hardened valve seat installation 2

[lapisb]

Contacted a local motorsport machine shop today to ask if they could install a set of hardened exhaust valve seats in my cosworth BDA aluminium cylinder head.

They said they could do it but there was no guarantee for the seats staying in place afterwards...

When i queried them as to why the factory seats don't fall out of their recess i was told because they are done right and nobody has the equipment/technology in the aftermarket to do it like the factory...

Has anyone heard of anything like this and could someone explain the 'right' procedure that would be employed to install the seats so they stay in place??

Regards

Kal

 

[turbocohen]

Find another shop.. Contact Del West and ask who installs seats for their F1 customers.

http://www.delwestusa.com/

 

[patprimmer]

Aircraft cylinder head repair shops can normally replace valve seat inserts in aluminium heads.

Regards

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[swall]

One of my EE friends works on BMW m/c engines on the side (no pun intended). He says that the seat needs to be properly sized and the pocket in the head needs to be in good shape (possibly some machining clean up required). Then heat the head, freeze the seat and work fast because you only get one shot at it. He hasn't screwed one up yet, but knows this day is coming!

 

[Majik]

Yeah I just got done doing a e36 m3 head that is being turbo'd with larger valve seats and larger valves. It's very difficult working with hardened seats. most diesel shops don't mind the work but probably don't have the tooling to work with valves that small... alot of automotive shops don't want to be bothered by a difficult job when there are plenty of easy's. I'm booked through mid december here for race stuff. That's probably a shops way of polightly telling you no I don't want the job espically if they're a rate place like $20 per seat. $320 is not enough for custom seat work in anyones book.

 

[lapisb]

mmm, intersting. Think i will ride out the old seats as long as possible with additive before it becomes necessary to take the next step.
Thanks for the input guys.

I'll just add something i found while doing some research which is the variance you find in technique and tolerances used by various engine builders for seat removal/refitting.
One will say you only need .001 inch interfernce while another will say .006 another will say they stake the seats for safety while the other will say if you're staking the seats then you're not doing the job right in the first place and the list goes on.

Problem is who should we trust...?

 

[sidsleeve]

Normal press fits for stuff this size would be .001-.002
thousands, but seats need to be tighter, around .006. As someone said, the condition of the counterbore is important.
It is common to put the seat in deep enough to enable a small
amount of aluminum to be rolled over the seat, just to be sure.

 

[evelrod]

I had new seats installed in my Lotus twincam head by Design Products Racing years ago and have had seats installed in aluminum heads by local machine shops on occassion---with proper caution, I might add---so far so good. Our current Cosworth head has new seats and all appears good to go. I think that the process is not 'rocket science' but, it does require proper preparation and quality, skilled personell to do the job correctly. I have one cylinder of my 1380cc Mini head with one set of seats to repair damage from a 'dropped valve' and I used just as much care in the repair as I would have on my Cosworth heads costing ten times as much.

Take the time to learn the proper procedure and then oversee the installation. If the machine shop objects to having you observe...find another shop. I learned my lesson as I have had shoddy work done by some pretty big name racing shops, BTDT!

Rod

 

[RacerRick]

Find another machine shop. Anyone who can't machine a seat pocket to the required .006 crush with serdi or sunnen etc. tooled machines is in the wrong line of work. I have install thousands of seats at $10/hole. I've never had 1 come out that I know of. With a decent head shop, Machinists can cut 4 pockets in a head and install the seats and finish machine them in under 45 mins. I always leave them flush and never peen the edge. Never heat the head or cool the seat. I use a product called Fluid Weld. It thermally binds the 2 materials for better heat transfer, locks them in place and lubes the seat going in. Its a spin off from the space shuttle I'am told.

 

[gbent]

Find a new shop. While not a job for a newbie, it can be done with 100% success. I have also completely rewelded and remachined seat pockets successfully to repair damages. And no, you can't make absolute statements about the amount of interference needed without considering the size of the insert or if it is the intake or exhaust.