Cylinder to head fitment seems loose

[jamesvomit]

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.

[jimmyhoffa]

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.
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1974 Chenowth 2RL #1244 Street Legal
My other car isn't ridiculous.

[jamesvomit]

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?

[ORANGECRUSHer]

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.
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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

[RWK]

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.
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73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530

[nsracing]

0.030" clearance is for the blind. That is like Mae West cut.

The loosest i will machine is 0.005" for head registers.

[oprn]

[modok]

Factory used 0.2mm (.008") clearance
93.8 cylinder OD in a 94mm head counterbore