XPZ or XP/Nitrous

**ls1camino** · 12-01-2011

So, I'm building a L36 engine out of the car, so I can just swap the motor/trans at one time and not have my car down for an extended period of time.

I was originally doing a VS cam, 90# springs, stock replacement timing chain, and a 75-shot of nitrous. I was scared of going bigger (XP and 105#'s) because I DD this car, and I don't need a snapped timing chain.

I then did some research into the double roller timing chain and found that the failures were due to the camfer of the crank gear not matching the crank (Aussie vs US). Since it seems like an easy fix to get the double roller working properly, I'll be going with that. That got me thinking...since I now have a bullet proof timing chain, why not go XP with 130#'s and spin her to 6500-7000rpms and spray the 75 shot?

I then got to thinking that it would be easier to just put an XPZ cam and 130#'s in the car and not have to mess with wiring the nitrous kit or having to fill the bottle. It'll also free up the kit, so I can install it on my Trans Am.

What are your thoughts?

I already have a Gen V, full size intercooler, 42# injectors, mildly ported heads with valve guides machined down for a .600" lift (is that enough clearance for an XPZ?), and I'll be ordering a built trans.

I only have the stock L36 apart. I was originally going to just reassemble it with new rings and bearings. Do you think the rods will hold, or should I find some L26 powdered rods?

**matt5112** · 12-01-2011

they're not bullet proof.

They wear just like a stock one does.

Just lasts longer.

XPZ approaches 570 on the intake as per ZZP.

Depends on your rockers.

IIRC: XPZ, 150's on the intake and 130's on the exhaust.

**boostedcompg** · 12-01-2011

Keep in mind a small wet shot makes for large gains just on the cooling aspect alone. So start small, but def keep spray on the build list

**SnowFlake** · 12-01-2011

Originally Posted by ls1camino

I was originally doing a VS cam, 90# springs, stock replacement timing chain, and a 75-shot of nitrous. I was scared of going bigger (XP and 105#'s) because I DD this car, and I don't need a snapped timing chain.

You should probably be more concerned about your timing set on the 90# springs. LS6 springs are more abusive than the 105s.

Originally Posted by ls1camino

I then did some research into the double roller timing chain and found that the failures were due to the camfer of the crank gear not matching the crank (Aussie vs US). Since it seems like an easy fix to get the double roller working properly, I'll be going with that. That got me thinking...since I now have a bullet proof timing chain, why not go XP with 130#'s and spin her to 6500-7000rpms and spray the 75 shot?

Broken rod bolts, no power, bad idea in general.

Originally Posted by ls1camino

I then got to thinking that it would be easier to just put an XPZ cam and 130#'s in the car and not have to mess with wiring the nitrous kit or having to fill the bottle. It'll also free up the kit, so I can install it on my Trans Am.

What are your thoughts?

I already have a Gen V, full size intercooler, 42# injectors, mildly ported heads with valve guides machined down for a .600" lift (is that enough clearance for an XPZ?), and I'll be ordering a built trans.

I only have the stock L36 apart. I was originally going to just reassemble it with new rings and bearings. Do you think the rods will hold, or should I find some L26 powdered rods?

I'd probably take L36 rods over L26 rods.
IMO you should just stick with an XP. You'll make good power without being too radical. Your setup will probably be good for 320-330whp SAE, how much more do you really want? Transmission is on borrowed time at that point and if you were to juice it on top of that you'd be looking at breaking other parts as well.

**darkhorizon** · 12-01-2011

xpz, and spray?

The cam is not going to make any more or less power... Your heads and nitrous pill are what will make power.

**blueguy** · 12-01-2011

Originally Posted by SnowFlake

You should probably be more concerned about your timing set on the 90# springs. LS6 springs are more abusive than the 105s. I'd probably take L36 rods over L26 rods.

HOLY ****

I agree.

Like I said before hand...90's can take it...but your timing chain/dampner is going to hate you...

**ls1camino** · 12-02-2011

Originally Posted by SnowFlake

Broken rod bolts, no power, bad idea in general.

With ARP Rod Bolts, I think I'll be fine. Probably set redline to 7k and shift at 6500. I'll see how it's acting once it gets on the dyno. If the power dramatically falls off before 6500, I'll drop the shift point accordingly.

Originally Posted by SnowFlake

IMO you should just stick with an XP. You'll make good power without being too radical. Your setup will probably be good for 320-330whp SAE, how much more do you really want? Transmission is on borrowed time at that point and if you were to juice it on top of that you'd be looking at breaking other parts as well.

My ultimate goal is low 12s or high 11s with a full weight car and ET Streets.

I'm sure the trans will hold...I'm not a fan of spraying off the line. When I had this kit on my T/A, I sprayed when I shifted to second.

**darkhorizon** · 12-02-2011

I wouldnt try replacing the rod bolts... It may work in LSx stuff but its not so easy in a 3800 from what I hear. Drop PRJ an email and see what he says.

As far as the RPMS and shifting stuff goes... You are thinking about it way too much. shift points and boosted 3800s have little to do with going faster or slower.... I have ran 10s shifting at 5300 rpms...

**blueguy** · 12-02-2011

Originally Posted by ls1camino

With ARP Rod Bolts, I think I'll be fine.

Keep in mind with ARP rod bolts the rod's MUST be machined for them...they aren't just toss on and go like head studs...same with main studs...the block MUST be align bored for them.

**ls1camino** · 12-02-2011

Originally Posted by bluegtp91

Keep in mind with ARP rod bolts the rod's MUST be machined for them...they aren't just toss on and go like head studs...same with main studs...the block MUST be align bored for them.

What needs to be machined for the rod bolts?

Should I just rebuild the block using stock replacement bolts? Where would I find replacement bolts besides the stealerships?

**blueguy** · 12-02-2011

Originally Posted by ls1camino

What needs to be machined for the rod bolts?

The recess for the factory bolt isn't large enough for the ARP bolt...it needs to be opened up to fit flush, if you will. Reason why I just went with L32 rods and factory GM TTY bolts...didn't want to **** with it.

Originally Posted by ls1camino

Should I just rebuild the block using stock replacement bolts? Where would I find replacement bolts besides the stealerships?

THAT, is your call. I think Head Studs at a minimum, but Main Studs are nice as well...I never have to buy head/main bolts again...and I'm not sure there, I have a local hookup so I get a good deal on factory stuff. Not sure if your auto parts stores sell them...

**ls1camino** · 12-02-2011

Originally Posted by bluegtp91

The recess for the factory bolt isn't large enough for the ARP bolt...it needs to be opened up to fit flush, if you will. Reason why I just went with L32 rods and factory GM TTY bolts...didn't want to **** with it.

Thanks...I'll hit up my machinist friend.

Originally Posted by bluegtp91

THAT, is your call. I think Head Studs at a minimum, but Main Studs are nice as well...I never have to buy head/main bolts again...and I'm not sure there, I have a local hookup so I get a good deal on factory stuff. Not sure if your auto parts stores sell them...

I'm going to do it once and do it right...once again, I need to call my friend

**matt5112** · 12-02-2011

Sounds like these rod bolts weren't made specifically for our motors.

ARP bolts distort the rods, you'd need them machined to correct that as well.

**ls1camino** · 12-02-2011

Originally Posted by matt5112

ARP bolts distort the rods, you'd need them machined to correct that as well.

Explain, please.

**SnowFlake** · 12-02-2011

Why not just get a low mileage L32 shortblock and be done? When you start messing with all the inner workings of the engine you could end up with a 200 mile motor. Your build isn't something you should need to have a built engine for.

**matt5112** · 12-02-2011

its similar to main studs.

They distort the rod/cap, so its out of round.

Have to have it resized.

But L32 rods are cracked.

Supposedly can't resize them.

**ls1camino** · 12-02-2011

Originally Posted by SnowFlake

Why not just get a low mileage L32 shortblock and be done? When you start messing with all the inner workings of the engine you could end up with a 200 mile motor. Your build isn't something you should need to have a built engine for.

My original concern was the bearings and rings. I just wanted those replaced. I thought it would be a good idea to just put ARP hardware in the motor while it was appart.

**SnowFlake** · 12-02-2011

I've seen a lot of motors built by people/shops, reputable engine builders, etc... Those motors almost never have a life expectancy like a stock motor. My advice is to ditch your current engine and just pick up a low mileage L32 shortblock. Your setup is gonna run low 300s for whp, well within the acceptable range for a stock bottom end.