can anyone tell me how much you can deck a 425 engine ,the deck is now 9.99 .they say stock is 10.023. need to take .015 more off is that ok. thanks
Stock decks are 10.015"-10.025". We have taken off as much as .050" with no seemingly adverse effects.
Can you explain how you measured the 9.99" ? If 9.990" is the distance from crankshaft centerline to the top of the block deck, don't you need to add 0.033" to get the stock deck height? The measurement from crankshaft CL seems tricky without knowing the reference point is good. (aligned mains, straight shaft, etc.)
I had a friend that owned a machine shop. He had a machined bar that would fit in the main saddles,,, he would bolt that bar in and then just measure from the surface of the bar to the deck.... most the biggest difference was from the front of the block to the back.... then there was the side to side square that had to be set with a level....both plumb and then level....not some thing that an amature should do at home.... If the basic machineing/blue printing is done right it will free up a lot of power and make an engine live a lot longer,,, but if it gets botched up , it will be ruined.....You got to have a good core block,,,, if you square up the deck , when you bore, the boring bar will be at 90 deg. to the centerline of the crank and the cyl may not clean up at the bottom.... then all you can to is to overbore and sleeve that cyl... can get expensive....and you dont know untill you do your basic measurements.... this is why you need an old machinist that has buick nailhead experience and white hair.....:laugh: :laugh: :laugh: some body like Tom....:laugh: :laugh:
I was considering cutting my decks down to the min spec, until our guru suggested I just order pistons with a lower pin location to bring the piston higher in the bore!.....that would eliminate any problems with intake manifold alignment. Pistons on a stock block are often 0.040"+ down in the bore. The NHRA guys cut them down to 0.010-0.020" to blueprint, and raise CR. Ever read the old 1966 Hot Rod article 'Blueprinting Buicks for Action'? ...it's a must read!
I talked to the machine shop, the engine was align bored. my stock deck height was 10.016, I should have said its now 9.998. he took .018 off one side and .0003 on the other to make it even.
your right but the machine shop and je pistons made the pin height 1.93 which is stock,after I told them that I wanted 0 deck height and 9.75-10:1 comp, they gave me 39.5 cc dome now Iam at .038 in the hole with 9.4 comp. any ideas.
Ouch. The stock pistons I measured were 46 cc. The Ross 425 forgings I picked up on eBay were a tad less, about 44 cc. I'd say they made your pistons wrong, and you should ask them to make them RIGHT. You do want a minimum piston-to-head clearance of 0.025- 0.035" just for safety....and that's with the head gasket installed. Cheryl mentioned she had to remove some material from the domes for proper clearance: http://www.v8buick.com/showthread.php?t=132335 I wonder if there are any tricks that can be used to bring the piston up further...like offset grinding the crank (and increasing stroke)0.020" :Brow:
Which Head gaskets are being used? .015 steel or Fel Pro? and remember to recheck the valve to piston clearance Especially if you are moving the cam timing I learned that a 2 degree move (advance) really changed the valve to piston to below minimum specs Roger
Hi Doc, thats not compressed. how much do they compresse. I might take .010 more off the block that would give 9.6 comp. the intake should still line up. is 9.6 good enough? thanks Joe
Intake bolt holes might need to be elongated and the runners filed on one side to line you back up. Also the more you cut off the heads and/or block, the more of a chance you will need shorter pushrods, even with Tom's roller rockers. (trust me, that's were I'm at now) Steel Head Gaskets might be an easier, cheaper way to get the compression you're loking for Roger
I'll second that! The stock steel gaskets are 0.015" thick. I give them a few coats of spray-on copper-coat gasket sealer to help seal the machining marks in block and heads. Make sure you get 425 gaskets as they are a larger diameter than 401 gaskets. Fel Pros are listed as 0.045" thick, I was told they'll compress to about 0.036". On my 0.020" over 401 rebuild, I calculated 9.83:1 CR with 0.015" head gaskets, and 9.39:1 CR with 0.036" head gaskets. Piston domes were 46.5 cc, heads (cut 0.007") were 126cc, and pistons were 0.045" down in the bore. What cam are you using?
Yep,,, Whatever gasket you use, you need to figure compressed thickness.... uncompressed thickness doesnt help you at all...and then figure in a safety margine too.....
je said they will make new pistons, first they said pin height was 9.05 stock, I told them its 9.3 stock. can some say for sure what is stock pin height is. now I have to talk with the machine shop he has take the pins out and balance again hope he says alright.
Hi Walt- You mentioned earlier that you did not deck the block to minimum specs. Did your deck require align hone of the crank journals? Did you take some off the deck after that to get the block square? If so, what deck height did you end up with?
