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jamesvomit Samba Member
Joined: May 13, 2022 Posts: 14 Location: Pace, Fl
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Posted: Fri Mar 22, 2024 7:52 am Post subject: Cylinder to head fitment seems loose |
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I bought a new set of 87mm P&C's from a guy on Facebook. He said he got them 20 years ago from a JC Whitney catalog. They have no manufacturer markings on the box they came in so I don't know who made them. I was dry fitting them and the jugs fit snug in the case, but are kind of loose in the heads (311-101-373A). I don't have a tool to accurately measure the size difference, but I'd guess it's about 30 thousandths. My question is, is this normal? I have only built one other motor, a stock 40hp, and that time the stock cylinders fit snugly in the stock heads. |
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jimmyhoffa Samba Member
Joined: February 16, 2014 Posts: 1059 Location: St. Louis
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Posted: Fri Mar 22, 2024 8:01 am Post subject: Re: Cylinder to head fitment seems loose |
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I usually machine for .012" or .015" but .030" isn't gonna blow it up. That should be totally fine. Send it! The sealing action occurs on the ring contact between the top face of the cylinder and the flat face of the head, by way of the head stud tension when you torque them. _________________ 1974 Chenowth 2RL #1244 Street Legal
My other car isn't ridiculous. |
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jamesvomit Samba Member
Joined: May 13, 2022 Posts: 14 Location: Pace, Fl
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Posted: Fri Mar 22, 2024 8:14 am Post subject: Re: Cylinder to head fitment seems loose |
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Sweet! I appreciate the response. Can I ask another related question? I rebuilt the 40hp motor I had because it had low compression on #3 cylinder. And someone recommended replacing all the pistons rings and using valve grinding compound to mate the cylinders to the heads. So I did, and it worked. The motor ran great. So on this new built I was going to use valve grinding compound to mate the cylinders to the head again. Is this necessary with new cylinders? Would it be a bad idea since they are a little loose? |
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ORANGECRUSHer Samba Member
Joined: June 09, 2006 Posts: 2678 Location: West Coast (Michigan's)
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Posted: Fri Mar 22, 2024 9:58 am Post subject: Re: Cylinder to head fitment seems loose |
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Don't take my word for it but I'm guessing if they are not an interference fit then you're not going to know where they will sit to lap them until it's all bolted up. _________________ Brian H.
I may not know everything,but I will try to help if I can
OrangeCrushER Berrien Warrior 2.4L Quad4
LAZY MARY 1970 Baja 1835cc |
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RWK Samba Member
Joined: June 24, 2009 Posts: 1349 Location: S.W. MI
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Posted: Sat Mar 23, 2024 7:34 am Post subject: Re: Cylinder to head fitment seems loose |
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Best thing to do if the heads are used is to have the cylinder seal surfaced faced off a bit, or decked as some call it. _________________ 73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530 |
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nsracing Samba Member
Joined: November 16, 2003 Posts: 9481 Location: NOVA
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Posted: Sun Mar 24, 2024 6:52 pm Post subject: Re: Cylinder to head fitment seems loose |
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0.030" clearance is for the blind. That is like Mae West cut.
The loosest i will machine is 0.005" for head registers. |
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oprn Samba Member
Joined: November 13, 2016 Posts: 12759 Location: Western Canada
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Posted: Sun Mar 24, 2024 7:20 pm Post subject: Re: Cylinder to head fitment seems loose |
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ORANGECRUSHer wrote: |
Don't take my word for it but I'm guessing if they are not an interference fit then you're not going to know where they will sit to lap them until it's all bolted up. |
Never seen one with an interference fit... ever! _________________ We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age) |
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modok Samba Member
Joined: October 30, 2009 Posts: 26794 Location: Colorado Springs
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Posted: Sun Mar 24, 2024 7:32 pm Post subject: Re: Cylinder to head fitment seems loose |
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Factory used 0.2mm (.008") clearance
93.8 cylinder OD in a 94mm head counterbore |
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