Loosing Power after rebuild

[Lextreme II]

I took my blown head gasket Previa to another place besides my normal hi-pro builder. Anyway, I got new pistons/rings and bore and hone with a complete valve job and resurface the head. Complete new gaskets. The van ideas perfect! However, the lower end is lacking of power. I have about 400 miles now and still not much lower end power. No CEL. One of the mechanic suspect clogged cat, so I replaced and not much chance. Before the BHG, I was able to do burn out with it and tires almost slip when take off from a dead stop, but now not much going with that. What do you guys think?

 

[spf_lexus]

carbon buildup possibly raised your CR? a little bump in CR w/ a blower can be felt. Just an idea.

were the new pistons oem or after? maybe they have a CR drop?

maybe reset ecu?

 

[cribbj]

Maybe you've wound up with a lower compression ratio than before. That would produce a less responsive motor on the bottom end. Even though the head was refaced, and you'd think you'd have higher compression after that, if the rebuild guy went with thicker head gaskets and/or stacked them, it could happen. That would also kill the design of the quench area (if your head has a typical quench design)

I'd do both a compression and leakdown test and see how well that motor is sealing up.

 

[Lextreme II]

I actually use higher compression pistons. Jump from 8.9:1 to 9.3:1. Compression and leakdown test is a must. I suspect possible valve clearance issue.

 

[Amskeptic]

Often, aftermarket cylinder honing/piston rings have much more friction than a factory build. Let the rings break in, and you may find your power improves after 500-1,000 miles.
Colin

 

[spf_lexus]

hey lex does your Prev have 5vz w/ trd m90?

what if ecu is pulling timing to account for the higher CR? also like cribbj said, resurfacing will add a point or 2. If stock thickness HG's are used there's a possibly your actually running 9.5 and possibly pushing the ecu's "comfort zone"? I guess keep riding it and see..

 

[Lextreme II]

Often, aftermarket cylinder honing/piston rings have much more friction than a factory build. Let the rings break in, and you may find your power improves after 500-1,000 miles.
Colin

That is very conforting. Love to see more hp as the engine increase in mileage.

hey lex does your Prev have 5vz w/ trd m90?..

It has a version engine from Tacoma (2RZFE). It is calle 2TZFE and the supercharger it came with factory is SC14

 

[jibbby]

I was able to do burn out with it and tires almost slip when take off from a dead stop, but now not much going with that. What do you guys think?

A Previa Mini Van that spins tires????? Lex you really are one extreme dude. Now that's a sight that would be entertaining to watch.. Talk about a sleepers..

Mini van power, you go man!!!!

 

[JustenGT8]

Could be a million things mate but i'd suspect ECU issues before anything physical.

If you upped the comp ratio could be as simple as the knock sensor pulling timing out...get a decent shop to run error codes on it 1st Lex

 

[Smitherz]

The computer is probably learning the fuel curve right now. I know on newer cars they run really wimpy for a while until you get some miles on them. I can't say I have experience with those of course. Have someone check the codes for sure. I also agree that the engine needs to be broken in for a while. It should gain a little more grunt once things settle into place. Needs to loosen up like an AK-47...