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Decoding/Numbers / 186 heads - 1.94 vs. 2.02 valves

« on: October 17, 2021, 01:51:29 AM »

Hello All,

I have a question for anyone who has experience with '69/'70 186 heads... 

Are the castings and port sizes/runners identical for 1.94 vs 2.02 186 castings??  In other words, would 1.94 heads upgraded to 2.02 valves flow the same as factory 2.02's without additional port work?? 

Ultimately I want the correct casting number and spec heads on my '69 302 so that it performs exactly as new once it's rebuilt - I'm not worried about date codes.  It has a CE engine dated 1971 - warranty replacement, and has been running a set of 492's since the original heads gave it up in the 80's... 

So I located a set of 186 castings and had them completely rebuilt.  These 186 heads were supposed to have come off a '70 LT1, and are date coded for May 1970.  They did have the screw-in studs and guide plates when I got them, but of course these could have been added if they had been upgraded to 2.02 valves in the past.

However...  when I picked them up from the machine shop, they said they thought these heads had started life as 1.94's...  they were unclear on why they suspected this.  I have to decide whether to use these heads, or maybe do more work to them; so I popped an intake valve out of both the 186 head and a 492 head (2.02's) to compare the bowls and runners. 

 - I couldn't find any dimensions that were smaller in the 186's, and although the "uneven" machined shoulder below the valve seating face makes it look narrower; in fact if anything all the 186 bowl dimensions were marginally wider than the 492.  I think either these 186's actually are factory 2.02's, or there's virtually no difference between the 1.94's and 2.02's other than the larger valves.

I've posted some photos below compare the 186 and 492.  Appreciate if anyone can point out something I'm missing...
If it looks like these are legit 2.02 186's, (or nearly identical), then I'll bolt them on and be happy.

What do you guys think???

Thanks! Len 

2

Decoding/Numbers / '69 Z/28 Muncie M21 Date Code - Missing digit?? "P903B"

« on: October 06, 2021, 07:52:28 PM »

Is anyone aware of any irregularities in date codes on early '69 Muncies?  Here's a pic of my (believed to be original) M21 in my '69 Z/28. 
02D build date on the car, partial serial number is correct - what you can see of it.  It looks like the month code is missing - I would expect it to be "P9A03B" perhaps; but it simply shows "P903B"??   ... Also, the "B" appears to be inverted?

I'm relatively confident this is the born-with transmission.  I bought the car from older owners (long-time friends) who have had it since 1974.  To their knowledge the transmission was never replaced (or they forgot); and if it was in the early days, did people bother to re-stamp back then?  Nobody cared about numbers when these cars were nearly new...

As the car has a CE engine (replaced under warranty in '71); it's possible the transmission was replaced under warranty as well at some point. 
Would there have been different date designations for warranty Muncies which may explain this?

Thanks in advance!