Drilling heads for extra headbolts L67
 

Hi all im new to this forum and wonting some info on drilling L67 heads for extra head bolts. I'm having or what sounds like a purculating sound from the cooling system recently. Could be heads lifting or air escaping from the intake runners into the cooling galleries.. don't know yet. Any info is much appreciated, pictures would be great too..


for those wonting to know a little about the car video link below


https://www.streetmachine.com.au/str...nder-commodore


Cheers

That's impossible to add extra head bolts...

Im pretty sure I had read somewhere that intense or zzp have done it, could be wrong

The zzp alluminium heads has provision for extra head bolts

3800 Parts ZZP Aluminum Heads for 3800

Why is the extra bolt needed?

Refer to my original post... lifting heads possibly at higher boost levels.

Other option ive seen is drilling out for larger head bolts 1/2inch

I am using ARP head studs, torqued properly and using gm head gaskets. 24psi, 594whp, 20+ Dyno pulls, street pulls, etc. Never had a issue here with lifting a head....

X2, I'm running the same stud/gasket setup and have also not had an issue with pushing water. Granted I'm making less power and a little less boost.


What is your setup OP? IMO this level of work should be done by a machine shop. To do it right, I'd think you'd want to re-hone the cylinders since the clamping forces will distort the bores slightly differently.

Plus I think the ZZP heads have a thicker deck too, although that may just be to make up for the aluminum.

setup is as follows

L67 stroked to 4.2 (billet crank), H-beam rods, wiseco forged pistons, 8.0:1 compression, o-ringed block, copper head gaskets, ported heads, custom grind turbo cam, double roller timing chain, 150lb springs, YT platinum rockers 1.6, Garret GTX3582 turbo, all bolts and studs ARP ( including head studs )

thats the main things, making 686rwhp @29psi drops off to about 26,27psi

Never use to push water but can now hear a purculating sound when i turn engine off and expansion tank is full


funny thing is still makes power and no signs of anything wrong on the dyno.

There is a guy that just dyno'd 718whp using a turbonetics 75mm on pump fuel+meth on around 24psi. He has no issues as well

That's nice numbers, what car is the engine in? What trans and any trans work done? Still running pump fuel? What did you do for a fuel pump?

Sorry, I thought you were referring to studs on the outside of the heads for some reason.