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XPZ or XP/Nitrous

ls1camino

ls1camino

New member
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?
 


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.
 
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
 
ls1camino said:
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.
Click to expand...

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

ls1camino said:
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?
Click to expand...

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

ls1camino said:
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?
Click to expand...

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.
 
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.
 
SnowFlake said:
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.
Click to expand...

HOLY ****

I agree.

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


SnowFlake said:
Broken rod bolts, no power, bad idea in general.
Click to expand...

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.

SnowFlake said:
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.
Click to expand...

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.
 
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...
 
ls1camino said:
With ARP Rod Bolts, I think I'll be fine.
Click to expand...

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.
 
bluegtp91 said:
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.
Click to expand...

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?
 
ls1camino said:
What needs to be machined for the rod bolts?
Click to expand...

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.

ls1camino said:
Should I just rebuild the block using stock replacement bolts? Where would I find replacement bolts besides the stealerships?
Click to expand...

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...
 


bluegtp91 said:
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.
Click to expand...

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

bluegtp91 said:
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...
Click to expand...

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


SnowFlake said:
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.
Click to expand...

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.
 
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.
 
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