Cam and springs on l31 motor

[vizionwolf]

What is the most lift I can do without getting the heads modified I have 550lift valve springs but heard something about the heads themselves having issues and also any lifters anyone suggest to get for it and also cams to

 

[Erik the Awful]

You have to measure your valve seal thickness and your retainer height. I'm running a .515" lift cam on factory Vortec heads with no machining, but I used LS2 valvesprings and Comp Cams 787-16 retainers, which have more clearance than the stock retainers. I'm also using thinner umbrella valve seals instead of the factory-style positive metal-clad valve seals. I'm completely clear for up to .530" lift.

But take your time and make your measurements. Don't blindly trust some random dude on the internet like me.

 

[rebelyell]

What is the most lift I can do without getting the heads modified I have 550lift valve springs but heard something about the heads themselves having issues and also any lifters anyone suggest to get for it and also cams to

When L31 or L30 new from GM, Many times the factory OE seals are Not seated far enough down onto the guide. The higher a seal sets, the less clearance there is between seal & bottom of retainer. Near top of guide itself is a large machined Bevel. The bottom of the seal should be seated just far enough above Bevel to leave a gap to the Bevel of between 1 and 2 mm ... but NOT crushed down onto the Bevel. When seal is properly positioned, with OE retainers & OE seals, should be room for at least 0.470" lift.

You can DIY a "ghetto grind" on bottom of retainers, facing about 0.090" from retainer bottom
That, in and of itself, will net about 0.090" ADDITIONAL clearance for lift.

You should read a manual about setting up valve spring clearance. You must know what Your spring's coil bind height is ... then add another 0.040" - 0.060" combined total gaps between coils. You'll find differing opinions on this subject, both here & elsewhere. When done right, ghetto grind works; it's cheap & easy but not idiot-proof. But, what else is?
If you cannot accurately & precisely measure this stuff, best turn it over to a pro.
Good luck with your project.

 

[Erik the Awful]

I wouldn't grind the retainers. If you break a retainer you drop a valve and trash your motor.

Instead, take a few thousands off the tops of the valve guides. It's not rocket science and can be done with an angle grinder. Just go slow and only take off as much as you need. Deburr the tops after you're done.

 

[rebelyell]

No thanks.
The portion of retainer that is properly faced-off contributes nothing to retainer's strength or integrity; losing it doesn't weaken retainer.

 

[Erik the Awful]

There are tools for cutting the top of the valve guide. Nobody makes a tool for cutting down the retainers. I had to cut down the guides on my 472 Cadillac to fit the cam in it. I did it with an angle grinder. It was my first time doing cylinder head modification and I did a terrible job of it, and it's still fine.

I've had to do a valve swap and inspect a piston because of a broken retainer. That race ended up being a full-on fail. The bottom of the retainer definitely contributes to the strength of the retainer.

But, hey, you do you. Have you actually cut retainers and run them? Or are you passing something you've heard elsewhere? Just because retainers are cheaper than heads, it doesn't make them the preferred part to cut on.

Valve Guide Top Cutter

www.cylinderheadsupply.com

 

[rebelyell]

Yes we have. And, like most folk, learned from others.
Have you actually shortened guides on-head; using an angle grinder? No thanks, but your money your car.
Agree to disagree?

In a pinch, we've had to stuff an orphan 6" rod & piston in a 5.7" motor; not suggested but it worked.

 

[Erik the Awful]

Have you actually shortened guides on-head; using an angle grinder?

I had to cut down the guides on my 472 Cadillac to fit the cam in it. I did it with an angle grinder.