Anybody know how far you can cut the spring seats in a 350 head? I want to reduce my spring pressure a bit, about 40 pounds. I don’t know how close to water those seats are, cutting the seats is my only option…… I think
Mark there is no problem with cutting them deeper. I just look at the mule heads I have here and the roof all around the guide area is solid with no water passages to fret over. In fact here’s what I measure there just for kicks. This was taken from just in front of the valve guide boss on the roof of the port to the factory cut spring seat with my caliper loaded in thru the runner. This is the thinnest part of the roof around the whole guide. even if you ported the roof around the guide there should be no issue, because as you can see from the face of my inside caliper the thickness is .540”. if you have gone down to 11/32” valves then .050” offset keepers would be another way you could go provided that you still had enough retainer to rocker clearance with the valves closed.
First step is to determine how much you need to lose 40 lbs.. .050? .100? That will help decide the proper course of action.
I would be concerned about the structural integrity of the valve guide if material is removed from the spring seat. If too much is cut, isn't it possible for the guide to break from the head, especially if you have a high lift cam ant the geometry isn't perfect.
Mark, I'd put the spring on without the locator and check pressure. Then measure thickness of locator seat. Then you can tell how much to cut. They will lose a little pressure over time so go for 150 lb.
If a valve is side loading a cast iron guide enough to break it then the geometry is so far off that other valvetrain stuff would be getting chewed up before hand! Have you ever looked inside some full on aluminum race heads and seen how short the bronze valve guides are and how thin they have been reworked to where they stick out into the runner?
Good to know thank you! That’s my target more or less 150 lbs on the seat. Most of the spring seats are .060 (some have been sanded when they installed them) So yes, I do have to measure and look at my notes of installed height and figure my highest height. This is making my head hurt. I’m not concerned either about the guides breaking, they’re pretty long actually.
Offset keepers if you can find them for your angle and valve size is an easy way to move the retainer up by .050
Mark, If you have aftermarket single groove valves these may work. Stock Buick valves have oddball Buick keepers. If you get these, check rocker to retainer clearance. Locks, Keepers, Hardened 3/8" X 7 Degree, .050" Up Locks, 1/2 Set - Alex's Parts Sales (alexsparts.com)
I’ve heard guys call them “liberty locks” I don’t know why, something to do with the weird 11 deg. angle??? I know the later V6 (maybe just the Turbo V6) had the standard 7 deg. locks with the step (lock) in them and some locks had the step higher or lower, pretty cool to adjust height!
I know the Buick V6 has them, but those use the more available 7 degree locks, my GN had ‘em. The goofy 11 deg. V8 locks have no groove so to speak.
Another question, can I use an old valve stem for an arbor or should I buy the proper arbor for the cutter. The arbor is 50 bucks The seat cutter is 120. If I have to buy the arbor I will, but figured I’d ask those “in the know” first.
Don't use an old valve stem. I would guess they fit too loose.... allows the cutter to move and not stay centered
You can use a valve stem its not a concern, but some cutter body's do not take a round shaft they take a triangular section up in the body so that the Allen set screw holds them in tight. Either way the end the goes in the guide needs to be lubed up well, and it's best to use a drill press, not a hand drill.
Mark, Summit has this arbor: COMP Cams Valve Spring Seat Cutter Steel 3/8" Arbor/Pilot for Seat/Guide Cutters | eBay
Cool, thanks Jim. Also, on the cutter itself, it has two dimensions, guide size and seat width. I’m more concerned about the “ cuts guide” dimension as I want it to match what’s already been cut by the other shop years ago so the spring seats sit properly, the only reason I’m still going to use the spring seats is they locate the inner valve spring, unless I can find a cutter that cuts the guide to .748/.750 In the pic the step is where I measured .620 Is this the “cuts guide” dimension I’m looking for?
