help me choose my piston

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USCG CHARGER

USCG CHARGER

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I wanted to bump my stock compression up so I thought about one of these two pistons for my 360. which one will be better for my Street rod and what kinda CR should I expect w/a felpro gasket?

Speed-Pro Hypereutectic Pistons H405CP Compression Distance (in): 1.637 in.

Or

Keith Black 107's Comp. Ht: 1.675


Jason
 
I go with the higher compression, it let you run a bigger cam without killing your vacuum.

Do you live were its 93 octane gasoline or 91, if its 93, squeeze that motor. I say 10-1 with iron heads would work good.
 
thx guys I was hoping u would say the more expensive of the two.... lol....

What kinda CR should I expect w/these 107's
 
depends on the heads cc and if you deck the block to make it flat with the top of the pistons
 
I havent asked my machinest to make my block SQ.. not sure if thats in my budget..lol
 
Looks as if they are 65 cc

3671587 65cc-73cc 1.88 1.6 1973 360 w/air pump; 1973 340
 
I don't know, I hear most Mopar heads are about the same. If your heads are not crack-most likely they are not, might be better just to put some $$ in to them. Why chance on another "good buy".

Now those are better heads and they sound like a good buy, they just might need a valve job and thats it, you could even run them as is and rebuild later on. I pulled my heads in the car, not a bad job
 
Rough guess,without really knowing how far your pistons will be down?Or which head gasket you will use?

Between 9.5 and 10:1.
 
not sure bro.. I guess whatever the rebuild kit comes with they dont ask what thickness I want them in.
 
you could always get some kb 191s like i have and then you dont have to worry about chamber size as youll be porting the pockets for quench clearance. i spent over 40 hours porting and quenching my heads but now im married to pop ups.
 
I would go with the kb 107s,if you dont zero deck the block the kbs will wind up around .015 in the hole and felrpros are right around .040 compressed.Unless the heads have been milled they will be in the 70s range for ccs,I would go with the mopar perfomance gasket (4.060 bore/.028 thickness),they are cheap and you should wind up around 9.5 ballpark assuming the above is correct.
 
My KB-107's +.030 went to a zero deck without decking the block. I hope yours does as well.
The Fed-Mougal pistons with the anti scuff skirts would be a better long life piston. The minor height difference plays into your hands for pump gas better. But you can still get a zero deck with decking the block.

I have the same heads. J's w/2.02's. I used on my 360 with the above KB-107's and I used a Fel-Pro gasket. The gasket was .039 thick, but bore diameter I forget. It was huge though.

The above combo works out to be 9.76-1 with gasket stats @ 4.1 bore and .039 thickness. The J head, un-milled is 72cc's. The KB-107's have a 5cc valve relief.

Assume the gasket bore is large since I do not remember exactly what it was. A 9.8-1 is what they rated it at and thats about exactly what you'll get.

You can drop the ratio .32 to 9.44-1 with a Fel-Pro thats .055 thick and a closer to actual diameter bore size gasket. I think it's the 1008 or 1009 gasket.

At 9.8-1 this engine was pretty much 93 octane only with the iron heads. Remember, no quench and max advancement on the timing because of that.
 
For A Little More You Can Get Speed Pro Hp116. They Have Close To The Same Comp. Ht. As Kb107. (your Comp. Will Be About The Same As The Kb). But They Come With Rings, They Weigh Close To Stock Pistons. Which Means You May Not Have To Balance, You Also Dont Have To File The Rings, And You Get The Coated Skirt. They Cost A Little More. But Add A Set Of Rings To Kb107 And The Time It Takes To File Them. The Hp116 Are The Better Choice. But That Is Just My Opinion . Good Luck With Your Build And Which Ever Piston You Choose
 
rumblefish360 said:
My KB-107's +.030 went to a zero deck without decking the block.]
My posted info was based off the few engines Ive seen built with the 107s,my brothers were exactly .015 and a friends were around .017-you were a lucky man rumble!.
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DARTLARRY said:
For A Little More You Can Get Speed Pro Hp116. They Have Close To The Same Comp. Ht. As Kb107. (your Comp. Will Be About The Same As The Kb). But They Come With Rings, They Weigh Close To Stock Pistons. Which Means You May Not Have To Balance, You Also Dont Have To File The Rings, And You Get The Coated Skirt. They Cost A Little More. But Add A Set Of Rings To Kb107 And The Time It Takes To File Them. The Hp116 Are The Better Choice. But That Is Just My Opinion . Good Luck With Your Build And Which Ever Piston You Choose
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Wouldn't you think that if I'm going through all this trouble and changing the pistons I should w/out a doubt have the assy balanced? At what point do I say no need to balance? How many grams?

Jason
 
USCG CHARGER said:
Wouldn't you think that if I'm going through all this trouble and changing the pistons I should w/out a doubt have the assy balanced? At what point do I say no need to balance? How many grams?

Jason
Click to expand...

I would do it,factory balance is not even close to precision to begin with,Ive run'em unbalanced before but it was either stock or a "who cares if it blows" low mile bomber.
 
well if your going to have it balanced might as well have it checked for cracks or if it needs to be bored or what bore it even is, if those are stock pistons
 
lead69 said:
I would do it,factory balance is not even close to precision to begin with,Ive run'em unbalanced before but it was either stock or a "who cares if it blows" low mile bomber.
Click to expand...

Lead69 is right. The factory ballance wasn't very good. Any high perf. engine I build like your building I have balanced.
 
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