4.7L Newb question

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dweinhart

Member
From various searches I have read that you can use a thicker headgasket for NA application when mating 2uz block to 1uz head in place of machining pistons or getting custom Ross pistons although the results are not as good as a custom rotating assembly. Due to cost entailed when opening up a shortblock, I am wondering if it would be cost efficient to go headgasket route?

If so, what thickness would be required and what type of performance gains would be seen?Would this cause higher compression than milling 2uz piston or lower? Or has anyone tried this?
 
Welcome to forums...
What are you trying to achieve ??
Thicker gasket are generally used so more boost can
be added..
But for N/A engine ?? higher comp works o/k...
Keep a watch out for valve to piston clearance...
 
Thanks. I have been following Lextreme with much interest.

I am trying to accomplish 4.7L Hybrid without changing out pistons. I understand that 2uz design is different from 1uz design so there will be clearance issues with 1uz head. The optimal design is custom pistons however I also understand it is possible to just use a thicker headgasket to compensate for this. Because this would be an NA application I would want to run highest compression possible without causing 2uz pistons to hit the 1uz valves or preignition.
 
The problem with running thicker HG's to clear the piston domes is that for a naturally aspirated setup, you'll lose all the torque that would be normally gained over the standard 4.0L. I suppose if its tuned correctly, you could add a lot of timing w/ leaner AFR to somewhat gain back the tq lost from the low compression.

I built a 4.7L hybrid and when it came to eliminating the valve interference, I was stuck with 8.8:1. Anything higher than that is a guarantee for bent valves. I also used stock pistons so I was limited in this area. What you need is a set of ross pistons w/ 1uz profile, but with 2uz bore.
 
So although you can, it sounds like it would defeat the purpose.......and I'm sure there has already been an attempt to find a stock piston with similar bore and pin characteristics to 2uz with 1uz dome characteristics..... :(
 
How much horsepower do you lose over custom pistons by machining 2uz pistons to worK?
Click to expand...

Cant really say. I started school right when I finished the engine and ran out of time. The only reason I opted for stock pistons was that I needed lowered compression for my supercharger anyway. Forged pistons for FI was only needed for high boost and I had planned for moderate boost and in the end would have been a waste of cash. Now if I plan to run the engine naturally aspirated, I would definently open the block up and install some ross pistons in 11:1 or so compression.

the pistons sort of make the swap a deal breaker due to cost but this setup is very potent when built/tuned correctly. David (mr Lextreme) let me test drive his 1st hybrid 4.7L and it was brutal fast. He also installed his stage II cams and stock compression ross pistons. It was also run off the stock computer and it ran great on the stock fuel system.
 
I'm new to this..
Is there an issue with piston to valve clearance ??
What I've done on push rod engines is use another old head
make cutter out of the valve or araldite some emery paper
on head of valve and cut piston often with slightly oversize valve..
Using a battery drill..
Then use clay or play doh spread on piston assemble head and turn engine
at least two revolutions then check thickness of clay or doh..
Sounds messy depending on how much is required..
.020 to .040 can be cut very easy..
In most cases it's an angle cut any way...
Min clearance on pushrods is .080...
This is one area you DON'T want to over look...
 
Is there an issue with piston to valve clearance ??
Click to expand...

Just resting an early UZ head on an early 2uz block w/ a stock HG in between would not rotate. the valves would life the head several millimeters before setting it back down again. I had my builder machine the 2uz piston's rounded dome gradually until it was as flat as a stock 1uz piston. He used a similar plastigauge in lou of the clay but same procedure. There is a lot of curvature w/ 2UZ pistons and thats the problem, there isnt a piston within the UZ family that comes close enough for any kind of OEM swap. Its either low CR for boost or spend the extra cash and get the ross pistons and then gains through natural aspiration can be made.
 
Can I rejuvinate this......? I have the same noobish questions.

Is spf still around? I tried to pm him, and his pm is set to off.

My personal engine build is going far from as planned lol, so now I'm interested in alternative builds. I have a 98 gs4 and would like to go with the 4.7 block. Change rods to 1uz, and have the oem pistons machined.

Is upgrading or swapping the 4-6 bolt a wise needed move?

Where can I have the pistons machined to make this setup (4.7 block 1uzfe vvti heads) work, an cost?

I plan to supercharge the engine in the future, what's a safe time frame on this low comp hybrid to be ran until I get it charged?

As for headwork what should I do, I have a set of road/street cams in the making, thoughts on valves, porting, valvetrain? If I missed anything please school me in the ways of the wise. Honestly!!!!

I greatly appreciate the answers forehand,
Joel
 
When it comes to machining pistons and talk about forced induction ...
I would suggest you get both engines pistons and talk to guys like
http://www.cp-carrillo.com/
They can make you a strong lower compression set of pistons, rings for
around $1k with correct valve notches, ring height etc..
 
That's overkill for my goals but thank you. I know those companies exist but $1k is not logical if stock components have been known to hold up for my power goals ( aiming & 350whp ).
 
Lol...im not looking for anything insane or crazy HP. I'm in need of a new block regardless of how much hp I make. If I make more awesome. So now I hope you see where I'm coming from with the 2uz block questions.

I just need a 2uz block, some 1uz rods, and machine some pistons from what I've read recently. I just wanted the most info. Possible to do this setup successfully and quickly.

Does anyone have a mil spec/amount that needs to be removed from a 2uz piston?
Thanks,
Joel
 
Firstly.... Have you checked the piston to valve clearance ?
You may not actually need to do anything?

Get it physically measure before you spend any money
It may just need a intake centre line cam shaft change rather than all this other work....
 
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