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Viterbo

5K build help request

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I'm planning a tune up rebuild on my 5K and I'm gathering some info, so I'm going to ask a few questions.

It will be mainly a road car with some hits at the track and other racing activities.

This will be done to an European 5K, dished pistons with twin squish head from a 4K.

Head (including camshaft and rocker gear)

  • Intake and exhaust ports will be ported and polished. How much do you advise porting each of them?
  • I heard 1mm bigger valves can be fitted without changing the valve seats. Is this correct? Is it worth the money going bigger than that?
  • I intend to send my camshaft to Kent Cams UK so they can grind it to T124 specs as they don't sell it anymore. Worth going to T125 (no need to send my own)? (specs attached). What about Adjustable Pulley and Springs?
  • I made a DIY conversion from hydros to solid lifters but I'm not happy with it. I want to buy solid lifters from Toyota for the 3F engine (same as 5K). What pushrods can I use?

 

As for compression, I don't know my current compression ratio but I'm getting around 12,5bar per cylinder and I'll probably keep it that way.

 

Block

Block will be almost stock. Stock rods and pistons, crankshaft will be a lightened and polished one.

Have a dual row timing chain setup.

Have a lightened flywheel (around 5kgs).

  • Is it worth to put the washer in the oil pump spring?
  • I thought on polishing the rods, worth it?
  • What do you think about an oil cooler?

I'll be using quad CBR600 36mm Keihins.

 

 

What I want is a balanced engine that I can use at the track and at sunday sea trips.

What power can I expect? I was aiming to around 110/115hp at the crank.

 

I've read almost every guide available online but real feedback on the parts I have and want is more useful to me.

 

Thanks to anyone who spends some time to answer me.

All machine work will be done by a professional shop.

 

 

sg.PNG

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Intake and exhaust ports will be ported and polished. How much do you advise porting each of them?

PM Oldeskewltoy!   Certainly enlarge them to match them to the one-piece gasket.

Quote

I heard 1mm bigger valves can be fitted without changing the valve seats. Is this correct? Is it worth the money going bigger than that?

You'll probably gain as much by re-shaping the back of the valve & polishing it, and shaping the valve seat area. Its all in that curvy flow when the valve is part-open, as it spends much more time partly open than fully open.

The cam is whatever suits your purpose, remember that it might be a dog to drive in traffic if everything is too wild. I'd save a few bucks by sticking with a cam that uses stock springs, and the adjustable cam gear shouldn't be needed until you take it off the road as a full-time racer.

The compression ratio will be apparent when its all finished. The cranking compression will probably be worse, but will climb to higher figures with revs, so you'll have to see how you go with fuel octane and ignition timing..

The block work sounds fine. You could grind the block walls smooth and paint them if you were keen, anything to get oil back down. If the oil pump is in good condition you shouldn't need the washer.

Put plenty of work into the ignition timing curve. Find an electronic dizzy if you haven't got one.

 

Chat to Tommy about his KE10 motor, your ideas are similar and his is a rocket-ship.

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You could just try ordering the 5k solid lifters from toyota. The part number is 13751-61020

Lots of guys have had good results with datsun a15  1mm oversize valves. You may need to swap over to 4k adjustable rocker gear

Id look at the ports short radius and see if you can improve, but apparently the twin squish head ports are heaps better for velocity than all of the ther k series heads. Maybe have your machinist velocity and flow test after larger valves are installed. Yes, you can use your seats.

what is the duration at .050 and lift of those cams?

what is the fuel octane rating in your country?

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19 hours ago, altezzaclub said:

PM Oldeskewltoy!   Certainly enlarge them to match them to the one-piece gasket.

You'll probably gain as much by re-shaping the back of the valve & polishing it, and shaping the valve seat area. Its all in that curvy flow when the valve is part-open, as it spends much more time partly open than fully open.

The cam is whatever suits your purpose, remember that it might be a dog to drive in traffic if everything is too wild. I'd save a few bucks by sticking with a cam that uses stock springs, and the adjustable cam gear shouldn't be needed until you take it off the road as a full-time racer.

The compression ratio will be apparent when its all finished. The cranking compression will probably be worse, but will climb to higher figures with revs, so you'll have to see how you go with fuel octane and ignition timing..

The block work sounds fine. You could grind the block walls smooth and paint them if you were keen, anything to get oil back down. If the oil pump is in good condition you shouldn't need the washer.

Put plenty of work into the ignition timing curve. Find an electronic dizzy if you haven't got one.

 

Chat to Tommy about his KE10 motor, your ideas are similar and his is a rocket-ship.

Thanks tezza, I'm gonna take a look at Tommy's build!

 

8 hours ago, 7000rpm said:

You could just try ordering the 5k solid lifters from toyota. The part number is 13751-61020

Lots of guys have had good results with datsun a15  1mm oversize valves. You may need to swap over to 4k adjustable rocker gear

Id look at the ports short radius and see if you can improve, but apparently the twin squish head ports are heaps better for velocity than all of the ther k series heads. Maybe have your machinist velocity and flow test after larger valves are installed. Yes, you can use your seats.

what is the duration at .050 and lift of those cams?

what is the fuel octane rating in your country?

What pushrods can I use with the 3F solids?

In Portugal we have 95 and 98 RON. 

Do you think it's worth going with the Datsun valves?

As for duration and lift I'm gonna present you a print from the Kent Cams catalogue with the camshaft data (T124 "Sports R" and T125 "Competition").

 

 

sg.PNG

Edited by Viterbo

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1 hour ago, Viterbo said:

What pushrods can I use with the 3F solids?

The ones from the 4k twin squish.   amayama had New originals in Stock 2-3 years ago

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5 minutes ago, tojo2 said:

The ones from the 4k twin squish.   amayama had New originals in Stock 2-3 years ago

Really? I have around three 4Ks twin squish disassembled, so I have a few sets of their pushrods. That's good news as I will only need to buy the lifters

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The usual max lift is 0.4" before you need aftermarket vavle springs, although guys on here say you can easily go higher.

The 50thou comment is because some cams open and close more slowly than others, so the duration at a 50thou tappet gap gives a better idea of the working duration than the 'advertised' duration.  If you don't have options for a cam supplier it just doesn't matter, but you can see it in the 5 companies cutting cams for K motors over here.

You can see the diffrence here-  look at the Tighe 154 two durations, and then the 609. The advertised durations are close, but the Camtech cam has a lot more at 50thou, which means more performance.

59543bdf36b4c_camtechcams.jpg.aefa3b2fc1be395f23cbced877682e9d.jpg

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ps, personally I wouldn't polish your head ports, leave them rough so you get better mixture of your air/fuel, been there, done that, better results from being rough,

 

cheers!

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Just my 2 cents worth, but why do people insist on going to solid lifters........

A lot of mixing and matching parts for little or no gain in performance, with the added maintenance issues.

And don't tell me that you need to do a solid conversion so you can run a cam or pull big revs.  Been there done that with hydraulic lifters. 

Edited by coln72

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12 hours ago, altezzaclub said:

The usual max lift is 0.4" before you need aftermarket vavle springs, although guys on here say you can easily go higher.

The 50thou comment is because some cams open and close more slowly than others, so the duration at a 50thou tappet gap gives a better idea of the working duration than the 'advertised' duration.  If you don't have options for a cam supplier it just doesn't matter, but you can see it in the 5 companies cutting cams for K motors over here.

You can see the diffrence here-  look at the Tighe 154 two durations, and then the 609. The advertised durations are close, but the Camtech cam has a lot more at 50thou, which means more performance.

59543bdf36b4c_camtechcams.jpg.aefa3b2fc1be395f23cbced877682e9d.jpg

I get it, I'm gonna contact Kent and ask for diagrams with more deep info.

Thanks

12 hours ago, Clapped out said:

ps, personally I wouldn't polish your head ports, leave them rough so you get better mixture of your air/fuel, been there, done that, better results from being rough,

 

cheers!

My head currently has the moulding lines shaved and a rough polish. Maybe I'll open the ports to match the gasket and keep this kind of polish

11 hours ago, coln72 said:

Just my 2 cents worth, but why do people insist on going to solid lifters........

A lot of mixing and matching parts for little or no gain in performance, with the added maintenance issues.

And don't tell me that you need to do a solid conversion so you can run a cam or pull big revs.  Been there done that with hydraulic lifters. 

I had a big trouble that was the noise they were making and I suspect they were not working as they should. The 5K wasn't sold in Portugal so it's very difficult to source specific parts. I prefer buying new solids than new hydros

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Increasing your valve head diametre increases the curtain area which assists with flow and cylinder fill.Typically the compression ratio is also increased by doing this, pending the valve concave.

yes, there are many builds around that this is claimed to be a worth while mod.

I believe a number of 5ks had solid lifters standard. Whilst hydraulic units still perform, you are at no risk of lifter "pump up" and essentially increased mechanical  efficiency through direct contact of the components. Same reasons i believe  people use roller rockers.

there is actually a guy in portugal that has posted up his 4k build in the facebook page i just kicked off called "toyota k series engine projects and spare parts"

depending on the quality of fuel in your country, id be aiming for 10-10.5:1 compression and a road engine and over 11for racing 

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The t125 looks more like in line to your goals to me. With single barrel per cylinder carbys, it should be nice enough to drive 

I run a more aggressive cam and twin webers which smoothed out the idle and low rpm pulsing. On a single carby, sounded like a rotary haha!

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Lifters pumping up. Never had that happen, and my 5k would see 7500 rpm plus most of the time.

 

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Not saying yours has. I'm pretty sure my old 5k did

out of interest, is most of your high rpm driving on dirt tracks?

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5 hours ago, 7000rpm said:

The t125 looks more like in line to your goals to me. With single barrel per cylinder carbys, it should be nice enough to drive 

I run a more aggressive cam and twin webers which smoothed out the idle and low rpm pulsing. On a single carby, sounded like a rotary haha!

I think the T125 has the need for dual valve springs but on the other hand doesn't have the need of me sending my stock cam for regrind. Would an adjustable pulley be needed with the 125?

 

About the Datsun oversize valves, I find contraditory information regarding the stem diameter. In some places I find A15 valves with 8mm stem and in other places I find A15 vales with 7mm (same as 4K stem).

Would a machine shop be able to find suitable valves?

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