Fitting Bigger Valves 3/4/5K

[megamannz123]

I'm looking for bigger valves for the 5K, the standard sizes are

IN 36x100x8mm

EX 29x100x8mm

I went to see my engine guy today and he thinks we can fit 37-37.5mm IN valves without changing the seat. I don't want to spend the money to cut out and fit lager valves seats.

Does anyone know what will work in the K series engines? or have had fitted to their motors?

The Datsun A15 is 37x103.8x8mm so that may be able to be cut down to work.

 

Ideas?

 

Cheers

[KEI069]

I'll make a call tomorrow and get back to ya, see what I can find out for ya

[joshua.mathews]

I used the ex and in valves from the a15 engine in my 3k bigport head but you have to cut seat to suit the valves

[bruce]

Feral4k used valves from a Fiat and Alpha:

 

http://www.rollaclub..._75#entry667499

 

I've had a look at using 3T valves into a 4K head:

 

 

3T inlet has 41mm diameter, and the exhaust is the same as the 4K inlet at 36 mm.

 

3T valves have 8mm stem, but are longer:

 

 

So could use 4K inlet and turn it down to 33 mm to use for the exhaust.

Then use the 3T inlet valve turned down to 40mm, shortened to a length of 100mm, and cut a groove for the collet.

 

Looks like 40mm inlet and 33mm exhaust is the biggest that can fit without offsetting the valve guides. Would need to shape out the chamber and run a larger lift camshaft to get around shrouding issues.

Not sure if the K head can be ported to make use of these sizes. In the TRD manual stage iii, 3d (Fig. 4) it looks like the inlet can be opened to 33mm diameter and 35.5mm at the valve throat. TRD used 38mm inlet, 33mm exhaust:

 

http://www.rollaclub...embly_standard.

 

Say for example with 40mm inlet valves, the valve seat width can be 2mm, giving a inner valve throat diameter of 36mm. This diameter would probably breach the coolant galleries if it was ported all the way though, so could possibly go rounded square shape ports to achieve the same cross-sectional area, something like a Chev cylinder head. Something to think about if it was for a 7K.

[kickn5k]

I have the TRD head you're talking about, Bruce. I'll try and confirm sizes for you tonight. Some photos here http://www.rollaclub.com/board/topic/9733-my-white-ke-11/page__st__285

Edited April 27, 2015 by kickn5k

[KO 10]

Just a thought if you want to use the 37x103.8x8 valves you may be able to adjust your tappets to take them

(Its an advantage if you've got a high lift cam)

It will reduce the rocker angle in the same way recessing your seats would

But this is just a theory I haven't done this and I'm not even sure if there would be enough adjustment and then the springs maybe stuffed up anyway has got me thinking what would fit : )

[styler]

Work needed with Valves, Deshrouding, Seats, Ports, Guides, Compression.

Need a much longer valve length to be able to cut off the old groove and cut

a new one in, also look at lash caps as the stellite ends will be cut off.

[brendan]

Can anyone recomend someone in sydney to enlarge the valves

[styler]

Enlarge valves? Could use bigger diameter valves and install bigger seats and deshroud chamber and port match it up if thats what you mean...

Most engine shops should be able to do this, its getting the bigger valves that is generally the issue. Standard are 36x8x100 intake, 29x8x100 exhaust.

So you need bigger valves, thats where the search begins...

Edited May 3, 2015 by styler

[styler]

Kameari do datsun A series oversize valves at 38x8x103.6 and 32x8x103.6. Might be able to be used, price is up there though.

Edited May 3, 2015 by styler