 Question on sealing heads / cylinders, Advice needed on lapping cyls to head |
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| Joe Owensby |
 May 5 2007, 12:37 PM
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JoeO  Group: Members Posts: 527 Joined: 7-January 06 From: Spartanburg, SC Member No.: 5,385 Region Association: South East States  |
I have done a search here, and have found some info, but not all I needed. Most say to just lap the cylinders to the heads. I have a 2056 kit from Raby, with all new parts. How precise should the interface of the head to the cylinder be? My new heads have small machining grooves on the area where the head will mate. Small, but can be felt with a fingernail. The cylinders also have small machining grooves fromt he lathe cutting. I have lapped the cylinder to the head on one cylinder. I have done this to the point of getting a uniform type of mating all around the surface. However, this is to the point that the small grooves are still there, ie it is not a completely flat polished surface. I am guessint the grooves are about 3 thousandths deep or so.
I was wondering if the grooves could actually help sealing, as I have seen a lot of gaskets, etc. that have circumferentially grooved or ribbed surfaces to allow a higher unit contact pressure around the full surface, and maybe allow for accomodating slight imperfections in geometry. I also saw on Jake's website where someone, I think Len Hoffman, said there was a taper machined into the cylinder mating surface, about 0.0015 or so. On this site, there was a mention by Jake to first lap the cylinder on a glass pane, and then lap the cylinder to the head. Any clarification you can give to this will be greatly appreciated. Thanks, Joe O. |
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| Jake Raby |
Aug 27 2007, 01:33 PM
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
We all have our different methods..
My method has worked well for me, it has held 20+ PSI of boost and up to 14.75:1 CR on some race engines and at the same time it has kept us from EVER having a returned engine due to a head leak. One should machine the head to the best of their ability, and then follow up the process with the lapping to get a better match between the cylinder and the head. This can eliminate irregularities from the surface of the cylinder- not just the head surface. Thats just my way of doing it and I have based it upon my experience- just llike the Cap'n bases his. |
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Posts in this topic
Joe Owensby Question on sealing heads / cylinders May 5 2007, 12:37 PM
orange914
I have done a search here, and have found some in... Aug 26 2007, 09:24 PM davep It is Jake's kit, best to get the clarificatio... Aug 26 2007, 09:28 PM alpha434 Do not lap on a glass pane. Glass is NOT flat. Mac... Aug 26 2007, 10:08 PM Twystd1 Joe,
You really need to post this question up on J... Aug 26 2007, 10:53 PM
brer
Joe,
You really need to post this question up on ... Aug 26 2007, 11:58 PM Twystd1 What he said..........
CCC Aug 27 2007, 12:15 AM Cap'n Krusty Lemme see. You take precision machined heads, don... Aug 27 2007, 01:08 AM alpha434 Fixture in a mill? Depend on whether it's a 5 ... Aug 27 2007, 01:14 AM Cap'n Krusty
Fixture in a mill? Depend on whether it's a 5... Aug 27 2007, 11:17 AM mike373 Jake uses a paste made from ajax and a little wate... Aug 27 2007, 02:35 AM blitZ
Jake uses a paste made from ajax and a little wat... Aug 27 2007, 06:14 AM brer I sell that tool.
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