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Registered
Join Date: Jan 2000
Location: Vista, CA USA
Posts: 38
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Head gasket question
I was just talking to a guy that runs his 914/4 motors without head gaskets. Have any of you guys ever built a motor without 'em? The 914 type 4 is the only VW/Porsche aircooled that came with head gaskets isn't it? Anyone know why?
------------------ Mike '73 914 2.0 |
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08-09-2000, 11:28 AM
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Registered
Join Date: Dec 1969
Location: Dade County, FL.
Posts: 1,145
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There is actually a VW tech bullitan that states removing head gaskets helps with cylinder sealing. I have taken apart a leaking T-4 motor and it took forever to pound the cylinder off the head. I guess the leak melts the gasket and makes a nice soldered joint.
The TB says when the gasket is removed base cylinder shim height should be increased to keep the comp ration the same, but on our motors like the 1.8L 's thant have lower CR's to reduce emmisions a bump up in CR is a good thing. I've heard it bumps it up about 1/2 a point. With the 1.7L and 1.8L big bore kits no gasket is the norm because of the smaller sealing area. |
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08-09-2000, 04:01 PM
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Registered
Join Date: Apr 1999
Location: Huntington Beach, CA, USA
Posts: 399
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JP.. you mentioned shims.. do you have any sources that might point to a *safe* thickness of shims that can be used?.. i'm on the verge of commencing my turbo project, and i'd like to drop the compression a bit (yeah, even more than the 7.5:1).. i called up J.E. Pistons, and they want something rediculous like 700+ for a set of 4 custom forged pistons with 6.7:1 compression.. so that's out of the question.
anyone with a good idea?.. TIA, Jeff |
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08-09-2000, 04:58 PM
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Unregistered
Join Date: Aug 2000
Location: a wretched hive of scum and villainy
Posts: 55,652
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FAT performance, Orange, Ca.
------------------ Gerald Gore II (turbo2.0) |
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08-09-2000, 06:12 PM
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Hey, Jeff--do the measurements to your motor, and use the spreadsheet that Jim T put together.
http://www.pelicanparts.com/914/technical_specs/914_compression_ratio.htm --DD |
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08-10-2000, 06:18 AM
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Registered
Join Date: Apr 1999
Location: vienna,VA,usa
Posts: 148
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i have the tech bulletin but in talking to vw mechanics, i did use cylinder head gaskets on my 2.0L l-jet vanagon and my 2.0L 914 engines in recent rebuilds but they are stock engines. i think all type 4's would have come w/gaskets, don't know what the current wisdom is. in addition to the gasket delete in the tech bulletin, it also increased clearance btw cyl and piston.
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08-10-2000, 07:41 AM
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Registered
Join Date: Dec 1969
Location: Dade County, FL.
Posts: 1,145
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Bob Hoover and Tom Wilson talk about any thickness of shims up to 60 thou being O.K. The main thing is to only use ONE base shim. DO NOT STACK SHIMS, it can cause cylinder base leaks. Like the other post says FATS has shims, their 96-97 catalog lists .020, .030, and .040" they grind Blanchard spacers for any bore and thickness, "EXAMPLE: CS380-103x, 120" thick." I assume they mean .120" thick.
I would think anything thicker than .060" and you will have to think about valve train geometry. Longer pushrods, or milling the rocker shafts? I dunno, ask FATS. Cool thing would be that with all that deck height space you can use a REALLY high lift cam, but I don't know if turbos like all that lift. |
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08-10-2000, 10:38 AM
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Unregistered
Join Date: Aug 2000
Location: a wretched hive of scum and villainy
Posts: 55,652
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Turbo's do like high lift within reason, but not overlap or high duration. Around 270 degrees max. A high overlap cam will allow pressurized air/fuel to escape out the exhaust without ever getting to burn, or worse, under certain conditions it may explode in the exhaust and damage the turbo.
------------------ Gerald Gore II (turbo2.0) |
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08-10-2000, 07:17 PM
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74 Porsche 914 2.0 
