Stock 360 deck height

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dartjack

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Pulled a stock 360 apart yesterday. After getting all the pistons out I thought now would be a good time to check the deck height. Pulled the rings for easy reinstallation. Snugged the bearings back up. Dirty bathwater Batman!!! It was between .095/.100. Wasn't interested in closer measurment, just wanted to get my jaw off the floor before I stepped on it and tripped! Talk about compression and quench. None to be had there. Had a truck oil pan on it so I checked for piston differences in the catalog. Both use the same piston listed as 8.0 compression. In reality that would figure out to be mid to low 7's squeeze. Mister Whipple squeezes the Charmin harder than that. Anyone else been shocked or awe'd by this. So much for a stock rebuild with a few goodies. That would be like the kid's sand bucket filling a sink hole.
 
This is actually normal. Deck heights vary and mostly come in taller than listed. This also pushes the piston down into the hole farther. My last all stock 360 came in @ 7.7-1. My 400 came in @ 7.8-1.

In your rebuilding effort, you can ethier;

Mill the deck and /or heads for more compresion

or

Get new slugs like the KB-107 or the Speed Pro/Fed-Mougal slugs for the 360. Though, they were designed with the idea of being a zero deck slug for 9.8-1 ratio w/open 72 cc heads, the taller deck height and possible extra amount of head cc's along with a thicker head gasket can drop this ratio real good and even down passed 9.5-1 easy.

Really, a 9.0-1 ratio is all you'll need for the street. The rest is cam timing, head flow for power, followed by gear ratio and converter for torque/power release.
 
The blueprint spec I beleive is 9.59. The factory machining usually leaves them between .020-.050 taller.
 
Non Magnum is 9.600" Magnum is 9.588". This is the reason why the SBM never ran all that great from the factory, save for thr 68-71 340's(they were .020" out of the hole and 68-69 273(they were at zero deck)
 
Last time I had mine out and apart, I checked from deck to center of dish on piston and it checked about 1/4" down in bore. Of course the edge around top of piston wasn't that deep. Mine are KB hyper pistons stock replacement.
 
Which pistons did you use with the .070 deck cut? Went down the block decking road 40 years ago. I still wake up hiding under my pillow from that one. We did .125 then on a Chebby 283. Cut hte pistons too. Valve clearance was way too low. Only 283 to not turn 6 grand. 5600 and valves bent. About 6 sets. All 16!!! Did you go below the 9.600 height?

I was only half owner of that Chebby. And it was and WILL BE the last(also first) one!
 
Yes it was in the pistons, they had a higher CH. A 67 273 should have been down about .030-.040"

And there is a misprint in my post. The Magnum blocks are 9.580" deck height, not 9.588"
 
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