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Intake Valve Diameter Reducing?

General engine tech -- Drag Racing to Circle Track

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CnC74
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Re: Intake Valve Diameter Reducing?

Post by CnC74 »

Sorry 40/80 Faza cam too
Nut124
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Re: Intake Valve Diameter Reducing?

Post by Nut124 »

I buy from:

Vick Autosports
Midwest-Bayless
Auto-Ricambi

I have a set of 40DCNFs I no longer need plus a lot of jets, venturis.
CnC74
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Re: Intake Valve Diameter Reducing?

Post by CnC74 »

Is that where you sourced the valves? If I can get away without reseating and using a slightly bigger 1mm valve then I'll be good with that for sure
CnC74
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Re: Intake Valve Diameter Reducing?

Post by CnC74 »

Nut124 wrote: Sat Jan 02, 2021 3:24 pm I buy from:

Vick Autosports
Midwest-Bayless
Auto-Ricambi

I have a set of 40DCNFs I no longer need plus a lot of jets, venturis.
Never tried the Auto-Ricambi but do order from Vic's and Matt at Midwest
BlitzA64
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Re: Intake Valve Diameter Reducing?

Post by BlitzA64 »

Use the margin to your advantage. If there's plenty of valve to piston clearance, you can use it to bump the compression ratio a tiny bit if needed. If you plan on refreshening it often, the valves will last through a couple more valve jobs. If you value a lightweight valve train more, cut them down to reduce the weight.
What effect would a thick margin have on intake flow/reversion if any?
dannobee
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Re: Intake Valve Diameter Reducing?

Post by dannobee »

BlitzA64 wrote: Tue Jan 05, 2021 12:27 pm What effect would a thick margin have on intake flow/reversion if any?
It depends. Wider margins *usually* help intake flow a couple CFM, but not always, and need to be checked on a flow bench. On the exhaust side you can use the wider margin to put a radius on the edge to help the exhaust flow.
CnC74
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Re: Intake Valve Diameter Reducing?

Post by CnC74 »

Decided that rather than throw caution to the wind and start hacking at the valves and risk messing up any hardening treatment that they might have teceived when they were manufactured I'm going to leave them as is and buy a set of seats to match from a very knowledgable Fiat fellow out of Australia. Any porting help, tips, advice or direction would be greatly appreciated. I know that most of the guys here deal with much more HP and performance but I'm sure that the same principles apply so I can use the help.
Thanks so much for the help already given guys
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Re: Intake Valve Diameter Reducing?

Post by mt-engines »

CnC74 wrote: Fri Jan 08, 2021 9:15 am Decided that rather than throw caution to the wind and start hacking at the valves and risk messing up any hardening treatment that they might have teceived when they were manufactured I'm going to leave them as is and buy a set of seats to match from a very knowledgable Fiat fellow out of Australia. Any porting help, tips, advice or direction would be greatly appreciated. I know that most of the guys here deal with much more HP and performance but I'm sure that the same principles apply so I can use the help.
Thanks so much for the help already given guys
Cliff
Or you could just open up the SBI catalog and order whatever seat ring you need.
If you are having a shop install the seats, just have them order the seats. I'm sure you can get a set locally for less than the shipping from Australia.
CnC74
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Re: Intake Valve Diameter Reducing?

Post by CnC74 »

Already tried and no luck.
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Re: Intake Valve Diameter Reducing?

Post by Momus »

CnC74 wrote: Fri Jan 08, 2021 3:53 pm Already tried and no luck.
This thread has turned into a train wreck. :?

Be aware that re inserting and re valving a head is far more fraught with difficulty and unpleasant possibilities for neophytes than cutting valves- which by the way are usually uniform hardness through the head.
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Re: Intake Valve Diameter Reducing?

Post by modok »

CnC74 wrote: Fri Jan 08, 2021 3:53 pm Already tried and no luck.
You need to know what size seat ring you want. The part number is the OD OR the suggested counter bore size. Read front of catalog to learn more.
It is easier to machine the seat to fit the seat pocket, than it is to machine the seat pocket to fit the seat.
Once again making things harder for yourself from the sound of it.
CnC74
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Re: Intake Valve Diameter Reducing?

Post by CnC74 »

Trainwreck? Well, maybe I suppose. Once again I would like to apologize if my inquiries have annoyed anyone. My goal here has only been to seek advice from those who know what they are doing. Isn't that the whole idea of these forums?
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Re: Intake Valve Diameter Reducing?

Post by dannobee »

Momus wrote: Sat Jan 09, 2021 2:59 am Be aware that re inserting and re valving a head is far more fraught with difficulty and unpleasant possibilities for neophytes than cutting valves- which by the way are usually uniform hardness through the head.
^^^This^^^

Since exhaust valves routinely get over 1200degF, if there was any "hardness" before, it sure ain't gonna be the same after a good romp or two. The only thing hardened is sometimes the tip where the rocker touches the valve.

If you have your doubts, practice cutting up an old valve first. You can even buy brand new valves for what, $4 each? This really is a very basic machining exercise. Replacing the seats, as Momus said, is very much more involved. And even very experienced machinists have had them fall out/loosen up in service. And valve seats are often hardened where the valves aren't.
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