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351w valve seats

General engine tech -- Drag Racing to Circle Track

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FirstEliminator
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351w valve seats

Post by FirstEliminator » Tue Jun 23, 2020 2:30 am

Hey guys,
I'm back to fooling around with my seat and guide machine. I'm working with a 351w with a set of C9 heads. I put guides and hardened exhaust seats in one head. I wasn't planning to do the seats. But, as I started to cut a 3 angle seat I realized the 60 degree angle wasn't touching as the casting was undercut below the seat. So I put seats so there is some material to work with. I got the seats in place, then trimmed them down to the chamber surface. I cut the 30-45-60 and I'm looking at the 45 and the seat width looks mammoth. It's gotta be 2mm? I compared a new cutter with a 1.50mm 45 angle and i the cutter I used is wider by 25-30%. It seems like this is too wide. What width angles should I be targeting on a mild 351w? I was thinking to change the cutter to the 1.5mm for the exhaust and 1.0mm for the intake seat angles.
What would be the best way to attack narrowing the current seat? It seems I could carefully adjust the 1.5 cutter to meet up with the 30/45 angle, then I think the 60 cut in until the cutter just touches the 30/45.
Worst case scenario I will have to pull the seats. One thing I am not sure how to measure or if a measurement is specified... is how to not sink the valves in the head. I can make the valves all the same, but not sure how to determine what their proper height position is.

thanks
Mark

mag2555
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Re: 351w valve seats

Post by mag2555 » Tue Jun 23, 2020 7:12 am

Intake seats do not need to be any wider then .055" with .040" being minimum as seen on my flow bench provided you have a bottom cut atleast .080" tall.

Exh seat wise .065 to .075" is the range I shoot for, and if I am not mistaken those heads have a 15 degree top cut from the factory on both valves.
Once you get the OD of the seat of either valve maxed out to within no more then .010" of the valve diameter then using a bottom cut to narrow the 45 if needed WILL start to sink the valve above the amount needed to get the main seat cut and freshened up.

Going up to a 1.90" or 1.94" valve in those original 1.782" valves ( or whatever those stock size valves are in the 351W heads ) heads is a great way to go and will fatten up the flow numbers a bunch with a 3 angle job from .150" on up to .300" even!

It also regains the chamber CCs you would have lost from reusing the stock valves and sinking them some due to the valve job.

FirstEliminator
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Re: 351w valve seats

Post by FirstEliminator » Tue Jun 23, 2020 2:40 pm

There are new Ferrera valves going in. The exhaust valves are 1.55 diameter and the intake are 1.94. The more I think about it, I believe I am going to have to pull the seats and start over. I don't know, but I feel like the seat is as low as it should be...or any lower would be too low. Then again, I just looked at it and the valve margin is above the chamber surface.

Is the "bottom cut" the 30 or the 60 degree angle? Or, the one on the chamber side or the port side?

BillK
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Re: 351w valve seats

Post by BillK » Tue Jun 23, 2020 7:57 pm

FirstEliminator wrote:
Tue Jun 23, 2020 2:30 am

What would be the best way to attack narrowing the current seat? It seems I could carefully adjust the 1.5 cutter to meet up with the 30/45 angle, then I think the 60 cut in until the cutter just touches the 30/45.
Depending on where the seat is hitting the valve you might just be able to go in with a straight 60 degree cutter and narrow it some. Or a 30 degree if it is hitting way out on the od.
FirstEliminator wrote:
Tue Jun 23, 2020 2:30 am
One thing I am not sure how to measure or if a measurement is specified... is how to not sink the valves in the head. I can make the valves all the same, but not sure how to determine what their proper height position is.
You can measure some known good heads or you can join the AERA and get the information :)
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

www.enginerepairshop.com

FirstEliminator
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Re: 351w valve seats

Post by FirstEliminator » Wed Jun 24, 2020 9:27 am

Hi BIll,
I'm considering AERA. Other than resurfacing heads for local shops, I only do engine rebuilding for myself. There might not be much use of the services for me. Although the spec manuals that come with joining looks to be well worth the price. ……..I just joined.

Mark

BillK
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Re: 351w valve seats

Post by BillK » Wed Jun 24, 2020 9:31 am

FirstEliminator wrote:
Wed Jun 24, 2020 9:27 am
Hi BIll,
I'm considering AERA. Other than resurfacing heads for local shops, I only do engine rebuilding for myself. There might not be much use of the services for me. Although the spec manuals that come with joining looks to be well worth the price. ……..I just joined.

Mark
Mark,
I simply cannot imagine owning an automotive machine shop and not being a member. Sort of like a general automotive shop not having AllData, Shopkey or something similar for service information. I also subscribe to the Prosis Pro software but you really dont have to. You can call or e-mail one of the tech guys and get the information. They have an amazing tech library also :)
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

www.enginerepairshop.com

FirstEliminator
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Re: 351w valve seats

Post by FirstEliminator » Wed Jun 24, 2020 7:54 pm

Yes, it sounds like a necessary "tool" for automotive machining. As a transmission shop I have multiple tech resources for transmission information. I'm looking forward to the tech books they send out with the membership.

FirstEliminator
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Re: 351w valve seats

Post by FirstEliminator » Thu Jun 25, 2020 8:55 am

Last night I measure the center of the original seat to the deck surface using Goodson's pointer with the indicator over the guide pilot. The original seat was .020 higher than the ones I cut. Then I tig welded a washer in the seat, slid a nut that fits my slide hammer up through the exhaust port and yanked the seats out. With the welding cooled, it pulled the seat in and they came out easy. I put new seats in last night, but didn't cut anything yet. I've realized the original seat is right on the chamber surface. When I cut them, I brought in the top angle(?) ----not sure if it could be called that because the head is upside down. The angle that is between the 45 and the chamber surface. I brought that angle in too big. With some reading, it seems like people just get it to show a thin line and that's enough. How do I make sure I am not going to far?

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