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Valve seat sizes for 38/46 setup

cwdodson88

cwdodson88

Well-known member
Joined
Oct 27, 2011
Location
The Dalles, Oregon
Looking for some insight on valve seat material and id/od/thickness. I?m hoping to have some new seats/guides and valves installed in my b20. So far my research says copper alloy seats, but I?m not certain what dimensions are for b20 stuff or if the jump from stock to way oversized Is going to be too large for stock sized.

What are you 8v guys doing with Gary?s valves?
 
The 38 exhaust and 46mm intake valve upgrade fits on stock seats with the aluminum head ohc engines. Not sure about the B20. If the B20 is early there are no valve seats. Just the later unleaded heads from 72 and on have valve seats. The stock seats may work for those valve sizes. Someone with more B20 experience will chime in.
 
I'm using a B20F head. I'm upgrading from 35s to 37s pretty soon, and it looks to me that you can go to 38s and probably not have a big problem.

There's plenty of meat left with the 37s, so I'd say you should be safe. Any higher than that and you might have some problems with the geometry.

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Should probably note that these aren't fully seated, yet. I'm taking it to my machinist next week.
 
Is this a boosted application? Does the head already have seat inserts in it?
Either way, cast iron, chrome-moly, or harder powder metal seats for the inconel and SS will be fine. These should be $5-10/seat plus install.

If you want just a bit more cushion and higher heat transfer for the valves, Dura-bond killer bee seats, AMPCO45, or C630 Bronze (Kibblewhite valve seats). The bronze seats will all be about $30-50/seat plus install.

Just give the head to a machine shop and tell them what you're doing with it. They will take it from there and get the properly sized seats and the correct material.

See if the shop can give you a radius exhaust-seat profile and then blend the short side radius. The exhaust on the pushrod heads makes the OHC 8v look like a F1 port :-P
 
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culberro said:
Is this a boosted application?
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Jessir. I?ll be running ~20psi on pump, 350cc/min water meth. Had run before with a 15g at 18psi, put some miles on it and had a massive manifold failure leading to a new manifold, and got my hands on a Borg Warner efr7163, 0.80ar twin scroll, so made a new manifold and fired it up last weekend. Turns out, I?ve dropped compression on cyl 1/4, and no change with a wet vs dry compression test, so the heads coming back off, and I?ve got these valves in my toolbox, so while it?s off, might as well.
 
cwdodson88 said:
Jessir. I?ll be running ~20psi on pump, 350cc/min water meth. Had run before with a 15g at 18psi, put some miles on it and had a massive manifold failure leading to a new manifold, and got my hands on a Borg Warner efr7163, 0.80ar twin scroll, so made a new manifold and fired it up last weekend. Turns out, I?ve dropped compression on cyl 1/4, and no change with a wet vs dry compression test, so the heads coming back off, and I?ve got these valves in my toolbox, so while it?s off, might as well.
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See my edited response :)

If you're doing sustained high boost pulls, a powder metal seat that's meant for turbo/diesel applications or the AMPCO45 or C630 seats would be what I'd use.

Find a machine shop for the head yet?
 
culberro said:
See my edited response :)

If you're doing sustained high boost pulls, a powder metal seat that's meant for turbo/diesel applications or the AMPCO45 or C630 seats would be what I'd use.

Find a machine shop for the head yet?
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My local Napa will do it, but will not do homework or order anything but cast iron or hardened seats. Basically, he said that he would be happy to install other material seats, new guides, and roll a 30,45,60 seat cut. But he wants me to work out what seats to use, sized and ready for him to slam in. From my research and talks with my engineering director and manufacturing director, inconel likes something nice to send the heat to, so copper beryllium seats or something of the like... he?s a former F1 engine designer, and race bike engine machinist for some large teams, so I believe what they tell me.

That said, I have no problem deviating from this if there are other options available that fit logically with the metallurgy.

Now mostly I can?t find id od numbers for stock seats. So I may have to disassemble and knock em out then measure. But it?s time that I really don?t want to spend. It?s been a long time since I?ve just been able to jump in and drive the car. So my patience with the project are running thin, and the river is looking more and more like a good place to park it.
 
cwdodson88 said:
My local Napa will do it, but will not do homework or order anything but cast iron or hardened seats. Basically, he said that he would be happy to install other material seats, new guides, and roll a 30,45,60 seat cut. But he wants me to work out what seats to use, sized and ready for him to slam in. From my research and talks with my engineering director and manufacturing director, inconel likes something nice to send the heat to, so copper beryllium seats or something of the like... he’s a former F1 engine designer, and race bike engine machinist for some large teams, so I believe what they tell me.

That said, I have no problem deviating from this if there are other options available that fit logically with the metallurgy.

Now mostly I can’t find id od numbers for stock seats. So I may have to disassemble and knock em out then measure. But it’s time that I really don’t want to spend. It’s been a long time since I’ve just been able to jump in and drive the car. So my patience with the project are running thin, and the river is looking more and more like a good place to park it.
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It's hard to find the copper-beryllium material these days, as you know... cancer causing and such. But the Killer Bee seats, AMPCO 45, and C630 (Kibblewhite machine sells these) are what I'd suggest.

Honestly, the hardened seats that Napa is suggesting will be fine for most applications. I wouldn't use them for endurance racing your engine, but DD'ing, drag racing, track days, and what not.. they'll be fine.

For seat sizing, can you measure the approximate diameter of what's in there? You'll probably want one size over what you measure so the counter-bore can be cleaned up.

Another way to size the OD is to measure valve OD and then add ~1mm (minimum) to the diameter. Then use a seat ID that's ~86% (or less) of the valve diameter.

Easy way to remove the seats is to use your fancy TIG welder and run a bead around the 45 of the seat, and stick the filler on the last dab. Let it cool for a few minutes and use the filler rod to magically lift the seat out of the head.
 
cwdodson88 said:
Sounds good. Any preference for guides on SS and inconel valves?
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Manganese-bronze 100%.

SI Valve has b20 sets last time I checked. Your Napa should be able to get them. If not, you can call them to order, or I can always order you a set as well.
The SI guides are machined for stock 8v valve stems.

From the SI catalog:
Intake guide (same dims as 8v OHC): PN VG4716, OD:0.532", ID 0.3152", Length 2.050"
Exhaust guide: PN VG4717, OD:0.532", ID 0.3152", Length 2.300"
 
culberro;6101423 If you want just a bit more cushion and higher heat transfer for the valves said:
Ronald, I'm machining, porting and prepping a B18B head for use vintage racing with my 1800s. For now I'm using Manley stainless valves and have been looking for info about the compatibily of them and bronze seats.

Planning a second head for future use with titanium valves, which work best with copper-beryllium, but would prefer to use bronze seats instead.

Your thoughts on both applications?
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vintagewrench said:
Ronald, I'm machining, porting and prepping a B18B head for use vintage racing with my 1800s. For now I'm using Manley stainless valves and have been looking for info about the compatibily of them and bronze seats.

Planning a second head for future use with titanium valves, which work best with copper-beryllium, but would prefer to use bronze seats instead.

Your thoughts on both applications?
Click to expand...

The Manley SS valves don?t need anything special, especially for a NA motor. That is unless you?re running a crazy cam and want a softer landing for the valves. But, bronze seats wouldn?t be a bad thing in that engine.

Are the Ti valves coated? You can use a steel seat with a coated Ti valve and lighter springs (this is key!). The safest bet though, is to use a bronze seat of some sort. My dad builds a decent amount of air-cooled race motors that use Ti valves. He uses C630 seats from Kibblewhite with great success.
 
culberro said:
The Manley SS valves don’t need anything special, especially for a NA motor. That is unless you’re running a crazy cam and want a softer landing for the valves. But, bronze seats wouldn’t be a bad thing in that engine.

Are the Ti valves coated? You can use a steel seat with a coated Ti valve and lighter springs (this is key!). The safest bet though, is to use a bronze seat of some sort. My dad builds a decent amount of air-cooled race motors that use Ti valves. He uses C630 seats from Kibblewhite with great success.
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Thanks for your thoughts on the matter, I've been doing a lot of research on bronze seats beforehand and it has all been positive with both SS and Ti valves. Yes, regardless of seat is chosen coated Ti is the way to.
 
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vintagewrench said:
Thanks for your thoughts on the matter, I've been doing a lot of research on bronze seats beforehand and it has all been positive with both SS and Ti valves. Yes, regardless on the seat coated Ti is the way to.
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Bronze seats will almost always be an upgrade worth doing, you just have to weigh it against the price.
 
culberro said:
Bronze seats will almost always be an upgrade worth doing, you just have to weigh it against the price.
Click to expand...

Because Ti intake valves would also wear less in use with bronze seats.....While we are discussing seats, I have two fairly rare 10:1 CR B20 1974 Canadian/European carb heads with 46mm intake valves and one of them could benefit from new intake seats because of long term wear, as the seats are sunk which hurts flow. Has anyone successfully bored these intake valve seats for inserts without breaking thru to the water jacket and has the installation held up OK after hard high RPM use?

In this case a thin-walled smaller OD insert would be the key to success but finding the info about how thin they can be and still hold up well is hard to find.
 
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