Rebuilding L67

[Bullet1]

G'Day,

Today i got bad (maybe not so bad) news from my mechanic and was told my cylinders are actually oblong and not circle so my block has to be bored and honed. He asked if i had any high performance plans for the future and if so to just do them now to save money in the long term.

So i was just wondering. I'm thinking about lower compression pistons(7.5:1 possibly?) what compression and brands would you guys recommend. It's having 40thou' bored out minimum and was wondering should i just go larger or leave it at 40thou' over?
It already has 4 Bolt mains and was thinking cross bolting? I'm having the block chemically cleaned and crack tested. It's still only running stock boost but will be bumping it upto 10pound asap and then further once all the engine work is paid off.

Is there anything else anyone can recommend or even suggest? I know its going to cost a sh*% load but i love my L67 and am proud to be a little different. By the way its a VT S pack L67.


I'd like a professionals say on all this aswell but all feedback is welcome and appreciated.
I'll also keep it updated with progress.

Cheers,
Rhys.

[BJ31OS]

ZZperformance will be your friend they have some very good parts and with the Aussie dollar being high it wont cost you a shit load

[Bullet1]

Yeah i've had a look before but obviously not for the stuff i now need, cheers.

[BJ31OS]

even try intense racing they have some good packages

INTENSE-Racing.com: 3800 - Performance Packages

[Bullet1]

Cheers, Whats the Commodore equivalent in America?

[BJ31OS]

grand prix GTP has the same engine as ours but any one that has L67 will be fine AFAIK

[chargedvx6]

7.5:1 comp would be a big mistake IMO.

Unless you are going for a mega lag turbo for drag only it will kill your drivability completely. Most L67 rebuilds are actually upping the comp to gain efficiency with good results. Where this works is if you are sticking with the mighty little M90 charger.

Most people fit a smaller pulley to the charger along with intercooling to increase the efficiency and overall volumetric output ability of the M90. This takes the M90 out of its efficiency range everytime and then it's a shit fight to maintain timing vs boost ratio in the tune. the best way to get a great compromise on these two is to up the comp which lowers the M90 power band thus allowing it to make its power/ torque at lower revs....................these are the revs we want the power at because if you start revving higher the efficiency of the M90 or moreso the intercooler goes south fast.

Bottom line is at least rebuild it to 8.5:1comp pr go for 9.5:1 with some noice Diamond forged pistons from ZZP. Stock L67 rods will be fine. I have not heard of many failing even when an engine starves of oil and spins shells the rods still fare well

[acarmody]

I don't think you can go over 40thou. I would only go 20 thou if you can, that way in the future if there is another problem, then you can go to 40thou.

[Bullet1]

I was thinking about upgrading the charger by the end of the year to a more potent charger and that's why I was thinking about dropping the comp. Stupid question but say if I did lower comp and I got a 10 pound pulley, would my boost actually drop because of the lowered compression already or what? Yeah I have to go 40thou over to get them cylinderical again.

[acarmody]

Yep lower compression means lower boost.

As chargerVX6 said, its much better to raise the compression as this gives you a boost upgrade without taking the charger out of its comfort zone.

[Vt_vic]

would a 4.2 stroker be out of the question?

[Bullet1]

It's not completely out of the question but i've heard about alot of the 4.2L strokers not being strong and shitting themselves destroying blocks and all sorts of nasty damage so i'm still undeicded on them.

I though it'd mean the boost would drop. If i raised the comp and put on a more potent charger would it still handle the boost? i was eventually thinking around 17PSI possibly more by the time i finished.

[chargedvx6]

Stock capacity FTW IMO. Either maintain stock comp or even increase it. Three main selling points of increased comp are:

1: Better internals due to your rebuild and cistom build tolerances so it will be capable of alot more boost/ power safely

2: Accessories and bolt on components will be vastly better than stock yet again and also tuning will keep everything in check and allow you to get the most from it in relative safety for the engine

3: FUEL!!!! E85 is a goer and will give higher knock threshold at tune time. It is similar in price to 98ron and better.

[Bullet1]

So lifting comp seems to be the way to go?
I haven't seen much E85 over here compared to over east so i'll most likely be running 98ron.

In the next few days i'm sitting down with the mechanic and choosing everything such as what forged pistons and compression and everything, he also said something about the rings which he'll explain on the day but i was just wondering if anyone maybe knew what he might have been talking about? He was on the line of forged pistons and dish and flat tops and then something about a type of ring or something?
It's not much to go on but yeah.

I'm thinking if i do go a stroker to get the Pro stroke? I only know of C.O.M.E and pro stroke having strokers for the V6 and from what i've heard and read pro stroke seem to be the better brand, an other i should have a look at?

[acarmody]

Hes probably just talking about piston rings, basically they keep the oil in the bottom, air and fuel in the top, and the piston dead on in the centre of the bore without scrapping the sides.

[Bullet1]

Nah i understand that it was something like moly rings maybe? I dunno im making wild guesses now haha, I'll find out when he faxs the parts lists to me to look over.

[chargedvx6]

Gapless rings are the way to go. They have a nearly perfect seal and don't give your precious boost away to PCV. I know for a fact that they are readily available for an ecotec/ l67

Total Seal Home

[neet_wagon]

I don't see how Pro-stroke would be better than COME?
Pro-stroke are just down the road from me, but im going COME stroker in mine.

I think the only reason as to why people think pro-stroke is better is that they see 'SCAT 9000' and go
'gee, thats sounds impressive'

COME do all thier own developing, manufacturing and testing. so i know where my hard-earned cash is going.

And no I don't work for them.
I have simply had lengthy discussions with them as to why they are better than the others, and what i should build, and they helped me to no end. (I have to admit though, they are short and sharp((some may say cold)) when it comes to answer time)

[stevoss]

hasnt most of the motors with strokers only failed because of the top end? old mate on here that has been threw 2 of them had the valves fail both times?