3.1 cylinder head warp spec and valve spring spec

[97oldscutlas]

so, more spec questions.

been diggin around the interwebs and found some pretty good reference sites like 60degreev6.com, torkspec.com, and enginebuildermag.com, but still haven't found the cylinder head warp spec confirmed.

 

*anybody know the head warp spec for the 3.1?

 

have found some info, but its from all over. anyone confrim?

looks like .003" max is typical recommendation

 

http://www.hotrodders.com/forum/warped-heads-212667.html

Very common condition for aluminum heads. .003" is max.

I do on the average 2-3 pairs of 3.1-3.4 Gm heads per day. Usual cut is .005-.008" to get them straight.

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c1528006228a

Place a straightedge across the gasket surface of the cylinder head. Using feeler gauges, determine the clearance at the center of the straightedge. If warpage exceeds 0.003 in. (0.08mm) in a 6 in. (152mm) span, or 0.006 in. (0.15mm) over the total length, the cylinder head must be resurfaced.

[RobertISaar]

alldata says:

more than .005" requires milling

replace head if more than .010" needs removed.

 

neat fact: milling the cylinder down .01" will bump your compression from 9.55 to 9.8. the reason you can't mill any further than that is due to piston to head clearance. at that piint, you're down to .030", running up to/over the rev limiter would likely make piston to head contact since there is always going to be some rod stretch at higher RPMs, even with the factory forged rods.

 

 

personally, i would mill them no matter what, i'd rather not go through another teardown.

 

 

 

also, what valvespring spec are you looking for?

[97oldscutlas]

Thanks for your feedback on the forum RobertISaar.

agreed, resurface is money well spent, especially on a keeper. we're just not sure if we want to keep investing in this old girl.

 

The wear spec on spring pressure is what i'm looking for using a valve spring tester. gotta know the free and compressed lengths too.

there should be a minimum range for wear before they "should" be replaced.. on a legit rebuild usually would replace all new, but not gonna drop that $ on a grocery getter.

gonna check for warp before spending the money for resurface, pressure check, and valve job and want to check the springs . planning on the aforementioned if warp is out of spec.

 

I probably should just join alldata at this point, but i just love playing detective and learning all the extras along the way..

 

http://www.dsmtuners.com/forums/newbie-forum/341287-how-test-valve-springs.html

[RobertISaar]

1.89" free length

closed load = 75lbs at 1.701"

open load = 230lbs at 1.260"

installed height of 1.701"

 

alldata lists those as both minimum and design specs.