[79transam79]

Does anybody know what the maximium lift you can go (6x heads) without modifying the valve length or head, the heads have been taken down to 95cc chamber size. Trying to fiqure out what the largest cam I can put in without spending a thousand to modify to longer valves, and bigger valves.

[Johnny406]

What I always heard was .500 with stock geometry parts.

I ran a Isky 292 mega cam with .505 lift using factory rocker arms and later 1.52 Comp Magnum Roller Rockers on a set of 6X-4's. Those were with stock valves, SSI springs and stock replacement seals (not PC) and new retainers.

With that in mind, I'm now running a XE274 (.488 lift cam) on a long valve (1.9 installed height, not kidding) milled .080 6X-8 heads. I could probably get away with .600 plus now but the motor doesn't need it.

[BILTIT]

I think anything over .470 is starting to push it with old springs.

[smagnotti]

Yes, .460" to .470" with stock springs and retainers. Piston to valve clearance you must check.

[79transam79]

Not planning on stock spring, planning on buying spring and cam package.Not sure which one.

[grandville455]

I run 75 6x-8's at 98.c.c and i use H.S 1.65's closer to 1.72 and with that i am at .556 lift int and exh with crower 68404 springs at 1.6 installed height,but i also have my heads cut for positive seals too...just check and double check everything before u fire her up

[GonicGM]

Everything stock on a d-port and running a pc seal, the stock retainer will contact the seal @ between .440 and .460 depending on the seal.

As Johnny406 states, you can run more lift with the simple o-ring valve stem seal below the keepers in the retainer. You may want to run the spring cups in that case also to further oil control.

[rad400]

What is the most lift you can run with stock valves and correct springs. I have #12 heads 406 motor

[GonicGM]

Originally Posted by rad400

What is the most lift you can run with stock valves and correct springs. I have #12 heads 406 motor

With stock or aftermarket retainers?
with or without a PC seal?
With guides cut down or not?

The number for stock guides and retainers and pc seals is already stated above. It's not a specific number, it will vary somewhat head to head based on the seal, factory maching of cylinder head, how sunk the valve is. Over .440 lift, I'd check it.

Valve reliefs in piston limit you at some point based on cam profile and cam timing, head surfacing, deck height and gasket thickness.

[smagnotti]

I have run .470" on #12 heads with one valve job, if the head is still vergin (just the factory valve job) I would go no more than .460" if you want to be able to just slap it together.

[79transam79]

So what I'm getting from the feed back is that I will need the longer valves and check clearance to get near a .500 lift. Are these type of heads worth spending 1000 dollars to do the work on?

[Will]

Umm, no, all you need is a set of Crower 68404-16 springs.

There are two clearances that determine how much lift you can run. The coil bind height of the springs and the spring retainer to valve seal clearance.

The Crower springs will easily handle .550" lift at an installed height of 1.60". The problem is that the retainer will contact the valve seal before you get to that lift.

You can have the bosses on the top of the valve guides cut down for a smaller seal and gain more clearance, or as mentioned you can run a different kind of seal such as an O-ring on the valve.

Some aftermarket spring retainers also give more clearance before they will contact the valve seal, but they won't retain the stock O-rings.

Oh, and stock installed height is 1.58". Once you've had a valve job done, you'll find that the installed height has increased to right about 1.60".

[smagnotti]

You do not need longer valves to hit .500" lift with out concern, just different springs and different retainers that unlike the factory ones, do not use the o rings and are shorter in overall hight.

[79transam79]

Do I need to do any machine work to except the different seals? I was planning on blocking the crossover and having the head cleaned up, was told about 300 or 400 (heads don't have more than 3000 miles on them at least that what I'm told) but as soon as I talked about longer and larger valve the price went to 1000 fast which is probably a fair price considering parts and labor, but not sure if thats the way to go.

[screamingchief]

Some aftermarket spring retainers also give more clearance before they will contact the valve seal, but they won't retain the stock O-rings.

Yessir,but for an exception to that look into the corresponding retainers that crower recommends for the #68404-16 springs,the retainers are #87048D-16,I used that set-up on a set of 6x8's I sold here a while back,that set-up had a ton of room and those retainers still sealed with the factory O-rings.

The crower #68404-16 springs also fit in the stock metal shields no problemo on those heads,just remember the shields take up some installed height (.030") but do note the crower retainers accounted for that fact as they are +.150" and that gives plenty of IH "adjustment room" for the pontiac heads.

And I checked this stuff pretty closely on those heads,both heads,both intake valves and exhaust valves,those heads had the stock valves in them with a standard "jobber" style valve job on them.

IIRC those 6x heads used a .060" shim under the spring and the IH was just a tic over 1.6",clearance I recall was easily enough to go .525" or so as I remember but I advise checking on any specific heads to be sure.

The cam I was going to use with those heads was the crower #60210,and that cam has .501" lift on the exhaust side with 1.5 rockers and I felt perfectly safe with that combo,and with a "true" 1.65 rocker the retainer to guide clearance (.050"-.060") was right on the edge I believe,but those heads were'nt slotted for the 1.65's so they were'nt in the plans with those heads.

The crower valvetrain parts would be my most "basic" valvetrain choice for most any "high performance" pontiac head use,JMO.

[79transam79]

Trying to fiqure where to start, do I pick my cam first or send the heads out and see what my limits will be. Just want to do this job once?

[screamingchief]

Well,that depends,are these heads getting ported?

If not than there is really no need to be overly concerned with lifts much beyond what has been discussed here already as the head really wont flow any better at higher lifts.

What sorta cam are you thinking about?

Like has been advised,the crower #68404-16 springs are the best for more or less stock IH heads (1.60" appx.).

And like I said the crower "recommended" retainers for those springs add some extra clearance while still sealing with the OE O-ring valve stem seals and shields,this is when the crower retainers are compared to the OE retainers,the other alternative is the OE retainers can be "ground" for some more clearance,and they too will still seal,but that is time consuming IMO and I prefer to just buy the crower retainers myself.

And if you machine for the viton seals often there is a little bit more room to be found if it's done correctly.

But if your after lifts much beyond say .550" lift or so,yeah your probably gonna be machining the spring seats or adding longer valves and corresponding longer pushrods to use the 1.70" installed height and the corresponding springs for that IH.

Does that help?

[Skip Fix]

If you look at how deep a 6X chamber is you'd have to have a BIG cam to even need piston notches. They are almost 0.200 deeper than a RAIV head!

One other reason to look at other springs even IF the stock ones wouldn't hit is most cams with more lift are more aggressive and need more seat pressure to keep things where they should be.

[rad400]

I have crower 68405 springs and aftermarket lock retainers seals and o rings heads are unported. could I get a bigger lift cam or use 1.65 rockers with out braking factory valves? cam is 60210 heads #12

[79transam79]

Yes that helps, I,m planning on about .500 lift, so with a little extra machine work I can get out of it kinda cheap and not worry about a problem. Will the larger valve help much?