S10xGN

iTrader: (11)

If they've been milled and how much? Is there a dimension one can check to determine this?

Russ

Sales2@Texas-speed

iTrader: (5)

You can check the head thickness from the lower head bolt hole (under the header). Get a decent set of dial calipers and measure from the surface where the head of the bolt rests against the head, to the deck surface of the head. On stock, unmilled, GM LSx heads (excluding LS7's) it will be right at 1.615".

S10xGN

iTrader: (11)

Thanks, Matt. Can I ASSume that this dimension will cover both flat and angle milling? On that note, if one was to angle mill a set of heads, would the outer edge(s) get more taken off? Seems like that would stand the valves more upright (lower valve angle)...

Russ

Sales2@Texas-speed

iTrader: (5)

Yes, it would vary depending on the milling angle.

02*C5

iTrader: (1)

Look have some one who does this professionally do it for you. I mean it is great to learn, but why learn the hard way. If you are off .001 it could mean the difference between having to fly cut your pistons with a big cam or not. Some times is better to have some one teach you how to do it while you pay them so they you have peace of mind, and you can do it yourself next time, then to learn the hard way you where off.

novaflash2002

iTrader: (51)

i will bet if you measure 10 stock un-milled heads from measuring from the bolt surface to the deck surface that they would all measure different. the best way to check is to cc the head. rule of thumb tends to be for every .006" the head is milled it drops 1cc. During assemblie set the head on the block with out a gasket, and check the ptv clearance. the reason for no gasket is, you will give yourself some more room if you do have to fly cut. you just subtract the compressed thickness of the gasket from the total amount need to fly cut, and you will the correct clearance for the valve reliefs. also it is always a good idea to use a push-rod legnth checker. they are what 50-75 dollars, worth the money. thats my .02

Sales2@Texas-speed

iTrader: (5)

Guessing at how much a head is milled by measuring the chamber size is as much or more of a guess than measuring the thickness at that spot because the chambers aren't linear when milling and again, when angle milling comes into play that rule of thumb is out the window!

novaflash2002

iTrader: (51)

i imagine when he asked about how much they are milled he was looking to see what his compression would be, and clearance issues. you guys start machining your own engines or do you still sub-contaract out?

Sales2@Texas-speed

iTrader: (5)

You assume too much. Still trying to claim that you hold tolerances to within .0001" on "your" machining?

novaflash2002

iTrader: (51)

yep and my engines still last longer than 5000 miles too.

StreetSilverado

iTrader: (17)

S10xGN

iTrader: (11)

Do what? I'm not worried about flycutting or pushrod length, I'm perfectly capable of assembling an engine. Right now, I'm simply asking if there's a way to determine if a used pair of heads has been milled or even surfaced w/o setting up a CC bench.

Russ

novaflash2002

iTrader: (51)

whats the reason (or maybe there is no reason) that you think they have been milled? as matt stated depending on the milling angle it will differe; there isnt a super accurate way to measure it. it will give you a idea measuring from a bolt hole down, but if you cc, it and it still shows 66 to 67 cc's they havent been milled ( if its a 241 or 853 or any stock ls1 head).

Damian

iTrader: (89)

I also recommend having ANY set of used heads pressure checked at your local machine shop before installation. This has saved me tons of time in the past while building a car, to find the problem before a used set of heads go on the engine.

S10xGN

iTrader: (11)

Somewhere down the road, I'll be building a 416" LS-3 and when that happens, I'll be head shopping in earnest. For the most part, I'm always looking for bargains and if a viable set of used heads happens to come available, I'd like to know what I'm looking at. I find most of my stuff on E-Bay so it's a bit hard to be checking CC's from 1500 miles away...

Russ

novaflash2002

iTrader: (51)

well now that you mention that, why dont u just ask the seller lol. there is no real way to check if they are not in your possesion. if your working on a ls3 you might got to the gen iV section.

GrahamHill

iTrader: (6)

Just about every build (or piston change) should include a combustion volume check. Is something we do quick and usually charge about nothing to do it. I wouldn't hesitate to prod around machine shops to see if someone can check it for ya.

Couple other things... even with the best cutter heads you can see if its been milled. How much? Just cut the guess work out and CC the chamber. Gen 1 heads wont have the "inner third" of the deck cut any if they are angle milled. If the heads have been used they'll probably have silicone on the front and rear to seal off oil leaks. Im not sure about the Gen 3 stuff on that. Should be the same.