how much milling off 6.0s for 11:1
05-16-2004, 10:29 PM
#1
Banned
Thread Starter
Join Date: Sep 2002
Location: Azle/Saginaw, Tx
Posts: 5,581
Likes: 0
Received 0 Likes
on
0 Posts
how much milling off 6.0s for 11:1 i have a set of 6.0 (317) heads that are currently on my silverado, but i'm thinking about pulling them off and putting them on my Z28, how much will need to be milled to achieve 11 to 1 compression.
the catch is that i'd like as much p/v clearance as possible (thinking about a t-rex) any help will be great. thanks guys
the catch is that i'd like as much p/v clearance as possible (thinking about a t-rex) any help will be great. thanks guys
05-17-2004, 10:44 AM
#3
TECH Senior Member
Join Date: Nov 2001
Posts: 10,341
Likes: 0
Received 0 Likes
on
0 Posts
You will have a REAL hard time with PtoV on a stock piston (even with valve reliefs cut in) with that cam and that much milling of the heads.
also intake sealing might be an issue as well.
also intake sealing might be an issue as well.
05-17-2004, 11:06 PM
#4
Banned
Thread Starter
Join Date: Sep 2002
Location: Azle/Saginaw, Tx
Posts: 5,581
Likes: 0
Received 0 Likes
on
0 Posts
Chris, do you have any ideas of what i should do in that case? the cam i mentioned is only a thought right now...i just like the power it's making on stock heads, and think it would make my car a flyer. BUT, i'm open to suggestions for cams to get this thing into the deep 10s with some good flowing heads. thanks
05-18-2004, 08:39 AM
#5
TECH Senior Member
Join Date: Nov 2001
Posts: 10,341
Likes: 0
Received 0 Likes
on
0 Posts
I think you are going to need to look at another head choice or a custom piston.
0.030 milling gives ~stock compression with a stock gasket. There are guys taking .050-.060 off 6L heads but you will significantly affect your PtoV clearance and you might need to make modifications to the intake to get it to seal properly.
Most guys that go that route (I am going to be taking off about .050 off my 6L heads)also have a custom piston with fairly deep valve reliefs.
The ideal scenario with a high comp 6L headed motor is to leave the heads alone and select the piston that gives your your desired compression. (ie: domed) I ended up changing head configs after the pistons were ordered so I have compromise. (Combo of milling and decking)
You can run a flat top a little higher out of the hole ~.010 vs stock which is about .006. (Can acheive this through decking the block)
0.030 milling gives ~stock compression with a stock gasket. There are guys taking .050-.060 off 6L heads but you will significantly affect your PtoV clearance and you might need to make modifications to the intake to get it to seal properly.
Most guys that go that route (I am going to be taking off about .050 off my 6L heads)also have a custom piston with fairly deep valve reliefs.
The ideal scenario with a high comp 6L headed motor is to leave the heads alone and select the piston that gives your your desired compression. (ie: domed) I ended up changing head configs after the pistons were ordered so I have compromise. (Combo of milling and decking)
You can run a flat top a little higher out of the hole ~.010 vs stock which is about .006. (Can acheive this through decking the block)
Last edited by Chris ARE 360; 05-18-2004 at 08:46 AM.
05-18-2004, 04:19 PM
#6
TECH Fanatic
Join Date: Apr 2003
Location: Albuquerque, NM
Posts: 1,109
Likes: 0
Received 0 Likes
on
0 Posts
Yeah, I agree with Chris. Shaving is OK but the ammount you want will cause issues with the intake ports and mounting. The composite intakes do not like to be played with! Getting that kind of CR with the huge 72cc chambers of the 317's is gonna be tough.
Actually, unless you are running nitrous or a blower the bigger heads are probably hurting more than helping. The stock 862 heads with a little cleaning and porting would be a better bet, else the custom pistons would be the least of all evils.
Keep us up on the progress, Slowverado!
Actually, unless you are running nitrous or a blower the bigger heads are probably hurting more than helping. The stock 862 heads with a little cleaning and porting would be a better bet, else the custom pistons would be the least of all evils.
Keep us up on the progress, Slowverado!
05-18-2004, 07:07 PM
#7
Banned
Thread Starter
Join Date: Sep 2002
Location: Azle/Saginaw, Tx
Posts: 5,581
Likes: 0
Received 0 Likes
on
0 Posts
what about having my 5.3 heads ported and putting my 2.02/1.60 valves in them, and not milling at all. would that still cause problems with p/v with the t-rex? i might just have to wait till i build a 348 for it to put something that big in it....