decking a 360 block
- Thread starter ike61
- Start date
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OwdKasd
Well-Known Member
Maybe changing the pistons would be a better option. Here's why I say that. If you deck the Block or heads, then the intake may not match up any more. I know it can and is done all the time but it seems like the harder riskier way to do it.
moparlover
Well-Known Member
agreed. it's a three prong approach
you get pistons that give you the right comp ratio, zero deck the block/quench, and those both match the heads you are using.
Keith Black has a myriad of pistons, it depends on what gas you want to run/which heads you are using. (how many CC's they are, open/closed)
if it's street gas you would get a piston for around 10:1 or so
it gets kind of technical, but basically heads & pistons & deck height have to be matched up. just machining the deck a little bit or the heads a little bit can get you some compression, yes, but you wont have the quench right and could have a real pinger on your hands.
http://www.kb-silvolite.com/kb_car/...=search&mfg=Chrysler&EngSize=360&RodLen=6.123
you get pistons that give you the right comp ratio, zero deck the block/quench, and those both match the heads you are using.
Keith Black has a myriad of pistons, it depends on what gas you want to run/which heads you are using. (how many CC's they are, open/closed)
if it's street gas you would get a piston for around 10:1 or so
it gets kind of technical, but basically heads & pistons & deck height have to be matched up. just machining the deck a little bit or the heads a little bit can get you some compression, yes, but you wont have the quench right and could have a real pinger on your hands.
http://www.kb-silvolite.com/kb_car/...=search&mfg=Chrysler&EngSize=360&RodLen=6.123
pishta
I know I'm right....
Decking the block (or heads) requires the intake to be milled so it sitt and lines up properly. You are now married to that combo and any change will require more machine work. Flat top pistons on the other hand are not expensive, you can weight the old and new and if your lucky, the new ones weigh a little more than the old and you can lighten them so you dont need a rebalance of your crank ($$) and you can use your old longblock. Choose your path, both are gonna be ~200 and up. Now a Cam that is ground to your low comp motor may be the other option, they will factor in your low compression and get you a grind that maximizes cylinder filling. ITs only money.
Measure what you have first. Deck heights is one of Chrysler's worst specifications. The blocks are routinely really long on deck surface and uneven. Until you measure and square and blueprint the deck height you really don't have a starting point.
LETSRACE
Well-Known Member
I have read about guys taking so much off the doll pins bottomed out keeping head gaskets from sealing. Not knowing what you are trying to get, or where you are now needs to be stated. Some other things you need to look at are how high do the current pistons come out of the hole (if at all), how much do the valves go into the hole (cam lift), how thick is the current head gasket. Most machine shops will cut just enough to true a block up not to gain compression.
OwdKasd
Well-Known Member
I guess the moral of the story is there's really no short cut. My good friend is a machinist and he swears that the most significant gains are on the head itself. Especially if on a low budget. Porting & Polishing, Rollers, Bigger valves etc...
Not trying to talk you out of shaving the block or anything. Just trying to help with the thought process.
Not trying to talk you out of shaving the block or anything. Just trying to help with the thought process.
moper
Well-Known Member
If you're goign to cut something a lot, cut what gives the most return... The head chambers are larger than the bore, so if you gut more off the heads, the volume will decrease more for any given amount. You can cut the deck a lot, but by the time you've got all the parts affected by that cut fitting and working properly you will have spent relatively similar money to just getting better pistons into it.
Salty Dog
Well-Known Member
Most here start with the KB-107 or a Federal Mougal CP116 Hyper-U's pistons to up the slugs height. Then decking the block is a small amount. Finish up with calculations of the heads chambers and gasket dimensions.
IF you decide to deck the block, for every .010 off the deck, cut .0144 off the front and rear block rails (often over looked when block is decked alot). This is from the MP engine book, 1982 edition. Then check distriburer engagement in the dis/oil pump drive, you don't want to bottom out hard.
Good luck,
Jim Burch
Good luck,
Jim Burch
fishy68
Tyr Fryr's Inc.
One way you can get around that is to eliminate the use of the cork end gaskets and just use RTV. I started doing that over 20 yrs. ago and love it. No more problems with end gasket leaks.
True enough, that is excatly what I did; however between the deck cut to 9.580 and the cut on my Eddies to get a 60cc chamber, my intake bottomed out on the end rails anyhow. RTV so thin it was transparent.
Just one of those things to keep in mind.
fishy68
Tyr Fryr's Inc.
Wow you must have taken the Eddy's down quite a bit, maybe thin gaskets too. I have my 360 decked to 9.58 also but the heads are new EQ's with no milling. Had about 1/8" of space left. Yes it is good to keep it in mind and set the heads and intake on with the gaskets in place to check fitment before anything is installed in the lower end.
OOOPPPSS!! My bad (I work nights and don't think too clear sometimes), it wasn't my Eddy's that the intake bottomed out, it was the "J" heads before! They were cut .035 and I was using the thin MP composits (crush in the neighborhood of .024-.026).
It's just something to remember.
It's just something to remember.
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