The Head Thread For IDI Engines "So you wanna put this head on that engine?" - FAQ/Tech Tips/Please Read First - VWDiesel.net The IDI, TDI, and mTDI source.
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The Head Thread For IDI Engines "So you wanna put this head on that engine?" by maxfax on 04 Nov, 2009 02:21
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*DISCLAIMER, THIS IS BASED ON MY PERSONAL EXPERIENCES, I DO NOT RECOMEND OR GUARENTEE THIS WILL WORK THE SAME FOR YOU! IT IS ALWAYS BEST TO FIND THE PROPER HEAD FOR YOUR ENGINE
This section is dedicated to the 1.5L (1977 – 1980 engine code CK) and the early 1.6L (1981 and some early 82 engine code CR). These are mechanical lifter engines with 11mm head bolts
First and foremost if you have either of these engines read this thread first!
http://www.vwdiesel.net/forum/index.php?topic=21948.0
Moving on. The differences we need to concern ourselves with when talking of a head swap are the size of the front center oil return port, the longer stroke of the 1.6 and the swirl chamber volume.
The 1.5L originally had 23.5:1 compression whereas the 1.6L originally had 23:1 compression. The 1.5 has slightly smaller precups, which yield a volume of about 11.5cc above the piston at TDC. The 1.6 has about 12.8cc.
If one were to swap a 1.5 head on a 1.6, couple the smaller precup with a longer stroke and that would yield approximately 25:1 compression. Although this makes for some easy cold starting there are no other gains to be had from this, if anything it would rob you of power, economy, and durability.
Likewise if you were to swap a 1.6 head on a 1.5, couple the shorter stroke and larger precup that would yield approximately 21:1 compression. This would be the better of these two situations, although this could result in some difficult starting in cold temperatures…
Compression issues aside, there is also the matter of the front center oil return passage. Remember that a 1.5 has a smaller passage than a 1.6. There is a simple solution to this. One would need an adapter similar to this one http://www.vwdieselparts.com/1.5-1.6.htm. If installing a 1.5 head on a 1.6 block this would be installed in the block, and a 1.5 head gasket would be needed. If you were installing a 1.6 head on a 1.5 block this would be installed in the head, and a 1.5 head gasket would still be used. Some have attempted to “goo” the gap left with RTV or JB Weld, but long term this is usually an unsuccessful fix… There would also be the option to weld the hole so that it is smaller, for most this would be more so difficult.
Pictured Below is a 1.6 head with a 1.5 gasket placed on it.. Note the gap
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#1 by maxfax on 04 Nov, 2009 02:47
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Starting in 1982 VW changed from 11mm head bolts to 12mm stretch bolts. (The 11mm bolts have an allen head whereas the 12mm bolts have a tripple square head..) This vastly improved head gasket sealing, and decreased block cracking on the VW diesel. These were used until the end of the VW IDI engine production. In 1985ish VW introduced hydraulic lifters to the 1.6 diesels, we will address this later on. For this portion we will only be addressing the differences in 11mm and 12mm mechanical heads.
The swap is fairly cut and dry, although personally I would recommend just finding the proper head.
The head bolt holes in the head need to be drilled about .04” (1 mm) larger to use and 11mm head on a 12mm block. Drill size is approximately .49” (12.5mm) The holes need to be drilled darn near perfectly straight, use of a drill press is recommended. Remember that the second hole in from the flywheel side of the engine on the side of the vacuum pump is slightly larger for the oil to feed to the head. It also needs to be enlarged 1mm, but will be a larger size bit than the rest. Drill size for this passage is approximately .51” (12.9mm)… You would then use the standard 12mm bolts…
To use a 12mm head on a 11mm block one would need to find or fabricate some variety of spacer to fit around at least 2 of the head bolts as to properly align the head. I have also opted to install alignment dowels in the rear two oil return passages. Generally this will require slightly reaming those passages in the head so that it will slide down over them… The dowels should fit snugly into the block. The standard 11mm head studs would be used with the standard 11mm washers…
Everything mentioned earlier about 1.5 heads still applies, but it may be necessary to enlarge the bolt holes in the 1.5 head gasket for the 12mm bolts..
This ends the ins and outs of swapping mechanical heads among mechanical blocks. Coming soon (I hope), swapping mechanical and non-mechanical parts, and AAZ head swaps.
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#2 by foxracer1 on 28 Dec, 2009 23:47
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The 1.5L originally had 23.5:1 compression whereas the 1.6L originally had 23:1 compression. The 1.5 has slightly smaller precups, which yield a volume of about 11.5cc above the piston at TDC. The 1.6 has about 12.8cc.
Would you happen to know what is the volume of the 1.9 AAZ precup is? -
#3 by maxfax on 29 Dec, 2009 16:21
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Would you happen to know what is the volume of the 1.9 AAZ precup is?
I got my info from this thread.. http://www.vwdiesel.net/forum/index.php?topic=12633.0
Often thought it needed referenced in the FAQ.. Guess now it is...
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#4 by foxracer1 on 29 Dec, 2009 18:54
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Ahh very good yes thanks been playing around to figure out my compression ration with the 1.9 head. Wanna play with cams but don't wanna lower the dynamic compression to much more.
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#5 by maxfax on 29 Dec, 2009 21:57
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Did you swap a 1.9 head on a 1.6 by chance?? I've been slowly (okay very slowly) working on my next chapter for this thread, haven;t gotten the chance to calculate the compression for such a setup...
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#6 by foxracer1 on 30 Dec, 2009 10:10
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Yeah i have a 1.9 head on a 1mm over 1.6 MF block. I've been super happy with it even in the cold. I was gonna check compression but have yet to do that. Wanted to wait till its brokin in it for sure is now.
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#7 by Nignick09 on 22 Jan, 2010 21:55
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Quicken or pen and paper. MS Money should work for at least another 10 years while you find a suitable replacement.
Just joking about the pen and paper.