guppymech

iTrader: (7)

I spent my downtime today searching the net to see what the max dimension was for the distance from the top of the valve guide seal to the bottom of the stock LT1 spring retainer on stock heads. I had no luck searching . I've got a spare set of stock heads and I took a couple valves out of each one and measured and got .580 to .590 from the retainer to the seal (felpro type with small spring). Taking away the desired clearance of .060 leaves .520 to .530. Plenty of room for the .525 hotcam and close to enough for the CC503 depending on how picky you are.
Disclaimer, You should alway check these critical dimensions when changing parts but I admit I didn't when I initially installed my hotcam kit as other hotcam users didn't report any issues in this area.
Just posting this info to help the next guy out.

lt1-xjs

The only "desired clearance" I'm aware of is .060" from coil bind, not from interference of the valve seal.

guppymech

iTrader: (7)

Perhaps I should've said minimum clearance. Most cam mfg web sites list .060 as the minimum clearance between the valve spring retainer and the valve guide seal, some even want .100 between them. Otherwise the valve guide needs to be machined down like on the Vortec heads when aftermarket cams are used. Of course you don't want the valve springs to coil bind either.
http://www.cranecams.com/faqview.php?s_id=23

96capricemgr

iTrader: (1)

You know how often guys are going over .550 on stock heads?

Based on what we see guys actually do I have to question the validity of your measurements.

Hell just tonight a guy posted about over .600 lift on heads that have never been off the engine.

lt1-xjs

He is running the Patriot 8401 kit that uses a different retainer not the stock one.

Wicked94Z

iTrader: (26)

Who is running around with stock retainers and more than .525 or whatever lift anyway?? I can't remember what a stock retainer or guide or seal looks like for that matter, but i remember tons of guys running CC306 and GM847 with untouched longblocks...

guppymech

iTrader: (7)

All I can say is that is the dimension I measured on my spare set of stock aluminum LT1 heads with stock retainers. I didn't misinterpret the reading on my dial caliper. I know I won't assume there is adequate clearance in the future.
I'm not saying anyone running more than .530 lift is in for trouble, but that the head has it's limits and to be mindful of that.

trilkb

iTrader: (4)

how do patriot retainers make up for .070 clearance?

guppymech

iTrader: (7)

Did you measure your actual clearance when you installed your cam and valve spring/retainers? Any clearance is good as long as the valve springs don't loose control of the valves and even then the retainer is only going to hit the rubber valve stem seal which is probably .100 thick or more. It will probably take .700 to bend a pushrod.

trilkb

iTrader: (4)

Nope, I didnt measure anything. I just put it in and if something was wrong im sure it wouldve shown its face in 1000 miles and some 1/4 mile runs. Was a first cam swap lol, I was more suprised that the thing started up first turn of the key and ran like it was never dead.