12 replies to this topic

[Project_1275_GT]

Hi 

 

The more i do the more confused i get.. 

 

I have chosen to use Rimflow inlet valves and st/st exhaust valves, after assembling last week i noticed the collet did not seat in the top cap when using the new single grove collets. Fine, I ordered new top caps advised by mini spares AEA653 - They arrived today. Installed and when fitted they compress the spring by 2mm more than the exhaust valve with standard triple grove collet and original top cap. 

 

The question is - is this ok to have more spring compression on the inlet than exhaust? I have seen that Mini spares have another cap 88G617 that looks more original. Mini spares advised these top caps when i called last week. I have no idea if i get the other version if these will make any difference to the final height of the spring.

 

Does anyone know if this is normal when fitting Rimflow valves? and is uneven spring pressure on inlet and exhaust acceptable?

 

Thanks

 

Rob

[Ethel]

Don't know if it's normal, but don't see a problem with it either. I suppose you'd be 2mm closer to spring binding at full lift, but a miss is as good as a mile.

 

It'd mean a minor compromise if you intend setting the post heights just so.

[OzOAP]

What is installed height and seat poundage? Then you will know if either are correct for the cam you are running.
Is it different valve lengths or is the discrepancy in collet groove/collet/topcap?

Edited by OzOAP, 01 February 2021 - 02:41 PM.

[Project_1275_GT]

What is installed height and seat poundage? Then you will know if either are correct for the cam you are running.
Is it different valve lengths or is the discrepancy in collet groove/collet/topcap?

 

Just been and taken some measurements - 

 

exhaust valve - length from valve seat to top of valve stem 40.95 

Inlet valve - length from valve seat to top of valve stem 40.11

 

Measured with Vernier depth gauge so reasonably accurate 

 

exhaust valve - spring when installed with cap [not including cap] 36.15 

inlet valve - spring when installed with cap [not including cap] 33.8

 

 IMG_2811.JPG   27.9K   0 downloads    IMG_2815.JPG   24.79K   0 downloads

 

The springs are mini spares double spring, they don't provide poundage but state 515 thou lift - the cam is also mini spares Evo 001 CAM LIFT IN 264 EX 289

[Project_1275_GT]

Don't know if it's normal, but don't see a problem with it either. I suppose you'd be 2mm closer to spring binding at full lift, but a miss is as good as a mile.

 

It'd mean a minor compromise if you intend setting the post heights just so.

 

Think it will work ok with the lift, but i will assemble and check as the block needs pocketing. I tried to calculate the lift but think a better plan would be to assemble and measure. Just looks odd with the springs at different heights, cant see it will do any harm having a little extra pressure on the inlet. 

[Turbo Phil]

There is a difference in installed heights between single and triple groove, & collets and top caps are not interchangeable as you've found out. 
Are the valve heights even with the seats cut to an even depth? 

Phil. 

[Project_1275_GT]

There is a difference in installed heights between single and triple groove, & collets and top caps are not interchangeable as you've found out. 
Are the valve heights even with the seats cut to an even depth? 

Phil. 

 

The seats are all cut within around 0.2mm [this will be final cut after final chamber work] - that's checking them from the head face chamber side to the valve face 6.8mm depth - all spring seats were checked and they are also level - brass guides fitted to 13.85mm depth from the spring seat. Its defiantly the valve with single grove collet that makes the difference. I don't see a big problem but thought it wise to check. 

 

Thanks

 

Rob

[Shooter63]

Is it me or have you got different stem protrusion on the valves

Shooter

[nicklouse]

Ok basics.

 

the collets and top caps are different and can not be mixed. IIRC the 3 ring are 14 degree and the single ring are 10 degrees.

 

as to instal height differences no idea as I would not mix and match like that.

[VLChurchill]

Are the measurements from the head of the valve to the gasket face all the same as each other ?

[Project_1275_GT]

Is it me or have you got different stem protrusion on the valves

Shooter

 

All valve stems are the same length, all valve faces set at equal heights 

 

Thanks

 

Rob

[Project_1275_GT]

Ok basics.

 

the collets and top caps are different and can not be mixed. IIRC the 3 ring are 14 degree and the single ring are 10 degrees.

 

as to instal height differences no idea as I would not mix and match like that.

 

Yep I agree, single grove valves require different collet and top cap. I know its odd to mix valves but its a turbo application and the two different valves should make a good combination, I think.. I cant see it being a big problem, just a little extra spring tension on inlets than exhaust. 

 

Thanks

 

rob

[Project_1275_GT]

Are the measurements from the head of the valve to the gasket face all the same as each other ?

 

All valve faces measure 6.8mm [within 0.2mm] from the gasket face to valve face. all equal. #

 

Thanks

 

Rob