Jump to content
Sign in to follow this  
79gooser

3k-c rebuild advice

Recommended Posts

Hi all,

I'm working on a rebuild of my 3k-c with a few upgrades. I want to put a bigger cam in there, but with that I know that I will need to do a few other things including increased compression, stiffer valve springs, and a better flowing exhaust. As for valve springs I am open to any suggestions as to certain brands or companies to go with. The exhaust I can make myself. I have heard that you can get higher compression with a 3k-b head on the 3k-c block, but I do not know much about this. I like the idea of a new head because that means that I do not need to get mine machined, I am just not sure about the logistics. If I were to get a 3k-b head, would I use a 3k-b head gasket, or one for a 3k-c? Also, does anyone have a suggestion as to where I might get a gasket kit for the whole engine? I haven't been able to find many. Any rebuild advice in general would be nice. Sorry if these seem like silly questions, this is an unfamiliar engine to me, and I'm having troubles finding information and parts for it. I figure there are some pretty knowledgeable people on here and it would be greatly appreciated if some wisdom could be shared. Thanks in advance!

Goose

Share this post


Link to post
Share on other sites
Members dont see this ad

Hi Goose,

There are a few cam grinders in both aus and NZ that have a list of 3k profiles available, pending on your use and goals.

Heavy duty valve springs are a good idea, as your new re-ground cam will probably have more valve lift, and if you want to rev it will support high rpm operations.

 Increasing your compression ratio will definitely wake it up. Wether you work with decking your head or getting another, will end up with the same result. I would suggest at least 10:1 compression ratio.

Both vavle springs and head decking can be looked after by an engine machinist. While you are there, try getting the bores oversized to increase the capacity, as you can't beat cubes.

Genuine toyota gasket kits will be your best option, as aftermarket head gaskets, rear main seals and sump gaskets can cause issues.

This company has pistons etc

http://www.precisionintl.com/Engine.aspx?ID=1728&EID=13084

I have started a Facebook page on performance k series engines 

https://www.facebook.com/groups/231132903963672/requests/?notif_id=1520517331304944&notif_t=group_r2j&ref=notif

  • Upvote 1

Share this post


Link to post
Share on other sites

3 k-b engines were 10:1 compression from the factory. 50 years down the track, your best bet is to find the best condition head you can, and not get excited about whether it is a C or B head. Get it shaved, ported  matchported to the manifold etc. etc the rollaclub  wiki has some useful info too

https://www.rollaclub.com/wiki/index.php?title=Tech:Engine/K_Series/How_to_build_a_tough_K_motor

Share this post


Link to post
Share on other sites

Depending on the cam specs, try going at least 11:1 compression. For example: 270deg with 10.5mm valve lift needs 11:1 static compression to function properly. Kent cams have stiffer single valve springs to suit mild cams like the one I mentioned. Also decking the block will help with optimizing quench and getting the compression up without shaving the head to the point of collapsing in the water passages. Rally engines here in Finland have usually pistons protruding 0.5mm from the block deck surface.

Too many videos on youtube with angry cams and nothing done with compression... They sound like shit and won't go anywhere.

  • Upvote 1

Share this post


Link to post
Share on other sites

Depends... Basically it's the effect as shaving the head down. But when you get the cam reground, it has the opposite effect on pushrods. My experience is only with the dished piston head, but in my case original pushrods were ok. You can see how much the lobes are actually ground, when the base circle is almost flush with the cam core.

14505316.t.jpg

 

Share this post


Link to post
Share on other sites

I think it’s pretty safe to say that for your purposes, you wouldn’t need to go down that route. 

Its fascinating though

Share this post


Link to post
Share on other sites

There is heaps of adjustment in the rockers. I decked my head to go from stock 32ish cc to 26cc. Flat top pistons and cam with 11.5 mm lift. Used all stock gear

  • Upvote 1

Share this post


Link to post
Share on other sites

I don't know if this is the right place to ask, but I'm trying to buy parts from precision, and I'm having troubles getting everything together. The site seems confusing. I got a list and ordered the parts, but they emailed me saying that the sizes didn't match. You'll have to again pardon my lack of knowledge and helplessness, but can anyone help me figure out what this means?

Screenshot_20180604-200040.png

Share this post


Link to post
Share on other sites

You've asked for .040" over pistons, you will need to order .040" over rings, too. Similar for the mains/conrod.

Are you having help with this anywhere else?

Cheers - boingk

Share this post


Link to post
Share on other sites

Ah, I see now, thank you. I was under the impression I ordered factory spec parts. Guess I need to do a bit more research. And no, I'm not getting any other help, just trying to figure out what I can.

Share this post


Link to post
Share on other sites

I wouldn't order parts until you have the engine out of the car and micrometered the mains and bores to see what you need. Its useless buying maximum oversize pistons and bearings if you only need standard replacement items - or possibly nothing at all if your engine is in good condition.

If its in the car and running without issues I would get another engine to do a full-on rebuild, and depending on where you are in the world there are certainly a few options around.

Either way, do you know the condition of the engine at the moment? Check its oil pressure and compression. If these are within specifications then there is no point putting rings and bearings in it. A camshaft, valve springs and set of headers may be all you need to give it a bit of an edge.

 - boingk

 

Share this post


Link to post
Share on other sites

I appreciate the advice, but I've already got the engine apart. I fired it up one day and it sounded like a diesel so I tore it open to see what was wrong. Turns out I had cracked a piston and totally smoked the cam, so I'm getting a set of new pistons and rings, and I figured might as well get some new bearings and seals while I'm in there. Also leaning towards a little more compression and a bigger cam, but stock size intenals. At first glance I thought that the parts on the Precision site were factory spec, but I see I have more research and measuring to do.

Share this post


Link to post
Share on other sites

This is something you need to have done by someone who knows what they are doing.

Otherwise you are going to have a disaster.

By all means have a go at putting it all together (use a factory manual) but get the block, crank and rods assessed by an engine builder and let them order the correct size parts for you.

  • Upvote 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

×
×
  • Create New...