change just the sohc to dohc on sohc block

[240SXREX]

can you change just the heads on the sohc to dohc without removing the block? Probably have to change the whole timing chain assembly but surely you wouldn't have to change anything else if heads match up?:2f2f: please help.

[Killa_D]

wow just google it before asking this question. Also just to answer your question no it wont work because most of the oil and water hole dont match the ones off the head.

[projectRDM]

Asking this proves you've never seen either engine.

The oil pump, distributor, and other accessories are completely different. The timing covers are nowhere near the same. The block passages aren't even remotely close. Just looking at them would tell you it's nowhere near possible without a ton of wasted machine work and fabrication.

[Brew]

Quite possibly actually, my buddy did it. Ran it off SOHC electronics with a block off plate for the DOHC distributor. Used the SOHC lower timing cover and DOHC upper timing cover with a flat steel plate to cover the hole that's left between the two.

I can't remember exactly which parts of the timing kit he used from either engine, but it was a mix-match of the two and some trimming was involved on the guides.

That being said, it's a waste of time as he's now building a full DOHC. After a few months the hybrid blew up and we believe what happened was the pistons hit the cylinder head, lifted it and caused the head gasket to blow out... not sure why though.

It only had the later SOHC dished pistons, not the flat tops and it went pretty good.

[Killa_D]

Quite possibly actually, my buddy did it. Ran it off SOHC electronics with a block off plate for the DOHC distributor. Used the SOHC lower timing cover and DOHC upper timing cover with a flat steel plate to cover the hole that's left between the two.

I can't remember exactly which parts of the timing kit he used from either engine, but it was a mix-match of the two and some trimming was involved on the guides.

That being said, it's a waste of time as he's now building a full DOHC. After a few months the hybrid blew up and we believe what happened was the pistons hit the cylinder head, lifted it and caused the head gasket to blow out... not sure why though.

It only had the later SOHC dished pistons, not the flat tops and it went pretty good.
how is that even possible the oil/water galleries are no where close to matching, your story just doesn't make any sense.

[Brew]

how is that even possible the oil/water galleries are no where close to matching, your story just doesn't make any sense.
I'd have to ask him, I don't recall him saying anything about problems with them lining up though. I'll post back when I have some more info.

[Killa_D]

I'd have to ask him, I don't recall him saying anything about problems with them lining up though. I'll post back when I have some more info.
trust me i have compared both block and yeah not even close in matching.

[Brew]

Well trust me, he had a DOHC head running fine on a SOHC block for months, haha.

[brian3676]

Well trust me, he had a DOHC head running fine on a SOHC block for months, haha.

Sure it did not just have SOHC pistons maybe?

[Brew]

100% Positive.

[Biggamehit]

Quite possibly actually, my buddy did it. Ran it off SOHC electronics with a block off plate for the DOHC distributor. Used the SOHC lower timing cover and DOHC upper timing cover with a flat steel plate to cover the hole that's left between the two.

I can't remember exactly which parts of the timing kit he used from either engine, but it was a mix-match of the two and some trimming was involved on the guides.

That being said, it's a waste of time as he's now building a full DOHC. After a few months the hybrid blew up and we believe what happened was the pistons hit the cylinder head, lifted it and caused the head gasket to blow out... not sure why though.

It only had the later SOHC dished pistons, not the flat tops and it went pretty good.

http://memegenerator.net/Instances/369/Cool-Dog--COOL-STORY-BRO.jpg

[Brew]

Found his old thread from another forum. From July '07, since it's so old some of the pictures don't work anymore. I'll post them up if he still has them somewhere.

I guess i got bored, and figured I'd try and build my first motor, haha.
I thought about trying the supercharger route but decided to cheap out go the high compression route.
I used the 8.5:1 pistons with the dohc head, which my understanding is supposed to result in 11.1:1 cr.
I had to modify lower timing chain tensioner from the sohc to fit, the dohc tensioner won't work with the lower timing cover.
I also had to modify the lower tensioner guide from the sohc to fit.
Brendan and I started the motor up few hours ago, and aside from my base timing being a bit off, it ran great. It even idled beautifully.
Thanks to those to helped out, especially Brendan who helped greatly with with actual swap, and Graham who helped with getting a bunch of the parts.

I'm going to fix time timing tomorrow though, I don't feel like pulling the oil pump off tonight :S.

The block I started with.
http://img297.imageshack.us/img297/913/dsc02457ax6.th.jpg (http://img297.imageshack.us/my.php?image=dsc02457ax6.jpg)

The cylinder head I used after coming back from the machine shop for cleaning and decking.
http://img146.imageshack.us/img146/2914/dsc02484oz9.th.jpg (http://img146.imageshack.us/my.php?image=dsc02484oz9.jpg)

http://img146.imageshack.us/img146/1828/dsc02487wk7.th.jpg (http://img146.imageshack.us/my.php?image=dsc02487wk7.jpg)

The tensioner and guide modified.
http://img46.imageshack.us/img46/6606/dsc02495sh2.th.jpg (http://img46.imageshack.us/my.php?image=dsc02495sh2.jpg)

The old and the new.
http://img176.imageshack.us/img176/1245/dsc02500dp7.th.jpg (http://img176.imageshack.us/my.php?image=dsc02500dp7.jpg)

Just after being started

[rioredstang]

You guys are way off. I have a sohc block in my race car right now. To put a dohc head on a sohc block you need every thing off a dohc motor. Oil pan, timing covers, timing chains and guides, tensioner, water pump, distrubutor. There are (2) oil passages in the block, one is for pickup tube, the other is for oil pressure to the filter. This passage way lines up fine. I filled the other to prevent any leaks.

I had blown a motor up and needed one in a hurry. Someone gave me this bottom end to get it out of their way. I transferred all my parts to the sohc block. No special machining. I did check piston to valve clearance to make sure they did not hit. I think the higher compression is the only thing that is worth the swap.
I do not think it is a good choice to do since you will need so many parts from a de motor. I think you can buy a complete de motor for less than what it would cost to do the swap.
BUT IT CAN BE DONE.

[Brew]

So... where are the haters now?

[prodigy212718]

it can definitely be done, someone on nico had one running awhile ago. the dohc head on the sohc block raises the compression ratio to 11.5 or 12 iirc. i used sohc pistons in my old de to have the same effect and promptly blew the stock hg :bash: within the first couple thousand miles.

[slim_240]

just out of curiosity, why would you want to run a SOHC block? too lazy to swap the complete motor out?

[Walperstyle]

Yeah old balls up there is right. It can work. Wow you guys.

Might also want to chime in that changing heads over might want to also change the ECU and a few other things too. All depends on what the plan is.

Might also want to look into degreeing cams too perhaps, and make sure you know where TDC is. Search on ka-t.org but you are totally better off pulling the whole thing if you can.

[240SXREX]

Just curious to see if it can be done. I appreiciate everyones input. I heard that the SOHC block had more compression but I took some thought and research and yes it is cheaper to buy ka24de motor complete. Thanks guys. 240sxrex