Valves Leaking After Headwork

[Razkin 0]

I had an engine builder doing a 3 angle cut modification on an RFS head. The work looks ok, but when I wanted tot measure valve clearance 12 of the valves are leaking.

I am using air(6bar) tot push the valves in their seats and since 4 valves are fully closed. I am suspecting that the headwork isn't done right, or is air pressure not enough to close the valves?

[welshpug 1,680]

were the hydraulic tappets emptied before fitting? what's the oil pressure like?

 

could be pumped up tappets.

 

unsure how much it would take, but it may be that the tappets are bottoming out due to the valve stems being too high after machining the seats back meaning the tappets are bottoming out.

 

could be bent valves of course, bottom pulley confirmed as ok? cams not rotated independently?

Edited February 5, 2012 by welshpug

[Razkin 0]

The build isn't complete. I want to measure up valve clearance so I can narrow down the search for camshafts. So I am pressurizing the cilinder to close the valves and set the dial gauge to 0.

 

Just loose valves and seals not springs,tappets etc.

Edited February 5, 2012 by Razkin

[kyepan 291]

what engine is this?

[Razkin 0]

"standard" xu10j4rs block, balanced bottom end, wiseco pistons(86,5) and pec conrods compression should be around 11.6:1

[welshpug 1,680]

have you tried swapping the valves that seal to another cylinder?

 

may be that the seats were not cut concentrically to the valve guide.

[Razkin 0]

Not yet, I did not have time to take the head off. Next week I will continue with the build so I will swap valves over to see the effect.

[kyepan 291]

perhaps it could be the same issue as i had, as per welshpug's comment.

 

if you take the cams out does it still leak out from the valves?

that is how to rule out the lifters as the issue.

 

Cheers

 

j

[Razkin 0]

No cam or springs are installed...

[24seven 104]

Try putting the springs in just to rule that out as a cause. It shouldn't take long if you've got a quick clamp spring compressor.

[kyepan 291]

The spring pressure holds the valves closed, you need them to get a seal.

 

how would blowing air seal them? especially if the air is coming from the inlet or exhaust port, pushing the valved open.

 

also have you lapped the valves into their seats?

 

cheers

 

J

[Razkin 0]

Installing the springs is something I will do when I get around to it. But if 4 valves sit perfectly tight in their seal with 6 bar air pressure why are the other 12 blowing, some slight some more.

 

@keypan air is coming in through the sparkplug hole and puts quite some force under the valve, no way you can press it down with your hand for example. The valves were lapped in bij the shop that did the headwork and haven't moved to other positions in the head since.

[Paul_13 212 1 Cars]

No cam or springs are installed...

 

I think that's your problem, no springs installed.

[kyepan 291]

so you are using a leak down tester?

 

check the lapping with some engineers blue.

 

check the valves are straight

 

either way, you need to find out why they are not sealing.

[Razkin 0]

It is not a leak downtester, I can not see the leak %, but the same principle apllies.

Since I have payed someone to do the lapping/checking of valves etc I am unwilling to mess with it. I do not want any warranty issues. I justed wanted to do my homework when I explain to the builder the work isnt done correct.

[kyepan 291]

in that case - before you take the head back.

 

http://www.youtube.com/watch?v=reAuAbazfOc&feature=related

 

and

 

http://www.youtube.com/watch?v=Q5eF6jq7Ruo

 

springs should really be installed..

[GilesW 41]

Out of interest:

Are peoples expectations that valves will totally seal with just the seats cut - or will they need lapping as well?

 

Are you using used valves, or brand new?

[Razkin 0]

Used valves that belong to the head.

 

If you alter the seats cuts you automatically need to lap the valves in.

[Sandy 191]

As a footnote, slightly tipped valve heads will often seal ok on RS engines with a fluid test like above, then reveal themselves by falling off later. The thing I'd be looking at, is valve seats possibly cut too deep, bottoming out the followers.

Edited February 6, 2012 by Sandy

[petert 616]

 

If you alter the seats cuts you automatically need to lap the valves in.

 

I never lap valves in now. That's a bit old skool. If seats are done with a modern seat cutter, on serviceable guides, and valves ground, they should seal without springs.

 

Cutting new seats in worn guides could be the problem here.

[pug_ham 245 3 Cars]

Out of interest:

Are peoples expectations that valves will totally seal with just the seats cut - or will they need lapping as well?

 

Are you using used valves, or brand new?

When I refurbed a head last year I had new seats cut but still lapped the valves back in when I got it all home & once the head was rebuilt with the springs etc in place I leak checked them by pouring 20ml of old petrol into the inlet & exhaust ports to see if any leaked out.

 

It didn't.

 

g