere...

[fiznowler]

I would be pissed either way. If he was rebuilding your buddies motor if I were him I would want MY motor. Not just another motor he had laying around that was supposed to be the "same". Does it really matter if the sohc swap was the reason or not? If it has that few miles I would think the shop would stand behind thier work and make it right. That is just me though I would be super pissed if he switched blocks without saying anything.

[martins_240sx]

okay as far as the head goes...every thing lines up exactly the same...i know because on my single cam i use a cometic headgasket, cometic does not make a single cam gasket. you have to modify the timing area. all ports line up. as far as the blowing up a cometic. ive blown up one in less than 20 miles. granted if it is a stock engine it should have lasted longer. but if this guy did swap heads...which i dont think he did...the compression would be no where near stock. it would be around 10-1 iirc. so that would be the reason for the bad gasket. but one other thing is, if the timing cover is bolted up with no mods then this guy lied to you and he just messed something up.

[rsmithdrift]

okay as far as the head goes...every thing lines up exactly the same...i know because on my single cam i use a cometic headgasket, cometic does not make a single cam gasket. you have to modify the timing area. all ports line up. as far as the blowing up a cometic. ive blown up one in less than 20 miles. granted if it is a stock engine it should have lasted longer. but if this guy did swap heads...which i dont think he did...the compression would be no where near stock. it would be around 10-1 iirc. so that would be the reason for the bad gasket. but one other thing is, if the timing cover is bolted up with no mods then this guy lied to you and he just messed something up.

well it somehow bolted right up cause I even looked at it today (went by the shop on the way to work) and it's a SOHC block with a DOHC head. It looks stock like DOHC but you can tell cause of where the knock sensor is and where the pully's are on it. It's not the same exactly.

And I said he used WiseCo pistons and rods rings etc and it's supposed to be around 10:1 compression with this combination. The DOHC head is unmodified but everything is new in it. I watched the head get timed so I know it's the DOHC head that was origionally on the 93 engine.

It's normal to be able to blow a cometic that quick?? I thought cometic metal headgaskets were the ones MADE to handle 10:1 compression and were near impossible to blow up....

[zerepdivad]

pretty sure sohc ka's lack a knock sensor.

[Gabes13]

Everything should line up (coolant ports and head bolts) but you'll need the full head assembly, front timing cover, timing assembly, full intake manifold assembly and depending on whether or not the distributer has an internal coil then you'll need the ecu of the same year. And I believe the internal coil dizzy motors also look for a knock sensor and CAS. Not to mention the compression change like Martin said.

[martins_240sx]

i would love to see pictures of this said motor. and not some hey here it is pics...i want detailed pics showing us proof of your sohc block and dohc head and all these proofs that it is what you say it is...not trying to be a d!ck just want to see.

oh the cometic is very finiky. its all on the installation...but even if everything was good, you running that much compression can still cause a strong gasket to break. especially if your timing is not spot on. all it takes is one good detonation and bye bye it goes. when you get it changed check the gasket. if it detonated you will see a burn or bend at the cumbustion ring area. if its jacket leak then you will see a shinny streak from the hole. and i would also not be running stock torque specs. go like 10 ftlbs tighter.

[martins_240sx]

I think you are right...they look exactly the same in the front. the block does have tiny differences here and there but it is damn near identical...im very interested to see how the block looks underneath the cover...this leaves me almost begging i destroy my block so i can run the stroker kit on my sohc using the dohc block:)

[rsmithdrift]

I'm going down their today to check the compression of my motor.. I'll take the camera. Hopefully he's working on it and its out of the car already.

[Kalypso]

martin do you have a build thread for that motor in your sig?

( that single cam is looking quite tasty. )

[martins_240sx]

yes type in true pig build....im actually assembling it as we speak. so there will be new pics up

[martins_240sx]

oh and for rs...on the block exhaust side right under manifold it will say what block it is

[breadbox]

the differences in timing cover have to do with the external vs internal oil pump and the distributor. Then obviously the accessories are different on each, Thats why I say keep DOHC parts together and keep SOHC together. outside of motor parts everything is pretty swappable.

[rsmithdrift]

Just found out what happened... apparently the bottom radiator hose was clogged or something like that and the preassure it created blew out the top of the radiator making it look like compression blast from a blown gasket and the break in oil apparenlty just has a greenish color to it by nature. He gets conspiracy theorist crazy when anything goes wrong and assumes the worst... haha.

No engine damage done. Fixed cooling system and it runs perfectly again now.

Sry I couldn't take pictures the other day my mom left the camera at work so I couldn't take it with me... :/

[martins_240sx]

hmmmm....not so sure about your mechanic you have there....should have took all of 5 mins to determine it wasnt a head issue......

[rsmithdrift]

hmmmm....not so sure about your mechanic you have there....should have took all of 5 mins to determine it wasnt a head issue......

Well the mechanic did only take 5 minutes lol.... He had it at his shop for like 3 days and he only worked on it for like an hour lol. I wasn't their I was at work. My buddy dropped the car off their friday night and got it back yesterday... He basically just compression checked it and said it's not the head gasket then proceeded to flush the coolant system and found a clog is what I heard...

Like I said my friend is a conspiracy theorist so when it started overheating and blew coolant out with preassure he assumed it was because the gasket blew out and it was blowing the compression out the radiator. lol. I've just been going by what he told me on the phone the last few days. I haven't actually seen the car since thursday when he brought it by where I work. If I'd of looked at the oil I could have told him if it was a head gasket or not right off... But I can't be around to help him with his car all the time. I work 50 hours a week and am in the process of moving into an apartment on top of that.. very busey right now.

[martins_240sx]

ohhh okay..i see now. well good luck with your car and stay on track. i know how difficult it can be to find time to turn a wrench here and there. 16 hrs a day courtesy of the USMC makes things difficult for me everyday.