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Old 19-09-2018, 09:17   #1
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Volvo Penta 2020B Head Question (Exhaust Port)

In dealing with a partial rebuild of the top end of our engine (1995 VP 2020B with 1700 hours) we have run into yet another set back (beyond the price of parts). It turns out that we need to replace the seat on our #2 exhaust port but have found that there are no listed parts for the exhaust seat. There is for the intake seat. I have checked the Perkins parts people and the Japanese version as well and have found that the same issue exists there. The machinist is going to look at improvising a fix but before we did that I wanted to check in with others experience.

My question is does anyone know why the exhaust seat is not serviceable? Is the wall of that area too thin to allow for the normal procedures of replacing? If we grind out for a new area are we going to further compromise that area of the head?

A new head is $1700+ CND and is back ordered. Gotta love Volvo.

PS At what point does one throw up one's hands up and buy a Beta and escape the VP choke on part pricing?

Rob Purgavie
Catalina 30
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Old 19-09-2018, 09:30   #2
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

Your machinist can do this. It would be easier if he could just remove the old seat and install a new one. But installing a hard seat is pretty common. V-8's from the 60's all need hard exh seats because of the no-lead fuel.
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Old 19-09-2018, 12:57   #3
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

Any half way decent machinist should be able to apply stellite to the existing seat and machine in situ.
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Old 19-09-2018, 13:42   #4
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

Any head or businesses that do the machining of engines, even gas engines, will be able to mill in a new seat or have a supplier that does. Not at all uncommon. They either have a drill press looking mill that holds the head or do it with a jig in the valve guide to hold the tool while it mills out the area for the seat. Aluminum heads have installed seats. A good race shop can mill it, too.
I would be amazed if the island doesn't have at least one business that does seats.
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Old 19-09-2018, 20:00   #5
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

Thanks all. Will approach a fix using the existing seat and follow recommendations of a competent machinist.

R
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Old 19-09-2018, 20:35   #6
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

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Any half way decent machinist should be able to apply stellite to the existing seat and machine in situ.
That is so ridiculous.
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Old 19-09-2018, 23:14   #7
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

I'm curious to know which piece of NoTies information was ridiculous?
Genuine question as I know nothing about how to use Stellite as a valve seat.
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Old 20-09-2018, 00:32   #8
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

Stellite flows on easily with an oxy-acetylene flame and then can be machined back to the original specs of angle, margin etc. We did it often when I was rebuilding engines in my training days. I guess old technology leaves me open to ridicule from some quarters.
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Old 20-09-2018, 10:11   #9
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

Talk to Barbara or ted at:-

Barbara Mark
NextWave Marine Systems Inc.,
5-3125 Van Horne Road,
Qualicum Beach. BC Canada
V9K2R3
email: bmark@suredrivemarine.com
www.suredrivemarine.com
250 752 1790 Telephone
250 752 2791 Fax
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Old 20-09-2018, 11:44   #10
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

I've never been to Guatemala but, judging by your outburst, we are a lot more civilised and polite in Vanuatu. Not all cylinder heads have removable valve seats and a lot of cylinder heads do not have enough material to machine out the surrounding metal and install an after market seat. The valve seats are usually placed close to cooling passages to allow for rapid dispersal of heat so machining them out weakens the area unacceptably.
But, I guess the multiple valve seats that I have built up in the past with stellite and re-machined were all part of my imagination. I prefer that possibility than the possibility you are calling me a liar.
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Old 20-09-2018, 12:17   #11
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

That's great, you're a master of a lost skill. That doesn't make almost every other shop in the world half assed.
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Old 20-09-2018, 12:23   #12
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

It's not a lost skill and is by no means difficult. It is one of the easiest gas welding processes there is and I was doing it when still an apprentice. I was also still doing it on large ship's valves when I worked at sea and that was less than 20 years ago.
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Old 21-09-2018, 07:09   #13
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

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Originally Posted by NoTies View Post
a lot of cylinder heads do not have enough material to machine out the surrounding metal and install an after market seat. The valve seats are usually placed close to cooling passages to allow for rapid dispersal of heat so machining them out weakens the area unacceptably.
From your experience what are the variables that one should look for in terms of weakening the area unacceptably? Minimum stock on the head? Ratio of head stock thickness and seat thickness? I'll be having a conversation, head in hand, with a well-respected machinist that has retired and I wanted to be able to make an informed decision based on that conversation.
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Old 21-09-2018, 11:15   #14
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

Puregravy...Just a well intentioned reminder, When In business it was always wise to get three quotes. Now IF the required Item had a standard manufactures suggested list price and a part number, This obviously could be done over the phone,


For buying a service intended to fix a problem such as you have described here... it was always wise to visit all three locations in person, To show and tell the problem, Try to get a consensus of opinion. (watch the 'Experts' face plus body language) listen to what they say and how they say it. Get feel for how confident you feel about them: Plus how reassuring they seem to be about their ability. Plus their level of conviction and confidence that their point of view is right. This process of course also nets you the three quotes.


If everyone tells you the same answer that can be quite reassuring concerning convincing the way forward. BUT this is NOT always the case; About a year ago I my friend on Vancouver Island asked me to take him around the the foundries here on the mainland. with a large diesel engine piston. I was more than surprised when I got three completely different reactions, suggested molding methods and a huge spread of prices. in that case his customer cancelled the job.
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Old 21-09-2018, 15:16   #15
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Re: Volvo Penta 2020B Head Question (Exhaust Port)

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Originally Posted by Puregravy View Post
From your experience what are the variables that one should look for in terms of weakening the area unacceptably? Minimum stock on the head? Ratio of head stock thickness and seat thickness? I'll be having a conversation, head in hand, with a well-respected machinist that has retired and I wanted to be able to make an informed decision based on that conversation.
At the risk of having my ability and honesty called into question yet again by Ecos I will say that I am not aware of absolute guidelines for minimum thickness but I would suggest that if removable valve seat inserts were not fitted as standard then there is a high likelihood that they are not an option for repair.
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