Finished!! Forged piston block, Custom valve head (flowbenched)

[lookin]

basically your cc vac setup .... well .... sucks .... a bit too much.

but you knew that.

sometimes I think you just enjoy smokin motors.

then again .... you knew that too.


carry on

[lookin]

nevermind

wgwid?

[Ondonti]

The stock motors don't have massive blow bye like the bad clearances built motor...I originally built the system to help deal with blow bye that was pushing oil out of all the motor's seals.

Sometimes its hard to remember what the purpose of something like this is as it moves from being a bandaid to something that really helps HP.....well until it sucks the crankcase dry. Most of the oil returned to the pan after the pull, most of it was probably in the heads and the smoke show out back was from the oil pan vent with inadequate oil air separator.
Might be away from my cars for a bit in the next few months but I will get back to the projects. Hopefully find some work in Jan ish and save a little money so I can get the awd stuff together. If i get decent $ saved i might look at a 3.8L for future use in a compound turbo setup. Or I may run around on a low power AWD setup, maybe even not turbo (put turbo stuff on 3.0 Spirit)! Who knows.

[Ondonti]

BTW, what cranks are in the 2.5L 24v sohc 6g73's? Those are not so hard to find. Not sure if this crank is damaged or not.

[SpeedyEd]

Hey Brent,
You can check the block with a long straight edge thru the mains. If you have good main bearings, put the crank in & tighten the main caps. If it binds, there's a problem.
Don't know about the 2.5 crank, but the balance would be different because of piston weight.
SpeedyEd

[SpeedyEd]

Hey Brent,
I ran across this article on sealing the heads of the 3.0 on FelPro's web site. Thought it might help.
SpeedyEd

http://www.felpro-only.com/tec_notes..._3.0L_SOHC.pdf

[Ondonti]

Well I have the exact same problem that I read a LOT about years ago on the 3si.org boards. the Forged cranks pound out main bearings if you detonate around 850whp.
Cast crank has a lower threshold for this. So what happened.

Lower main bearings get pounded out and some of their material moves up to the upper bearing closing up the clearances on top :(

Then a very very short oil starvation situation = instant metal on metal.

The fix for this is polishing the main journals and just installing new main bearings. That is as long as nothing weird happens to the cast crank. The forged crank seems to not be too bugged by this. Just needs polishing (not turning).

If this was rod, then I would be worried.

The moment I popped the top mains out the crank turned fine. Made no difference when i removed the girdle because those bearings were not the problem, they just created the problem. Only the center 2 mains suffer large amounts of damage (still all damaged some) because thats where the crank flexes. If I had the aluminum flywheel in this probably would have been even worse. Heavy flywheel is also used to combat this issue, but so is proper tuning.

I now have timing control so no more crazy high timing under big boost.
Will check out the felpro article.

[Tim_K]

When you redid the ring gaps on this stock short block, what were the ring gaps measurements stock, and what did you change them to to ensure they would not butt?

Better to have a little too large of a gap than not quite enough!

[Ondonti]

The top rings were .011"-.019" (terrible tolerances, that .011" cylinder would have nuked itself).
the stock 2nd rings were .018-.022"

Its also strange that the 2nd ring gap is larger because thats a new technique for ring gapping.

I gapped the tops to about .024" and the 2nd rings to about .030"
I believe I gapped 3,4 larger, and 5,6 slightly larger then that. I have it written down somewhere. The larger gap probably saved these pistons from busting when it detonated.

If I did it again, I would gap 2 slightly larger, then 4 and 6 much larger since on a stock front manifold those 2 cylinders get a LOT of reversion from the crappy front manifold.