Look what I found

I pulled the motor out of my truck for some "upgrades" and look what I found when pulling it apart




The worst one is #4 the other is #8. All others were fine and the truck didn't smoke but it would foul the rear plugs every so often but I thought that was a carb issue. Just lost a $100 on a race too lol. Any idea how much hp it was down? Motor made around 575 id say. Not sure when this happened but its been like this awhile.

Detonation is happening LONG before you can actually hear it.
Although, one photo is aluminum MELTING so, it was also too lean; (or to hot)..

You need better gasoline or less compression ratio.

could be improper ring gap also.

Well this is with nitrous and junk KB hyper pistons. I pull a lot of timing from 34 total when I spray it. It's only 10:1 or so. I run on 93 in the tank and have a separate 1 gal cell with c16 for nos. I just can't believe it ran as good as it did with 2 hurt pistons lol. I couldn't tell it was broke. Hopefully the new pistons are much stronger.

looks to me that u were to rich on the nitrous tune and took out a ring land

I'm running KB piston also did u gap the rings for nitrous or add nitrous after the build... you got me worry now been spraying the hell out of mind... going to stay on motor till after Drag Week

The motor was set up to run n/a I bought it as is. I think it happened when I was talked into stepping up from a 73 jet to an 82. I only pulled it to switch short blocks it ran fine. Ran 5.6psi 73n/61f but stepped up to an 82n/73f tune up but it didn't pick up anywhere. I guess this is why lol. That was around 5 months ago. I wouldn't be scared just don't get too greedy lol.

Like you said, the KB Hyper, is a "junk piston"! At the end of the day, it is still a cast piston. They are the least desirable piston to run with nitrous.

Charlie

I'm assuming your putting a forged piston in?

A lot more experience on this than me,but I would say not enough ring gap,especially running nitrous. Like Charlie said about the hyper piston. imo a hyper piston is still only a good cast piston at its best and NOT a race piston especially on the bottle. 

Cast piston or not I got a couple of forged that look like that in the same spot where the piston is thin at the releaf. Also on the corner holes as well where it may be lean. The Mafia manifold will help balance the corner holes over the victor.

Dave De wrote:Cast piston or not I got a couple of forged that look like that in the same spot where the piston is thin at the releaf. Also on the corner holes as well where it may be lean. The Mafia manifold will help balance the corner holes over the victor.

Thanks Dave guess I'll just spray the shit out of it.... Hows the converter and did the engine get hurt when we were in Ugly... Oh Cobra Bill is renting the track again Sept 20 and a rain date of the 27 if I survive DW I'm going

dfree383 wrote:I'm assuming your putting a forged piston in?

Forged SRP piston, h beams, cast 4.15 crank. I was hoping to use the motor for another project but I guess not without some repairs lol.

Dave De wrote:Also on the corner holes as well where it may be lean. The Mafia manifold will help balance the corner holes over the victor.

Has this been proven on a nitrous motor? I am going with a 4500 soon but planned to open up my current intake since it was machined down in the front and back and lines up perfect to the heads.

tfsbbf466 wrote:

Dave De wrote:Also on the corner holes as well where it may be lean. The Mafia manifold will help balance the corner holes over the victor.

Has this been proven on a nitrous motor? I am going with a 4500 soon but planned to open up my current intake since it was machined down in the front and back and lines up perfect to the heads.

I dont spray anything but also assume that flow distribution wont matter between spray or nat-asp as both should be the same. My TFS manifold has had little work done to it and the plugs are fairly close at each hole. I couldnt say the same for the Victor even when it was ground on for over 4 hours.

tfsbbf466 wrote:I pulled the motor out of my truck for some "upgrades" and look what I found when pulling it apart




The worst one is #4 the other is #8. All others were fine and the truck didn't smoke but it would foul the rear plugs every so often but I thought that was a carb issue. Just lost a $100 on a race too lol. Any idea how much hp it was down? Motor made around 575 id say. Not sure when this happened but its been like this awhile.

from my experance even the std diamond forged are only about .060-.080 thick in that area of the valve relief cut.the diamond pistons for heavy nos use will have greater thickness in that area.anytime you are tuneing for nos use you must first check the all motor tune using the fuel you are going to use for nos with fresh pulgs each time until you get the correct color.then back off the timeing for the hp shot you are going to use,autolite AR3932 or 5820 ngk plugs are what most people use.dont be a fool and only check the corner plugs:shock: also a cam with the 2 and 8 fireing order swap will help with the intake distribution.

tfsbbf466 wrote:

dfree383 wrote:I'm assuming your putting a forged piston in?

Forged SRP piston, h beams, cast 4.15 crank. I was hoping to use the motor for another project but I guess not without some repairs lol.

Most of the SRP stuff is 4032 alloy.....2618 alloy would be better for the spray.

Well hopefully ill be ok. They are 4032 alloy part #154167. This is the first piston I've ever broken and I've had nitrous since 05 on many different set ups cast and forged and all has been good. I plan on a little heavier nitrous use with this motor though up to a 93 jet I hope.