4K Engine Build (First time building an engine)

[Thomas Dillon]

Hi Team, 

 

So I've had a few Kp's in the past and have done pretty much everything with them except for opening up the motor an attempting a rebuild. I Decided recently that I wouldn't mind trying to build a hot wee 4k in the shed through winter and as natural progression follows, finding a kp rolling body to dump it in when the opportunity presents itself. 

 

We're not going for a crazy build here, this is an opportunity for me to tinker in the shed and try my hand at building an engine from the bottom up on the work bench. Street driven, peppi town driving and passing a few mazda demios on the highway haha. 

 

Basic run down of the build as I see it rolling out: Feel free to interject 

1. Completely tear down the engine
2. Send the head & block off to be acid washed/cleaned 
3. Head skimmed 
4. Block resurfaced/cleaned up
5. Honed/bored out 40thou for acl pistons?

Build spec: 

1. Pistons 
2. Mild cam 270 Deg?
3. Main bearings 
4. Frost plugs 
5. Head gasket 
6. Timing chain 
7. Valve spring set
8. webber 32/36 downdraught
9. lightened fly 
10. Extractors
11. Electronic dizzy 

My Questions: 

1. When it comes skimming heads, resurfacing blocks and the thickness of the head gasket... My knowledge begins to disappear. Remember, we're ultimately building this in the shed for 1. Me to learn 2. to have a bit of fun 3. to not break the bank. But with that in mind I'm happy to spend money where necessary as I want to make a good solid job of it. Basically, my question is this.. Should I be skimming to make higher compression or should I just get the head & block resurfaced so we can slap it back together. If the answer is skim for higher compression, what else needs to be considered when upping the comp? when we start talking about measuring cc's and all that jazz I'm all out of ideas. 
2. Should I send my factory cam away for a regrind or go with something aftermarket? 
3. Valve springs.. Kelford performance valve springs? 
4. Balancing the engine, Is it necessary? 
5. OEM Headgasket or go with a metal head gasket? 

 

Thank you for taking the time to read and help out, I have done my research through various forums but I can't seem to find a dumbed down answer for my application. 

I plan on picking the motor up this week and firing into the methodical and well organised tear down. 

 

 

Edited May 5, 2024 by Thomas Dillon
Wasn't bloody finished, sausage fingers posted it by mistake

[Banjo]

Hi Thomas,

                   Welcome aboard, & plenty of people on here, that would be only too willing, to offer you advice, when necessary.  

If you are working to a budget, then I would suggest, that once you get the engine home; that You strip it gradually, & tag everything, so that when you put it back together; in months to come; & that everything is in plastic bags or bottles, clearly marked; particularly nuts & bolts.

Once it is completely stripped, you will be physically able tp inspect things like bores & rings, & big end & main bearing slippers etc.  If your 4K happens to be a 4K-U model, You will be in luck; as that variation of the 4K; put out more horsepower, than the regular 4K-C, which had a lot of California compliance gear on it. (hence the "C")

Once you've inspected everything, you'll have a much better idea, of what needs to be done, as a minimum.  Then if you budget allows, you can tackle other items like cam grind, performance valve strings, & maybe working the head.  Greatest issue in trying to "get more power", from a K Series motor was the head design. Not being cross-flow doesn't help, but the intake & exhaust passages were pretty ordinary, & the engine can be made to perform much better, with port & polish, & removing lips etc, that reduce flow.

My advice is, to take lots of photos, whilst you are stripping it down.

K Series engines are getting pretty olde now, & it could be original, or it may have already had a reco, at sometime in it's life.

You are about to find out.

We look forward to hearing about the teardown, & seeing some pics, as you go.

Cheers Banjo

 

 

[Thomas Dillon]

Hi mate, 

Thanks for a prompt response!

From a recon perspective we're not too limited on budget and at a bare minimum I'd like to have the pistons out to do rings and main/rod bearings. We're treating this as a learning exercise more than anything so I'd like to give everything a bit of a once over if we can.

Will take a heap of photos and get back to the thread sometime in the next week or so. 

I think this'll be a good thread to run with some input & photos from a complete learner on the first build. We're not under any time pressure either as i don't have a rolling body yet so we'll just chip away steadily and get it right.  Really looking forward to it. 

 

Thanks again for for a snappy response, really appreciate it. Cheers Banjo 

[altezzaclub]

This!!

"You strip it gradually, & tag everything, so that when you put it back together; in months to come; & that everything is in plastic bags or bottles, clearly marked; particularly nuts & bolts. "

Then run up a  budget and see what costs the most and what gives the best bang for buck. Think about what you're going to use the car for and what rpm you'll be using..

Most of what you are talking about I did in here-

https://www.rollaclub.com/board/topic/42407-the-girls-ke70/

Its not hard to cc a combustion chamber, the answer I got was 31cc, the area was 30Sqcm and in the end I took 20thou off the head, in theory giving it 9.7:1 compression ratio. Nothing great or radical. It ran on E10 most its life. The thing most people don't have is a pipette to measure the volumes of turps put in a head, its worth buying a 25ml one. The area is just tracing around a bit of graph paper and counting  the squares. Then a stock motor has a cylinder volume of 322cc, that's just multiplying bore & stroke, so add 7.3cc for the head gasket and add the chamber volume of 31cc and you get a total volume of 360cc, which crushes down to 31+7=38cc. That's a compression ratio of 9.4:1, which is just what Rollaclub Wiki says...

 

I sent my cam off & bought a Crow 606 grind, not wild but an improvement, and you don't need to change valve springs. I had the flywheel lightened, bought some extractors and then the hard work started.

I wouldn't use a DD Weber, go for SUs or better would be a single DCOE Weber, and I reckon best would be quad bike carbs off a 1000cc Suzuki GXR or similar, the Keihins are pretty common on older bikes.  Tommys KE11 has them on here-

Make sure the manifolds all line up perfectly & give the ports a bit of a cleanout to match all the joints. Have the electronic dizzy looked over for its timing advance curve, you don't want it as slow as a forkhoist!

Another really handy tool is a mixture display, especially if you're tuning things yourself.

Let us know how you go-

 

 

 

Edited May 5, 2024 by altezzaclub

[Thomas Dillon]

Fellas, thank you both for your input. outstanding!

I've had a wee looking into measuring cc's etc, as you say, looks rather easy with a pipette. 

All things to be discussed further down the track once we've had a good look inside. I look forward to coming back to you both with pictures of where we're at hopefully by Sunday. 

All the best team, cheers