Author Topic: Cut down 427 "tulip" valves in a 428CJ head..  (Read 1529 times)

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gt350hr

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Cut down 427 "tulip" valves in a 428CJ head..
« on: January 21, 2022, 02:19:54 PM »
 I think I remember that the CJ head liked a "flat valve'' and a tulip valve hurt HP . I have a set of XE valves that appear to be 427 MR's cut to 2.095 and they have a 45* seat , not 30*. Before I cut the angle in my otherwise unmolested 68 heads I would like to know if it's a good move. I could always cut the valve to 30*s as there is enough margin to do so .
  Thanks ,
   Randy

cammerfe

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #1 on: January 21, 2022, 06:18:51 PM »
As I remember, it's the exhaust valves that benefit from being tulip-ed. Intakes should be flat.

KS

pbf777

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #2 on: January 21, 2022, 07:27:26 PM »
     Hey Randy,

     The biggest advantage (in my book.   ::) ) to the "nail-head" vs a "tulip" is the additional port area presented in the bowl on the backside; though this value observation is of typical American "inline-valve" cylinder heads often presenting a rather low port presentation and short-turn to the back-side of the valve; whereas for example hemi-heads demonstrating steeper port presentations with more direct shot to the back of the valve do better with the greater back-side angles of the "tulip" valves.

     In my experience  (again!   ::) ) of porting and flow benching work, a superior flow value of a 30° or a 45° seat angle has more to do with the leading and trailing angles and distances on each side of the seat angle involved (but there are other influences such as port bowl choke below the valve seat machining and chamber roof profile) not truly that one versus the other is just always better, and unfortunately this often may have more to do with the condition of the current seats and with these old castings also previous work done by others post the O.E.M..  Remember, at this point in time, often much of this work is as much of a "salvage" operation as it is one of performance betterment and the sum of material to work with is somewhat limited, this meaning more, particularly on rare and/or valuable castings, when referring to removal of seat casting material, isn't always a better idea.  Also be sure that the tulip valve, particularly when head diameter is cut-down from something greater, that there truly is a back-side profile that will accept the 30° seat angle and permit an undercut angle to define the seat width and position in the relationship to the cylinder head.   :-\

     Then there is the fact that the velocity of the incoming mixture volume, as it enters the cylinder, is at it's highest as crossing the valve and cylinder head seating surfaces (point of constriction), so this translates into a certain sum of directional control for this stream into the cylinder thru seat angles.  Awful lot of considerations here, including for example valve shrouding by the chamber and cylinder walls; but for thought, I was told by a quite knowledgeable guy ages ago that generally 30° seats were deemed superior at lower engine speeds hence mixture velocities for better dispersion of the mixture thru-out the cylinder, and the 45° was deemed superior at greater engine speeds with faster piston motion down the cylinder coupled with the higher port velocities had, and that even if less efficient in the initial distribution within the cylinder the higher piston velocities with greater turbulence on the up-stroke aids in offsetting such.   :)

     But in answer to your question, in my experience (oh-boy! ::) ), it seems most have chosen to use "Nail-Head" valves cut to 45° for the small valve FE's; they're lighter in weight too!  But I wouldn't like the idea of changing the 30° seats to 45° in a set of "virgin" heads, and I do agree with the idea of the exhaust valve having more valve head back-angle dimension.  8)

     Scott.

     

     

     

     
« Last Edit: January 22, 2022, 12:16:33 PM by pbf777 »

pbf777

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #3 on: January 22, 2022, 12:28:19 PM »
r
« Last Edit: January 24, 2022, 02:56:22 PM by pbf777 »

gt350hr

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #4 on: January 24, 2022, 10:18:30 AM »
  Thank you I wanted to know before I cut up these NOS MR valves , to match the used XE valves. I'll probably put them up for sale.
« Last Edit: January 27, 2022, 11:56:57 AM by gt350hr »

Joe-JDC

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #5 on: January 24, 2022, 11:19:25 AM »
I have cut the hollow stem intake valves down for use in CJ heads, and aluminum heads at 2.150" with 45* seat and 30# back angle.  The heads cut for the 45/46* seat and flow increases over the 30* seats quite a bit.  The lightweight of the valves allows less spring pressures on flat tappet camshafts for less break-in issues.   Joe-JDC
Joe-JDC '70GT-500

gt350hr

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #6 on: January 24, 2022, 01:10:48 PM »
   Thanks Joe.

Posi67

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #7 on: January 26, 2022, 03:22:15 PM »
When having my Dove CJ heads done years ago we found the "nailhead" valve on the intake picked up considerable flow over the Tulip. I ordered a custom set of Manley 2.15" and think I have a new set of Ferrea tulip valves here still. Basically parroting what was said above.

KMcCullah

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Re: Cut down 427 "tulip" valves in a 428CJ head..
« Reply #8 on: January 29, 2022, 09:27:40 AM »
Years ago I found a smokin deal on a set of Manley tulips for a 427 LR. At the time I was mud dragging a std bore 390 so I cut the valves until they fit in a 4.054 cylinder. Ended up with 2.150 and 1.65. Sent the valves and a set of beat down C4-G castings to Les Schmader.
He came up with some pretty decent flow:
235/181@.300
285/200@.500
295/203@.600
300/205@.700

They worked well with a port matched Performer RPM and an 830 Nascar carb. Won a few races too.
Kevin McCullah