[GPCONV]

Picked up a set of 4X heads that were off a 12 second, mechanical lift cam motor, started tearing them down to check them over and found the intake valves are longer, is that something they do as a mod to the Poncho heads for some better flow?

[screamingchief]

Assuming your talking about physically longer valves,,,and not just a taller spring installed height...

Longer valves (either intake or exhaust) are typically used mostly just to allow one to use a taller installed height valve spring,that is done to gain more retainer to guide/seal clearance when employing higher lifts @ the valve.

Now does that help flow,maybe yes,maybe no,depends on how you look @ this,if the head flows well at such higher lifts,then yeah it'll help flow some to do such (open the valve further),if the head(s) are pretty much already well past their peak flow,then no it really wont help flow much @ all.

You'd need to post flow numbers for the given head,and cam specs to get a good idea if that was close to optimum or not.

HTH

Bret P.

[GPCONV]

Thanks for the reply chief, the clearance thing would explain why a bunch of the valve stem seals are damaged. I'm trying to get the heads back to stock configuration for a hydraulic cam, am I assuming right I should probably get matching and correct length valves?

Steve

[screamingchief]

Well,yeah it's a good idea,that way all the valvetrain components are mostly the same.

As yours is now,it should have had two different lengths of pushrods in it as well,seeing as it has different height valves.

I often use the '67 to '70 length (5.095"/5.110") valves in the "smog" heads,as it allows one to use the springs that install @ 1.700" IH,and gives plenty of room for additional lift,as they are +.100" longer than the OE length for the "smog" heads.

But should the cam your going to use be fairly mild in the lift department,and standard ratio rockers are being used,the stock length (4.980" appx) will do fine with the right springs.

HTH

Bret P.

[PONTIAC DUDE]

You need to have the same height across the tips of the valves to run the right pushrod & rocker arm geometry.

They might be different but all the same height in that area. Check that first.

You can always cut the guides down for retainer to guide clearance. Plus you can also cut the pockets to get your installed height............... within reason.

[GPCONV]

The heads will be stock configuration with a mild cam and matched springs, got rid of the roller rockers so I can have my factory valvecovers wA/C, thanks again for the numbers chief, I think I remember that 5.110 length from a set of '69 heads I worked on years ago.

DUDE, that looks like some wild stuff, you got a sound bite of that superchager?

Steve

[PONTIAC DUDE]

No sound bite. LOL.

Like I said. install all the valves, use weak springs on the outers from like Home depot and check with a straight edge for same height.

Becareful with stock rockers and cam lift. Also spring pressure. One of the weakest areas of a Pontiac is the valvetrain. Pushrods bend and rockers break in the ball area depending on the camshaft use.