Valve seat pocket depth

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Datsunworks
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Valve seat pocket depth

Post by Datsunworks »

Got a question about valve seat pocket depth on a brand new aluminum casting.

Say the seat is .250 thick. How deep would you generally cut the pocket from the lowest point of the chamber? Do you like to leave it proud and touch it up when you cut the seats? Shoot for flush? go deep by a few thousandths ? It's a 4 valve pent roof chamber so there isn't a ton of area where the flat plane of the seat interacts with the chamber.

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Derek
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Dave Koehler
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Re: Valve seat pocket depth

Post by Dave Koehler »

Not seeing it I have to apply some generalities.
Too deep and you mess up your spring height and valve to cam clearance. Think sunk valves.
Too proud just makes for extra work.
I suspect the original was even with the chamber floor.

If you find a solid reason to do either go for it.
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Re: Valve seat pocket depth

Post by Datsunworks »

Thanks Dave.

Just to clarify I bit I was selling the head without seats and guides and this has be causing various issues. In order to make things easier I want to sell them with guides and seats installed and the builder will handle the valve work from there. Just trying to get a feel for what some of you would like to see if it was plunked down in front of you and you were tasked with cutting the seats. Although proud of the chamber is more work I feel like the machinist can then set that surface where they feel it should be.
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Re: Valve seat pocket depth

Post by Dave Koehler »

sounds to me like you are working with raw castings.
Either leave it to the purchaser or do some measuring on a oem head.
Sacrifice a head and try your different heights to see how it works out with the valve position, cam, etc.

I guess it boils down to your target customer. Race shops used to having to do this work or the end user.
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Re: Valve seat pocket depth

Post by BILL-C »

We make new sb ford cast iron C6FE 289 heads from raw castings. We always install the guides and seats and cut appropriate valve job for the application to ensure that everything is in the right spots. Most customers would have a hard time getting everything right.
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Re: Valve seat pocket depth

Post by Datsunworks »

Hi Bill

The problem I'm running into is having the guides and seats installed is one more road block to selling the heads. I'm also finding, and this is pure conjecture, that putting guides in a brand new aluminum casting isn't the same as changing guides in a used head. If brute force is used as opposed to a heat/shrink method of installation the guide will follow to some degree the blows of the hammer and it becomes a broach. The long and the short of it is I'm wholly unqualified to do a proper angle valve job but proper shrink fitting of parts is something I do frequently. I have the ability to heat soak the heads and access to nitrogen so I'm thinking it will be better for everyone if I start selling the heads with seats and guides installed. I'll leave the rest of it to whomever the customer wants to use. That's why I'm asking all these questions here. I wan't to provide a head that a "so so" machinist won't ruin and an top notch one can really dial it in.

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Derek
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Re: Valve seat pocket depth

Post by mt-engines »

I like heads that have a valve pocket barely cut and I use ID locators. I guess your problem lies I. Availability of shelf valve lengths.

It may be best if you just sell them bare with the guides bored and the valve seats out. Then a real builder can source their own seat and guide valves etc.

But if you are looking after the basic hobby guy, you may want them setup for stock length valves Yada Yada yada
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Re: Valve seat pocket depth

Post by Datsunworks »

I think I'm confused about the relationship between the valve tip location and how that relates to the cutting of the angle of the seat and the depth of the seat.

The head is a 6 cylinder version of a Honda K20 and uses all Honda K series valve train parts. The relationship between the combustion chamber and the spring seat is the same as the Honda. If the valve seat is sunk into the combustion chamber flush then isn't it the angle cutting of the valve seat that dictates the valve stem height?

Sorry for what may seem like basic questions but the more I know about the process the better I can understand how I should approach this.

Thanks
Derek
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Re: Valve seat pocket depth

Post by BILL-C »

The answers to your questions depend on the intended application of that custom head. Im not aware of a stock block that fits your head, so that means it would have to go on a custom billet race block. That would suggest that this is intended to compete against the Toyota 2JZ and Nissan skyline engines in some form of racing. That would suggest that oversize copper bronze seats would be desired.More info would be helpful.
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Re: Valve seat pocket depth

Post by Cubic_Cleveland »

Are the chambers finished minus valve seats? Who is cutting the seat registers?
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Re: Valve seat pocket depth

Post by Datsunworks »

BILL-C wrote: Mon Jun 14, 2021 6:52 am The answers to your questions depend on the intended application of that custom head. Im not aware of a stock block that fits your head, so that means it would have to go on a custom billet race block. That would suggest that this is intended to compete against the Toyota 2JZ and Nissan skyline engines in some form of racing. That would suggest that oversize copper bronze seats would be desired.More info would be helpful.
Hi Bill
This head fits the stock Nissan/Datsun L6 block found in the old 240,260,280z. as well as the older Skylines. They are not for racing but for street cars that want all motor power. I've been selling them for a while but seats and guides needing to be installed is proving to be a problem. I'm finding that not all shops have a head oven or nitrogen and that means that the installation of guides and seats becomes somewhat subjective.

Based on the responses I guess I've been clear as mud as to what I'm trying to find out.


Thanks for everyones help but I need to regroup and see if I can express what I'm trying to find out in language that we can both understand.


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Re: Valve seat pocket depth

Post by mt-engines »

In my humble opinion, if a machineshop can't install seats or guides. They shouldn't be touching a cylinder head period.
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Re: Valve seat pocket depth

Post by Datsunworks »

In my humble opinion, if a machineshop can't install seats or guides. They shouldn't be touching a cylinder head period.
While I agree with that I can take it a step further from my point of view. If a shop does not have a temperature controlled oven and a nitrogen supply they shouldn't be installing seats and guides in an aluminum casting. Now having said that I deal with three automotive machine shops that do great work that don't have either an oven or nitrogen.

In a perfect world you would want the parts to slide together with no effort necessary so that when the temps stabilize the contact surface between the parts is as even as possible for both grip and heat transfer. Every pound of force (hammer) required to make the assembly is improper since you are removing/distorting material at some level. It then becomes various degrees of wrong.
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Re: Valve seat pocket depth

Post by Dave Koehler »

Sounds like you will buying or making some equipment to further your program.
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Re: Valve seat pocket depth

Post by Datsunworks »

Dave Koehler wrote: Mon Jun 14, 2021 1:04 pm Sounds like you will buying or making some equipment to further your program.
I love reasons to buy more equipment:). Actually I already have the means to heat the heads. I usually borrow a dewar when I need to shrink something but I'll buy one since I'm at the "borrow 3 times then you should buy" policy I have. I need to make the head oven a little more user friendly.
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