How necessary is it to blend in the valve seats?

[ysmalkie]

I started to assemble my head (done by one the known UK shops), and it unfortunately tuned out that the inlet valve seat on cyl 2 is not cut straight. The valve was leaking so badly on one side that I had to re-cut it. Lapping did not solve the problem, as the hole was so big, that the light from the flash light was visible. (valve was straight)

This unfortunately means the seats are not blended on this valve.

Besides the fact that I am not very happy about it I have 2 questions:
- Is there a way I can blend the seat myself?
- Is it necessary? I have no way of telling how much it’s sunken in, probably about 0.03”

All other valve seats are blended in perfectly.

Or am I again overdoing it?..

Tadek

[Mich7920]

Hi,
For this kind of work you don't have the machines.
Go back to the shop and explain.
They must to repair their mistake.
Mich

[ysmalkie]

I verified it again after cleaning - it's sunken in by 0.018"..

It's not that easy to take it again to the shop that did it, I am in Poland shop is in the UK..

[Mich7920]

Oops, I understand...
If the seat isn't straight, the valve leak and this is not acceptable.
Appart a negotiation with the UK shop for the delivery, I don't see an easy solution.
Can someone else have the solution?

[JerryL770]

Does the valve seal?

That's surely the most important question. If it seats the full circumference the fact the stem goes in a few thou more is corrected by the tappet shim surely.

If it does not seal that is no good at all.

[dxke38]

If the valve seat has moved then a new one will have to be fitted. If you try to grind the seat and get it to seal it could be loose and move again which could cause extensive damage to the engine.

[abowie]

I verified it again after cleaning - it's sunken in by 0.018"..

That's crap. I would expect no more than a thou difference across the valves.

Can you find a shop in Poland? With the correct gear it's a pretty simple job.

[ysmalkie]

Just to make sure I am clear on this - I measured the 'space' available for the spring height across the cylinders, and here is how it looks now:

Spring height space - Inlet [in] 1.1457 1.1697 1.1563 1.1484 1.1579 1.1575
Spring height space - exhaust [in] 1.1543 1.1614 1.1606 1.1539 1.1622 1.1610

Spring height space - Inlet - DELTA 0.000 0.024 0.011 0.003 0.012 0.012
Spring height space - exhaust - DELTA 0.009 0.016 0.015 0.008 0.017 0.015

The delta value is measured from the smallest available height which happens to be on cyl 1 Exhaust.

This delta value for inlet cyl 2 was before 0.006" but now rose to 0.024"

Are you saying it's too much of a difference?

Or am I measuring something wrong...

Tadek

[christopher storey]

I have to say that I am having difficulty in understanding this. I just do not see how recutting a seat, presumably using the valve guide for the cutter, could result in an eccentrically cut seat. It seems far more likely to me that the valve you have used is bent . The picture suggests that the seat has been cut to a 3 angle pattern ( although the circumferential groove also suggest that the seat has been lapped with something trapped between valve and seat? . Did you try another valve to see if a different result was obtained ?

[abowie]

Depends on the setup. If they didn't square the head up properly, or moved it during cutting this could happen. Alternatively the valve insert could have moved.

[ysmalkie]

Well, I have no idea how Chesman (UK) did it, but however I turned the valve around to check if it's sealing properly, the gap was always in the same place - so the valve was (and still is) straight.

Tadek

[MarekH]

Tadek,
here is a test for you....

Is it possible to turn the head upside down and sit six very tall but perfectly squared off cylindrical bits of metal (spare valves?) onto the valve bases?

If all six appear not to deviate from the vertical, then the valves sit true in the valve stems and the valve seat is inserted skew.

If one sits at an angle to the other six then its valve guide has been reamed out and replaced skew but the valve seat may well be squarely seated.

kind regards
Marek

[dxke38]

Just to reiterate. If the offending valve seat was not a tight enough interference fit, then it could have bounced out of alignment when fitted to the head. This would mean the seat would have been cut with it askew. If the seat were slightly loose it could have realigned when fitting the valve and thus leave the valve with a gap to one side. If the seat were then cut to rectify this problem it would not resolve the loose seat. Just a thought that you should check on to reassure yourself that the seat won't fall out and damage the engine.

[JerryL770]

I don't quite understand your concern from 3 points of view.

Tadek has not said the seat is loose. Is it?

The pictures look as though the valve or cutter is seated the full circumference ?? If the valve is not seating on the full circumference of the seat, that is no good but cutting with the right tool then lapping it in should solve that surely. If that leaves the valve significantly depressed, that's maybe not so good.

I don't know how you (Tadek) could measure this spring height available but even so, think it is of little relevance. (How do you know originally the difference was .006" ?) Even with these differences, the spring length when installed will make little difference to the pressure of the valve on its seat. If that made any difference, can you be sure that every pair of valve springs would be of the exact same strength. I think that is something you are being over concerned about.

[rfs1957]

Funny sense of déjà vu reading this !!!

Chesman Engineering ? (Who, he ?!)

Ed : Private Eye inserts (Who he? Ed.) after the name of someone who thinks they ought to be well-known.

viewtopic.php?f=2&t=12746&p=108803&hili ... NT#p108803

Welcome to the abusive world of the Pearson Duo, as they're fondly known in the trade.

Good job you didn't get them to shim your valves, you might have got these -



but did they shorten your valves any better than mine ? -







or cut your seats too small for the valves, that they themselves supplied ?







They offered to collect the head and re-do everything, maybe they offer that service in Poland too ? I'd long since given up on them and as the only way of correcting this



is to change the seats, again, I couldn't face dealing with them any more as they were so abusive and unpleasant.

But I've not finished with them yet .......... their day will come !

[ysmalkie]

Well, Chesman has offered to redo the seat. As I am in the UK in 2 weeks, I will bring it over and have it redone there.
They have done 3 heads for me and this is the first one there is a problem with, so I m optimistic.

I do not think the seat is loose, but I have no way to check it as I am away this week..

I shall report back! :-)

Tadek