318 pistons to bring compression up

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;QUOTE="moparmat2000, post: 1973318208, member: 14566"]Rusty, I am looking at a similar build on a 1977 318. I was looking at the KB167s. The stock pistons before dissassembly are about .100" in the hole at TDC. Arent the KBs a bit taller, closer to a zero deck height? The block will need to be surfaced "decked" anyways. The heads I have are rockauto reconditioned 302s. I have not CCd them yet to verify. Going to borrow a burette from a buddy of mine to get a number. I am ready to pull the trigger on a set of KBs but dont want to if they wont help get the compression up there.[/QUOTE]

302 heads or 714 same head different part number will be at 64CC. With those KBpistons and 64cc head your CR will be pretty high im guessing in the 10:1 range but im not positive. If i were to use those pistons i would run a 360 cylinder head which are in the 72CC range and will lower your compression ratio if needed. it all about doing the math. good luck!
 
I was reading that the average mid 70s 318 had a compression height on 1.720" and the KB167s are 1.810" that's a .090" difference that the Keith blacks bring it up out of the hole. Very little decking. Just enough to ensure head gasket sealing would probably be perfect with these.
 
RustyRatRod said:
I wouldn't take it off either.
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Yep, taking half of that off the block and half off the heads is still too much for the OE castings. They are way too thin and flexible to start with. If you start decking that much off it won’t hold head gaskets worth a crap.


Doesn’t KB make a nice 318 piston that corrects that? I absolutely HATE the ring pack they use but the pistons are very nice.
 
moparmat2000 said:
Rusty, I am looking at a similar build on a 1977 318. I was looking at the KB167s. The stock pistons before dissassembly are about .100" in the hole at TDC. Arent the KBs a bit taller, closer to a zero deck height? The block will need to be surfaced "decked" anyways. The heads I have are rockauto reconditioned 302s. I have not CCd them yet to verify. Going to borrow a burette from a buddy of mine to get a number. I am ready to pull the trigger on a set of KBs but dont want to if they wont help get the compression up there.
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Yes, but I believe the OP is looking for budget.....at least that's my impression. But Lord yes, if he can swing the KBs, that's a great way to do it!
 
RustyRatRod said:
Yes, but I believe the OP is looking for budget.....at least that's my impression. But Lord yes, if he can swing the KBs, that's a great way to do it!
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Yes that is correct, Budget would be nice. Im thinking a slight overbore, with some stock heads with some at home port and and smoothing of the castings should help it out, I may just make a cleaner engine and keep my Whiplash cam since it is fun to drive I just regret not cleaning up the heads and one cylinder had a slight scar that I wish I would of overbored. Just wanted to see if there was a piston change to boost comp a tad but it seems like more more work and money than the gain is worth.
 
Yes I put KB 167 pistons in my 318 and it measured from the lowest to highest was .015 to .011 . Only 4 thou difference so I did not deck it, just ran it as it was with a 62cc head and .039 gasket it came out at 9.7 to one.
 
Gonna have to on my sons. Pretty wore out stock bore. The .030" KBs will likely be the ticket. Not sure .020" is gonna clean it up all the way.
 
stumblinhorse said:
So why don’t the kb399’s get mentioned to raise compression?
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Isn't the KB399 is a forged KB167?

There used to be TRW 11.5 domed pistons available for the 318. Gave around 10:1 with 340/360 heads and a Fel-Pro composition head gasket. Don't know if these are still available.
 
C130 Chief said:
Isn't the KB399 is a forged KB167?

There used to be TRW 11.5 domed pistons available for the 318. Gave around 10:1 with 340/360 heads and a Fel-Pro composition head gasket. Don't know if these are still available.
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no a kb167 is a +5cc flat top and a kb399 is a -6.2cc dome. Everything else is the same. Both are Hypereutectic aluminum.
 
stumblinhorse said:
no a kb167 is a +5cc flat top and a kb399 is a -6.2cc dome. Everything else is the same. Both are Hypereutectic aluminum.
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Probably because that could get compression a little too high. Nice dang piston though!
 
If you want a 318 to end up at 9.2 compression, get a set of 318 pistons with 10.5 compression, then put 340/360 heads on the engine and you will end up at 9.2 compression...

Been there done that....

Now you don't have to mill the block and/or head and then custom pushrods etc....
 
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Not sure if this helps, but I am using a set of KB167s in a 318. They measured out to be .004" below the deck height at TDC.
 
C2ndLTpigeon said:
Wanted to see if someone can point me to the correct stock type pistons to bring a 318 to the earlier 9.2 compression. I currently have a 73 core with flat tops. I see some for sale that have 4 valve reliefs are those higher compression than flat tops?

Thanks
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Going from memory, so may be slightly off with the numbers I list.

IIRC 1.755 is the tallest stock compression height 318 piston including the 5.2 magnum.

It takes about 1.80 to get to the blueprint zero deck height on an LA 318, but block machining is all over the place so has to be measured. 5.2 magnum blocks are usually a little shorter deck height but still need to be measured.

For reference I think the high compression factory 340 piston has a 1.84 compression height, and usually sits about .018 to .022 proud of deck height on a factory block, but again your mileage may vary..

If I were going to build a 318 I would likely use the stocktype magnum piston (entire magnum assy if avaialbe) and get the block decked to get as close to zero deck as possible.

Again these numbers are just for info, everything will have to be measured with parts on hand.

Down and dirty cheapo note- I have had several 5.2 magnum engines that I have put head gaskets on. The carbon buildup on the piston tops brought the piston height up a good bit. Leave the carbon on the piston top if you come across a good used 5.2 short block for the free compression bump. Combine it with a Mr. Gasket .028 thickness head gasket for a little more compression.
 
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the late 90s LA roller cam engines had a CH of 1.78 that set .042 in the hole for 9.2 compression... cant buy any stock replacement that comes close tho'...

so 530 dollars for KB's with CH of 1.81 or..... fer cheap fuxx's


a .040 283 chevy piston Sealed Power 235NP 40 - fits a 3.915 bore, and 235NP 60 fits a 3.935 bore, has a 1.78 CH,.. but has a .927 pin vs mopar .984 pin, can bush the rod or open up pin holes .054! or open up pin holes .054 off set .042 and end up at a CH of 1.82 and should put deck height at 0 ,....all for 160 bucks + shipping and cost to open up pin holes...
 
But look at the cheapness..... they seemed too good to miss :)

nice rock hard small expansion small clearance pistons. loose on compression but gain on ring seal.

and they run the thin oil control ring bit less friction

just an option

Dave
 
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