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Turns out that the two heads that I picked up at a garage sale are not exactly the same. They are both single port heads which I had hoped to use in my 1500sp stock rebuild sometime in the future. Today is a nasty day and I decided to get them out and give a careful look-see. One of them is 311.101.373A and the other a 113.101.373B both are VW. It is my understanding that these heads are the same and are interchangeable. Both look the same but on close examination with a real good light, the 113 head appears to have been reworked to allow the cylinder to sit into the head an additional 2.5mm. The 311 head has an inset of 12mm where the 113 head is 14.5mm. It seems that this would substantially raise the compression ratio and pressures in the 113 head since the combustion chamber is smaller. ?? Am I thinking correctly here?
So my question is, should I get the 311 head cut 2.5mm deeper? If my 113 head was cut deeper with the intent of making it a fire breathing 2100+/- cc engine. I don’t want to ruin my stock (?) 311 head and cut it deeper only to find that now I can not use either. Both heads have new seated valves, guides, springs, retainers, rockers, washers, and look pretty nice – the idea of new seated valves etc, is what got me wanting to use the new heads in the first place. I do not expect there is anything wrong with my currently installed ones. Any help advice would be appreciated.
I think the 311 part number heads are for a Type 3 engine used in VW squarebacks, fastbacks and notchbacks. Possibly a VW Thing. For VW beetles (Type 1) the part numbers usually start with 113.
Allen Caron
VW based 53MGTD - "MoneyPenny"
"If one thing matters, everything matters" - from the book The ShackAllen, you are right that the factory numbered them that way, but it was my understanding that they were interchangeable. No??
Yes they should be interchangeable. The only ones I’m not certain about are the fuel injected heads.
Allen Caron
VW based 53MGTD - "MoneyPenny"
"If one thing matters, everything matters" - from the book The ShackWhy not check the combustion chamber volumes? Just set them face up and level, get a good measuring cup or graduated cylinder (or just a turkey baster will do). Fill one of the chambers on the head you suspect is cut for less compression ratio up to the ridge where the cylinder wall will seat. Then suck out all the water with your baster and fill up one of the chambers on the other head. If it overflows the ridge on that one, then you were right thinking the heads aren’t the same. If not, then probably not.
Obviously won’t work if your valves leak but, hey, if that happens, it’s good to know now, eh?
Ed. Did it! The combustion chamber volumes are the same. I was surprised. Optical illusion. The extra 2.5mm is in the length of the sleeve/skirt that fits down around the outside of the cylinder wall. So, I guess that makes them exactly the same, – only different. Thanks guys.
Dontcha love it when a plan comes together?
Good job! 
Allen Caron
VW based 53MGTD - "MoneyPenny"
"If one thing matters, everything matters" - from the book The ShackRoy a good engine shop should be able to CC the heads corectly for a small charge.Worth it in the end result.VW has to tight of tolerance to guess.Also don’t forget there is cylinder shims that can be used to set correct compresion ratio,if the head chambers are to small.
Thanks all. These heads were (reportedly) both reworked by the same (but unknown) machine shop. Regarding cc’ing the heads, I have a graduated srynge (sp?) but don’t know what “normal” is. I know that I have read it somewhere but can’t find it. I don’t want anything other than stock or very close to it.
Roy important head update
You have 2 different heads from 2 different motors.
Sorry I was bored
the 311-101-373A is a 67-70 1600 sp with 35.5×32 valves
the 113-101-373B is a 1300 sp with 33×30 valves
this info tells me that the chambers are different between the 2
The valves are the same in both heads. I measured them at 38×32. I’ll cc the heads and let you know.
Just to close this thread out: Both heads cc’d at 50cc. I installed them. Compression ratio calculated at 7.8/1. Compression pressures is 133-135 all around. All’s well. See the other thread on cylinder heads.
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