[sdbob]

Stopped at local small machine shop. Asked about 6x heads. He is saying stainless steel valves. Instead of Pontiacs std o ring at top valve he wants to use another positive seal. Should I install 1.77 exhaust valves ? No porting. I'm not going racing just street 455,cam RA IV type. Dual carter afbs on bathtubs for my 63 Lemans. Any pointers I havent done any machine work in 30yrs.

[25stevem]

Yes the guides should be topped for positive Viton type seals.

Yes, ditch the stock valves for stainless.

No need to go up to the bigger Exh valves with the RA4 Cam for usage up to 5200, but do put a 30 degree back cut on the new Exh valves for better low lift / blow down action.

Have the shop trim off the remains of the machined lip on the short turn in each Exh port which is a 2 minute job and you have 5 to 8 more cfm which helps that big motor make a tad more power and also run cooler.

With the .469" lift of that Cam the valve springs need to be up graded and with the install of the positive valve seals the stock valve spring oil sheilds should not be used.

The stock 3/8" top rocker arm studs need to be up graded to 7/16" and a set of poly locks to adjust the valves.

New valve keepers should go on your list of parts also.

[Skip Fix]

I'd go longer 5.09 "standard D port" SS valves so you can get a taller valve spring installed height

[sdbob]

Thanks guys for the small ideas. I'll use them.

[NeighborsComplaint]

I had 1.77 exhaust valves installed in mine. The machine shop said it was no more expensive to cut the new seats that machine the existing. The seat area is induction hardened so no need to install new hardened seats.

Go with the Ram Air IV length valves (5.213" Intake/5.230" Exhaust) instead of the standard Dport length and you're set for 1.7-1.8" installed height springs for .500"+ lift without cutting the heads for spring pockets. You can fine tune your installed height with dropped retainers or offset locks without resorting to machining and/or shims.

[Cliff R]

Longer valves will require custom length pushrods so plan accordingly.

For "mild" set-ups with stock 6X iron heads you can use the stock length valves, they are just a tad under 5". With stock retainers and oil shields installed height is 1.586" for stock springs. Loose the shields, PC seals and stock retainers come in really close to 1.6".

Use Crower 68404 springs set at 1.600". Check the clearance between the bottom of the stock retainers and the top of the new PC seals. You should have enought clearance without any addtional work. If not you can remove some material from the bottom of the stock retainers with a grinder. That area is only to seal the factory "O" rings so not hurting the strength of the parts.......

[Skip Fix]

Cliff my 6X-4s with a 0.050 ,ill and 5.09 valves took a stock length pushrod.

The "stock" 6X valves are 4.98".

[Cliff R]

I guess ...498" qualifies as a "tad" under 5"! Was going from memory and didn't want to take the time to look up the specs.

I've built quite a few of these engines with iron heads using the Crower 68404 springs at 1.600" installed height. Pretty easy to get there, and with a little work you can EASILY run up to about .550" lift with plenty of retainer to seal clearance.

Moving up to 5.100" valves and 68405 springs you can get there with less work and run cams with more lift. Have done it both ways and it really doesn't much matter about having to go to custom pushrods because it's pretty rare these days if stock length pushrods fit the bill anyhow.......

[25stevem]

No every cam has the same base circle so this is where different push rod lengths may be needed .

[NeighborsComplaint]

RA IV length pushrods put everything back in alignment.

[sdbob]

I have brand new RAIV push rods,valves in my parts. After hearing about possible problems with theRA valves I'll go stainless steel.

[NeighborsComplaint]

When I built mine I was going to go with the Manley SS valves with the undercut stems. They were pretty expensive and at that time Ferrea was not even around. I wound up buying an NOS set of SealedPower OEM RA IV replacement valves. Couldn't tell you if they were 2 piece or not, but I buzzed that motor pretty hard with a Comp Magnum 305 cam and 4.56 gears and had no valve issues.

When I re-freshed the motor 10 years later with different pistons and heads, I went with the Manley one-piece SS valves with the undercut stems in RAIV length. I figured the undercut stems helped reduce the valve weight a bit and added some low-lift flow. They were a "thing" at that time and are still around but I never hear them mentioned on this board.