Valve reliefs (piston notching)

Reply Subscribe

Thread Tools

Search this Thread

Jan 31, 2004 | 05:52 AM

lowdowndirty

Thread Starter

Burning Brakes

Joined: Jul 2003

Posts: 1,104

Likes: 0

From: "In a van down by the river" CO

Valve reliefs (piston notching)

At what point (size of cam) do the LS1's need th pistons notched for clearance w/ stock heads/valves/rockers and gaskets? TIA Chris.

Jan 31, 2004 | 04:31 PM

Bink

Safety Car

Joined: Mar 2002

Posts: 4,928

Likes: 1

Cruise-In V Veteran

St. Jude Donor '09

Re: Valve reliefs (lowdowndirty)

Depends on durations. I believe the initial concern, as duration is increased and LSA decreases, is the piston chasing the exhaust valve closed. Wider LSAs will help with this problem and allow greater duration and lift.

Maybe LG will step in as they've maximized duration and lift with their big cams.

Hope this helped some.

Feb 1, 2004 | 08:42 PM

lowdowndirty

Thread Starter

Burning Brakes

Joined: Jul 2003

Posts: 1,104

Likes: 0

From: "In a van down by the river" CO

Re: Valve reliefs (binksZ06)

LSA's 113, lift is 588"(?)/.601". I'll have to get the cam card for the duration.

Feb 2, 2004 | 01:17 AM

rwj383

Melting Slicks

Joined: Jan 2001

Posts: 2,635

Likes: 2

From: Aloha, Oregon

Re: Valve reliefs (lowdowndirty)

Quote:

LSA's 113, lift is 588"(?)/.601". I'll have to get the cam card for the duration.

Final lift is not so much a factor since piston/valve clearance issues happen as piston rocks over TDC and I and E valves are both open. The main factors are opening/closing ramp rates and overlap. Tight lsa (lots of overlap) and fast ramp rates (e.g.- X-ER Comp cams) will pose big threats to clearance. Another factor is how much the head gets milled, gasket thickness or anything else that brings the valves closer to the piston. For anyone to say 'yes, that cam will clear' or 'no, that one wont' would really be kind of guessing. We do know what will definitely NOT clear without piston reliefs, but really the cam clearance needs checked once installed. I have installed Carteks 2-X LS1 cam into a customers car with .030" milled heads and stock thickness gaskets and had plenty of clearance.

If you really want a wild agressive cam you can opt to have the stock pistons notched. Isky sells special cutting tools that cut perfect notches while pistons are still in the motor. This process requires a lot of know-how and should only be done by a very confident mechanic. Engine contamination, piston strength and integrity and uniformity for balance are all major concerns.

Robert
Gen 3 MS

[Modified by rwj383, 10:20 PM 2/1/2004]

Feb 2, 2004 | 02:15 AM

lowdowndirty

Thread Starter

Burning Brakes

Joined: Jul 2003

Posts: 1,104

Likes: 0

From: "In a van down by the river" CO

Re: Valve reliefs (rwj383)

Thank you sir. I already have the cam. It's a comp custom grind w/ the numbers stated above. Anyone else have any input?

Feb 3, 2004 | 01:59 PM

lowdowndirty

Thread Starter

Burning Brakes

Joined: Jul 2003

Posts: 1,104

Likes: 0

From: "In a van down by the river" CO

Re: Valve reliefs (lowdowndirty)

Ok, someone give me some good news. Here are the actual specs:
.588/.601" lift
228/236 dur. @ .050"
113 LSA

HELP!
TIA Chris

Feb 3, 2004 | 03:54 PM

0Kaley@DragonRace

Supporting Vendor

Joined: Mar 2002

Posts: 2,073

Likes: 0

From: Loveland CO

Re: Valve reliefs (lowdowndirty)

Can anyone give us the specs on the LGMG5X3 cam? I know that that cam is pretty big. Thanks, Kaley

Feb 3, 2004 | 05:38 PM

lowdowndirty

Thread Starter

Burning Brakes

Joined: Jul 2003

Posts: 1,104

Likes: 0

From: "In a van down by the river" CO

Re: Valve reliefs (2C5only21)

Alright, I guess if all else fails, help yourself, right? I talked w/ Al from LAPD and also LGM. Both said I should be fine. LGM says they're G5X3 has .611" lift on the exhaust and will install w/ stock heads and no problems w/ clearance. Al was very helpful and even gave me some tips for install. Thanks guys! Chris.