[Chambers]

OK I'll try to make this as short as possible: I built a blower motor several years ago and made the mistake of not double checking the machinists' work and also not making sure a torque-plate was used. So a few months ago I suffered an oiling system problem which tore up #7&8 rod bearing/crank journal,#7 being the worse of the two and resulting also in piston to head contact busting the piston. Ok: so I ordered a replacement piston (ARIAS custom dished silicon blower pistons), well nowdays you have to buy a minimum of 4 , so I did @ $387.00 . Well when the new pistons arived they came with specs so by this time I had sold my 197HO heads and tore down the motor completely and noticed alot of thrust side wear in the cyl walls and decided to check the piston to wall clearance with the specs, and the reccommended clearance is .005 ,well my existing cylinder clearance in the wear area is .009 to .011 depending on the cyl, but all cyl are nowhere near .005 in any location in the bore. So my conclusion is that the wrong clearance was originally machined. Now I have a '70 std bore 455 that I am planning on using. I have already hardblocked it half way and am going to transfer the billet main caps,have it decked, cut for o-rings etc.. Sorry for the history but it was neccessary. My problem is this: I hate to go all the way to .060 on a std bore block just to use these pistons (8 + 3 spares) and have no room for future overbore if neccessary, and this is my last block. Should I try to sell these pistons,(any takers) and get some .030's or stay with the .060's that I'm upside down in. My money tree died along time ago and either way I'm not going to make the PSN this year so time is no longer an issue. I'm loosing sleep over this so help me out here!!! Thanks

[Chambers]

OK I'll try to make this as short as possible: I built a blower motor several years ago and made the mistake of not double checking the machinists' work and also not making sure a torque-plate was used. So a few months ago I suffered an oiling system problem which tore up #7&8 rod bearing/crank journal,#7 being the worse of the two and resulting also in piston to head contact busting the piston. Ok: so I ordered a replacement piston (ARIAS custom dished silicon blower pistons), well nowdays you have to buy a minimum of 4 , so I did @ $387.00 . Well when the new pistons arived they came with specs so by this time I had sold my 197HO heads and tore down the motor completely and noticed alot of thrust side wear in the cyl walls and decided to check the piston to wall clearance with the specs, and the reccommended clearance is .005 ,well my existing cylinder clearance in the wear area is .009 to .011 depending on the cyl, but all cyl are nowhere near .005 in any location in the bore. So my conclusion is that the wrong clearance was originally machined. Now I have a '70 std bore 455 that I am planning on using. I have already hardblocked it half way and am going to transfer the billet main caps,have it decked, cut for o-rings etc.. Sorry for the history but it was neccessary. My problem is this: I hate to go all the way to .060 on a std bore block just to use these pistons (8 + 3 spares) and have no room for future overbore if neccessary, and this is my last block. Should I try to sell these pistons,(any takers) and get some .030's or stay with the .060's that I'm upside down in. My money tree died along time ago and either way I'm not going to make the PSN this year so time is no longer an issue. I'm loosing sleep over this so help me out here!!! Thanks

[Gach]

Here's my advise to you, first if it's a 455 block, have it SONIC TESTED, before you even think of going .060, some have very thin walls. Even if your going to fill the block. The thrust side is really important, I'd make sure that it's no thinner, then .120 after boring. Figure your going to lose .030
off each wall. Usually it's near the top of the cylinder were it's the thinist., about an 1½ down.

If it checks out ok, then use it. You can always later hone it .002 to clean it up, and still not have a ring sealing problem. Make sure your measuring the clearance in the right place, on the pistons, most I think want you to measure near the pin, for side clearance. Your better off miking the
pistons, rather the using feeler gauges.Very easy to be off, if your not checking in the right place, or if your usinf feeler gauges. You may find that your wrong.

[77TA]

Hey Gach what about sleaveing the block ? I was told by a engine builder here that it was not uncommon for him to sleave all 8 holes in some SBC that were all out drag motors running blowers and big dooses of NOS to make 1000 plus hp as the sleaved blocks stood up better than the non sleeved blocks under this abuse. I wonder if this would work for a pontiac ? If so that might be an option to reuse his old block have 8 sleaves put in about 50 bucks each may have to realign hone as it might cause some shift in the block maybe not. That would be maybe 300-400 tops and saves the standard block for another day. Just and Idea from the spectator seats.

[This message has been edited by 77TA (edited 04-28-2001).]

[Chambers]

I dropped the block off today at the machine shop told me that on a filled/half filled block he usually sets the piston clearance at .008 with silicon type pistons. The specs for my pistons state .005 and I know there are variables What should this clearance be on a half filled block? a
Also I've heard that blower motor clearances are different, but if I'm running an intercooler then I would think I could run a tighter clearance or at least what is reccommended by the mfg of the piston.