I was just putting together my stroker engine again for the 3rd time. I used keith black pistons that kept popping the tops off. This time I wised up and got forged trw pistons. The problem with the pistons is they are hitting the crank. So apperently they are for an old school small block and not an lt1. I was wondering if you guys could recommend a budget forged piston to buy? I am getting tired of always buying the wrong stuff. Any help would be great. I am using the 5.7 rod.

Thanks

Shawn

 

i am guessing the skirt is hitting the counterweight on the crank shaft? did you get pistons that were setup for the 5.7 rod?

these are srp, 3.75 stroke, 5.7 rod, 4.030 bore.....

click here

 

I'm running the Mahle Powerpack forged pistons in my 385. If you're not going to run a lot of boost or nitrous these are the ticket for a street engine. You can set them up at .0025" to .003" clearance and have little to no piston noise. Depending on your current bore size you might be able to even run them at close to .002" clearance if it's a moderate horsepower/RPM build, not sure on that though. They last longer than the race forgings (low silicone alloys) also. I think these are the best pistons you can buy for a street engine that is driven a lot and isn't far out there on the horsepower scale.

By the way, when you say the Keith Black pistons were popping the tops off are you talking about the outside edges above the rings? If these are the hypereutectic pistons you have to run a really large end gap on the rings. The high silicone content makes the domes run pretty hot and if the ring end gap is too tight the ends will butt together as it expands from the heat and break the ring lands off. If I remember right you have to run .020" or more on the top ring, maybe a good deal more with nitrous or boost.


Good luck, Michael

 

The ones I ordered out of summit are for the 5.7 rod but the bottoms of the piston are definately hitting. I'll take a look at the one's you suggested. I hope there about the same weight as the trw. I just had the rotating assembly balanced and don't won't to pay for it again.

Shawn

 

I'd bet the Mahle pistons are a good deal lighter than the TRW forgings. You can probably call the manufacturers and get an idea on the weight. The last set of TRW's I used were bricks, very thick and heavy. Probably pretty hard to break though.

Michael

 

Grammerman, I just bought the mahle powerpack for my 383. What makes you think the pistons wouldnt be for nitrous, or beefy application? I am going to be driving mine on the street, so it is good somewhat that they are good in that aspect.

 

What crank are you running? Crank manufacturers cut the counterweights differently for different length connecting rods. If you have a crank with counterweights for a 6" rod, and you put 5.7 rods on it, the pistons can hit the counterweights depending on the length of the skirts.

As mentioned above, KB's require very large top ring end gaps in order to prevent the ring ends from butting together and pulling off the ring lands. I am running .030" top gaps on mine with no issues for over 5 years in a blower application.

Rog

 

The crank is definately for a 5.7 rod. The pistons before worked great as far as hitting. The tops definately came apart.
Shawn

 

Whose / what part number crank and pistons do you have. This should be easy to figure out.

 

The Mahle Powerpack pistons run a higher silicone content than the standard alloy used in the race type forged pistons. This keeps the expansion as they heat up minimal so you can run tighter clearances. Makes them harder and the alloy has better wear properties. This decreases the thermal conductivity and less of the heat in the dome can flow out into the piston sides/skirts and transfer into the cylinder walls. I don't have any personal experience with running boost or nitrous on these high silicone forgings but the standard rumour is that they are somewhere between a race forging and a stock cast piston in tolerating abuse. I might be scared to run a 300 shot on them but if tuned properly ( you don't go lean and/or rattle it) I would think a 150 shot would be pretty safe.

Later, Michael

 

Probe Industries has your piston. I am running them in my set up.

 

The crank is 3.75 made by scat. i believe the original pistons were speed pro h860 I'll have to do more checking though.

Shawn