J Have install a Procharger on my 370 Hp 7,4L engine
After some test drives ca 1 houer my engine was dead.
Now I open the Block and three pistons are broken.
I think that is comming from knocking and hot water temp.
The Lamda was always good 0,8 and the EGT at 1300° at the ellbows.
Can you say me what was wrong.
What shell I do that my engine life longer?
And whitch parts,pistons are the best for my set up?

I forgot my setup:
SX Performance fuel pump,
Mallory pressure reg with Bypass
4160 Holly Vacuum sec.
Mallory unilight distributor
Dual Ram Mainfold
Hi Perf.rec. Heads
Gil Headers
T - stat 140° and circulation pump
Comp.Ratio 8,5
7 psi boost M1 ProCharger
92 Okt fuel
SSM 3 1:1,33 25`* 14,5Cleaver

What's the total ignition advance set with the distributor. It's a good idea to keep it in the 26-30 degree (total) with a supercharged engine.
My $0.02
Gary

The total ignition timing was 32°/4000
and 16° at idle

I wouldn't set the timing advance more than 30. i have mine set at 28 degrees total advance...just to be on the safe side.

the way i set it is i set hte total at 28, then don't worry about where the base timing falls....The module takes care of that.

Hi-perf is right. 28 is safe, especially for a 7.4 piston. I started to test mine at 22 total and checked the plugs after a full boosted run. Each time the plugs looked good I moved 1 or 2* up in advance. If the plugs are looking lean before you get to 28 total then it's time for more fuel to the pistons. Remember, more fuel-cooler pistons. Just dont wash out the rings. Keep checking the plugs even with the EGT. I guess it's time for forged pistons. They will take more punishment. Good luck!

Detonation is what distroyed your engine. Do you have just broken pistons or are some parts melted. If parts are melted that means way too lean on fuel. Carb jetting is VERY important. Just last October I distroyed an engine & never opened it up. I was having carb problems & leaned motor out at part throttle.

When you go back
1. get rid of T - stat 140° and circulation pump , cooler motor less chance of detonation.
2. Polish all sharp edges on pistons, heads & top of cylinter walls.
3. Make sure engine is running rich, Start rich & then lean down form there. When testing do plug test at part throttle first & to wide open last.

What is CFM of carb? What jetting were you running? Pover valves?
I am not sure what dual ram intake is? Is this a single 4 barrel intake?
I am questioning the use of a vac secondary carb. I am not sure in a procharger setup this might have been a cause of motor leaning out. TomCat, Corbra Marty Chime in on your thoughts on vac. carbs being used in blowthru.

Cast pistons with 7 PSI much boost and 8.5:1 static compression???

I would not expect it to last long especially if it ran lean.
I've seen cast pistons that were in the early failure stage- the piston tops had large pits where the aluminum gave up.

I would consider forged pistons a must-have item.

Hey guys. I know he listed it as a 7.4 (damn europeans and their metric system) but he also indicated it was a 370hp motor (365?). Doesn't the 365hp motor have forged pistons?
I think everyone agrees it had detonation problems. Too much advance or it ran too lean.
Sven, I assume this is a blow thru system with a plentum around the carb. Is the carb and fuel pump set up as per Prochargers directions? If you set it up yourself, I hope you're not trying to push 7 psi fuel pressure into a carb plentum at 7 psi.
Gary

As has been stated, it was the fact your motor was lean.
1300* at the elbows is atleast 1500* at the exhaust port.

Carb Jetting is most likely the problem.
Get rid of the T-stat and circulating pump as has also been suggested.

Contrary to popular belief it is ok to run the timing to more than 28-30*
The amount of timinig to put in is relative to the cylinder temp and octane available.
That's the part you have to figure out according to your set up.
Example; I ran a Pro Charger with 7# all last year, no t-stat and 35* of timing.
Yes, 35* of timing. I just took my engine apart this year and everything was perfect.
I did use 94 octane however.

Point is, octane slows the burn. In order to get a complete burn timing has to be advanced the more octane you have. Up to a certain point of course.

In my opinion, if you get your fuel supply issue settled with no t-stat your 32* will be fine.

I have a question for you:
Did you change the cam, and or exhaust from stock?

DAVE