63?? 327 swirl polished valves

[David H.]

I would like to know just when and or if swirl polished valves were used in the factory 327 hi-perf engines. thanks: David

[Joe L.]

Re: 63?? 327 swirl polished valves

I would like to know just when and or if swirl polished valves were used in the factory 327 hi-perf engines. thanks: David

David-----


My recollection is that swirl-polished valves were first used for Corvettes for the 1964 model year with the introduction of the 2.02" inlet and 1.60" exhaust valves. These valves were GM #3849814, inlet, and GM #3849818, exhaust.

The GM #3849814 inlet valve was used for all 2.02" valve size applications from 1964 through 1979 (L-76, L-84, L-79, L-46, LT-1 and L-82). The GM #3849818 exhaust valve was used for all 1.60" exhaust valve applications from 1964 through 1972.

[David H.]

Re: 63?? 327 swirl polished valves

Joe; you are the man!!!

I was discussing this with Keith M. tonight and my guess was when they raised the HP. very good info; thank you much; David H.

[David D.]

Re: 63?? 327 swirl polished valves

David or Joe,

I have a '64 327x365hp but have no idea what thou meanest by 'swirl polished valves'......

Not sure this is the correct venue for a dumb question but, any chance I could get an explaination, example, or picture posted showing what this means or looks like? I'm always interested in learning more.
Thanks in Advance,
David

[Joe C.]

Re: 63?? 327 swirl polished valves

David or Joe,

I have a '64 327x365hp but have no idea what thou meanest by 'swirl polished valves'......

Not sure this is the correct venue for a dumb question but, any chance I could get an explaination, example, or picture posted showing what this means or looks like? I'm always interested in learning more.
Thanks in Advance,
David

David,

I believe that "swirl polished" is "marketing speak" for polished, or smooth finish, primarily in the area between the seat and the stem radius. It is "code" for "more money"! I believe that this is done in a lathe or drill press, using fine abrasive to polish the surface. This can be done at home, so why pay for it?

Same "market code" applies to "stainless steel racing valves". Here is en excerpt of what I have been able to learn from metallurgists:

"Inlet valves were typically SAE 1547, which is essentially a medium carbon steel (.47% C nominal) with modified (higher) manganese content (~1.5% Mn). This was/is by far the most common for intake where temperatures are modest.

Exhaust valves were typically 21-4N (21% Cr, 4% Ni) or 21-2N in later years (21% Cr, 2% Ni, 2% N). Although these exhaust valve steels exhibit 'stainless' qualities (since they contain >11% Cr), their numbering convention does not fall into one of the familiar 'stainless families', like type 304, etc, so they're often not looked upon as a 'stainless' material. The 21-2N came about as a way to avoid the high cost of 4% nickel by substituting 2% nitrogen. The nitrogen has a hardening affect -- like carbon -- but does not have the 'toughness' or corrosion resistance of the higher nickel 21-4N.

Stem coating is via hard chromium plating, since it has a low coefficient of friction and can retain lubricants. Nitriding is sometimes used in 'modern times', but much less frequently because it's a cyanide process & is not always compatible with intake valve materials."

To my knowledge, exotic, expensive materials are unnecessary unless your engine runs alcohol, or is turbocharged/supercharged. Normally aspirated engines running exhaust temps less than (about) 1000* Fahrenheit can use ordinary "alloy steel" (sometimes lumped into "stainless"). Of course, this primarily applies to the exhaust valves.

High strength is not an issue, unless your engine runs in excess of (about) 8000RPM and/or has a very high lift roller cam with high tappet acceleration, which requires very stiff valve springs.

Most important consideration is optimized profile and seat config., closely followed by smooth, polished finish (especially on the exhaust side). Low inertial weight probably enters in at RPM's over (about) 6500 RPM.

Very important is how the stem tips are hardened, and the thickness of the chrome plating on the stems, adjacent to the valve guides.

[Duke W.]

Re: 63?? 327 swirl polished valves

My second addition Chevrolet Power manual refers to a 2.02" "swirl polished" valve, and the part number is 3849814. This is also the replacement number in my '77 P&A catalog, and I think this part number jibes with a late CY 1963 release date, which supports Joe L's conclusion that the first 2.02" valve received this treatment.

Typical valves have a somewhat rough surface on the "backside" (upstream side- opposite the "face", which is what faces the combustion chamber) and polishing this surface likely has some benefits to flow, especially at low lifts. Also, for maximum performance the unused portion of the valve's seating surface should be ground down with a 22 deg. stone leaving about .010" overhang. This is often referred to as a "backcut" off the valve, and it should aid low lift flow. If the valve you select is not polished, it can be so polished on a valve grinding lathe - or any lathe for that matter. The F-M catalog codes such treatment as "FM" for "fully machined."

My valve recommendation for engine restoration is "OE equivalent" as the OE valves have never been problematic and are much cheaper than stainless. Often original inlet valves can be used - and I think this is okay if stem wear is no more than .0005". Exhaust valve stem wear is usually greater than on the inlet side, and if the stems are worn more than .0005" I recommend replacing them even if they have sufficient margin for grinding.

The OE valves from the sixties can be characterized as "alloy steel". None from that era were stainless steel AFAIK, but if the exhaust valves need replacing a 21-2N stainless should be more than adequate. SS on the inlet side is a total waste of money in my opinion.

Back in '61-'63 SHP/FI engines with 461X heads did get a "special" 1.5" exhaust valve that had a Silichrome #1 tip, and many current replacement valves are fabricated entirely from "Sil 1".

The following is list of materials used to make replacement valves:

1541 - basic managanese valve steel - okay for most inlet valve applications

8440 - higher alloy with some chromium - very good material for restoration engine inlet valves.

Sil 1 - 8.5% chromium, good basic choice for exhaust valves.

Sil XB - Ferritic stainless steel 20% Cr, 1.3% nickel - an upgrade from Sil 1

21-2N - Stainless, 21% Cr, 2% Ni - bulletproof material for restoration engine exhaust valves.

21-4N - Stainless 21% Cr, 4% Ni - way overkill for any road engine application.

When choosing valves for an engine restoration project, always make sure that the stem surface is compatible with the valve guide rebuilding technology being used. The best source would be to talk directly to the valve guide system manufacturer. Don't take the machinist's or "engine builder's" word as gospel.

Joe C. - The 2N refers to 2% nickel instead of the 4% of the 21-4N material. The nitrogen content is 0.2-0.4%, a little more in 21-4N

http://www.cartech.com/products/wr_products_valve_212n.html

http://cartech.com/products/wr_products_valve_214n.html

Note that exhaust emission controlled engines - which usually implies "ported vacuum advance" and a generally retarded spark advance map from what is optimum for maximum performance and fuel efficiency causes the exhaust valve to run much hotter in normal driving, which places considerably more thermal stress the valve, and this is justification for upgrading at least one material level from what was OE on the antecedent non-exhaust emission controlled engine.

For a C1/C2 Corvette engine restoration that is not going to be endurance raced or used to haul 6000 pound trailers, an 8440 inlet valve and Sil 1 exhaust valve are good choices, and is an upgrade from most OE valve materials. Put what you save over stainless steel valves into bullet proof connecting rods and head massaging.

Duke

[J M.]

Re: 63?? 327 swirl polished valves

David,

I believe that "swirl polished" is "marketing speak" for polished, or smooth finish, primarily in the area between the seat and the stem radius. It is "code" for "more money"! I believe that this is done in a lathe or drill press, using fine abrasive to polish the surface. This can be done at home, so why pay for it?

Joe:
I think if you look at a quality swirl polished valve, i.e Manley, you will notice that they are not polished smooth but are finished with a swirl polish in the area between the seat and stem.

[David D.]

Re: 63?? 327 swirl polished valves

Thanks everyone....

I was worried about asking such a dumb question, but I am so curious about this stuff that I figured I take my chances and post the question anyways.
You all are gentlemen and scholars.

Thanks Again,
David

[John N.]

Re: 63?? 327 swirl polished valves

David-----


My recollection is that swirl-polished valves were first used for Corvettes for the 1964 model year with the introduction of the 2.02" inlet and 1.60" exhaust valves. These valves were GM #3849814, inlet, and GM #3849818, exhaust.

The GM #3849814 inlet valve was used for all 2.02" valve size applications from 1964 through 1979 (L-76, L-84, L-79, L-46, LT-1 and L-82). The GM #3849818 exhaust valve was used for all 1.60" exhaust valve applications from 1964 through 1972.

Joe
Swirl-polished valves were used in 57 on at least the 270 & 283 HP. I believe they were used on most high horse applications.
Regards

[Barry H.]

Re: 63?? 327 swirl polished valves

Joe, My 57 283 FI had swirl polished valves, intake & exhaust from the factory. Also found same in my 62 327 360 hp FI engine.
Barry Holmes #940

[Clem Z.]

Re: 63?? 327 swirl polished valves

these valves have a ground finish along the stem and under the head done by a shaped grinding wheel. std valve have just as forged finish in this area which will cut down on the flow compared the the so called swirl polished.

[David D.]

Re: 63?? 327 swirl polished valves

Clem,

Thank you for the picture, but unfortunately when I click on it and it expands it is very blury. At least for me.

Could I request you try to re-take and post again?

David

[Clem Z.]

Re: 63?? 327 swirl polished valves

this is another try as my camera does not want to focus in when you try to take close ups even using the macro setting

[David D.]

Re: 63?? 327 swirl polished valves

Clem,
Much better....thanks again.
David

[Michael H.]

Re: 63?? 327 swirl polished valves

Joe:
I think if you look at a quality swirl polished valve, i.e Manley, you will notice that they are not polished smooth but are finished with a swirl polish in the area between the seat and stem.

Yup, the word "polished" should never have been used to describe the valve underhead. It has basically nothing to do with polishing.
The real meaning is the method used to machine the underhead of the valve. The machining, or actually grinding in this case, is much different than a typical lathe cut valve. If you inspect the grinding, you will see that it moves across the head on an angle and continues on a third dimension angle up the stem.
The purpose of the angle grinding is for strength.

Lathe cutting automatically creates stress risers, especially at the worst possible area of a valve, the transition of head to stem.

The process should have been called swirl grinding instead.

Also, this process was used long before the 1964 model. Seems I remember these from as far back as 1961?