I am putting the heads on my 454 today and found something that may be a major problem. My rebuild/modify block chevy book says all big blocks have valve reliefs cut into to corner on the cylinder walls for valve relief they illustrated a picture of this. When I look at my block 72 454 2bolt, I have no reliefs cut into the block. Cylinder walls are just like a small block. Is this a problem or mabey just used on 396-427 blocks. I dont want to put my heads on untill I can verify this with some of you guys. BTW the block was all stock never decked or bored before I got it and I didnt deck the block either. Just want to be sure because the motor goes in tomorrow.
thanks,

I *think* this is a common occurance, what I would do is put on one head with just the gasket and 3 bolts, just snug up the bolts with a 3/8 ratchet, don't torque them at all. Install the pushrods and rockers for one cylinder, adjust the valves and turn it over slow, feeling for interference.

If this doesn't give you a feeling of confidence, pull one piston, put the head back on and look up from the bottom while opening a valve, see for yourself how much room there is between the valve and cylinder wall.

If it's a used block, you know it ran before like that....

Tom

I have an untouched 73 454 block out in the garage and it doesn't have reliefs either.

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JT
71 SS Vortec 355
www.angelfire.com/co/KellyMotorsports (http://www.angelfire.com/co/KellyMotorsports)

I believe the only time this was common at all was on 396 bores.

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Tom Parsons

Thanks, I called a friend and he doesnt have them either. Dont know why my book syas they all do. I will go ahead and put the heads on keep my plan of putting the motor in tomorrow.

thanks,

I am not sure but I think the reliefs were for some type of flame travel or flow or something like that. Emmissions maybe? But it wasn't for clearance reasons.

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Mike Hurta
(Aug98)
Gold#25
Clute, Texas
www.chevelles.com/feature/aug98.html (http://www.chevelles.com/feature/aug98.html)

RUN IT. my 427 uses a 73 454 block. No reliefs. No problemo. Run a Crane with modest lift though, .544/.564. Incidentally, my 1970 L88 block doesn't have 'em either.

DZAUTO is right, only on the small bore rats did GM whack in the big valve reliefs in the block. I you open the heads and use 2.300 valves, you need to check on the 4.250 bore blocks for proper clearance.

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Wally
Gold #67
67 malibu

yep,
my 396 had em,my 427 has not.67rat member #199

Update--- '69 396/375 horse block, and my '70 LS6 block BOTH have the relief cut into the wall. the relief is not as big on the LS6, but is there none the less. As mentioned, the relief was to unshroud the valve for more flow. also, as mentioned, if running super-large valves, be sure to check clearance.

Put the heads on this weekend and installed one lifter on intake and exhaust, layed some clay on the piston and everything looks fine. Using 540 lift cam and didnt run into problems.

thanks guys