Does anyone know how much can be shaved of the top of the head??? I know the 2.4s are a zero clearance motor so u can't take off of the top of the block. Any help or concerns would be greatly appreciated

yes you CAN take off the block. you just gotta make sure that the pistons have enough clearance to the bottom of the head. the stock pistons are down in the hole a ways anyway. its the VALVES that make them an interference engine.

according to gm, .020 is safe to take off the head. ive ran more and so have many others. the problem with shaving anything is the cam timing. these engines love to have the cam timing PERFECT. if you dont they wont have the performance. even if you get both timing marks dead nuts on, the cam timing will still be off.



It's nice to be injected but I love being blown.

So how much would u recommend taking off or how much has been taking off before with no problem. And is it best to just take off the block or just take it off of the head there seems to be enough relief in the head to just cut the head?

GM said no more than .020 total off with a stock thickness gasket. That is if you take .010 off the head and 0.010 off the block you are ok.




PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

Why not just .020 off the head or .020 off the block what's the difference ? Or maybe it's best to do both because of trueing up both surfaces?

That is all what GM states. A lot of people have taken more than that off the block, and ran a thicker head gasket. The head seems to be worse. If you take to much of the head it seems like the quench area is affected.....in a negative way...






PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

where are you getting that info mike? is there proof of that claim? seems to me the negative effects of decking comes from the cam timing being off...



It's nice to be injected but I love being blown.

-Z Yaaaa- wrote:where are you getting that info mike? is there proof of that claim? seems to me the negative effects of decking comes from the cam timing being off...

This is the only forum I have ever seen someone say this. Youre taking .020 of an inch out. A half of a millimeter. Your cam timing is probably affected more by a tensioner tensioning a timing chain with slack in it. We can start to talk about how much a factory timing belt will stretch on an engine turning 9k rpms. Thats a lot more than .020in.

@!#$ up your quench areas will hurt your power more than the quarter or a degree or whatever miniscule amount the cam timing is affected. Plenty of engine builders will tell you to NEVER deck a head more than just a quick buzz to get a smooth mating surface. I dont completely agree with this myself because it depends on what kind of build youre doing.

Frankly a lot of this is splitting hairs but its the difference between and engine that lasts for 50k miles and one that lasts for 10k miles. And one that runs awesome and one that runs ok.

JBO is the only forum that has people that ask for proof? weird, i would have thought the opposite.

so you have proof on a 2.4 head that decking it causes quench "issues?" idk where you are hearing this but ive read in many places online that tightening up the quench area actually improves performance....

please read this article for more info

in my experience with LD9's if you have the cam timing off, even slightly, they run like dog ish.



It's nice to be injected but I love being blown.

GM service manuals, and build books.
We are also talking about what "GM" says, which isn't always 100% true. I agree twin cams get a little bitchy if the timing is off...even a little, but messing with the quench area has a ton more effect on performance than a degree or two does. In my opinion. Now if your a tooth or two off with the timing....it runs like @!#$.







PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO