which kbs???

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DusterBoy15

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im looking to run 9.1-9.5 compression in my motor with a xe274 what kb piston is better for it the kb232 or the kb107 becasue i heard with the 65cc head the 107 will be at like 10-10.5 compression and with a 65cc head the 232 will be at 9.1 because its 9.3 at 63cc so what pistons are better if im looking to RUN 91 Octane at most
 
A KB107 will be high in number, but because of the heat transfer rate of aluminum, it acts like it's a 1 point down ratio. Thats why the Edelbrock heads are 65 cc's.

A 9.8-1 ratio can be obtained with the KB107 and a 72 cc head (J, X etc... ) and .039 gasket.
If you used this combo but with Edel. heads, it will run better, cleaner with less advance.

Been there done that still have the T-shrit and parts.
 
i have the stock 76 J heads i think smog port so i should go kbs and run what ever compression it makes? i need to run 91 max octane
 
i have the stock 76 J heads i think smog port
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J heads never made it into '76. If you have a J head, that letter is cast into the head near the spark plug holes. You do not have smog ports on a J head. If you have smog ports on your heads, you need to look for the numbers ethier under the valve cover or under the head cast into the middle 2 runners.

so i should go kbs and run what ever compression it makes?
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Not what I would call a good idea. cc the heads and do the math for the ratio. Do so assuming a zero deck piston. If you exceed 9.5-1 without a healthy cam, your probably headed for trouble.

i need to run 91 max octane
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I'd yeild at a 9.0-1 ratio
 
so would i use the 232s? then ????


also i know of a station that sells 100 octance but its a little far like 10 miles from my house
 
KB107 flat tops with typical unmachined block (0.012 to 0.018 in the hole), 72 cc open chamber 340/360 heads and an 0.039" thick head gasket will yield a compression ration of around 9.3:1.

To get to 10:1 you will need to machine the block for zero deck or have 65cc chamber heads which would also take a lot of machining.
 
ok but if i get kb107s and i dont have a 72 cc head and its less or if i get a thinner gasket that raises the compression
 
DusterBoy15 said:
ok but if i get kb107s and i dont have a 72 cc head and its less or if i get a thinner gasket that raises the compression
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Yes.

dgc333 KB107 flat tops with typical unmachined block (0.012 to 0.018 in the hole),
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Typical? Reallly. Not in my corner of the world. 2 engines out of car into machine shop with boring only and presto, zero deck. But your right about these things having the potential of sitting in the hole easy. Factory blocks have a small variable everywhere.
 
so to to zero deck i have to shave the block or bore it? some one please give it to me straight......

i want to run my xe274 with 9.1-9.5 compression what pistons do i need?
 
Give it to you straight, Get a book, or 2. How to rebuild my small block MoPar and hot to hot rod my s?b mopar and read up. It will answer many questions for you.

So far, reading most of your posts, you could have read the answers by now easy.

Your answer is mill. (AKA Shave)

Take your block to a machinest and have him check it out. Best bet is a blue printing.
 
i have that book ok so i believe what i need to do is get my block done with kb107s and dont zero deck them
 
rumblefish360 said:
Typical? Reallly. Not in my corner of the world. 2 engines out of car into machine shop with boring only and presto, zero deck. But your right about these things having the potential of sitting in the hole easy. Factory blocks have a small variable everywhere.
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Well it took almost 0.020" off the deck to get my KB107's to zero deck and Hughes Engines lists in there catalog 0.011 typical and KB says that your have to have nominal deck hight to achieve zero deck. Plus most all sb mopar engines have lower compression than advertised suggesting the deck height is pretty much always over, I think the .012-.018 is a realistic number to expect.
 
DusterBoy15 said:
ok but if i get kb107s and i dont have a 72 cc head and its less or if i get a thinner gasket that raises the compression
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You said you had stock 76 heads so unless there has been machining done to the deck on the heads they are not going to be 65 cc's typically they are around 72cc's.

If you want 9.5:1 compression you will need to take the engine apart and measure the deck height and you will need to cc the heads then you can calculate where you need the pistons to sit in order to achieve your compression ratio. Because of the variables when these engines were built no one can give you a shopping list of parts that will go together everytime with the same results.

If you don't have the means to make the measurements yourself the best bet is get the block and heads to a machine shop and tell them what you want to accomplish and let them tell you what machining is necessary.

You also mentioned using the KB232 piston. This piston is intended for magnum engines and you will need to have the small end of LA rods narrowed to use them.

I would suggest that you use magnum heads (typical 64cc's) for your build. The KB107 at zero deck, a 0.039" head gasket and the magnum head will give you 10.6:1 compression. I have this set up with an XE268H cam and it is very detonation resistant with the close quench magnum head. It will run on 89 octane with no audible detonation. If you go with the KB232 piston at zero deck and the magnum head you will have about 9.2:1 compression and might actually get away with regular 87 octane gas. But that XE274 would sure like the 10.6:1 compression.

NOTE: I chose the XE268H came just because the step up to the XE274 required a much stouter double spring and since my car is strickly a street car I didn't want to take the hit on valve train longevity you do when you start using really stiff springs.
 
dgc333 said:
Well it took almost 0.020" off the deck to get my KB107's to zero deck and Hughes Engines lists in there catalog 0.011 typical and KB says that your have to have nominal deck hight to achieve zero deck. Plus most all sb mopar engines have lower compression than advertised suggesting the deck height is pretty much always over, I think the .012-.018 is a realistic number to expect.
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OK, cool. My luck I guess. We have been around this engine building block before and know that things can vary a bit. He he he.

The next post you put up is very good and this gets big thumbs up. The kid should listen;

dgc333 said:
I would suggest that you use magnum heads (typical 64cc's) for your build. The KB107 at zero deck, a 0.039" head gasket and the magnum head will give you 10.6:1 compression. I have this set up with an XE268H cam and it is very detonation resistant with the close quench magnum head. It will run on 89 octane with no audible detonation. If you go with the KB232 piston at zero deck and the magnum head you will have about 9.2:1 compression and might actually get away with regular 87 octane gas. But that XE274 would sure like the 10.6:1 compression.

NOTE: I chose the XE268H came just because the step up to the XE274 required a much stouter double spring and since my car is strickly a street car I didn't want to take the hit on valve train longevity you do when you start using really stiff springs.
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DusterBoy15, notice the difference in pistons and there intended engine and rods. It is not that it isn't do-able, just a pain and more money spent on making the wrong parts fit.
DGC's engine is high in it's comp ratio but resistant to the deadly ping. Why, the quenched area and effecient burning heads coupled with a decent cam.
 
see i dont know what to do now because magnum heads would meana different intake because the one i have isnt for magnum heads

and i dont want 10.5 compression

im just going to run the heads i have with kb107s no zero deck and that .039 gasket and jsut run 9.5 max
 
The quench gives the hi-comp a break making it do-able.
 
and another possible idea is porting my 302 heads out to 360 and bc the valves and putting them on the 360 that way i can use speed pros and raise the compression
 
ok this is my final decsion im going to use the stock 360 heads i have with kb107s unless i find some 308 heads or some 915 j heads i just whant 9.1-95 compression but i WONT BUY MAGNUM HEADS and have to change all the parts i already have
 
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