Valve sizes for 360 head stroker?

[Moparmal]

One for Moper, BJR etc -

Wondering which would be better -

Engine will be 318/390 cui SB stroker running cast '586' 360 heads that currently flow around 235 @.550-

1.5 Factory adjustable rockers (yeah I know - 1.46:toothy10

Heads have been taken out as far as my guy wants to go.

Am I better off :

A - Running the existing 1.96 tulip valve with 3 angle valve job - or

B - A 2.02 backcut nailhead with a 5 angle valve job?

No other options available due to budget - but I have the SS Nailheads in the shed.

 

[BJR Racing]

Mal,
For a 390 CI engine I would run the 2.02's and redo the bowls. This should make the heads flow in the 250-260 range at .550.

 

[Moparmal]

Thanks Bobby,

The 2.02s won't cause any "shrouding"?

 

[BJR Racing]

You would see it more in a 318 head than you would in a 360 as the chambers are larger in the 360 head width wise. For comparison it would be like a 1.88 in a 318 head, verses the 1.78. Also to the CI's will need the larger valve. Reguardless of shrouding.

 

[moper]

2.02 nailheads and the 5 angle, definately. It will shroud on the 3.94 bore, but the net gain will be more than the losses. On the larger bore engines I have the chamber cut larger with the 5th angle cutter. Out to the head gasket bore. But on this one it will cause a bigger step where the top of the block is vs the side of the chamber. If you're at all curious, when the heads are done, bolt one temperailly to the block with no pistons or crank and look "up" from the crankcase side. Look at the cylinder wall area adjacent to the intake valve and you'll see the step I'm talking about.

 

[C130 Chief]

Moper, not to hijack, but when you refer to "nailhead" I assume you me an SBC pattern valve, correct? I know the Chevy valve used to be a popular swap because they had a smaller 5/16" stem (lighter) and stainless valves were cheaper and more available. Would a 1.94 intake be a reasonable compromise with a 3.94 bore? Also, how does the overall length compare?

 

[Moparmal]

Thanks for the info -

Chief - Its all good, its a relevant question you ask.

FWIW, My 1.96 are tulips, and my local porter reckons they fall on their face at around 230 cfm -

My concern was shrouding but the gains seem to be worth it (Thanks BJR and Moper).

Mine are 2.02 Chev Echlin SS Nailheads - I have run them before on other heads.

They are 1/10th longer - so I got the springs shimmed

They are tough as Billygoats teeth.....I had a P-V problem early with my old engine, and even after punching dents in the forged slugs,

..........I gave the valves to a local ex NASCAR machinist and they spun up absolutely perfect and true!!

 

[moper]

Chief, I may have it a little wrong here... But I call the shape of the peformance valves nail heads. The ones with the basic flat head... I know Buick made the "nail head" 425 or something like that but I dont know if that was a different style valve. The SI stainless valves I use are like that too.

 

[1wild&crazyguy]

engine pro makes a good stainless 11/32 under cut nail head valve.

with the small bore I like the idea of 1.94 11/32 under cut valves myself.jmo