Hey guys, Im on my next 3800 build. having the block bored .20 over, using JE forged pistons, eagle crank, H beam rods while having this all balanced. most likely going back to 93 octane for now, and will eventually go back to e85 since i have the fuel system fully upgraded to support the corn. My question is should i stay with my XPZ cam or should I swap to an IS4 cam? I will be running the stage 2 very expensive aluminum heads from zzp, as well as a TVS2300 blower from harp i have recently acquired with a matching intercooler that adapts to the gen V manifold(ported to match). i will also be using an 85mm TB with and LS1 maf.
The blocks compression was close to 10:1 so I'm having the shop dish the piston heads to reduce that resulting in 9:1 compression which is still slightly high for a boosted application. Looking to run between 20-25lbs of boost.
I am looking to maximize this setup if you can't already tell, and i am looking for the best cam for this max effort build. i feel the xpz will have a better mid range compared to the IS4 but the IS4 will outperform the XPZ with the setup i am building.
Thanks in advance- Zack

 

Why .020, is the block in that bad of shape? Theres no power to be gained with tiny over bore but there can be impacts on sealing, especially with big power. I'd do as little machining as needed to clean up existing damage and let it go.

Given this is a max effort build, neither. Get a custom specd cam for what you're trying to do.

The XPZ has actually made more power than the IS4 in multiple setups, but its optimized for the M90. A 2.3 is going to move a lot more air. Being that neither cam was designed for your setup, I'd get one that is.

I'd think twice about that. 10:1 would be nice on E85, especially since you've got the fuel setup. Sure 9:1 is better for regular gas, but for an all put build, why not just go e85 (or race gas) full time? Or just take the belt off until you're ready for E85 again.

You can also play with DCR on your cam profile as well when going custom.

 

hey bump, i was expecting you to reply lol. i wanted to go .20 over which is not much but it will slightly increase the volume of each cylinder. Also, 10:1 is way too much compression when I'm trying to run between 20-25lb possibly near 30. i don't drive the car much as the e85 washed everything out and left my rod bearings in pieces in my oil pan. i realized now i should have changed the oil more frequently since corn is very corrosive. my buddy is tuning the car on 93 since he's not comfortable with e85. i will than bring it to the dyno to get a number of where it is at and reduce the pulley size from there if there is more to give. yes e85 will give me more power with less boost but i want to be safe on initial tuning and driving since I've went overboard on a 3rd build with parts.
Where do you suggest i get a custom grind from?

 

My point is just that the displacement increase is negligible. Its literally 1 cubic inch (which would give less than 1 hp on a NA 3800). No sense in eating up your sealing structure for 1 hp unless the current bore is trashed and needs that much to clean up. If you're looking for power gains by boring- the only righr way to do it on a 3800 is to go nuts and sleeve it.

Way too much per who? Theres not much out there on 3800s, but take a look at LS engines on E85 and high compression with big boost. You'll be surprised how much the fuel can hold as long as you dont go nuts on timing.

Just saying, if this really is an all out build destined for E85, 9:1 is too conservative.

​​​You sure that's from the E85? Did you have a crazy rich idle or something? Theres just a ton of flex fuel E85 cars out there with no issues tearing up rod bearings. Shouldn't really have that much fuel in your oil to start with.

That's a bit concerning TBH. Just seems odd to handicap performance so severely because your tuner wont touch it. Also seems odd to then have to tune it twice.

Given the crazy money you'll have wrapped up in it, I'd just get a pro tuner from the start. Youd hate for your buddy to make some small mistake and toast your brand new all out build.

I'd probably start with the places that offer off the shelf cams. You could also contact the cam manufacturer directly - I believe Cam Motion made the Intense cams.

As with some of the other stuff above, if you're buying all these crazy parts and are actually worried about the single digit horsepower gains from a .020 over bore, why limit yourself to a bunch of cam profiles designed for the M90?

 

100% that the e85 washed everything out. The oil stunk like e85, and there was no other reason to cause the engine failure from what me, my buddy who is a master tech and the machine shop that’s been in business since the 60s could find.
I agree about the cam. The cylinder walls were not hurt at all so it’s not being sleeved. .20 is not a huge amount but at the time I ordered the JE pistons that’s all I considered to bore it over. Yes I could have had the shop locate all the parts to have a bigger bore but it didn’t cross my mind.

 

Only reason I mention it is because that's not normal at all. There are a ton of flex fuel cars out there and even a lot of E85 3800s, and these cars aren't all spinning bearings like crazy.

If the oil smelled that bad, it probably had a ton of fuel in the oil in general which is known to destroy bearings, regardless the fuel type. Wonder if it was running crazy rich or something at some point? Rich idle is definitely one of the worst culprits for passing fuel past the rings.

Just hate to see it burn up that new bottom end.

 

I know I thought the same thing. For now 93 will be sufficient. I just want to get the car up and running. The numbers will always haunt me but depending on if and when I move I know 93 will be in the area I will
be moving to but unsure of e85. I will look into it and plan on switching back over to corn.
I assume it was running very rich