I've got almost everything together to start my LS/Vtec build, but I'm getting some negative feedback on the combination. So I'm hoping many of you LS/Vtec'ers out there can give your opinion.

*Keep in mind, this car drives to the racetrack and back. I don't have a car tow, but I don't drive this car AT ALL, only to the dragstrip and home. And I have no problem with using 100% race gas at all times.

The major parts are:

B18B1 block Stock
GSR head that is ported and polished w/ a 3 angle valve job, but not decked or milled.
ITR Cams
(OEM) CTR pistons
Stock LS rods

I'm using ITR cams because I happen to have a set, but that can be changed easily anytime. However, I'm hearing that using a GSR head and CTR pistons in an LS/Vtec is going to be rediculously high compression, however NO ONE can ever say how much. I was hoping to run 12.5:1 on race gas, which sounds just fine to me for a NON street car.

Can anyone advise further? Thanks

 

Bad choice of pistons.

 

yaap b16 head ctr pistons good choice.

 

I'd say type r pistons.

 

Okay, but this is the same problem I'm getting when I ask this. You guys aren't giving me any reasons to what you're saying. You say "no but try this instead"... okay... WHY? Whats wrong with the setup?

 

CTR pistons are best suited to a B16B. They are acceptable in B16 applications, but not good for 1.8 liter engines. The compression height is all wrong. You will probably run into piston to cylinder head contact issues. The compression ratio is way too high for pump gas and your cam selection.

 

you will hit the head with those pistons and head

 

"Call Robert at GOLDEN EAGLE MFG". They can help you with any build problems. He is helping me do a light build on my B18 engine that will produce good power and pass Cali smog crap rules.

 

go for it man its only money just do what you think is best

 

Type R are what I have seen most common in LS/V builds. They make good power and can handle a decent nitrous setup.

 

I'm not using any nitrous or anything, and have no plans to. Straight all motor. And I don't need to use pump gas so I'm not worried about that. I know the combo has been used, it's not like no one else thought of it. Its on the web, but I just can't read reviews.

I have a B16 in the car now, I COULD use the head instead, but as I've researched from different tuning shops/dyno results, a GSR head is better for the application, however it's more rare due to price/availability.

 

Okay, what is it? What's your opinion of too high? Because some people think 12+ is too high, and I'm hoping for 12.5:1. And I don't need pump gas.

 

itr pistons ftw

 

from zeal auto works calculator, your compression on stock valves, 81 mm bore and no shaving or decking your compresion should be 14.5 cr

i would recommend itr pistons or b16 pistons

plus it wont work really any ways you will have contact issues with the head to pistons with out a custom headgasket

 

This is the same vagueness I found about this setup when I was researching my build, which consisted of PCT pistons in a LS with a GSR head. It can be done and it will make crazy power, just clay you motor to make sure your clearances are fine and don't rev it to 9000. I should have mine done in the next month and will post numbers.
The compression is approximately 12.5:1 with dished valves, an unmilled head and a stock thickness head gasket. With a tuner that knows what he's doing, this can be ran on 93octane.

 

BINGO!!


OP, its not a definate in everyones case however given the fact that your placing a piston which features a higher compression height (not nessasarly reffering to the dome but overall distance from the wrist pin centerline to quench pads) in a combustion chamber designed with a "pentroof" (quench on the IN &EX sides) you may encounter problems with contact. Especially if the head has already been surfaced.

IMO, sell em and get a set of ITR's...

 

so you havent driven or started this engine yet? your compression will be higher than that. you might want to look into a thicker head gasket

 

Okay, see I don't need to use the CTR's, my goal was to just get high compression. There's many methods to doing this, but I'm deciding on pistons so lets stick to that topic for now please. I'm not going to bore out the block, just keep it stock and use the stock LS rods and the valves, springs and retainers will be upgraded before I assemble this (I didn't buy them yet).

So If I keep the GSR head,(motor will be fully tuned) what would you're experience recommend for PISTONS to keep compression at 12.5 (or if I can safely get away with a little higher with tuning and race gas; as long as the car can drive the 20 minutes to the track and back, but thats it).

As far as what you might consider "TOO HIGH", here's a post from the all motor dyno section of honda-tech:

HEAD
-K20A TYPE R
-Supertech Valvetrain
-Skunk2 stage 3 cams
- The "PAGAN SPECIAL" lol

BLOCK
-K24A4 Block
-Blueprint Rods
-13.8:1 compression
-ARP Head Studs
-ARP Rod Bolts
-Stock Crank
-Stock Bore

Making 301whp.

Obviously total different setup, but I'm only showing the compression example; 13.8

I have a strong running B16A right now that I can use the head, but the GSR was just port/polished and they have a great power outcome when you see these LS/Vtec dyno posts.

 

By using B16 pistons and flat-face valves you can get to 12.5:1 while using a GSR head.

 

man if i was you, use the gsr head. You just need to check you clearances. Its just like buying a stroker kit. They say they fit but youd be suprised how many stroker kits don't fit a block. YOU need to put it together and see if it fits. IMO the only problem your gunna run into is the wonderfull detonation if you don't tune it right. Your gunna need a good ignition....
And whats the worse that can happen? You try and fit it and they don't clear...you take them out and put in new ones...simple.

 

Lol, let's see what he's doing that you are not.

Big primaries
a lot of duration
variable overlap
light weight piston

Ahh, you might want rethink that example.

 

K's have the ability to adjust the cam angle to decrease detonation. which is not a good comparsion.

look, im running a Ls/vtec with 82mm Us spec ITR pistons flat supertech valves, milled and decked head. my compression is floating around 12.5 compression. i dont give 2 ***** about the compression numbers if he wants to run over 93 octane or pull a *** load of timing and make the engine a slug then go ahead. im making a statement that the PCT pistons are meant for a 1.6 liter engine and the Pct in a ls or gsr block tend to stick out the cylinder causeing head contact with the gsr head due to the square chambers. he needs to not work about valve contact to pistons its piston the head.

if your going to run the pistons the atleast do not mill the head or deck the block to much, run a thicker head gasket and or use a B16 head.

 

the big difference will be in wether or not you run a b16 or gsr head.
And if its just a track car, it might be worth the experiment. But its not worth it if you not gunna put more money towards a better ignition system, full fuel system(bigger injectors) and a tedious tune.

 

the main point your missing is that compression is not the best way to make power.

you will make more power and go faster on less compression and more FLOW.

the combination can work, but not with a cam as small as the r cam. the problem being as you user a higher lift cam to lower the dynamic compression and allow you to give the motor the littlest bit of timing, you will run into clearance issues.

on top of that the flame travel on the ctr's is crap, so ive read, never experienced.

moral of the story...lower compression and higher flow is all the rage nowadays.

 

Okay, thank you everyone for the input. After reading your feedback and doing continual research, I'm going to ditch the CTR pistons and use P30's with flat face valves. This "should" keep me in the compression range of 12.1:1 to 12.4:1, which is what I was shooting for and keep me safe from potential piston contact.

Now, I went looking around at the different options for P30's. With this setup fully tuned, I'm hoping to be closing in on 200hp. I don't think I really need forged pistons for that power range, unless someone can convince me otherwise.

However, I'm not having too much luck finding OEM P30's (new at least). I keep seeing NCP or something like that and other aftermarket stuff. Is there a reason to stick with OEM for this, or does it not matter?