ok so i floated my heads about 7 months ago and so i bought a truck and gave the car a break for a bit. Now the time is getting near for me to jump back into it. I've decided that i'm going to keep my 18g kit because i really like the response of them on the street, they're reliable, and much rather poor the money into the engine then into a turbo kit. I'm going to do either BC stg 3 or JWT C8 cams and P&P the heads, but here is the real question, 3.8L or 4.2L? I know many people here are totally against sleeves and i was as well but the more i talk to different shops most of them support sleeving the VQ at the power levels i'm wanting to run. Oh also i was planing on running 100shot on top of the boost. i was hoping to be around 850 - 900whp with C18 and the juice but most shops say the stock sleeves will give up. I've talked to alberto and well we all know where he stands. but what do yall think?...........and if youre a supporter of the 3.8L what kind of power do you think it can make?

 

Well the 3.5l will make the power, so a 3.8 should be even better. If I were you I would have Nickies do a custom spray on cylinder liner, and then a 3.8l. Don't be fooled, the liners are expensive, very expensive. I'd also look at getting a custom closed deck install... but then again that's just me and my 'dream build'.
my 2c.
Ps, if you are already going to spray, I would just get a "mild" turbo setup (greddy, maybe 20g or JWT 700bb) and then just get a slightly bigger shot. That way you can 'have the power' but still have a super responsive car...

 

I shyed away from going with Darton sleeves based on some of the issues other members in the forum have experienced. It has been said, however, that the issue is the installation of the sleeves and some shops stand by them when correctly installed. Contact Injected Performance about their experiences. There was discussion on this in a recent thread. Use the search feature of the forum to find that thread.

 

what about the 4.0, its doesnt require sleeves. ...

 

well, i plan on keeping my 18g kit.....so whatz the deal with having the cylinders coated?.....how does that help with cylinder pressure?

 

Having just built a 3.8L motor to handle that power, I would really suggest you get a quote for how much it costs. Its astronomical to say the least, esp if you wanna do heads as well.

You'll need a girdle, carrillo rods, the stroker kit, ARP everything, hks headgasket, all new head parts to handle the boost/cylinder pressure, etc... you cant skimp on anything at that power level.

 

yeah i thought about that but i'm scared to thin the factor sleeves out that much

 

oh, i've already built one vq........right now i got bc rods, wiseco std bored pistons. My problem with the first build was that it was in 06 and L19's haven't really got that popular yet so i had L17's......which did ok i got 40K miles on that build @ 17psi then when it became a secondary vehicle i decide to do a race gas c18 tune and @ 22psi the L17's gave up the ghost

 

that said, i've seen some pretty solid 18g dynos on a 4.2L. Based on that potential, I'd probably go sleeved 4.2L. Probably talk to VTR or Injected since they stand solid that they never have a problem doing sleeved blocks.

 

i've search for some 18g 4.2L and 3.8L dyno graphs but the only thing i can find is forged's roadster and Z that GTM did back in the day and thats it

 

OP,

What's the reason you want to increase displacement while retaining the standard 18G Greddy kit versus doing a sleeved 3.5L? I understand why you want to sleeve the motor for your power goals, but I don't understand why you want an increase to 3.8 or 4.2L.

With the same turbo kit, higher displacement will shift your power curve to the left, but it won't net any peak horsepower gain beyond what the 18G turbos are capable of on a 3.5L block. Plus, 18G turbos spool pretty quickly with stock displacement and you can achieve your power goals with 3.5L. IMO, a bump to 3.8 or 4.2L would make more sense in conjunction with larger turbos than 18G.

No slam on the OP. Just trying to understand the thought process here.

 

It in theory would make the cylinder walls stronger, and (imho) also should be far less likely to fail than a darton sleeve... That would allow you more possible power. Although this is totally and completely debate-able.

I am also unsure as to why you need to increase the displacement....

 

well, i figured using alittle more displacement would help with the power goals esp. if i got to sleeve it i might as well change the engine displacement. Plus, i figured the extra displacement would spool the already pretty quick 18g's alittle faster and allow me to use bigger cams to push the power curve to the right without losing some mid range power. And lastly i can't see myself spending another 7k on a kit verse putting that money to use else where

 

^what he said

 

and it seems to me if my memory serves me correctly that everyone that has increased displacement in the past before the 20g kits came out made more power easier and with less boost then the 3.5L

 

I vote 5.7L

GM V8 power LS1 baby

 

It's to be expected that a stroker kit would require less PSI of boost to make the same power level as on a 3.5L. But did they make more peak horsepower than the 700+whp we have seen with the 18G turbos maxed out on a 3.5L?

 

thats a good question but i would think so cause if a stroker is making the same amount on less boost then you have more boost to work with. For example if it takes a 3.5L 18psi to make 600whp but it only takes a 4.2L 12psi to make 600whp then you still have about 8 or 9psi of efficiency on the 18gs left to work with. Regardless of the displacement the turbos will flow the same amount of cfm. So if i'm making more power with less boost then i would think i will make more peak power

 

But it doesn't always work out that way. A turbo will max out sooner and at lower PSI on a larger displacement motor. For example, a single Precision billet 6765 has maxed out at 900whp on a 2.0L Evo but makes about 800whp when maxed out on a 3.0L Supra.

 

interesting............would love for some of the engine guru's to get on here and give theire opinion........because i'll tell ya that if i can get the power i want out of a 3.5L and the stock sleeves hold up then i'll be a happy camper