I am in the process of building a 410. I have the 390 block with the 428 crank on the way, i just got my D2's heads back from the machine shop with CJ Valves installed and am going to be running an edelbrock alum intake with a 750 holley, 343941 cam and want to run around 10.5-1 compression or somewhere in that ballpark, Running 93 octane is not a problem. what would you guys suggest I use for pistons, this is my first 390 build and want to do it right. Thanks.

 

HB390, if you wanted to mimic the mercury 410 of '66 & '67, you could use speedpro 381Ps or silvolite 1139s. Either of those would get you the 10.5 you're looking for. But why stop at 10.5 to 1, depending on where you are in wisconsin, there might be lots of 105 octane fuel available near you. DF, on work's old cast off 'puter

 

Has anyone looked into KB150 pistons then cut the step down for a zero deck clearance? Granted they are 1.78 vs 1.66 for the 1139 pistons but then this would allow for a zero deck for a tight quench or even above the deck depending on the head gasket thickness.
This step alone is taller than .120" difference between pistons, this number would be less allowing for a flush deck. Just ideas.

 

Beemer, the KB150s are too tall, as delivered to work in a 410. But they are worth considering- if you milled that step till you had a nice D-cup piston, I think you might have a winner. DinosaurFan, on work's old discarded 'puter

 

I definatley dont have to stop at 93 but where I run up north farther there is nothing more than 93 and 93 is hard to come by. I could always fill up some tanks to bring up with me though. What did you have in mind? You got me excited when you said that.

 

bumpbumpbump

 

Where can I get either of these pistons for the cheapest i cant even find the 381P's at all. Thanks

 

HB390, where in wisconsin do you live ? Here in michigan, the shop I'm with can get you 381Ps in less than 24 hours if you want them. They shouldn't be hard to find at all. But in wisconsin, I would give serious thought to running E85 and using speedpro/TRW L2291Fs, with about .100 shaved from the tops. That'll give you something close to 12 to 1 and with Ethanol85's 105 octane rating, your engine would be very happy. If range is a problem, mount a 55 gallon drum on its side in the bed for extra capacity. You might check with BarryR, he might have some nice diamonds that will work for you. When I built my stroker, there wasn't alot available, so I had the TRWs milled. We have more choices now......DinosaurFan, @ work on lunch

 

Would I just have my machine shop shave these down or what? I would be interested in doing that. How much would it cost to have this done. Thanks

 

Dino; .100" off the top isn't a shave considering this is a full surface area off the top minus the 10cc's dish. Think about the weight / balance factor besides the elevated heat added to the top ring which aready runs hot. granted 2291F pistons have the top ring deep down from the top. Compressions going to be steep on this build as the dish is only 10cc's before cutting, what amount when done, ouchie?
On the KB 150's the pop up is a small area vs total piston area, cutting without reducing piston top to ring overall support and mass for heat absorption.
Hell you can cut a 1.776" piston down .070" allowing for a flush deck but then top of piston to top ring would be too thin causing land failure due to thin support and heat mass causing overheating and possible failures.
Not knocking your pistion selection vs mine, just would be cool if both had the same CR and dynoed.

 

What would you suggest to use for pistons if I kept everything the same except for putting in a 390 crank instead of a 428 crank, and what would i lose for torque with that.

 

Beemer, what dish are you talking about ? My L2291Fs had a flat tops with four eyebrows for valve clearance. After milling .100, most of the valve notches dissappear, then I had just two new ones cut in each piston. The TRWs are thick and heavy, you can get away with alot. Mine started at something like 728 grams and were about 100 grams lighter each after cutting. IIRC, with .041 thick gaskets and heads with something like 80ccs in the heads gave 11.7 to 1. If you don't open the heads as much as I did, you could easily have 12 to 1 or more. With E85 available at 105 octane ( winter ) and 109 (summer), the high compression is no problem. How tall is the step on the KB150 ? as long as it is more than .100, cutting a set of those is even easier. BarryR knows guys that can do it for you. But, Barry also can get you some really nice pistons that don't need any of this extra work- when I built my 421 (390, .060, 410 crank ) several years ago, milling the TRWs or using H381Ps were the only options.
HB390, you could just build a 390 with SP H395Ps, or silvolite 1131s or 1130s or 1116s. Your loss at peak torque could be as low as 20-30 ft-lbs, but you'll have to run a higher rpm to get 450 lbs-ft out of a 390 than I will to get 480lbs-ft of torque from my 421, and you're going to be down on power through the whole rpm range as compared to the stroker. I would certainly use the longer crank if you already have it. DinosaurFan, @ work on lunch

 

I dont have the crank yet, i wasted a deer with my new truck and i dont have the money for the 428 crank anymore. What would my compression be at with those pistons in a 390 I would still run high compression if I can. And what kind of numbers would i be looking at with the 390 build instead of 418. Thanks for all your help DINO, its so nice having good people to help you get something done right.

 

HB390, I wouldn't use the TRW L2291Fs in a 390. They would do fine, but they are SO heavy. We have more choices now. But the flat L2291Fs will give you something like 9.7~ 10.0 to one if you use them with shim gaskets and the D2TE-AA heads that should be on your truck. Are you in a hurry ? Would it be worth it to wait till you could get the 428 crank ? After owning and driving an FE powered truck with both the 390 stroke crank in it and with the 3.98 crank, I want the longer crank. DinosaurFan, on work's old 'puter

 

I want the build done as soon as I can and want to run as high of compression as i still can I would like at least 10.5, I am using it for strickly offroad use on and very little street use. THe only thing i want to change about the build is the crank. Is it possible to still run 10.5 or 11 and if i could what pistons would i use if no i guess i could stay with the 10 but would prefer higher. thanks